Crustal Architecture and Isostatic Support in Zagros and Central Iran: Evidence from Seismic and Gravity Analysis

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The results reveal significant spatial variations in Moho depth and crustal thickness, reflecting the tectonic complexity of the region. Crustal thickness gradually increases from eastern Iran (∼40 km) to Central Iran (∼42 km) and reaches its maximum beneath the Sanandaj-Sirjan Zone (SSZ, ∼58 km) and the Urumieh-Dokhtar Magmatic Assemblage (UDAM, ∼52 km). This thickening is attributed to the underthrusting of the Arabian Plate beneath Central Iran and crustal shortening associated with the Zagros orogeny. Low shear-wave velocities (Vs < 4.1 km/s) observed in the uppermost mantle beneath Central and Eastern Iran indicate variations in lithospheric composition and thermal structure. Correlations between crustal thickness, topography, and free-air gravity anomalies demonstrate the role of isostatic support and lithospheric flexure in shaping regional surface features. Positive gravity anomalies in the southern Zagros are linked to crustal underthrusting, while high-density rocks in the SSZ and UDAM contribute to short-wavelength gravity highs. These findings enhance our understanding of the geodynamic evolution of the Zagros and Central Iranian tectonic domains, highlighting their distinct geological histories and ongoing tectonic interactions. Crustal Thickness receiver function Isostatic Support Zagros Central Iran Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Article Highlights Crustal Structure and Tectonic Variations: The study reveals significant variations in Moho depth, ranging from 40–45 km in Central Iran to 45–50 km beneath the Zagros region, highlighting the contrasting tectonic regimes and the role of lithospheric flexure in shaping topographic features. Geodynamic Insights into the Zagros Collision Zone: The research emphasizes the underthrusting of the Arabian Plate beneath Central Iran and associated crustal thickening along the Zagros suture zone, supported by low-velocity zones in the upper mantle and gravity anomaly patterns. Integration of Multi-Dataset Analysis: By combining crustal thickness data, topographic analysis, and gravity anomalies, the study provides a comprehensive framework for understanding the tectonic evolution and lithospheric dynamics of the Iranian plateau. 1 Introduction Iran is seismically active, with earthquakes concentrated in zones such as Zagros, Alborz-Binalud, Kopeh Dagh, Makran, and Central and Eastern Iran (Vernant et al. 2004 ). Tectonic deformation is primarily due to the northward subduction and closure of the Hercynian Ocean, as seen along the Sanandaj–Sirjan belt (Berberian and King 1981 ). The Central and Eastern Iran region is composed of different blocks that were once separated by an ocean, which was subducted and closed during the Cretaceous period (Berberian and King, 1981 ). The Zagros collision zone, extending from Eastern Turkey to the Oman Sea, consists of key tectonic elements: the Zagros fold and thrust belt (ZFTB), the Sanandaj–Sirjan Zone (SSZ), and the Urumieh–Dokhtar Magmatic Assemblage (UDMA) (Fig. 1 ). Crustal thickness in Iran varies significantly, with the Zagros fold and thrust belt (ZFTB) showing Moho depths of 42–46 km (Hatzfeld et al., 2003 ; Paul et al., 2006 ). This depth increases towards the Main Zagros Thrust (MZT), reaching 54–67 km beneath the Sanandaj–Sirjan Zone (SSZ) (Paul et al. 2006 ). Studies by Motaghi et al. ( 2015 ) and Tatar and Nasrabadi ( 2013 ) have reported Moho depths of 50–59 km beneath Zagros and the SSZ, indicating a significant increase in crustal thickness from west to east. Additionally, Moho depth estimates show a 30–35 km range in the western Zagros, gradually increasing to around 45 km in Central Zagros (Shiranzaei et al. 2021 ). In Central and Eastern Iran, Moho depths range from 42 km in the central regions to 50–58 km in the western parts of Central Iran (Tatar and Nasrabadi 2013 ; Motaghi et al. 2015 ). The observed variation along the Sanandaj-Sirjan Zone and the Urmia-Dokhtar Magmatic Assemblage, along with evidence of seismically active yet silent slabs at depth, raise questions regarding the ongoing processes such as slab steepening or break-off in the northwest Zagros or the underthrusting of the Arabian plate beneath Central Zagros (Mouthereau et al. 2012 ). Understanding the crustal velocity structure and Moho depth variation is crucial for unraveling the tectonic history of seismotectonic zones like Zagros, central and eastern Iran. By utilizing velocity models obtained from this research, we can enhance the precision of earthquake locations, reveal more linearity in epicenters, and better define active faults. In this study, we investigate crustal structure and Moho depth variations across Zagros, Central Iran, and Eastern Iran using joint inversion of P-receiver functions and Rayleigh wave phase velocity dispersion, utilizing data from 19 broadband seismic stations of the Iranian Seismological Center (ISC) and Iranian National Seismic Network (INSN) (Fig. 1 ). 2 Materials and Methods Receiver functions were computed using teleseismic waveform data spanning three years (2012–2014), including 375 seismic events with epicentral distances between 30° and 90° and magnitudes greater than 5.5 (Fig. 2 ). Instrumental corrections were applied to each event, and high-frequency noise above 0.5 Hz was filtered out using a Gaussian smoothing factor of 1. The P-wave direct arrival times were determined using the TauP package with the IASP91 velocity model (Kennett 1991 ). The accuracy of the P-phase arrival was visually verified and adjusted using SAC software (Seismic Analysis Code, http://ds.iris.edu/ds/nodes/dmc/forms/ sac) Receiver functions were calculated using the time-domain iterative deconvolution method developed by Ligorria and Ammon (1999), which is more stable with noisy data compared to frequency-domain methods (Julia et al. 2005 ). To enhance the signal-to-noise ratio, receiver functions were grouped by azimuth and distance (< 10°), and the receiver functions within each group were stacked. Phase velocity dispersion information was obtained from tomographic images of regional fundamental-mode Rayleigh waves propagating across Iran, based on data from Rahimi et al. ( 2014 ). Phase velocity estimates were derived for periods ranging from 10 to 100 seconds. The two-station method of Mitchell ( 1995 ) was used to determine phase velocities, and frequency-domain Wiener filtering (Hwang and Mitchell 1986 ) was applied to analyze the phase spectra of Green’s functions. Joint inversion of the receiver functions and phase velocity dispersion curves was performed using the JOINT96 code (Herrmann and Ammon 2003 ). The inversion utilized a damped least-squares method (Menke 1989 ) to derive the S-wave velocity model. The initial model was a homogeneous, isotropic, flat-layered structure, with fixed layer thicknesses and adjustable layer velocities within a specified damping limit. 