Accurate prediction of the 2022 MS 6.9 Menyuan and MS 6.8 Luding earthquake epicentres

Accurate prediction of the 2022 MS 6.9 Menyuan and MS 6.8 Luding earthquake epicentres | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Accurate prediction of the 2022 M S 6.9 Menyuan and M S 6.8 Luding earthquake epicentres Yiqing Zhu, Xiong Yang, Yunfeng Zhao, ShouChun Wei, Guoqing Zhang, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4530628/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 25 Nov, 2024 Read the published version in Scientific Reports → Version 1 posted 10 You are reading this latest preprint version Abstract In 2022, the M S 6.9 Menyuan (Qinghai Province) and M S 6.8 Luding (Sichuan Province) earthquakes occurred successively on China's North–South seismic belt. Both earthquakes caused serious property losses, and the Luding earthquake caused 100 + casualties. Gravity observations performed in the North–South Seismic Belt before the two earthquakes indicate that gravity changes occurred near the epicentres and exhibited four-quadrant distributions. In this study, We reviewed the successful prediction of these two earthquakes by using gravity data. The distances between the actual and predicted epicenters of the two earthquakes were < 56km in 2022 and < 10 km in 2021. Before both earthquakes, gravity changes first showed as a gradient zone consistent with the strike of seismogenic fault, and then subsequently exhibited a four-quadrant distribution around the epicentral regions. The earthquakes occurred near the centres of the four-quadrant change and the zero isoline of gravity change. In summary, the gravity data reflected both earthquakes well. The findings indicate that such four-quadrant distributions and gravity change high-gradient zone may be precursor information of earthquake preparation. The results of this study provide a reference for future earthquake monitoring and prediction, with implications for earthquake hazard assessment. Earth and environmental sciences/Solid earth sciences/Geophysics Earth and environmental sciences/Natural hazards Earth and environmental sciences/Solid earth sciences 2022 MS6.9 Menyuan earthquake 2022 MS 6.8 Luding earthquake gravity change structural activity earthquake prediction Figures Figure 1 Figure 2 1 Introduction Earthquakes can have substantial impacts on human survival and socioeconomic development owing to their unexpected and destructive nature. In 2022, the M S 6.9 Menyuan and M S 6.8 Luding earthquakes occurred successively in China’s North–South Seismic Belt. Before the earthquakes occurred, gravity anomalies were observed near the epicentres, and successful mid-term predictions (Medium-term prediction refers to the prediction of the region and intensity where destructive earthquakes may occur in the next one or two years) were conducted. Table 1 summarises the predicted locations and magnitudes of the two earthquakes, which were obtained from the "Comprehensive Analysis of Dynamic Changes of Gravity Field in Central and Western Chinese mainland" sections of the 2021 and 2022 earthquake trend research reports produced by the Second Monitoring Centre of the China Earthquake Administration (hereafter the Second Measurement Centre). Table 1 Actual and predicted epicentres of the 2022 M S 6.9 Menyuan and M S 6.8 Luding earthquakes Earthquake Actual epicentre Predicted epicentre/magnitude (2021) Predicted epicentre/magnitude (2022) Menyuan M S 6.9 37.77° N, 101.26° E 37.8° N, 101.2° E/ M S ~6 37.5° N, 101.8° E/ M S ~6 Luding M S 6.8 29.59° N, 102.08° E 29.6° N, 102.0° E/ M S ~7 29.2° N, 102.0° E/ M S ~7 Table 1 indicates that the Menyuan and Luding earthquake epicentres predicted in 2021 and 2022 were very accurate, with distances from the actual epicentres of less than 56 km. In particular, the epicentres predicted in the 2021 report were less than 10 km from the actual epicentres, which is the most accurate prediction of the potential location for strong earthquake (magnitude 6 or above) at home and abroad. In recent years, significant gravity anomaly changes have been observed in the mobile gravity data before several strong earthquakes in the North–South Seismic Belt. Although the manifestations of the anomalies have not been consistent, some earthquakes occurred in the high-gradient zone and zero-value isoline area where the positive and negative gravity anomalies transitioned, and some earthquakes occurred at the centres of the four-quadrant distributions of the gravity anomalies. However, the potential locations and magnitudes of strong earthquakes can be investigated using the ranges and amplitudes of the gravity anomalies, as well as the gravity anomaly gradient sizes and characteristics [ 1 , 2 ] . Based on the anomaly changes in the regional gravity field, we have previously made mid-term predictions for the 2008 M S 8.0 Wenchuan, 2013 M S 7.0 Lushan, and 2017 M S 7.0 Jiuzhaigou earthquakes, which were consistent with the actual earthquake locations [ 3 – 6 ] (72km [ 4 , 7 ] , 77km [ 5 ] , and 220 km [ 6 ] from the epicentres, respectively). Although few gravity measurement sites were located near the Jiuzhaigou earthquake epicentre (distance between sites > 100 km), and the predicted epicentre was more than 200 km from the actual epicentre, it is explicitly mentioned in the location determination to pay attention to the possibility of earthquakes occurring in the area of Jiuzhaigou and Zoige in Sichuan [ 6 , 8 , 9 ] . After the 2017 Jiuzhaigou earthquake, the China Earthquake Administration strengthened mobile gravity monitoring on the eastern margin of the Qinghai-Tibet Plateau, particularly the observational density in key risk areas (two observations per year, 30–60 km between sites), which provided reliable data for the Menyuan and Luding earthquake predictions performed in 2022. In the past, the predicted epicentre of the earthquake was basically more than 70 km away from the actual epicentre of the earthquake. The epicentre of the M S 6.9 earthquake in Menyuan and M S 6.8 earthquake in Luding in 2022 was determined to be within 50 km, which is two accurate predictions. These predictions confirm that high-density gravity data have unique advantages for determining the locations of future earthquakes [ 2 , 9 , 10 ] . In this study, we analysed the spatiotemporal evolution characteristics and laws of the regional gravity field before the Menyuan M S 6.9 and Luding M S 6.8 earthquakes in 2022, summarized the process of earthquake prediction and the basis of prediction, and proposed a new seismic monitoring model based on gravity observations, which will point out the direction of the innovation of future seismic monitoring methods and prediction practice [ 11 , 12 ] . 2 Data and Methods The mobile gravity seismic monitoring network in mainland China comprises relative gravity survey and absolute gravity control networks [ 9 , 13 ] , and regularly repeated seismic gravity surveys are performed annually. The North–South Seismic Belt is a key earthquake monitoring area in mainland China, and hosts many absolute and relative gravity measuring sites. The absolute gravity was measured using FG-5 absolute gravimeters, which have an accuracy better than 5×10 − 8 ms − 2 [ 14 , 15 ] . Burris, LCR-G, CG5, and CG6 gravimeters were used to measure relative gravity, with measurement accuracies better than 10×10 − 8 ms − 2 for gravity segment differences [ 12 , 16 ] . We use the classical adjustment method to adjust the observed data of absolute gravity and relative gravity in the north-south seismic belt as a whole [ 2 , 16 ] , and use the absolute gravity values as the starting basis to obtain the gravity values at each measurement point. We used these data to determine the dynamic change characteristics of regional gravity field at different time and space scales before the 2022 Menyuan and Luding earthquakes. 