Contributionof subsurface fluids to tectonic activities beneath the Kii Peninsula, southwestern part of Japan

Contributionof subsurface fluids to tectonic activities beneath the Kii Peninsula, southwestern part of Japan | 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 Research Article Contributionof subsurface fluids to tectonic activities beneath the Kii Peninsula, southwestern part of Japan Akira Watanabe, Makoto Uyeshima, Satoru Yamaguchi, Yoshiya Usui, and 7 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7562430/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract The Kii Peninsula in the forearc region of southwestern Japan has distinct structural and tectonic features due to the subduction of the Philippine Sea (PHS) slab. To solve this problem and investigate the fluid supply process, deeper shape of plutonic rocks, and their tectonic influence, we reanalysed all Network-MT data acquired in the Kii Peninsula to construct a wide and deep resistivity structure model by conducting 3-D inversion analysis. The 3-D resistivity structure model obtained contains highly resistive zones that are widely distributed in the eastern part of the Kii Peninsula shallower than 20 km below the surface. The highly resistive zones reach depths of approximately 30–40 km in their deepest portions and correlate well with previously identified high seismic velocity zones and gravity anomalies. This correspondence implies that the highly resistive zones are interpreted as acidic rock bodies because the high resistivity of a rock body implies a lack of interstitial fluid in the body. High-resistivity zones were surrounded by low-resistivity zones. Based on the obtained 3-D resistivity structure, the Kumano and Ohmine Plutons have a relatively low permeability. This may prevent the upward flow of fluids supplied by the PHS slab and control earthquake occurrence with deep fluids. Comparison with DLFE distributions shows most of the DLFEs occur in the area where the Kumano and Ohmine plutons reach above the top of the PHS slab. A comparison with regular earthquake distributions shows that microseismicity epicentres are concentrated at the margins of the high-resistivity zone. This may be due to differences in local lithological characteristics, such as permeability. This indicates that the local lithological characteristics of the upper plate, such as permeability and brittleness, in the vicinity of the plate boundary control deep fluid transport and influence seismic activities such as DLFEs or micro-seismicity. Network-MT Kii Peninsula Philippine Sea plate Subduction zone dehydration of oceanic crust deep fluids fluid pressure electrical resistivity structure non-volcanic seismic swarm deep low-frequency earthquake Full Text Supplementary Files Graphicalabstract.jpg 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-7562430","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":519073140,"identity":"34504bc6-7c09-4c19-9163-2215437ef453","order_by":0,"name":"Akira 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Japan","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"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":"Network-MT, Kii Peninsula, Philippine Sea plate, Subduction zone, dehydration of oceanic crust, deep fluids, fluid pressure, electrical resistivity structure, non-volcanic seismic swarm, deep low-frequency earthquake","lastPublishedDoi":"10.21203/rs.3.rs-7562430/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7562430/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe Kii Peninsula in the forearc region of southwestern Japan has distinct structural and tectonic features due to the subduction of the Philippine Sea (PHS) slab. To solve this problem and investigate the fluid supply process, deeper shape of plutonic rocks, and their tectonic influence, we reanalysed all Network-MT data acquired in the Kii Peninsula to construct a wide and deep resistivity structure model by conducting 3-D inversion analysis. The 3-D resistivity structure model obtained contains highly resistive zones that are widely distributed in the eastern part of the Kii Peninsula shallower than 20 km below the surface. The highly resistive zones reach depths of approximately 30\u0026ndash;40 km in their deepest portions and correlate well with previously identified high seismic velocity zones and gravity anomalies. This correspondence implies that the highly resistive zones are interpreted as acidic rock bodies because the high resistivity of a rock body implies a lack of interstitial fluid in the body. High-resistivity zones were surrounded by low-resistivity zones. Based on the obtained 3-D resistivity structure, the Kumano and Ohmine Plutons have a relatively low permeability. This may prevent the upward flow of fluids supplied by the PHS slab and control earthquake occurrence with deep fluids. Comparison with DLFE distributions shows most of the DLFEs occur in the area where the Kumano and Ohmine plutons reach above the top of the PHS slab. A comparison with regular earthquake distributions shows that microseismicity epicentres are concentrated at the margins of the high-resistivity zone. This may be due to differences in local lithological characteristics, such as permeability. This indicates that the local lithological characteristics of the upper plate, such as permeability and brittleness, in the vicinity of the plate boundary control deep fluid transport and influence seismic activities such as DLFEs or micro-seismicity.\u003c/p\u003e","manuscriptTitle":"Contributionof subsurface fluids to tectonic activities beneath the Kii Peninsula, southwestern part of Japan","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-10-06 12:18:19","doi":"10.21203/rs.3.rs-7562430/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":"24d7d684-52e6-4b8f-95c0-9c34daba7660","owner":[],"postedDate":"October 6th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-04-09T04:26:51+00:00","versionOfRecord":[],"versionCreatedAt":"2025-10-06 12:18:19","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7562430","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7562430","identity":"rs-7562430","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}