3 Results We performed joint inversion for all back azimuths from the 19 selected stations, providing key insights into the crustal structure beneath the study area. The inversion showed excellent agreement between the observed and calculated receiver functions, particularly focusing on the Ps phase. Additionally, a high level of concurrence was observed between the predicted and observed surface wave velocity dispersion values, confirming the reliability of the inversion technique. Results for the TKDS station are presented in detail. The final crustal velocity model for the TKDS station, shown in Fig. 3 , reveals a complex, heterogeneous structure. We refined the model by selecting the simplest configuration that still captured the essential features of the observed data. Through forward modeling, we produced synthetic receiver functions and dispersion curves, which were then rigorously compared with the original data and joint inversion results. Figure 4 presents the outcomes of this validation process for the 11 receiver function stacks at the TKDS station. To evaluate the uncertainty and resolution of the final model, we conducted an error analysis by perturbing the Moho depth by ± 2, ±4, ± 5, and ± 10 km. Synthetic data generated from these perturbed models were compared with the observed data. Remarkably, even with a Moho depth offset of up to ± 2 km, the synthetic data remained consistent with the observed data, highlighting the robustness and reliability of our results. The simplified crustal model for the TKDS station reveals significant velocity discontinuities at depths of 3, 6, 10, and 42 km. Above the 32 km thick crystalline crust, with an average shear wave velocity of 3.8 km/s, velocity variations occur within the first few kilometers below the surface. At a depth of 42 km, a distinct velocity jump from 38 to 44 km/s marks the Moho discontinuity, representing the crust-mantle transition. The Moho depth estimate is in agreement with previous studies in the region. Nasrabadi et al. ( 2019 ) estimated a Moho depth of 36 km beneath TKDS, while Mottaghi et al. (2015) reported Moho depths of 35 km and 38 km for nearby TAR and CHA stations, respectively. These findings align with the 40 km estimate by Paul et al. ( 2006 ) for the same area. The joint inversion was successfully performed for the remaining 18 selected stations, and the results for all 19 stations are summarized in Table 1 . 4 Discussion Our study has provided insights into the crustal structure and Moho depth variations across different regions. The obtained results contribute to a better understanding of the tectonic processes and geological evolution of the study area, we discuss the implications of our findings below: 4.1 Crustal Thickness Variations and Tectonic Evolution Four profiles AB, CD, EF, and GH were used to investigate crustal thickness variations across the study area (Fig. 5 ). The 2-D absolute S-velocity structure derived from the AB profile reveals significant Moho depth variations. In eastern Iran, we observe an average Moho depth of 40 km, which gradually increases towards the central region, reaching 42 km beneath stations located in Central Iran. Notably, towards the Urumieh-Dokhtar Magmatic Assemblage (UDMA) and the Sanandaj-Sirjan Zone (SSZ) in the western margin of Central Iran, the Moho depth increases significantly, averaging 52 km beneath the UDMA, 58 km beneath the SSZ, and 44 km beneath the Zagros Fold-Thrust Belt (ZFTB). Figure 5 also highlights a notable low-velocity zone extending from the Main Recent Fault (MRF) in the Zagros suture to beneath the SSZ and UDMA. This low-velocity zone likely reflects crustal faulting along the MRF, indicating decoupling within the upper crust. These findings align with previous studies, particularly those by Motaghi et al. ( 2017 ), supporting the hypothesis of underthrusting of the Arabian crust beneath Central Iran. The observed structural configuration, with the deepening Moho from the MRF to the SSZ and UDMA, provides evidence of crustal doubling due to the underthrusting of the Arabian crust into Central Iran. Table 1 Locations of the broadband stations and resulting average values for Moho depth Region Station Lat N Long E Elevation (m) Average Moho depth (km) Eastern Iran NHDN 3139 6005 1307 40 SZD1 2448 6086 1364 40 Central Iran AFRZ 3343 5901 1497 40 TKDS 3363 5712 1206 42 TNSJ 3396 5660 1123 42 YZKH 3245 5467 1226 46 ANAR 3318 5372 1323 40 KRSH 3397 5213 1630 44 CHMN 2986 5754 2663 48 KHGB 3037 5648 2057 56 NGRK 2964 5676 3132 56 TVBK 2929 5676 2586 46 Sanandaj-Sirjan Zon SNGE 3509 4734 1940 58 BZA 3447 4786 2330 54 BRJ 3190 5126 2300 55 Zagros DOB 3378 4817 1948 46 DHR 3470 4638 1840 44 SHI 2963 5252 1600 50 AHWAZ 3133 4864 19 42 The observed variations in crustal thickness, along with the presence of distinct tectonic boundaries, highlight the complex geological history and ongoing tectonic activity in Iran. These findings have significant implications for regional geodynamics, the mechanics of the Zagros collision zone, and the interactions between the Arabian and Central Iranian plates. The relatively reduced crustal thickness observed at the eastern stations in Central Iran may be attributed to the absence of a major collision zone in Eastern Iran’s geological history. the predominance of strike-slip faulting and the minimal shortening rate reported by Vernant et al. ( 2004 ) suggest a lack of tectonic forces contributing to crustal thickening in this region. Conversely, stations located in the UDMA and SSZ (CHMN, KHGB, NGRK, and TVBK) in the western margin of Central Iran exhibit significantly higher crustal thickness (approximately 52 km) compared to those in the central and eastern parts of the study area. 4.2 Implications of Tectonic Processes and Upper Mantle Velocities The slow northward movement of the Arabian plate and the subduction of the Neotethys oceanic crust beneath the southern margin of Central Iran (Sanandaj-Sirjan Zone) have led to the closure of the Neotethys and the subsequent collision between the Arabian and Eurasian plates. This tectonic process gave rise to the Urumieh-Dokhtar Magmatic Assemblage (UDMA), an Andean-type magmatic arc. Based on regional tectonic studies and previous research (Motaghi et al. 2015 ; Tatar and Nasrabadi 2013 ; Paul et al. 2006 , 2010 ; Sepahvand et al. 2012 ), the Sanandaj-Sirjan Zone (SSZ) is characterized by significant crustal thickening, while the UDMA in Central Iran exhibits an average crustal thickness. Beneath most stations in Central Iran, shear wave velocities (Vs) in the uppermost mantle remain relatively low, with Vs values of less than 4.1–4.2 km/s. Velocity maps from Kaviani et al. ( 2020 ) confirm the presence of a low-velocity uppermost mantle (Vs ≤ 4.1 km/s) beneath the Lut block in eastern Iran, in line with the relatively thin crust (< 40 km) observed beneath this region. To provide a comprehensive and reliable model for the Iranian plateau, we integrated Moho depth estimates derived from this study with validated results from previous research. The compiled Moho depth model for the Iranian plateau is shown in Fig. 6 . This figure synthesizes findings from our study alongside key contributions from Shiranzaei et al. ( 2021 ), Motaghi et al. ( 2017 , 2015 , 2012 ), Tatar and Nasrabadi ( 2013 ), Paul et al. ( 2006 , 2010 ), and others (Radjaei et al. 2010; Raven 2004; Javan and Roberts 2003; Yamini-Fard et al. 2006 , 2007 ; Afsari et al. 2011 ; Taghizadeh-Farahmand et al. 2010; Mangino and Priestley 1998 ; Gok et al. 2008; Gritto et al. 2008 ; Mellors et al. 2008 ; Al-Damegh et al. 2005 ; Cakir and Erduran 2004 ). Additionally, Fig. 6 includes a long-term topographic map of Iran, created by applying a 100 km Gaussian filter to raw topographic data, as well as a short-term free air gravity anomaly map of the region. Together, these datasets provide a multi-faceted perspective on the Iranian plateau's crustal structure and tectonic framework. 