3 Results 3.1 Dynamic gravity field changes before the Menyuan earthquake From October 2018 to October 2020 (Fig. 1 a), a negative gravity change occurred on the northern side of the Qilianshan Fault, with a corresponding positive gravity change on the southern side of the fault. A WNW-trending gradient zone between the gravity changes was located near the Qilianshan Fault, and turned around near the 2022 Menyuan earthquake epicentre. The differential gravity changes on both sides of the Qilianshan and Lenglongling faults near the epicentre were greater than 60×10 − 8 ms − 2 . From October 2020 to July 2021 (Fig. 1 b), positive gravity changes occurred in the Gulang area east of Menyuan, whereas negative gravity changes occurred to the south of Menyuan. Thus, a four-quadrant distribution of gravity changes formed that was centred at Menyuan. The gravity changes at the Menyuan earthquake epicentre were weak and close to zero. Gravity differences between the southeastern and northwestern sides of Wuwei, Gansu–Menyuan, Qinghai were greater than 90×10 − 8 ms − 2 , and the 2022 Menyuan earthquake occurred near the zero isoline of gravity change at the centre of the four-quadrant distribution. 3.2 Dynamic gravity field changes before the Luding earthquake From September 2019 to September 2020 (Fig. 2 a), gravity changes throughout the study area ranged from − 40 to + 70×10 − 8 ms − 2 , with a general W–E negative–positive gravity change trend. The trend of the gravity change isolines was consistent with that of the main faults in the area, thereby indicating strong tectonic activity. The study area can be divided into eastern and western regions by a boundary located along Daofu–Kangding–Jiulong. The western region exhibited gentle negative gravity changes on the western Sichuan Plateau, whereas the eastern region exhibited substantial positive gravity changes at Xiaojin, Luding, Shimian, and Mianning. The gravity change isoline was curved and intersected near Kangding and Luding on the Xianshuihe fault zone. The 2022 M S 6.8 Luding earthquake occurred near the turning part of the gravity change high-gradient zone. From September 2019 to September 2021 (Fig. 2 b), gravity changes throughout the study area ranged from − 60 to + 70×10 − 8 ms − 2 , and the W–E gravity change trend was negative to positive. Two local positive gravity change anomalies (maximum of 70×10 − 8 ms − 2 ) were located at Jiulong and Mianning (south of the epicentre), as well as at Xiaojin (north of the epicentre). Gravity change high-gradient zone were located along the Longmenshan Fault and on the Xianshuihe fault zone in Wenchuan, Ya’an, Luding, and Kangding. The gravity changes exhibited a four-quadrant distribution centred at Moxi and Shimian. The 2022 M S 6.8 Luding earthquake epicentre was located near the turning part of the gravity change high-gradient zone and the center of the gravity change four-quadrant distribution. 3.3 Menyuan earthquake epicentre prediction In the 2021 and 2022 earthquake trend study report, the Second Crust Monitoring and Application Centre of the China Earthquake Administration made mid-term predictions of the Menyuan M S 6.9 earthquake [ 16 ] . The prediction details are summarised in Table 1 . The 2021 prediction indicated that the earthquake would occur in the Gansu Jinchang–Qinghai Qilian area. The 2022 prediction indicated that the earthquake would occur in the central or eastern Qilian Mountains. On January 8, 2022, the M S 6.9 Menyuan earthquake (37.77° N, 101.26° E) occurred in the predicted area. The distances between the epicentres predicted in 2021 and 2022 and the actual epicentre measured by China Earthquake Networks Centre were 6 and 56 km respectively [ 10 ] . The regional gravity changes from October 2018 to October 2020 (Fig. 1 a) indicate that the southwestern Qilian and Menyuan areas of the Qilian Mountains underwent positive gravity changes, whereas the Shandan and Wuwei areas of the Hexi Corridor underwent negative gravity changes (difference of 60×10 − 8 ms -2 ). A gravity change high-gradient zone was located along the Qilian Mountain Fault, which changed direction near Menyuan. Based on these changes and the relationship between gravity changes and seismic activity studied by predecessors [ 8 , 9 ] , we believed in 2020 that a strong earthquake of magnitude 6 might occur in 2021 near the Menyuan area where the gravity change high-gradient zone bends southward. The regional gravity changes from October 2020 to July 2021 further indicate that the four-quadrant gravity change distribution was centred at Menyuan, and that the gravity difference between the southeastern and northwest sides of the Menyuan–Wuwei region in Qinghai was 90×10 − 8 ms -2 . In 2021, we moved the centre of the 2022 earthquake danger zone southeastward to the intersection of the zero isoline and the Lenglongling Fault, which is near the centre of the gravity change four-quadrant distribution (Fig. 1 b). The predicted magnitude did not change. Before the 2022 M S 6.9 Menyuan earthquake, gravity change first showed a gradient zone of gravity change that was basically consistent with the strike of Qilian Mountain fault belt (Fig. 1 a), and then exhibited a four-quadrant distribution around the earthquake epicentre (Fig. 1 b), which provided a basis for the location determination and mid-term prediction of this earthquake [ 2 , 9 ] . The Menyuan M S 6.9 earthquake occurred near the center of the four-quadrant and the zero isoline of gravity change. 3.4 Luding earthquake epicentre prediction The 2021 and 2022 reports by the Second Crust Monitoring and Application Centre of the China Earthquake Administration also made accurate mid-term predictions of the 2022 Luding earthquake. The prediction details are summarised in Table 1 . The 2021 prediction indicated that the earthquake would occur in the Sichuan Daofu–Yunnan Zhaotong area, whereas the 2022 prediction indicated that the earthquake would occur along the eastern Sichuan–Yunnan border. On September 5, 2022, the M S 6.8 Luding earthquake (29.59° N, 102.08° E) occurred in the predicted area. The distances between the epicentres predicted in 2021 and 2022 and the actual epicentre were 8 and 44 km, respectively [ 16 ] . The gravity changes along the eastern Sichuan–Yunnan border from September 2019 to September 2020 (Fig. 2 a) indicate that gravity change high-gradient zone were located along the Xianshuihe and Yulongxi faults, with a bend near Luding. The gravity changes east of the Daofu–Kangding–Jiulong gradient zone were positive, whereas those west of the gradient zone were negative, with a maximum difference of 100×10 − 8 ms − 2 . Based on the gravity anomaly changes, we believed in 2020 that the bend in the gravity gradient zone near Luding would be the potential earthquake epicentre in 2021, with a strong risk of a magnitude 7 earthquake in the area. However, data from September 2019 to September 2021 indicate that the area near Shimian was the centre of the four-quadrant gravity change distribution, which was bounded by the Xianshuihe and Daliangshan faults (Fig. 2 b) and had a maximum gravity difference of more than 100×10 − 8 ms − 2 . Therefore, we updated our prediction in 2021 to state that an earthquake of magnitude 7 could occur in this region in 2022. Before the 2022 M S 6.8 Luding earthquake, gravity changes first showed in a gradient zone that was consistent with the strike of the Xianshuihe tectonic belt (Fig. 2 a) and then exhibited a four-quadrant distribution around the epicentral area (Fig. 2 b). The 2022 Luding earthquake occurred near the centre of the four-quadrant distribution and the zero isoline of gravity change. Thus, the mobile gravity data accurately predicted the epicentre location of the 2022 Luding earthquake. The four-quadrant center of gravity change and the turning part of the high-gradient zone which is basically consistent with the strike of Xianshuihe fault are the main basis for determining the location of Luding earthquake. In summary, both the Menyuan M S 6.9 and Luding M S 6.8 earthquakes occurred in the four-quadrant center of gravity changes. The gravity data accurately determined the epicenters of the Menyuan M6.9 and Luding M6.8 earthquakes in 2022 13,16 . 