The role of fluids in earthquake swarms in northeastern Noto Peninsula, central Japan: Insights from source mechanisms

The role of fluids in earthquake swarms in northeastern Noto Peninsula, central Japan: Insights from source mechanisms | 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 The role of fluids in earthquake swarms in northeastern Noto Peninsula, central Japan: Insights from source mechanisms Sayaka Takano, Yoshihiro Hiramatsu, Yohei Yukutake This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4560873/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 26 Nov, 2024 Read the published version in Earth, Planets and Space → Version 1 posted 5 You are reading this latest preprint version Abstract A prolonged earthquake swarm has persisted since June 2018 in northeastern Noto Peninsula (central Japan), with activity focused into distinct southern, western, northern, and eastern clusters. To explore the role of fluids in the occurrence of this swarm, we analyzed the focal mechanisms of the earthquakes occurring from 1 January 2018 to 30 November 2022 and performed stress tensor inversions. The western, northern, and eastern clusters were dominated by a reverse fault-type mechanism with a horizontal P-axis oriented NW–SE. One of the nodal planes of those mechanisms aligns closely with the precisely relocated hypocenter distribution. The stress fields in these three clusters, as determined by stress tensor inversion, have maximum principal stresses oriented horizontally in the NW–SE direction and minimum principal stressesoriented vertically, aligning with the regional stress field. From these focal mechanisms and this stress field, we derived small misfit angles and large slip tendencies. These findings suggest that, in these three clusters, fluids diffused into faults largely aligned with the regional stress field, resulting in earthquakes with compatible focal mechanisms. Conversely, normal and lateral fault-type focal mechanisms, which are unfavorable to the regional stress field, dominated in the southern cluster. The estimated stress fields, deviating from the regional stress field, have maximum principal stressescloser to vertical and minimum principal stress oriented horizontally in the ENE–WSW direction. Misfit angles for earthquakes deeper than 15 km in the southern cluster are smaller for the local stress field than for the regional stress field, but the slip tendency is generally small for most earthquakes. These results suggest that earthquakes in the southern cluster, especially those deeper than 15 km, occurred on misoriented fault planes due to elevated pore fluid pressures. These findings provide strong evidence of the ascent of high-pore-pressure fluids from depth in the southern cluster and their subsequent diffusion into a southeast-dipping fault zone. fluid pressure stress filed stress tensor inversion misfit angle slip tendency Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Full Text Supplementary Files Additionalfile.pdf TableS1.xlsx Cite Share Download PDF Status: Published Journal Publication published 26 Nov, 2024 Read the published version in Earth, Planets and Space → Version 1 posted Editorial decision: Major Revision 23 Jul, 2024 Reviewers agreed at journal 26 Jun, 2024 Reviewers invited by journal 26 Jun, 2024 Editor assigned by journal 21 Jun, 2024 First submitted to journal 16 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. 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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-4560873","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":319506227,"identity":"48adffe3-1331-4a2a-b446-258c6e647ef3","order_by":0,"name":"Sayaka Takano","email":"","orcid":"","institution":"Kanazawa University: Kanazawa Daigaku","correspondingAuthor":false,"prefix":"","firstName":"Sayaka","middleName":"","lastName":"Takano","suffix":""},{"id":319506228,"identity":"17341e7d-46fc-46cb-b520-ae61c7a237dd","order_by":1,"name":"Yoshihiro Hiramatsu","email":"data:image/png;base64,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","orcid":"https://orcid.org/0000-0001-9874-5059","institution":"Kanazawa University","correspondingAuthor":true,"prefix":"","firstName":"Yoshihiro","middleName":"","lastName":"Hiramatsu","suffix":""},{"id":319506229,"identity":"d76f80d9-0f5d-4d9d-a13b-4e43cc7f7ef7","order_by":2,"name":"Yohei Yukutake","email":"","orcid":"","institution":"University of Tokyo: Tokyo Daigaku","correspondingAuthor":false,"prefix":"","firstName":"Yohei","middleName":"","lastName":"Yukutake","suffix":""}],"badges":[],"createdAt":"2024-06-11 03:10:08","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4560873/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4560873/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s40623-024-02099-0","type":"published","date":"2024-11-26T15:56:53+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":60541261,"identity":"d11c3e63-903d-480d-940d-d2acfd0695e7","added_by":"auto","created_at":"2024-07-18 02:25:29","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":120627,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Map locating northeastern Noto Peninsula. (b) The distribution of seismic stations used in\u003c/p\u003e\n\u003cp\u003ethis study (squares). The rectangle indicates the area shown in (c). (c) The distribution of relocated\u003c/p\u003e\n\u003cp\u003eearthquakes with MJMA ≥ 1.2 between 1 January 2018 and 30 November 2022 (Nishimura et al. 2023).