4.3 Isostatic Support and Lithospheric Dynamics The relationship between crustal thickness, topography, and gravity provides critical insight into the mechanisms of isostatic support and lithospheric dynamics shaping the Iranian plateau. The observed correlation between crustal thickness and surface elevation suggests that isostatic compensation plays a fundamental role in supporting the topography of mountain ranges in the region. In Central Iran, the crustal thickness ranges from 40 to 45 km for elevations below 600–800 m and gradually increases to 45–50 km beneath the Zagros region, where elevations exceed 3000 m (Fig. 6 ). This correlation highlights the role of lithospheric flexure in accommodating shorter-wavelength topographic variations, while isostatic mechanisms primarily support longer-wavelength features. Elastic thickness (Te), a measure of lithospheric rigidity, further delineates the contrasting flexural behavior across the region. Maggi et al. ( 2000 a) reported a Te value of 8 km for Central Iran, reflecting a relatively weak lithosphere that is insufficient to sustain long-period topography through flexural rigidity alone. By contrast, the Arabian Shield, with a Te of 15 km, exhibits greater lithospheric strength, enabling partial flexural support of local mountain ranges. These variations underscore the heterogeneity in lithospheric properties between the collisional zones of the Zagros and the Central Iranian block. This lithospheric heterogeneity has profound geodynamic implications for the region. In the Zagros collision zone, the thicker and more rigid lithosphere reflects the intense tectonic forces associated with the convergence and underthrusting of the Arabian Plate beneath Central Iran. This results in significant crustal thickening and deep-rooted structures that support the elevated topography of the Zagros mountains. In contrast, the relatively weaker and thinner lithosphere of Central Iran suggests that this intraplate region primarily accommodates deformation through isostatic adjustment and distributed strain, rather than localized crustal thickening. The disparity in lithospheric strength and behavior highlights the role of tectonic setting in shaping the mechanical and thermal evolution of the lithosphere. Collisional zones, like the Zagros, are characterized by crustal shortening, faulting, and mountain-building processes, while intraplate regions, such as Central Iran, exhibit a more subdued response to tectonic forces. This dynamic interplay between collisional and intraplate processes contributes to the overall complexity of the Iranian plateau, with significant implications for seismic activity, mountain-building, and the long-term stability of the region. The Free-Air Gravity map of Iran (Fig. 6 , bottom) reveals significant positive anomalies, even in regions where isostatic support dominates the topography. In the southern Zagros region, narrow (< 100 km) gravity anomalies are closely associated with folding at the deformation front. These anomalies are likely a result of the underthrusting of the Persian Gulf beneath the Zagros, contributing to the region's active deformation and elevated topography. In contrast, the northern Zagros region exhibits short-wavelength gravity highs corresponding to the Sanandaj-Sirjan Zone (SSZ) and the Urumieh-Dokhtar Magmatic Assemblage (UDMA). These areas are characterized by crustal rocks with higher-than-average densities (Ghasemi and Talbot, 2006 ). Such density variations, coupled with the presence of deep crustal roots, suggest that the crustal architecture in these zones is partially supported by the underthrusting Arabian Plate. This structural support further amplifies the topographic highs observed in the region. Overall, the integration of crustal thickness data, topographic analysis, and gravity anomalies enhances our understanding of the geodynamic evolution of the Iranian plateau. It also provides a framework for assessing the interplay between tectonic processes and lithospheric properties. The distinct signatures of Moho depth and crustal density variation emphasize the importance of combining multiple geophysical datasets to unravel the complexities of regional tectonics. 5 Conclusions This study provides a detailed investigation into the crustal structure, tectonic processes, and geodynamic evolution of the Zagros and Central Iran regions through the integration of crustal thickness data, topographic analysis, and gravity anomalies. The findings reveal significant variations in Moho depth, reflecting the contrasting tectonic regimes of these regions. In Central Iran, the crustal thickness ranges from 40 to 45 km, with relatively low elevations (< 600–800 m), whereas in the Zagros region, it increases to 45–50 km beneath elevations exceeding 3000 m. These patterns highlight the interplay between lithospheric flexure, crustal density variations, and isostatic mechanisms in shaping the region's topography. The results emphasize the role of tectonic processes such as the underthrusting of the Arabian Plate beneath Central Iran and the associated crustal thickening along the Zagros suture zone. The presence of low-velocity zones in the upper mantle beneath the Sanandaj-Sirjan Zone and Urumieh-Dokhtar Magmatic Assemblage aligns with regional collision dynamics and magmatic activity. Gravity anomalies further corroborate these findings, with narrow positive anomalies in the southern Zagros linked to folding and underthrusting, and short-wavelength highs in the northern Zagros reflecting denser crustal materials and deep roots. Overall, this study underscores the importance of integrating multiple geophysical datasets to unravel the complexities of regional tectonics. The observed lithospheric heterogeneity across collisional and intraplate regions provides insights into the geodynamic evolution of the Iranian plateau and enhances our understanding of the mechanical behavior of the lithosphere. These findings also have broader implications for natural hazard assessment, resource exploration, and the study of other tectonically active regions globally. Declarations The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Author Contribution The first and third authors led the research, developed the methodology, and conducted the seismic and gravity data analysis. They also assisted in interpreting the results, preparing figures, and drafting specific sections of the manuscript, as well as contributing to its review and refinement. The second author was involved in data acquisition. All authors read, reviewed, and approved the final manuscript. Acknowledgement We thank Associate Professor Habib Rahimi (University of Tehran) for supplying the dispersion curves. We thank the editor and anonymous reviewers for their constructive comments and suggestions. This work was supported by Iran National Science Foundation (INSF) under research project 96009525. References Afsari N, Sodoudi F, Taghizadeh-Farahmand F, Ghassemi M R (2011) Crustal structure of Northwest Zagros (Kermanshah) and Central Iran (Yazd and Isfahan) using teleseismic Ps converted phases. Journal of Seismology: 15, 341-353. https://doi.org/10.1007/s10950-010-9236-y Al-Damegh K, Sandvol E, Barazangi, M (2005) Crustal structure of the Arabian plate: new constraints from the analysis of teleseismic receiver functions. Earth and Planetary Science Letters: 231, 177-196. https://doi.org/10.1016/j.epsl.2004.12.023 Berberian, M, King, G C P (1981) Towards a paleogeography and tectonic evolution of Iran. 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Journal of Seismology: 17, 1321-1337. https://doi.org/10.1007/s10950-013-9383-0 Vernant, P, Nilforoushan, F, Hatzfeld, D, Abbassi, M, Vigny, C, Masson, F, Nankali, H, Martinod, J, Ashtiani, A, Bayer, R, Tavakoli, F, Chéry, J (2004) Present-day crustal deformation and plate kinematics in the Middle East constrained by GPS measurements in Iran and northern Oman. Geophysical Journal International: 157, 381-398. https://doi.org/10.1111/j.1365-246X.2004.02222.x Yamini-Fard, F, Hatzfeld, D, Farahbod, A M, Paul, A, Mokhtari, M (2007) The diffuse transition between the Zagros continental collision and the Makran oceanic subduction (Iran): microearthquake seismicity and crustal structure. Geophysical Journal International: 170, 182-194. https://doi.org/10.1111/j.1365-246X.2007.03478.x Yamini-Fard, F, Hatzfeld, D, Tatar, M, Mokhtari, M (2006) Microearthquake seismicity at the intersection between the Kazerun fault and the Main Recent Fault (Zagros, Iran). Geophysical Journal International: 166, 186-196. https://doi.org/10.1111/j.1365-246X.2006.03079.x Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-5912251","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":408199705,"identity":"0f8fa40f-41bc-43db-8e84-249e6499f2dd","order_by":0,"name":"MohammadReza