4 Discussion Earthquake is a form of tectonic activity on the earth. The preparation and occurrence of earthquakes will inevitably lead to a certain range of geophysical field changes in the source area and the surrounding area. Time-varying gravity measurements for earthquake monitoring and prediction in mainland China have been performed for more than 50 years, with consistently improved observation ranges, periods, and accuracies. We have gradually realised the capture of gravity fields before a strong earthquake, which will exhibit a gravity change four-quadrant distribution or gravity change high-gradient zones along a structural belt. Many major earthquakes were successfully mid-term predicted, such as Wenchuan MS8.0 in 2008, Lushan MS7.0 in 2013 and Jiuzhaigou MS7.0 in 2017 [ 3 – 6 , 17 ] . Based on a large number of strong earthquake cases, Pre-earthquake gravity changes indicate that large-scale orderly changes (i.e. field precursors) occur in the regional gravity field, and local gravity anomalies (i.e. a source precursor) related to pre-earthquake processes are generated in the source area, and the gravity change high-gradient zones or four-quadrant distributions also occur along seismogenic zones. Strong earthquakes are prone to occur near the four-quadrant center of gravity change associated with block tectonic activity, and on the high-gradient zone of gravity change, and at the turning part of the contour line of gravity change [ 7 – 9 , 12 , 18 , 19 ] . Earthquake magnitude is also closely related to the range, amplitude, and duration of the associated gravity anomaly changes. Larger magnitude events produce larger gravity variation ranges and amplitudes near the epicentre with longer durations. The gravity change distribution is related to the specific seismogenic region, and a four-quadrant distribution is an important indicator of short-term and imminent strong earthquake occurrence [ 2 , 8 , 19 ] . The 2022 Menyuan and Luding earthquake epicentres were located at the centres of their respective gravity change four-quadrant distributions, thereby indicating this distribution type can be used as a reliable precursor anomaly for strong earthquakes. The change of gravity field related to earthquake preparation is the response of the migration and change of underground material distributed at all depths of the crust. The preparation of strong earthquakes is controlled by the main active fault zones in the region. Differential tectonic motions in the tectonic belt and its vicinity are usually accompanied by significant gravity field changes. The enhanced regional stress field produces density changes in media at different crustal depths (including the focal medium), as well as changes in the surface gravity over a wide range. The migration of deep crustal and mantle materials along the weak parts of a fault structure leads to pre-earthquake creep along the fault, which produces a gravity change four-quadrant distribution or gravity change high-gradient zone. Strong earthquakes are likely to occur in such regions related to active tectonic boundaries, as they undergo strong material changes and tectonic deformation that can produce severe gravity changes and accumulate stress/strain. Therefore, at a specific spatiotemporal scale, the occurrence of strong earthquakes is related to the non-uniform spatiotemporal variations in the regional gravity field. Accurate determination of an earthquake epicentre is very difficult. However, if four-quadrant gravity change distributions associated with tectonic activity can be used to delineate the potential epicentre and magnitude of a future strong earthquake, only the timing of the earthquake would be unknown, thereby improving our prediction ability. Thus, performing earthquake tracking in and around the epicentre of a potential future strong earthquake is required, which may be helpful for short-term and imminent predictions. Previous studies have indicated that strong earthquakes tend to occur in high-gradient zones between positive and negative gravity change anomalies associated with active faults, and near the centres of gravity change four-quadrant distributions [ 1 , 2 , 7 , 19 , 20 , 21 ] . Thus, related observations should be made in potentially dangerous epicentral areas and their vicinities along tectonic belts [ 8 , 9 , 11 , 22 ] . These include dense network observations (e.g. gravity, seismic, electromagnetic), which could be used to capture pre-earthquake processes in the source area, explore short-term and imminent earthquake precursors, and make short-term and imminent predictions of strong earthquakes. We suggest that high-density absolute gravity network observations should be strengthened in epicentral areas of potential strong earthquakes in the future, particularly continuous absolute gravity observations using cold atom gravimetry (e.g. AQG, A-Grav, RAI-g, and ZAG types), to determine the potential timing of future strong earthquakes. In addition, absolute gravity observation networks with high spatial and temporal densities or relative gravity observation networks with good absolute gravity control should be established in potential high-risk areas. These networks could be used to determine the distributions of subsurface structures near epicentres in high-risk areas, extract the gravity change signals that accompany the source change during pre-earthquake processes, obtain high-precision absolute gravity changes, and analyse the variations in the gravity field during the sub-instability stage before an earthquake [ 23 – 25 ] . Such information could provide support for monitoring the pre-earthquake environment and processes, as well as determining strong earthquake locations accurately. Declarations Conflict of interest The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Author Contribution YZ and XY both contributed to topic selection, writing, and editing of the manuscript. YZ and SW contributed to the discussion section, data processing and review and editing of the manuscript. GZ and FL contributed to drawing, review, and editing of the manuscript. Acknowledgement We would like to thank the field gravity observers of the China Earthquake Administration for their hard work, which provided reliable data for this paper; This research was funded by the National Natural Science Foundation of China (No.41874092, No. 42374104). The authors express their appreciation to the National Natural Science Foundation of China (No.41874092, No. 42374104) for the financial support of this work. Data Availability The datasets used during this study are openly available in the repository ZENODO at https://doi.org/10.5281/zenodo.13139752 References Zhu Y Q, Zhan F B, Zhou J C, et al. 2010. Gravity measurements and their variation before the 2008 Wenchuan earthquake[J]. Bulletin of the Seismological Society of America, 100:2815-2824. Zhu Y Q, Liu F, Zhang G Q, et al. 2019. 