\u003c/p\u003e\n\u003cp\u003eRectangles define the four clusters (S, W, N, and E) of the earthquake swarm in northeastern Noto\u003c/p\u003e\n\u003cp\u003ePeninsula. Red lines are active faults (Inoue and Okamura 2010; Ozaki 2010).\u003c/p\u003e","description":"","filename":"Figs1.png","url":"https://assets-eu.researchsquare.com/files/rs-4560873/v1/d5bc8d923d742d2a712823a5.png"},{"id":60541639,"identity":"4d447073-076c-46b0-956b-36e83eb8c5a0","added_by":"auto","created_at":"2024-07-18 02:33:29","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":247190,"visible":true,"origin":"","legend":"\u003cp\u003eThe distribution of focal mechanisms (beach ball diagrams) estimated in this study: (a) cluster\u003c/p\u003e\n\u003cp\u003eN, (b) cluster E, (c) cluster W, and (d) cluster S. Colors represent focal depths. Colored circles are\u003c/p\u003e\n\u003cp\u003erelocated hypocenters (Nishimura et al. 2023). Black lines indicate the cross-sectional profiles shown\u003c/p\u003e\n\u003cp\u003ein Fig. 3.\u003c/p\u003e","description":"","filename":"Figs2.png","url":"https://assets-eu.researchsquare.com/files/rs-4560873/v1/ef37c40f74ae259e40cced68.png"},{"id":60541268,"identity":"13f6b56c-f6f2-4085-a225-599205a3620f","added_by":"auto","created_at":"2024-07-18 02:25:30","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":312493,"visible":true,"origin":"","legend":"\u003cp\u003eThe distribution of focal mechanisms (beach ball diagrams) and relocated hypocenters within\u003c/p\u003e\n\u003cp\u003ethe cross-sectional views along the profiles shown in Fig. 2 for (a) cluster N and (b) cluster E. Bold\u003c/p\u003e\n\u003cp\u003elines in the beach ball diagrams indicate nodal planes with the smallest misfit angle.\u003c/p\u003e","description":"","filename":"Figs3.png","url":"https://assets-eu.researchsquare.com/files/rs-4560873/v1/79f756bc4767b2ad0821414a.png"},{"id":60541265,"identity":"28aac0bb-695f-4aed-9d71-574053fa9fe0","added_by":"auto","created_at":"2024-07-18 02:25:30","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":225635,"visible":true,"origin":"","legend":"\u003cp\u003eResults of our stress tensor inversion for (a) all earthquakes in the swarm, (b) cluster W, (c)\u003c/p\u003e\n\u003cp\u003ecluster N, (d) cluster E, (e) earthquakes in cluster S shallower than 15 km, (f) earthquakes in cluster\u003c/p\u003e\n\u003cp\u003eS deeper than 15 km, and (g) clusters W, N, and E combined. The principal stress axis (black-rimmed\u003c/p\u003e\n\u003cp\u003ecircle) and its 95% confidence range are plotted in the lower hemisphere. Red indicates the 𝜎\u003csub\u003e1\u003c/sub\u003e axis,\u003c/p\u003e\n\u003cp\u003egreen the 𝜎\u003csub\u003e2\u003c/sub\u003e axis, and blue the 𝜎\u003csub\u003e3\u003c/sub\u003e axis.\u003c/p\u003e","description":"","filename":"Figs4.png","url":"https://assets-eu.researchsquare.com/files/rs-4560873/v1/89661291109ded55831f63bd.png"},{"id":60541263,"identity":"c77b9ab8-414f-4994-93b4-cceb452ab952","added_by":"auto","created_at":"2024-07-18 02:25:29","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":148377,"visible":true,"origin":"","legend":"\u003cp\u003eMohr diagrams for earthquakes of (a) cluster W, (b) cluster N, and (c) cluster E. Earthquakes\u003c/p\u003e\n\u003cp\u003ein cluster S are split between (d, f) source depths \u0026lt;15 km and (e, g) source depths ≥15 km. (d, e)\u003c/p\u003e\n\u003cp\u003eCluster S earthquakes calculated under reference stress field estimated by our stress tensor inversion\u003c/p\u003e\n\u003cp\u003eusing the focal mechanisms in clusters W, N, and E. (f, g) Cluster S earthquakes calculated using the\u003c/p\u003e\n\u003cp\u003ereference stress field estimated by our stress tensor inversion using focal mechanisms within\u003c/p\u003e\n\u003cp\u003ecorresponding source depths in cluster S. Black lines shows nearly lithostatic conditions. Smaller\u003c/p\u003e\n\u003cp\u003ecircles within the three Mohr circles are plotted based on the direction of the fault planes (Terakawa\u003c/p\u003e\n\u003cp\u003eet al. 2010). Symbol colors indicate (upper panels) slip tendency and (lower panels) misfit angle.\u003c/p\u003e\n\u003cp\u003eHistograms to the right of each plot show the frequency distribution of (upper panels) slip tendency\u003c/p\u003e\n\u003cp\u003eand (lower panels) misfit angle.\u003c/p\u003e","description":"","filename":"Figs5.png","url":"https://assets-eu.researchsquare.com/files/rs-4560873/v1/9794d41a8c161f243d41c214.png"},{"id":70388602,"identity":"298a86bf-b5b4-43a9-9436-2cefd278180a","added_by":"auto","created_at":"2024-12-02 17:26:44","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":960912,"visible":true,"origin":"","legend":"","description":"","filename":"manusicriptsubmission.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4560873/v1_covered_993dbe16-984d-48d8-8cc8-e11e1e6b53b2.pdf"},{"id":60541267,"identity":"2f1ccf95-04bb-4002-a7db-d9991046711e","added_by":"auto","created_at":"2024-07-18 02:25:30","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":231983,"visible":true,"origin":"","legend":"","description":"","filename":"Additionalfile.