Sepahvand","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA70lEQVRIiWNgGAWjYPCCAyDC8GEDjJ9ApBZjQ6AWCZK0mEnCteADug3sDx8X1NxJ7J/dvK1yxq/DdQzshx8wPNyDW4vZAR5j4xnHniXOuHOs7ObGvsMSDDxpBgwJz/BqYZPmYTtszHAjx+zmwx6gFoYcoF8O4NPC/vw3z7/DxvJALYVgLfxvCGlhMGPmbTssZwDUwrjhB1CLBCFbDvMYS8/sOyxneCOtWHJmQ7pkm8QzgwN4tRxvf/i54NthHrkbyRs/9vyx5ufnT3748AceLQzMYAQFjG0MDGwM0GjCBxBaGP4QUjsKRsEoGAUjEQAAci5W4nom6HMAAAAASUVORK5CYII=","orcid":"","institution":"Graduate University of Advanced Technology","correspondingAuthor":true,"prefix":"","firstName":"MohammadReza","middleName":"","lastName":"Sepahvand","suffix":""},{"id":408199706,"identity":"ca942497-c3d7-4111-a11a-fbe0c974b0dd","order_by":1,"name":"Mohammad Shishebori","email":"","orcid":"","institution":"Islamic Azad University","correspondingAuthor":false,"prefix":"","firstName":"Mohammad","middleName":"","lastName":"Shishebori","suffix":""},{"id":408199707,"identity":"7fbb9204-3ea1-414c-9b85-e5f5a8e9e230","order_by":2,"name":"Afsaneh Nasrabadi","email":"","orcid":"","institution":"Graduate University of Advanced Technology","correspondingAuthor":false,"prefix":"","firstName":"Afsaneh","middleName":"","lastName":"Nasrabadi","suffix":""}],"badges":[],"createdAt":"2025-01-27 12:38:09","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5912251/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5912251/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":75107139,"identity":"0c8eb3c5-7d86-447d-878e-7bda7a9430f9","added_by":"auto","created_at":"2025-01-30 14:41:44","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":625486,"visible":true,"origin":"","legend":"\u003cp\u003eLocation map of seismic stations used in this study (see Data and Resources) which are plotted as green triangles Solid lines represent the active faults (Hessami et al 2003). MZT: main Zagros thrust fault, Geological map modified from NGDIR (National Geoscience Database of Iran, http://wwwngdirir)\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-5912251/v1/ed736d12bfe109702d38229b.png"},{"id":75107448,"identity":"7e9aac9e-39e8-42ee-9c75-cf1b9d338bd7","added_by":"auto","created_at":"2025-01-30 14:49:44","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":244150,"visible":true,"origin":"","legend":"\u003cp\u003eLocation of teleseismic events that have been used for the receiver functions.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-5912251/v1/c615cadc860537463304d612.png"},{"id":75107141,"identity":"1724fd41-a9bd-445a-9d96-d1879548760a","added_by":"auto","created_at":"2025-01-30 14:41:44","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":146772,"visible":true,"origin":"","legend":"\u003cp\u003eJoint inversion results for station TKDS for 104˚ -108˚ back azimuth bin receiver function stack. The top right includes the real receiver function (blue) and the receiver function calculated by the program (red). The numbers on the left indicate the Gaussian filter parameter, the receiver function compliance rate, and the ray parameter. The lower right reveals the observed Rayleigh wave group velocity dispersion (points), with their error, and the calculated dispersion curve (red) are shown. The left part indicates the sub-receiver structure velocity model at the back-azimuth. The blue dashed lines reveal the initial velocity model, the red solid line, denotes the predicted model, and the solid green line, is the simplest model. The Moho boundary is shown by the arrow\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-5912251/v1/e92eeae812b2bb08aa594ac6.png"},{"id":75107449,"identity":"ebf6652e-cf94-46f0-a380-e6140362058f","added_by":"auto","created_at":"2025-01-30 14:49:45","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":322641,"visible":true,"origin":"","legend":"\u003cp\u003eLeft: Forward modeling results for the eleven receiver function stacks of station TKDS. Right: Forward modeling results for station TKDS for 104˚-108˚ back azimuth bin receiver function stack to find the level of complexity needed in a model of the Vs structure beneath the station\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-5912251/v1/bf62ea6c90eaa025106cf8de.png"},{"id":75107150,"identity":"ae9d99e0-151d-49d7-a8a3-064ee3e40c99","added_by":"auto","created_at":"2025-01-30 14:41:45","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":864427,"visible":true,"origin":"","legend":"\u003cp\u003eAB, CD, EF, and GH profiles were considered for investigation of crustal thickness variations, two-dimensional display of Moho depth, and elevation of stations for the profiles in the area of study. 2-D absolute S-velocity structure obtained for the crust beneath AB profile. The velocity distribution is made by combining the 1-D models up to the depth of 60 km positive signs show Moho depth beneath stations. Triangles show the stations onto lines Elevation variations along the profiles are also shown on the top of the panels\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-5912251/v1/fa11c7d03aa14dee2dacdab5.png"},{"id":75107144,"identity":"ecd91da8-16b7-4c8d-a5c6-b5e434c01258","added_by":"auto","created_at":"2025-01-30 14:41:44","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":1510503,"visible":true,"origin":"","legend":"\u003cp\u003eUpper long period topography (left) and Moho depth (right), Bottom: Map of the short period Free Air Gravity Anomalies for Iran region (from Bureau Gravimétrique International, BGI)\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-5912251/v1/8e8d66204c707600f42c6c90.png"},{"id":78757784,"identity":"4a20940f-be58-4821-8259-54a4bf616816","added_by":"auto","created_at":"2025-03-18 13:17:08","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4370632,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5912251/v1/e561fa01-3a55-4252-a902-5d54ca67efc3.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Crustal Architecture and Isostatic Support in Zagros and Central Iran: Evidence from Seismic and Gravity Analysis","fulltext":[{"header":"Article Highlights","content":"\u003col\u003e\n \u003cli\u003e\u003cstrong\u003eCrustal Structure and Tectonic Variations:\u003c/strong\u003e The study reveals significant variations in Moho depth, ranging from 40\u0026ndash;45 km in Central Iran to 45\u0026ndash;50 km beneath the Zagros region, highlighting the contrasting tectonic regimes and the role of lithospheric flexure in shaping topographic features.\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eGeodynamic Insights into the Zagros Collision Zone:\u003c/strong\u003e The research emphasizes the underthrusting of the Arabian Plate beneath Central Iran and associated crustal thickening along the Zagros suture zone, supported by low-velocity zones in the upper mantle and gravity anomaly patterns.\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eIntegration of Multi-Dataset Analysis:\u003c/strong\u003e By combining crustal thickness data, topographic analysis, and gravity anomalies, the study provides a comprehensive framework for understanding the tectonic evolution and lithospheric dynamics of the Iranian plateau.