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Cite Share Download PDF Status: Published Journal Publication published 25 Nov, 2024 Read the published version in Scientific Reports → Version 1 posted Editorial decision: Revision requested 09 Sep, 2024 Reviews received at journal 06 Sep, 2024 Reviews received at journal 03 Sep, 2024 Reviewers agreed at journal 26 Aug, 2024 Reviewers agreed at journal 23 Aug, 2024 Reviewers invited by journal 23 Aug, 2024 Editor assigned by journal 16 Aug, 2024 Editor invited by journal 05 Aug, 2024 Submission checks completed at journal 31 Jul, 2024 First submitted to journal 04 Jun, 2024 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. 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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-4530628","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":345344679,"identity":"024bc7bc-f6c5-4bf4-8a59-93c41064cb40","order_by":0,"name":"Yiqing Zhu","email":"","orcid":"","institution":"The Second Monitoring and Application Center, CEA","correspondingAuthor":false,"prefix":"","firstName":"Yiqing","middleName":"","lastName":"Zhu","suffix":""},{"id":345344680,"identity":"71211175-d2f6-4964-abc6-5fce916d6292","order_by":1,"name":"Xiong Yang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAz0lEQVRIie3RPwrCMBTH8ZQHr8vTOkbEiAcQAoFCQepVUgTP4Bgp2MUjeAhB6BwodHV1VApOLh7AP6tOjZtgvvsH3o/HmM/3gyFEt+b+mIoIwLqRbmiUJFyofoHajQiycY+wynYHko6Hcb1gnCAzFd2OV5aKiWkn9UlyVKu8s0+2bK5i20qyQmpJwxw65YCYzcp2MkduNQ/WQBdHQjX2jZXjDRA6knADKjBacUCVbKXDllFOQROYp5gdqvPxukxFK/mIu77mnXwrfD6f7y96Abu0OcKoOMXuAAAAAElFTkSuQmCC","orcid":"","institution":"The Second Monitoring and Application Center, CEA","correspondingAuthor":true,"prefix":"","firstName":"Xiong","middleName":"","lastName":"Yang","suffix":""},{"id":345344682,"identity":"27b23ea7-5e90-41ce-a72d-3044f4ac4b16","order_by":2,"name":"Yunfeng Zhao","email":"","orcid":"","institution":"The Second Monitoring and Application Center, CEA","correspondingAuthor":false,"prefix":"","firstName":"Yunfeng","middleName":"","lastName":"Zhao","suffix":""},{"id":345344683,"identity":"9c27be91-750b-4f5f-8ea2-10d4050f56d0","order_by":3,"name":"ShouChun Wei","email":"","orcid":"","institution":"The Second Monitoring and Application Center, CEA","correspondingAuthor":false,"prefix":"","firstName":"ShouChun","middleName":"","lastName":"Wei","suffix":""},{"id":345344685,"identity":"0bb50044-bccc-4c8d-9f95-c5385b2e91ae","order_by":4,"name":"Guoqing Zhang","email":"","orcid":"","institution":"The Second Monitoring and Application Center, CEA","correspondingAuthor":false,"prefix":"","firstName":"Guoqing","middleName":"","lastName":"Zhang","suffix":""},{"id":345344686,"identity":"55e28e47-a64a-43b0-a3dd-6b1920e1a65a","order_by":5,"name":"Fang Liu","email":"","orcid":"","institution":"The Second Monitoring and Application Center, CEA","correspondingAuthor":false,"prefix":"","firstName":"Fang","middleName":"","lastName":"Liu","suffix":""}],"badges":[],"createdAt":"2024-06-05 01:12:46","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4530628/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4530628/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s41598-024-79091-x","type":"published","date":"2024-11-25T15:57:31+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":63335987,"identity":"630ff26c-2d53-488b-aa63-5e547010c533","added_by":"auto","created_at":"2024-08-27 05:33:35","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1130645,"visible":true,"origin":"","legend":"\u003cp\u003eDynamic changes in the regional gravity field before the 2022 \u003cem\u003eMs \u003c/em\u003e6.9 Menyuan earthquake (a) from October 2018 to October 2020and (b) from October 2020 to July 2021.\u003c/p\u003e","description":"","filename":"fig1.png","url":"https://assets-eu.researchsquare.com/files/rs-4530628/v1/b56ed0c89b360564d77d163b.png"},{"id":63334957,"identity":"08e6f8ce-e1ad-4c73-948c-06d327863be0","added_by":"auto","created_at":"2024-08-27 05:25:35","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1659052,"visible":true,"origin":"","legend":"\u003cp\u003eDynamic changes in the regional gravity field before the 2022 \u003cem\u003eMs \u003c/em\u003e6.8 Luding earthquake(a) from September 2019 to September 2020 and (b) from September 2019 to September 2021.\u003c/p\u003e","description":"","filename":"fig2.png","url":"https://assets-eu.researchsquare.com/files/rs-4530628/v1/0ff12c1d8c6426d4ea0dcfe2.png"},{"id":70382722,"identity":"4ab1d261-e53c-4c0d-b04b-608e1bd1119e","added_by":"auto","created_at":"2024-12-02 16:29:43","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2791498,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4530628/v1/d7f2fc41-7f49-4624-9de8-e8a8addb5410.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eAccurate prediction of the 2022 \u003cem\u003eM\u003c/em\u003e\u003csub\u003eS \u003c/sub\u003e6.9 Menyuan and \u003cem\u003eM\u003c/em\u003e\u003csub\u003eS \u003c/sub\u003e6.8 Luding earthquake epicentres\u003c/p\u003e","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eEarthquakes can have substantial impacts on human survival and socioeconomic development owing to their unexpected and destructive nature. In 2022, the \u003cem\u003eM\u003c/em\u003e\u003csub\u003eS\u003c/sub\u003e 6.9 Menyuan and \u003cem\u003eM\u003c/em\u003e\u003csub\u003eS\u003c/sub\u003e 6.8 Luding earthquakes occurred successively in China\u0026rsquo;s North\u0026ndash;South Seismic Belt. Before the earthquakes occurred, gravity anomalies were observed near the epicentres, and successful mid-term predictions (Medium-term prediction refers to the prediction of the region and intensity where destructive earthquakes may occur in the next one or two years) were conducted. Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e summarises the predicted locations and magnitudes of the two earthquakes, which were obtained from the \"Comprehensive Analysis of Dynamic Changes of Gravity Field in Central and Western Chinese mainland\" sections of the 2021 and 2022 earthquake trend research reports produced by the Second Monitoring Centre of the China Earthquake Administration (hereafter the Second Measurement Centre).\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\u003eActual and predicted epicentres of the 2022 \u003cem\u003eM\u003c/em\u003e\u003csub\u003eS\u003c/sub\u003e 6.9 Menyuan and \u003cem\u003eM\u003c/em\u003e\u003csub\u003eS\u003c/sub\u003e 6.8 Luding earthquakes\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\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=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEarthquake\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eActual epicentre\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePredicted epicentre/magnitude (2021)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003ePredicted epicentre/magnitude\u003c/p\u003e \u003cp\u003e(2022)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eMenyuan \u003cem\u003eM\u003c/em\u003e\u003csub\u003eS\u003c/sub\u003e 6.