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4560873/v1/1a205e83dc2102af5cab6b89.pdf"},{"id":60541264,"identity":"45ff10a9-0cbb-4e6d-866d-d8a03f7f3b4b","added_by":"auto","created_at":"2024-07-18 02:25:29","extension":"xlsx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":29042,"visible":true,"origin":"","legend":"","description":"","filename":"TableS1.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-4560873/v1/80fc4c3f6fb658af5b8e1461.xlsx"}],"financialInterests":"","formattedTitle":"The role of fluids in earthquake swarms in northeastern Noto Peninsula, central Japan: Insights from source mechanisms","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"earth-planets-and-space","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"epsp","sideBox":"Learn more about [Earth, Planets and Space](http://earth-planets-space.springeropen.com)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/epsp/default.aspx","title":"Earth, Planets and Space","twitterHandle":"@SpringerOpen","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"fluid pressure, stress filed, stress tensor inversion, misfit angle, slip tendency","lastPublishedDoi":"10.21203/rs.3.rs-4560873/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4560873/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"A prolonged earthquake swarm has persisted since June 2018 in northeastern Noto Peninsula (central Japan), with activity focused into distinct southern, western, northern, and eastern clusters. To explore the role of fluids in the occurrence of this swarm, we analyzed the focal mechanisms of the earthquakes occurring from 1 January 2018 to 30 November 2022 and performed stress tensor inversions. The western, northern, and eastern clusters were dominated by a reverse fault-type mechanism with a horizontal P-axis oriented NW–SE. One of the nodal planes of those mechanisms aligns closely with the precisely relocated hypocenter distribution. The stress fields in these three clusters, as determined by stress tensor inversion, have maximum principal stresses oriented horizontally in the NW–SE direction and minimum principal stressesoriented vertically, aligning with the regional stress field. From these focal mechanisms and this stress field, we derived small misfit angles and large slip tendencies. These findings suggest that, in these three clusters, fluids diffused into faults largely aligned with the regional stress field, resulting in earthquakes with compatible focal mechanisms. Conversely, normal and lateral fault-type focal mechanisms, which are unfavorable to the regional stress field, dominated in the southern cluster. The estimated stress fields, deviating from the regional stress field, have maximum principal stressescloser to vertical and minimum principal stress oriented horizontally in the ENE–WSW direction. Misfit angles for earthquakes deeper than 15 km in the southern cluster are smaller for the local stress field than for the regional stress field, but the slip tendency is generally small for most earthquakes. These results suggest that earthquakes in the southern cluster, especially those deeper than 15 km, occurred on misoriented fault planes due to elevated pore fluid pressures. These findings provide strong evidence of the ascent of high-pore-pressure fluids from depth in the southern cluster and their subsequent diffusion into a southeast-dipping fault zone.","manuscriptTitle":"The role of fluids in earthquake swarms in northeastern Noto Peninsula, central Japan: Insights from source mechanisms","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-07-18 02:25:25","doi":"10.21203/rs.3.rs-4560873/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Major Revision","date":"2024-07-23T18:06:20+00:00","index":"","fulltext":""},{"type":"reviewerAgreed","content":"","date":"2024-06-26T22:16:58+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-06-26T21:49:21+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-06-21T06:44:58+00:00","index":"","fulltext":""},{"type":"submitted","content":"Earth, Planets and Space","date":"2024-06-16T20:51:49+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"earth-planets-and-space","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"epsp","sideBox":"Learn more about [Earth, Planets and Space](http://earth-planets-space.springeropen.com)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/epsp/default.aspx","title":"Earth, Planets and Space","twitterHandle":"@SpringerOpen","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"831caccb-4a8f-4d58-9178-7c2322782844","owner":[],"postedDate":"July 18th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-12-02T17:21:22+00:00","versionOfRecord":{"articleIdentity":"rs-4560873","link":"https://doi.org/10.1186/s40623-024-02099-0","journal":{"identity":"earth-planets-and-space","isVorOnly":false,"title":"Earth, Planets and Space"},"publishedOn":"2024-11-26 15:56:53","publishedOnDateReadable":"November 26th, 2024"},"versionCreatedAt":"2024-07-18 02:25:25","video":"","vorDoi":"10.1186/s40623-024-02099-0","vorDoiUrl":"https://doi.org/10.1186/s40623-024-02099-0","workflowStages":[]},"version":"v1","identity":"rs-4560873","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4560873","identity":"rs-4560873","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}