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"1 Introduction","content":"\u003cp\u003eIran is seismically active, with earthquakes concentrated in zones such as Zagros, Alborz-Binalud, Kopeh Dagh, Makran, and Central and Eastern Iran (Vernant et al. \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2004\u003c/span\u003e). Tectonic deformation is primarily due to the northward subduction and closure of the Hercynian Ocean, as seen along the Sanandaj\u0026ndash;Sirjan belt (Berberian and King \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e1981\u003c/span\u003e). The Central and Eastern Iran region is composed of different blocks that were once separated by an ocean, which was subducted and closed during the Cretaceous period (Berberian and King, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e1981\u003c/span\u003e). The Zagros collision zone, extending from Eastern Turkey to the Oman Sea, consists of key tectonic elements: the Zagros fold and thrust belt (ZFTB), the Sanandaj\u0026ndash;Sirjan Zone (SSZ), and the Urumieh\u0026ndash;Dokhtar Magmatic Assemblage (UDMA) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eCrustal thickness in Iran varies significantly, with the Zagros fold and thrust belt (ZFTB) showing Moho depths of 42\u0026ndash;46 km (Hatzfeld et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2003\u003c/span\u003e; Paul et al., \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2006\u003c/span\u003e). This depth increases towards the Main Zagros Thrust (MZT), reaching 54\u0026ndash;67 km beneath the Sanandaj\u0026ndash;Sirjan Zone (SSZ) (Paul et al. \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2006\u003c/span\u003e). Studies by Motaghi et al. (\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2015\u003c/span\u003e) and Tatar and Nasrabadi (\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2013\u003c/span\u003e) have reported Moho depths of 50\u0026ndash;59 km beneath Zagros and the SSZ, indicating a significant increase in crustal thickness from west to east. Additionally, Moho depth estimates show a 30\u0026ndash;35 km range in the western Zagros, gradually increasing to around 45 km in Central Zagros (Shiranzaei et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). In Central and Eastern Iran, Moho depths range from 42 km in the central regions to 50\u0026ndash;58 km in the western parts of Central Iran (Tatar and Nasrabadi \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Motaghi et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2015\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe observed variation along the Sanandaj-Sirjan Zone and the Urmia-Dokhtar Magmatic Assemblage, along with evidence of seismically active yet silent slabs at depth, raise questions regarding the ongoing processes such as slab steepening or break-off in the northwest Zagros or the underthrusting of the Arabian plate beneath Central Zagros (Mouthereau et al. \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). Understanding the crustal velocity structure and Moho depth variation is crucial for unraveling the tectonic history of seismotectonic zones like Zagros, central and eastern Iran. By utilizing velocity models obtained from this research, we can enhance the precision of earthquake locations, reveal more linearity in epicenters, and better define active faults.\u003c/p\u003e \u003cp\u003eIn this study, we investigate crustal structure and Moho depth variations across Zagros, Central Iran, and Eastern Iran using joint inversion of P-receiver functions and Rayleigh wave phase velocity dispersion, utilizing data from 19 broadband seismic stations of the Iranian Seismological Center (ISC) and Iranian National Seismic Network (INSN) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e"},{"header":"2 Materials and Methods","content":"\u003cp\u003eReceiver functions were computed using teleseismic waveform data spanning three years (2012\u0026ndash;2014), including 375 seismic events with epicentral distances between 30\u0026deg; and 90\u0026deg; and magnitudes greater than 5.5 (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Instrumental corrections were applied to each event, and high-frequency noise above 0.5 Hz was filtered out using a Gaussian smoothing factor of 1. The P-wave direct arrival times were determined using the TauP package with the IASP91 velocity model (Kennett \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e1991\u003c/span\u003e). The accuracy of the P-phase arrival was visually verified and adjusted using SAC software (Seismic Analysis Code, \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://ds.iris.edu/ds/nodes/dmc/forms/\u003c/span\u003e\u003cspan address=\"http://ds.iris.edu/ds/nodes/dmc/forms/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e sac)\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eReceiver functions were calculated using the time-domain iterative deconvolution method developed by Ligorria and Ammon (1999), which is more stable with noisy data compared to frequency-domain methods (Julia et al. \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2005\u003c/span\u003e). To enhance the signal-to-noise ratio, receiver functions were grouped by azimuth and distance (\u0026lt;\u0026thinsp;10\u0026deg;), and the receiver functions within each group were stacked.\u003c/p\u003e \u003cp\u003ePhase velocity dispersion information was obtained from tomographic images of regional fundamental-mode Rayleigh waves propagating across Iran, based on data from Rahimi et al. (\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). Phase velocity estimates were derived for periods ranging from 10 to 100 seconds. The two-station method of Mitchell (\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e1995\u003c/span\u003e) was used to determine phase velocities, and frequency-domain Wiener filtering (Hwang and Mitchell \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e1986\u003c/span\u003e) was applied to analyze the phase spectra of Green\u0026rsquo;s functions.\u003c/p\u003e \u003cp\u003eJoint inversion of the receiver functions and phase velocity dispersion curves was performed using the JOINT96 code (Herrmann and Ammon \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2003\u003c/span\u003e). The inversion utilized a damped least-squares method (Menke \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e1989\u003c/span\u003e) to derive the S-wave velocity model. The initial model was a homogeneous, isotropic, flat-layered structure, with fixed layer thicknesses and adjustable layer velocities within a specified damping limit.\u003c/p\u003e"},{"header":"3 Results","content":"\u003cp\u003eWe performed joint inversion for all back azimuths from the 19 selected stations, providing key insights into the crustal structure beneath the study area. The inversion showed excellent agreement between the observed and calculated receiver functions, particularly focusing on the Ps phase. Additionally, a high level of concurrence was observed between the predicted and observed surface wave velocity dispersion values, confirming the reliability of the inversion technique. Results for the TKDS station are presented in detail. The final crustal velocity model for the TKDS station, shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, reveals a complex, heterogeneous structure. We refined the model by selecting the simplest configuration that still captured the essential features of the observed data.\u003c/p\u003e \u003cp\u003eThrough forward modeling, we produced synthetic receiver functions and dispersion curves, which were then rigorously compared with the original data and joint inversion results. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e presents the outcomes of this validation process for the 11 receiver function stacks at the TKDS station.\u003c/p\u003e \u003cp\u003eTo evaluate the uncertainty and resolution of the final model, we conducted an error analysis by perturbing the Moho depth by \u0026plusmn;\u0026thinsp;2, \u0026plusmn;4, \u0026plusmn;\u0026thinsp;5, and \u0026plusmn;\u0026thinsp;10 km. Synthetic data generated from these perturbed models were compared with the observed data. Remarkably, even with a Moho depth offset of up to \u0026plusmn;\u0026thinsp;2 km, the synthetic data remained consistent with the observed data, highlighting the robustness and reliability of our results.\u003c/p\u003e \u003cp\u003eThe simplified crustal model for the TKDS station reveals significant velocity discontinuities at depths of 3, 6, 10, and 42 km. Above the 32 km thick crystalline crust, with an average shear wave velocity of 3.8 km/s, velocity variations occur within the first few kilometers below the surface. At a depth of 42 km, a distinct velocity jump from 38 to 44 km/s marks the Moho discontinuity, representing the crust-mantle transition. The Moho depth estimate is in agreement with previous studies in the region. Nasrabadi et al. (\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) estimated a Moho depth of 36 km beneath TKDS, while Mottaghi et al. (2015) reported Moho depths of 35 km and 38 km for nearby TAR and CHA stations, respectively. These findings align with the 40 km estimate by Paul et al. (\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2006\u003c/span\u003e) for the same area.