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e37.77\u0026deg; N, 101.26\u0026deg; E\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e37.8\u0026deg; N, 101.2\u0026deg; E/\u003cem\u003eM\u003c/em\u003e\u003csub\u003eS\u003c/sub\u003e ~6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e37.5\u0026deg; N, 101.8\u0026deg; E/\u003cem\u003eM\u003c/em\u003e\u003csub\u003eS\u003c/sub\u003e ~6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eLuding \u003cem\u003eM\u003c/em\u003e\u003csub\u003eS\u003c/sub\u003e 6.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e29.59\u0026deg; N, 102.08\u0026deg; E\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e29.6\u0026deg; N, 102.0\u0026deg; E/\u003cem\u003eM\u003c/em\u003e\u003csub\u003eS\u003c/sub\u003e ~7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e29.2\u0026deg; N, 102.0\u0026deg; E/\u003cem\u003eM\u003c/em\u003e\u003csub\u003eS\u003c/sub\u003e ~7\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\u003eTable\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e indicates that the Menyuan and Luding earthquake epicentres predicted in 2021 and 2022 were very accurate, with distances from the actual epicentres of less than 56 km. In particular, the epicentres predicted in the 2021 report were less than 10 km from the actual epicentres, which is the most accurate prediction of the potential location for strong earthquake (magnitude 6 or above) at home and abroad. In recent years, significant gravity anomaly changes have been observed in the mobile gravity data before several strong earthquakes in the North\u0026ndash;South Seismic Belt. Although the manifestations of the anomalies have not been consistent, some earthquakes occurred in the high-gradient zone and zero-value isoline area where the positive and negative gravity anomalies transitioned, and some earthquakes occurred at the centres of the four-quadrant distributions of the gravity anomalies. However, the potential locations and magnitudes of strong earthquakes can be investigated using the ranges and amplitudes of the gravity anomalies, as well as the gravity anomaly gradient sizes and characteristics\u003csup\u003e[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]\u003c/sup\u003e. Based on the anomaly changes in the regional gravity field, we have previously made mid-term predictions for the 2008 \u003cem\u003eM\u003c/em\u003e\u003csub\u003eS\u003c/sub\u003e 8.0 Wenchuan, 2013 \u003cem\u003eM\u003c/em\u003e\u003csub\u003eS\u003c/sub\u003e 7.0 Lushan, and 2017 \u003cem\u003eM\u003c/em\u003e\u003csub\u003eS\u003c/sub\u003e 7.0 Jiuzhaigou earthquakes, which were consistent with the actual earthquake locations\u003csup\u003e[\u003cspan additionalcitationids=\"CR4 CR5\" citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]\u003c/sup\u003e (72km\u003csup\u003e[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]\u003c/sup\u003e, 77km\u003csup\u003e[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]\u003c/sup\u003e, and 220 km\u003csup\u003e[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]\u003c/sup\u003e from the epicentres, respectively). Although few gravity measurement sites were located near the Jiuzhaigou earthquake epicentre (distance between sites\u0026thinsp;\u0026gt;\u0026thinsp;100 km), and the predicted epicentre was more than 200 km from the actual epicentre, it is explicitly mentioned in the location determination to pay attention to the possibility of earthquakes occurring in the area of Jiuzhaigou and Zoige in Sichuan \u003csup\u003e[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]\u003c/sup\u003e. After the 2017 Jiuzhaigou earthquake, the China Earthquake Administration strengthened mobile gravity monitoring on the eastern margin of the Qinghai-Tibet Plateau, particularly the observational density in key risk areas (two observations per year, 30\u0026ndash;60 km between sites), which provided reliable data for the Menyuan and Luding earthquake predictions performed in 2022. In the past, the predicted epicentre of the earthquake was basically more than 70 km away from the actual epicentre of the earthquake. The epicentre of the \u003cem\u003eM\u003c/em\u003e\u003csub\u003eS\u003c/sub\u003e6.9 earthquake in Menyuan and \u003cem\u003eM\u003c/em\u003e\u003csub\u003eS\u003c/sub\u003e6.8 earthquake in Luding in 2022 was determined to be within 50 km, which is two accurate predictions. These predictions confirm that high-density gravity data have unique advantages for determining the locations of future earthquakes \u003csup\u003e[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eIn this study, we analysed the spatiotemporal evolution characteristics and laws of the regional gravity field before the Menyuan \u003cem\u003eM\u003c/em\u003e\u003csub\u003eS\u003c/sub\u003e6.9 and Luding \u003cem\u003eM\u003c/em\u003e\u003csub\u003eS\u003c/sub\u003e6.8 earthquakes in 2022, summarized the process of earthquake prediction and the basis of prediction, and proposed a new seismic monitoring model based on gravity observations, which will point out the direction of the innovation of future seismic monitoring methods and prediction practice \u003csup\u003e[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e"},{"header":"2 Data and Methods","content":"\u003cp\u003eThe mobile gravity seismic monitoring network in mainland China comprises relative gravity survey and absolute gravity control networks\u003csup\u003e[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]\u003c/sup\u003e, and regularly repeated seismic gravity surveys are performed annually. The North\u0026ndash;South Seismic Belt is a key earthquake monitoring area in mainland China, and hosts many absolute and relative gravity measuring sites. The absolute gravity was measured using FG-5 absolute gravimeters, which have an accuracy better than 5\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;8\u003c/sup\u003e ms\u003csup\u003e\u0026minus;\u0026thinsp;2 [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]\u003c/sup\u003e. Burris, LCR-G, CG5, and CG6 gravimeters were used to measure relative gravity, with measurement accuracies better than 10\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;8\u003c/sup\u003e ms\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e for gravity segment differences \u003csup\u003e[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]\u003c/sup\u003e. We use the classical adjustment method to adjust the observed data of absolute gravity and relative gravity in the north-south seismic belt as a whole \u003csup\u003e[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]\u003c/sup\u003e, and use the absolute gravity values as the starting basis to obtain the gravity values at each measurement point. We used these data to determine the dynamic change characteristics of regional gravity field at different time and space scales before the 2022 Menyuan and Luding earthquakes.\u003c/p\u003e"},{"header":"3 Results","content":"\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Dynamic gravity field changes before the Menyuan earthquake\u003c/h2\u003e \u003cp\u003eFrom October 2018 to October 2020 (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea), a negative gravity change occurred on the northern side of the Qilianshan Fault, with a corresponding positive gravity change on the southern side of the fault. A WNW-trending gradient zone between the gravity changes was located near the Qilianshan Fault, and turned around near the 2022 Menyuan earthquake epicentre. The differential gravity changes on both sides of the Qilianshan and Lenglongling faults near the epicentre were greater than 60\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;8\u003c/sup\u003e ms\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eFrom October 2020 to July 2021 (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb), positive gravity changes occurred in the Gulang area east of Menyuan, whereas negative gravity changes occurred to the south of Menyuan. Thus, a four-quadrant distribution of gravity changes formed that was centred at Menyuan. The gravity changes at the Menyuan earthquake epicentre were weak and close to zero. Gravity differences between the southeastern and northwestern sides of Wuwei, Gansu\u0026ndash;Menyuan, Qinghai were greater than 90\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;8\u003c/sup\u003e ms\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e, and the 2022 Menyuan earthquake occurred near the zero isoline of gravity change at the centre of the four-quadrant distribution.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Dynamic gravity field changes before the Luding earthquake\u003c/h2\u003e \u003cp\u003eFrom September 2019 to September 2020 (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea), gravity changes throughout the study area ranged from \u0026minus;\u0026thinsp;40 to +\u0026thinsp;70\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;8\u003c/sup\u003e ms\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e, with a general W\u0026ndash;E negative\u0026ndash;positive gravity change trend. The trend of the gravity change isolines was consistent with that of the main faults in the area, thereby indicating strong tectonic activity. The study area can be divided into eastern and western regions by a boundary located along Daofu\u0026ndash;Kangding\u0026ndash;Jiulong. The western region exhibited gentle negative gravity changes on the western Sichuan Plateau, whereas the eastern region exhibited substantial positive gravity changes at Xiaojin, Luding, Shimian, and Mianning. The gravity change isoline was curved and intersected near Kangding and Luding on the Xianshuihe fault zone. The 2022 \u003cem\u003eM\u003c/em\u003e\u003csub\u003eS\u003c/sub\u003e 6.8 Luding earthquake occurred near the turning part of the gravity change high-gradient zone.\u003c/p\u003e \u003cp\u003eFrom September 2019 to September 2021 (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb), gravity changes throughout the study area ranged from \u0026minus;\u0026thinsp;60 to +\u0026thinsp;70\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;8\u003c/sup\u003e ms\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e, and the W\u0026ndash;E gravity change trend was negative to positive. Two local positive gravity change anomalies (maximum of 70\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;8\u003c/sup\u003e ms\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e) were located at Jiulong and Mianning (south of the epicentre), as well as at Xiaojin (north of the epicentre). Gravity change high-gradient zone were located along the Longmenshan Fault and on the Xianshuihe fault zone in Wenchuan, Ya\u0026rsquo;an, Luding, and Kangding. The gravity changes exhibited a four-quadrant distribution centred at Moxi and Shimian. The 2022 \u003cem\u003eM\u003c/em\u003e\u003csub\u003eS\u003c/sub\u003e 6.8 Luding earthquake epicentre was located near the turning part of the gravity change high-gradient zone and the center of the gravity change four-quadrant distribution.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Menyuan earthquake epicentre prediction\u003c/h2\u003e \u003cp\u003eIn the 2021 and 2022 earthquake trend study report, the Second Crust Monitoring and Application Centre of the China Earthquake Administration made mid-term predictions of the Menyuan \u003cem\u003eM\u003c/em\u003e\u003csub\u003eS\u003c/sub\u003e6.9 earthquake\u003csup\u003e[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]\u003c/sup\u003e. The prediction details are summarised in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The 2021 prediction indicated that the earthquake would occur in the Gansu Jinchang\u0026ndash;Qinghai Qilian area. The 2022 prediction indicated that the earthquake would occur in the central or eastern Qilian Mountains.\u003c/p\u003e \u003cp\u003eOn January 8, 2022, the \u003cem\u003eM\u003c/em\u003e\u003csub\u003eS\u003c/sub\u003e 6.9 Menyuan earthquake (37.77\u0026deg; N, 101.26\u0026deg; E) occurred in the predicted area. The distances between the epicentres predicted in 2021 and 2022 and the actual epicentre measured by China Earthquake Networks Centre were 6 and 56 km respectively\u003csup\u003e[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe regional gravity changes from October 2018 to October 2020 (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea) indicate that the southwestern Qilian and Menyuan areas of the Qilian Mountains underwent positive gravity changes, whereas the Shandan and Wuwei areas of the Hexi Corridor underwent negative gravity changes (difference of 60\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;8\u003c/sup\u003e ms\u003csup\u003e-2\u003c/sup\u003e). A gravity change high-gradient zone was located along the Qilian Mountain Fault, which changed direction near Menyuan. Based on these changes and the relationship between gravity changes and seismic activity studied by predecessors \u003csup\u003e[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]\u003c/sup\u003e, we believed in 2020 that a strong earthquake of magnitude 6 might occur in 2021 near the Menyuan area where the gravity change high-gradient zone bends southward. The regional gravity changes from October 2020 to July 2021 further indicate that the four-quadrant gravity change distribution was centred at Menyuan, and that the gravity difference between the southeastern and northwest sides of the Menyuan\u0026ndash;Wuwei region in Qinghai was 90\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;8\u003c/sup\u003e ms\u003csup\u003e-2\u003c/sup\u003e. In 2021, we moved the centre of the 2022 earthquake danger zone southeastward to the intersection of the zero isoline and the Lenglongling Fault, which is near the centre of the gravity change four-quadrant distribution (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb). The predicted magnitude did not change.\u003c/p\u003e \u003cp\u003eBefore the 2022 \u003cem\u003eM\u003c/em\u003e\u003csub\u003eS\u003c/sub\u003e 6.9 Menyuan earthquake, gravity change first showed a gradient zone of gravity change that was basically consistent with the strike of Qilian Mountain fault belt (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea), and then exhibited a four-quadrant distribution around the earthquake epicentre (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb), which provided a basis for the location determination and mid-term prediction of this earthquake \u003csup\u003e[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]\u003c/sup\u003e. The Menyuan \u003cem\u003eM\u003c/em\u003e\u003csub\u003eS\u003c/sub\u003e6.9 earthquake occurred near the center of the four-quadrant and the zero isoline of gravity change.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e3.4 Luding earthquake epicentre prediction\u003c/h2\u003e \u003cp\u003eThe 2021 and 2022 reports by the Second Crust Monitoring and Application Centre of the China Earthquake Administration also made accurate mid-term predictions of the 2022 Luding earthquake. The prediction details are summarised in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The 2021 prediction indicated that the earthquake would occur in the Sichuan Daofu\u0026ndash;Yunnan Zhaotong area, whereas the 2022 prediction indicated that the earthquake would occur along the eastern Sichuan\u0026ndash;Yunnan border.