\u003c/p\u003e \u003cp\u003eThe joint inversion was successfully performed for the remaining 18 selected stations, and the results for all 19 stations are summarized in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"4 Discussion","content":"\u003cp\u003eOur study has provided insights into the crustal structure and Moho depth variations across different regions. The obtained results contribute to a better understanding of the tectonic processes and geological evolution of the study area, we discuss the implications of our findings below:\u003c/p\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e4.1 Crustal Thickness Variations and Tectonic Evolution\u003c/h2\u003e \u003cp\u003eFour profiles AB, CD, EF, and GH were used to investigate crustal thickness variations across the study area (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). The 2-D absolute S-velocity structure derived from the AB profile reveals significant Moho depth variations. In eastern Iran, we observe an average Moho depth of 40 km, which gradually increases towards the central region, reaching 42 km beneath stations located in Central Iran. Notably, towards the Urumieh-Dokhtar Magmatic Assemblage (UDMA) and the Sanandaj-Sirjan Zone (SSZ) in the western margin of Central Iran, the Moho depth increases significantly, averaging 52 km beneath the UDMA, 58 km beneath the SSZ, and 44 km beneath the Zagros Fold-Thrust Belt (ZFTB).\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e also highlights a notable low-velocity zone extending from the Main Recent Fault (MRF) in the Zagros suture to beneath the SSZ and UDMA. This low-velocity zone likely reflects crustal faulting along the MRF, indicating decoupling within the upper crust. These findings align with previous studies, particularly those by Motaghi et al. (\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2017\u003c/span\u003e), supporting the hypothesis of underthrusting of the Arabian crust beneath Central Iran. The observed structural configuration, with the deepening Moho from the MRF to the SSZ and UDMA, provides evidence of crustal doubling due to the underthrusting of the Arabian crust into Central Iran.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eLocations of the broadband stations and resulting average values for Moho depth\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRegion\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eStation\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLat N\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eLong E\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eElevation (m)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eAverage Moho depth (km)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eEastern Iran\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNHDN\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3139\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e6005\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1307\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSZD1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2448\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e6086\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1364\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"9\" rowspan=\"10\"\u003e \u003cp\u003eCentral Iran\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAFRZ\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3343\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e5901\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1497\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTKDS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3363\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e5712\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1206\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e42\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTNSJ\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3396\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e5660\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1123\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e42\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eYZKH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3245\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e5467\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1226\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e46\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eANAR\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3318\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e5372\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1323\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eKRSH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3397\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e5213\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1630\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e44\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCHMN\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2986\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e5754\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2663\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e48\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eKHGB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3037\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e5648\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2057\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e56\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNGRK\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2964\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e5676\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e3132\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e56\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTVBK\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2929\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e5676\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2586\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e46\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eSanandaj-Sirjan Zon\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSNGE\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3509\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4734\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1940\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e58\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBZA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3447\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4786\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2330\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e54\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBRJ\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3190\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e5126\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2300\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e55\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003eZagros\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDOB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3378\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4817\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1948\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e46\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDHR\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3470\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4638\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1840\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e44\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSHI\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2963\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e5252\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1600\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAHWAZ\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3133\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4864\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e42\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe observed variations in crustal thickness, along with the presence of distinct tectonic boundaries, highlight the complex geological history and ongoing tectonic activity in Iran. These findings have significant implications for regional geodynamics, the mechanics of the Zagros collision zone, and the interactions between the Arabian and Central Iranian plates.