\u003c/p\u003e \u003cp\u003eOn September 5, 2022, the \u003cem\u003eM\u003c/em\u003e\u003csub\u003eS\u003c/sub\u003e 6.8 Luding earthquake (29.59\u0026deg; N, 102.08\u0026deg; E) occurred in the predicted area. The distances between the epicentres predicted in 2021 and 2022 and the actual epicentre were 8 and 44 km, respectively \u003csup\u003e[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe gravity changes along the eastern Sichuan\u0026ndash;Yunnan border from September 2019 to September 2020 (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea) indicate that gravity change high-gradient zone were located along the Xianshuihe and Yulongxi faults, with a bend near Luding. The gravity changes east of the Daofu\u0026ndash;Kangding\u0026ndash;Jiulong gradient zone were positive, whereas those west of the gradient zone were negative, with a maximum difference of 100\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;8\u003c/sup\u003e ms\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e. Based on the gravity anomaly changes, we believed in 2020 that the bend in the gravity gradient zone near Luding would be the potential earthquake epicentre in 2021, with a strong risk of a magnitude 7 earthquake in the area. However, data from September 2019 to September 2021 indicate that the area near Shimian was the centre of the four-quadrant gravity change distribution, which was bounded by the Xianshuihe and Daliangshan faults (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb) and had a maximum gravity difference of more than 100\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;8\u003c/sup\u003e ms\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e. Therefore, we updated our prediction in 2021 to state that an earthquake of magnitude 7 could occur in this region in 2022.\u003c/p\u003e \u003cp\u003eBefore the 2022 \u003cem\u003eM\u003c/em\u003e\u003csub\u003eS\u003c/sub\u003e 6.8 Luding earthquake, gravity changes first showed in a gradient zone that was consistent with the strike of the Xianshuihe tectonic belt (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea) and then exhibited a four-quadrant distribution around the epicentral area (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb). The 2022 Luding earthquake occurred near the centre of the four-quadrant distribution and the zero isoline of gravity change. Thus, the mobile gravity data accurately predicted the epicentre location of the 2022 Luding earthquake. The four-quadrant center of gravity change and the turning part of the high-gradient zone which is basically consistent with the strike of Xianshuihe fault are the main basis for determining the location of Luding earthquake.\u003c/p\u003e \u003cp\u003eIn summary, both the Menyuan \u003cem\u003eM\u003c/em\u003e\u003csub\u003eS\u003c/sub\u003e6.9 and Luding \u003cem\u003eM\u003c/em\u003e\u003csub\u003eS\u003c/sub\u003e6.8 earthquakes occurred in the four-quadrant center of gravity changes. The gravity data accurately determined the epicenters of the Menyuan M6.9 and Luding M6.8 earthquakes in 2022\u003csup\u003e13,16\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e"},{"header":"4 Discussion","content":"\u003cp\u003eEarthquake is a form of tectonic activity on the earth. The preparation and occurrence of earthquakes will inevitably lead to a certain range of geophysical field changes in the source area and the surrounding area. Time-varying gravity measurements for earthquake monitoring and prediction in mainland China have been performed for more than 50 years, with consistently improved observation ranges, periods, and accuracies. We have gradually realised the capture of gravity fields before a strong earthquake, which will exhibit a gravity change four-quadrant distribution or gravity change high-gradient zones along a structural belt. Many major earthquakes were successfully mid-term predicted, such as Wenchuan MS8.0 in 2008, Lushan MS7.0 in 2013 and Jiuzhaigou MS7.0 in 2017 \u003csup\u003e[\u003cspan additionalcitationids=\"CR4 CR5\" citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]\u003c/sup\u003e. Based on a large number of strong earthquake cases, Pre-earthquake gravity changes indicate that large-scale orderly changes (i.e. field precursors) occur in the regional gravity field, and local gravity anomalies (i.e. a source precursor) related to pre-earthquake processes are generated in the source area, and the gravity change high-gradient zones or four-quadrant distributions also occur along seismogenic zones. Strong earthquakes are prone to occur near the four-quadrant center of gravity change associated with block tectonic activity, and on the high-gradient zone of gravity change, and at the turning part of the contour line of gravity change \u003csup\u003e[\u003cspan additionalcitationids=\"CR8\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]\u003c/sup\u003e. Earthquake magnitude is also closely related to the range, amplitude, and duration of the associated gravity anomaly changes. Larger magnitude events produce larger gravity variation ranges and amplitudes near the epicentre with longer durations. The gravity change distribution is related to the specific seismogenic region, and a four-quadrant distribution is an important indicator of short-term and imminent strong earthquake occurrence \u003csup\u003e[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]\u003c/sup\u003e. The 2022 Menyuan and Luding earthquake epicentres were located at the centres of their respective gravity change four-quadrant distributions, thereby indicating this distribution type can be used as a reliable precursor anomaly for strong earthquakes.\u003c/p\u003e \u003cp\u003eThe change of gravity field related to earthquake preparation is the response of the migration and change of underground material distributed at all depths of the crust. The preparation of strong earthquakes is controlled by the main active fault zones in the region. Differential tectonic motions in the tectonic belt and its vicinity are usually accompanied by significant gravity field changes. The enhanced regional stress field produces density changes in media at different crustal depths (including the focal medium), as well as changes in the surface gravity over a wide range. The migration of deep crustal and mantle materials along the weak parts of a fault structure leads to pre-earthquake creep along the fault, which produces a gravity change four-quadrant distribution or gravity change high-gradient zone. Strong earthquakes are likely to occur in such regions related to active tectonic boundaries, as they undergo strong material changes and tectonic deformation that can produce severe gravity changes and accumulate stress/strain. Therefore, at a specific spatiotemporal scale, the occurrence of strong earthquakes is related to the non-uniform spatiotemporal variations in the regional gravity field.