\u003c/p\u003e \u003cp\u003eThe relatively reduced crustal thickness observed at the eastern stations in Central Iran may be attributed to the absence of a major collision zone in Eastern Iran\u0026rsquo;s geological history. the predominance of strike-slip faulting and the minimal shortening rate reported by Vernant et al. (\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2004\u003c/span\u003e) suggest a lack of tectonic forces contributing to crustal thickening in this region. Conversely, stations located in the UDMA and SSZ (CHMN, KHGB, NGRK, and TVBK) in the western margin of Central Iran exhibit significantly higher crustal thickness (approximately 52 km) compared to those in the central and eastern parts of the study area.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e4.2 Implications of Tectonic Processes and Upper Mantle Velocities\u003c/h2\u003e \u003cp\u003eThe slow northward movement of the Arabian plate and the subduction of the Neotethys oceanic crust beneath the southern margin of Central Iran (Sanandaj-Sirjan Zone) have led to the closure of the Neotethys and the subsequent collision between the Arabian and Eurasian plates. This tectonic process gave rise to the Urumieh-Dokhtar Magmatic Assemblage (UDMA), an Andean-type magmatic arc. Based on regional tectonic studies and previous research (Motaghi et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Tatar and Nasrabadi \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Paul et al. \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2006\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Sepahvand et al. \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2012\u003c/span\u003e), the Sanandaj-Sirjan Zone (SSZ) is characterized by significant crustal thickening, while the UDMA in Central Iran exhibits an average crustal thickness.\u003c/p\u003e \u003cp\u003eBeneath most stations in Central Iran, shear wave velocities (Vs) in the uppermost mantle remain relatively low, with Vs values of less than 4.1\u0026ndash;4.2 km/s. Velocity maps from Kaviani et al. (\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2020\u003c/span\u003e) confirm the presence of a low-velocity uppermost mantle (Vs\u0026thinsp;\u0026le;\u0026thinsp;4.1 km/s) beneath the Lut block in eastern Iran, in line with the relatively thin crust (\u0026lt;\u0026thinsp;40 km) observed beneath this region.\u003c/p\u003e \u003cp\u003eTo provide a comprehensive and reliable model for the Iranian plateau, we integrated Moho depth estimates derived from this study with validated results from previous research. The compiled Moho depth model for the Iranian plateau is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e. This figure synthesizes findings from our study alongside key contributions from Shiranzaei et al. (\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), Motaghi et al. (\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2017\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2015\u003c/span\u003e, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2012\u003c/span\u003e), Tatar and Nasrabadi (\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2013\u003c/span\u003e), Paul et al. (\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2006\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2010\u003c/span\u003e), and others (Radjaei et al. 2010; Raven 2004; Javan and Roberts 2003; Yamini-Fard et al. \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2006\u003c/span\u003e, \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Afsari et al. \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Taghizadeh-Farahmand et al. 2010; Mangino and Priestley \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e1998\u003c/span\u003e; Gok et al. 2008; Gritto et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2008\u003c/span\u003e; Mellors et al. \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2008\u003c/span\u003e; Al-Damegh et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2005\u003c/span\u003e; Cakir and Erduran \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2004\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eAdditionally, Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e includes a long-term topographic map of Iran, created by applying a 100 km Gaussian filter to raw topographic data, as well as a short-term free air gravity anomaly map of the region. Together, these datasets provide a multi-faceted perspective on the Iranian plateau's crustal structure and tectonic framework.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e4.3 Isostatic Support and Lithospheric Dynamics\u003c/h2\u003e \u003cp\u003eThe relationship between crustal thickness, topography, and gravity provides critical insight into the mechanisms of isostatic support and lithospheric dynamics shaping the Iranian plateau. The observed correlation between crustal thickness and surface elevation suggests that isostatic compensation plays a fundamental role in supporting the topography of mountain ranges in the region. In Central Iran, the crustal thickness ranges from 40 to 45 km for elevations below 600\u0026ndash;800 m and gradually increases to 45\u0026ndash;50 km beneath the Zagros region, where elevations exceed 3000 m (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). This correlation highlights the role of lithospheric flexure in accommodating shorter-wavelength topographic variations, while isostatic mechanisms primarily support longer-wavelength features.\u003c/p\u003e \u003cp\u003eElastic thickness (Te), a measure of lithospheric rigidity, further delineates the contrasting flexural behavior across the region. Maggi et al. (\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2000\u003c/span\u003ea) reported a Te value of 8 km for Central Iran, reflecting a relatively weak lithosphere that is insufficient to sustain long-period topography through flexural rigidity alone. By contrast, the Arabian Shield, with a Te of 15 km, exhibits greater lithospheric strength, enabling partial flexural support of local mountain ranges. These variations underscore the heterogeneity in lithospheric properties between the collisional zones of the Zagros and the Central Iranian block.\u003c/p\u003e \u003cp\u003eThis lithospheric heterogeneity has profound geodynamic implications for the region. In the Zagros collision zone, the thicker and more rigid lithosphere reflects the intense tectonic forces associated with the convergence and underthrusting of the Arabian Plate beneath Central Iran. This results in significant crustal thickening and deep-rooted structures that support the elevated topography of the Zagros mountains. In contrast, the relatively weaker and thinner lithosphere of Central Iran suggests that this intraplate region primarily accommodates deformation through isostatic adjustment and distributed strain, rather than localized crustal thickening.\u003c/p\u003e \u003cp\u003eThe disparity in lithospheric strength and behavior highlights the role of tectonic setting in shaping the mechanical and thermal evolution of the lithosphere. Collisional zones, like the Zagros, are characterized by crustal shortening, faulting, and mountain-building processes, while intraplate regions, such as Central Iran, exhibit a more subdued response to tectonic forces. This dynamic interplay between collisional and intraplate processes contributes to the overall complexity of the Iranian plateau, with significant implications for seismic activity, mountain-building, and the long-term stability of the region.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe Free-Air Gravity map of Iran (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e, bottom) reveals significant positive anomalies, even in regions where isostatic support dominates the topography. In the southern Zagros region, narrow (\u0026lt;\u0026thinsp;100 km) gravity anomalies are closely associated with folding at the deformation front. These anomalies are likely a result of the underthrusting of the Persian Gulf beneath the Zagros, contributing to the region's active deformation and elevated topography. In contrast, the northern Zagros region exhibits short-wavelength gravity highs corresponding to the Sanandaj-Sirjan Zone (SSZ) and the Urumieh-Dokhtar Magmatic Assemblage (UDMA). These areas are characterized by crustal rocks with higher-than-average densities (Ghasemi and Talbot, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2006\u003c/span\u003e). Such density variations, coupled with the presence of deep crustal roots, suggest that the crustal architecture in these zones is partially supported by the underthrusting Arabian Plate. This structural support further amplifies the topographic highs observed in the region.\u003c/p\u003e \u003cp\u003eOverall, the integration of crustal thickness data, topographic analysis, and gravity anomalies enhances our understanding of the geodynamic evolution of the Iranian plateau. It also provides a framework for assessing the interplay between tectonic processes and lithospheric properties. The distinct signatures of Moho depth and crustal density variation emphasize the importance of combining multiple geophysical datasets to unravel the complexities of regional tectonics.\u003c/p\u003e \u003c/div\u003e"},{"header":"5 Conclusions","content":"\u003cp\u003eThis study provides a detailed investigation into the crustal structure, tectonic processes, and geodynamic evolution of the Zagros and Central Iran regions through the integration of crustal thickness data, topographic analysis, and gravity anomalies. The findings reveal significant variations in Moho depth, reflecting the contrasting tectonic regimes of these regions. In Central Iran, the crustal thickness ranges from 40 to 45 km, with relatively low elevations (\u0026lt;\u0026thinsp;600\u0026ndash;800 m), whereas in the Zagros region, it increases to 45\u0026ndash;50 km beneath elevations exceeding 3000 m. These patterns highlight the interplay between lithospheric flexure, crustal density variations, and isostatic mechanisms in shaping the region's topography.\u003c/p\u003e \u003cp\u003eThe results emphasize the role of tectonic processes such as the underthrusting of the Arabian Plate beneath Central Iran and the associated crustal thickening along the Zagros suture zone. The presence of low-velocity zones in the upper mantle beneath the Sanandaj-Sirjan Zone and Urumieh-Dokhtar Magmatic Assemblage aligns with regional collision dynamics and magmatic activity. Gravity anomalies further corroborate these findings, with narrow positive anomalies in the southern Zagros linked to folding and underthrusting, and short-wavelength highs in the northern Zagros reflecting denser crustal materials and deep roots.\u003c/p\u003e \u003cp\u003eOverall, this study underscores the importance of integrating multiple geophysical datasets to unravel the complexities of regional tectonics. The observed lithospheric heterogeneity across collisional and intraplate regions provides insights into the geodynamic evolution of the Iranian plateau and enhances our understanding of the mechanical behavior of the lithosphere. These findings also have broader implications for natural hazard assessment, resource exploration, and the study of other tectonically active regions globally.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eThe first and third authors led the research, developed the methodology, and conducted the seismic and gravity data analysis. They also assisted in interpreting the results, preparing figures, and drafting specific sections of the manuscript, as well as contributing to its review and refinement. The second author was involved in data acquisition. All authors read, reviewed, and approved the final manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eWe thank Associate Professor Habib Rahimi (University of Tehran) for supplying the dispersion curves. We thank the editor and anonymous reviewers for their constructive comments and suggestions. This work was supported by Iran National Science Foundation (INSF) under research project 96009525.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAfsari N, Sodoudi F, Taghizadeh-Farahmand F, Ghassemi M R (2011) Crustal structure of Northwest Zagros (Kermanshah) and Central Iran (Yazd and Isfahan) using teleseismic Ps converted phases. 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Geophysical Journal International: 166, 186-196. https://doi.org/10.1111/j.1365-246X.2006.03079.x\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Crustal Thickness, receiver function, Isostatic Support, Zagros, Central Iran","lastPublishedDoi":"10.21203/rs.3.rs-5912251/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5912251/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis study investigates the crustal structure and lithospheric dynamics of the Zagros Mountains and Central Iran using a joint inversion of receiver functions and Rayleigh wave phase velocity dispersion for 19 seismic stations. The results reveal significant spatial variations in Moho depth and crustal thickness, reflecting the tectonic complexity of the region. Crustal thickness gradually increases from eastern Iran (\u0026sim;40 km) to Central Iran (\u0026sim;42 km) and reaches its maximum beneath the Sanandaj-Sirjan Zone (SSZ, \u0026sim;58 km) and the Urumieh-Dokhtar Magmatic Assemblage (UDAM, \u0026sim;52 km). This thickening is attributed to the underthrusting of the Arabian Plate beneath Central Iran and crustal shortening associated with the Zagros orogeny.\u003c/p\u003e \u003cp\u003eLow shear-wave velocities (Vs\u0026thinsp;\u0026lt;\u0026thinsp;4.1 km/s) observed in the uppermost mantle beneath Central and Eastern Iran indicate variations in lithospheric composition and thermal structure. Correlations between crustal thickness, topography, and free-air gravity anomalies demonstrate the role of isostatic support and lithospheric flexure in shaping regional surface features. Positive gravity anomalies in the southern Zagros are linked to crustal underthrusting, while high-density rocks in the SSZ and UDAM contribute to short-wavelength gravity highs.\u003c/p\u003e \u003cp\u003eThese findings enhance our understanding of the geodynamic evolution of the Zagros and Central Iranian tectonic domains, highlighting their distinct geological histories and ongoing tectonic interactions.\u003c/p\u003e","manuscriptTitle":"Crustal Architecture and Isostatic Support in Zagros and Central Iran: Evidence from Seismic and Gravity Analysis","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-01-30 14:41:40","doi":"10.21203/rs.3.rs-5912251/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"f37e7df2-dcec-48ec-a26a-cac977a0eac8","owner":[],"postedDate":"January 30th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-03-18T13:08:59+00:00","versionOfRecord":[],"versionCreatedAt":"2025-01-30 14:41:40","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5912251","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5912251","identity":"rs-5912251","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}