\u003c/p\u003e \u003cp\u003eAccurate determination of an earthquake epicentre is very difficult. However, if four-quadrant gravity change distributions associated with tectonic activity can be used to delineate the potential epicentre and magnitude of a future strong earthquake, only the timing of the earthquake would be unknown, thereby improving our prediction ability. Thus, performing earthquake tracking in and around the epicentre of a potential future strong earthquake is required, which may be helpful for short-term and imminent predictions. Previous studies have indicated that strong earthquakes tend to occur in high-gradient zones between positive and negative gravity change anomalies associated with active faults, and near the centres of gravity change four-quadrant distributions \u003csup\u003e[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]\u003c/sup\u003e. Thus, related observations should be made in potentially dangerous epicentral areas and their vicinities along tectonic belts\u003csup\u003e[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]\u003c/sup\u003e. These include dense network observations (e.g. gravity, seismic, electromagnetic), which could be used to capture pre-earthquake processes in the source area, explore short-term and imminent earthquake precursors, and make short-term and imminent predictions of strong earthquakes.\u003c/p\u003e \u003cp\u003eWe suggest that high-density absolute gravity network observations should be strengthened in epicentral areas of potential strong earthquakes in the future, particularly continuous absolute gravity observations using cold atom gravimetry (e.g. AQG, A-Grav, RAI-g, and ZAG types), to determine the potential timing of future strong earthquakes. In addition, absolute gravity observation networks with high spatial and temporal densities or relative gravity observation networks with good absolute gravity control should be established in potential high-risk areas. These networks could be used to determine the distributions of subsurface structures near epicentres in high-risk areas, extract the gravity change signals that accompany the source change during pre-earthquake processes, obtain high-precision absolute gravity changes, and analyse the variations in the gravity field during the sub-instability stage before an earthquake\u003csup\u003e[\u003cspan additionalcitationids=\"CR24\" citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]\u003c/sup\u003e. Such information could provide support for monitoring the pre-earthquake environment and processes, as well as determining strong earthquake locations accurately.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003eConflict of interest\u003c/h2\u003e \u003cp\u003eThe authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eYZ and XY both contributed to topic selection, writing, and editing of the manuscript. YZ and SW contributed to the discussion section, data processing and review and editing of the manuscript. GZ and FL contributed to drawing, review, and editing of the manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eWe would like to thank the field gravity observers of the China Earthquake Administration for their hard work, which provided reliable data for this paper; This research was funded by the National Natural Science Foundation of China (No.41874092, No. 42374104). The authors express their appreciation to the National Natural Science Foundation of China (No.41874092, No. 42374104) for the financial support of this work.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe datasets used during this study are openly available in the repository ZENODO at https://doi.org/10.5281/zenodo.13139752\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eZhu Y Q, Zhan F B, Zhou J C, et al. 2010. Gravity measurements and their variation before the 2008 Wenchuan earthquake[J]. 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Seismology and Geology，43(6): 1368-1380 (in Chinese). doi: 10.3969/j.issn.0253-4967.2021.06.002.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"2022 MS6.9 Menyuan earthquake, 2022 MS 6.8 Luding earthquake, gravity change, structural activity, earthquake prediction","lastPublishedDoi":"10.21203/rs.3.rs-4530628/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4530628/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIn 2022, the \u003cem\u003eM\u003c/em\u003e\u003csub\u003eS\u003c/sub\u003e6.9 Menyuan (Qinghai Province) and \u003cem\u003eM\u003c/em\u003e\u003csub\u003eS\u003c/sub\u003e 6.8 Luding (Sichuan Province) earthquakes occurred successively on China's North\u0026ndash;South seismic belt. Both earthquakes caused serious property losses, and the Luding earthquake caused 100\u0026thinsp;+\u0026thinsp;casualties. Gravity observations performed in the North\u0026ndash;South Seismic Belt before the two earthquakes indicate that gravity changes occurred near the epicentres and exhibited four-quadrant distributions. In this study, We reviewed the successful prediction of these two earthquakes by using gravity data. The distances between the actual and predicted epicenters of the two earthquakes were \u0026lt;\u0026thinsp;56km in 2022 and \u0026lt;\u0026thinsp;10 km in 2021. Before both earthquakes, gravity changes first showed as a gradient zone consistent with the strike of seismogenic fault, and then subsequently exhibited a four-quadrant distribution around the epicentral regions. The earthquakes occurred near the centres of the four-quadrant change and the zero isoline of gravity change. In summary, the gravity data reflected both earthquakes well. The findings indicate that such four-quadrant distributions and gravity change high-gradient zone may be precursor information of earthquake preparation. The results of this study provide a reference for future earthquake monitoring and prediction, with implications for earthquake hazard assessment.\u003c/p\u003e","manuscriptTitle":"Accurate prediction of the 2022 MS 6.9 Menyuan and MS 6.8 Luding earthquake epicentres","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-08-27 05:25:30","doi":"10.21203/rs.3.rs-4530628/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-09-09T04:36:37+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-09-06T14:10:09+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-09-03T13:55:12+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"291960186033306014539062452715597474577","date":"2024-08-26T17:02:52+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"85058414823084858886614132763631071748","date":"2024-08-23T10:31:19+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-08-23T04:32:24+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-08-16T19:00:31+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2024-08-05T05:19:28+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-07-31T07:47:33+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2024-06-05T01:11:29+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"031042c2-bd9c-47fd-acab-b7ff73ac4dd2","owner":[],"postedDate":"August 27th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":36624021,"name":"Earth and environmental sciences/Solid earth sciences/Geophysics"},{"id":36624022,"name":"Earth and environmental sciences/Natural hazards"},{"id":36624023,"name":"Earth and environmental sciences/Solid earth sciences"}],"tags":[],"updatedAt":"2024-12-02T16:01:58+00:00","versionOfRecord":{"articleIdentity":"rs-4530628","link":"https://doi.org/10.1038/s41598-024-79091-x","journal":{"identity":"scientific-reports","isVorOnly":false,"title":"Scientific Reports"},"publishedOn":"2024-11-25 15:57:31","publishedOnDateReadable":"November 25th, 2024"},"versionCreatedAt":"2024-08-27 05:25:30","video":"","vorDoi":"10.1038/s41598-024-79091-x","vorDoiUrl":"https://doi.org/10.1038/s41598-024-79091-x","workflowStages":[]},"version":"v1","identity":"rs-4530628","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4530628","identity":"rs-4530628","version":["v1"]},"buildId":"_2-kVJe1T_tPrBINL-cwx","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}