{"title":"近海地震仪网络和三维地震速度结构模型对近海地震中心矩张量分析的影响:日本海沟俯冲带的应用","authors":"Lina Yamaya, Hisahiko Kubo, Katsuhiko Shiomi, Shunsuke Takemura","doi":"10.1029/2024jb029944","DOIUrl":null,"url":null,"abstract":"Recently, a widespread and densely continuous-recording ocean-bottom seismograph network has been deployed in the Japan Trench subduction zone. Utilizing the offshore network data improves azimuthal station coverage for offshore earthquakes in the Japan Trench subduction zone. It has a potential to obtain centroid moment tensor (CMT) solutions more accurately than conventional analyses using onshore networks and a simple one-dimensional seismic velocity structure model. In this study, we conducted CMT inversion for subduction zone earthquakes that occurred between 1 April 2017, and 31 March 2024, with a moment magnitude range of 5.2–7.0. We used seismograms obtained from both the offshore and onshore networks. We calculated Green's functions using a three-dimensional seismic velocity structure model. Our CMT solutions with thrust-type mechanisms mostly indicated depths and dip angles consistent with the plate interface. For earthquakes in the outer-rise region, our CMT solutions were characterized as normal-fault mechanisms. The joint use of the offshore and onshore networks reduced the estimation errors of the CMT solutions compared with the only use of the onshore network, although the optimal solutions were consistent. The dip angles for the thrust earthquakes determined by our analysis were more consistent with the dip angle of the plate boundary than those determined by conventional CMT analyses. Additionally, we found that the conventional CMT analysis could introduce a systematic bias in depth and magnitude determinations. This finding highlights the importance of an offshore seismograph network and a reliable seismic velocity structure model for CMT inversions.","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":null,"pages":null},"PeriodicalIF":3.9000,"publicationDate":"2024-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Impact of the Offshore Seismograph Network and 3-D Seismic Velocity Structure Model on Centroid Moment Tensor Analysis for Offshore Earthquakes: Application to the Japan Trench Subduction Zone\",\"authors\":\"Lina Yamaya, Hisahiko Kubo, Katsuhiko Shiomi, Shunsuke Takemura\",\"doi\":\"10.1029/2024jb029944\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"Recently, a widespread and densely continuous-recording ocean-bottom seismograph network has been deployed in the Japan Trench subduction zone. Utilizing the offshore network data improves azimuthal station coverage for offshore earthquakes in the Japan Trench subduction zone. It has a potential to obtain centroid moment tensor (CMT) solutions more accurately than conventional analyses using onshore networks and a simple one-dimensional seismic velocity structure model. In this study, we conducted CMT inversion for subduction zone earthquakes that occurred between 1 April 2017, and 31 March 2024, with a moment magnitude range of 5.2–7.0. We used seismograms obtained from both the offshore and onshore networks. We calculated Green's functions using a three-dimensional seismic velocity structure model. Our CMT solutions with thrust-type mechanisms mostly indicated depths and dip angles consistent with the plate interface. For earthquakes in the outer-rise region, our CMT solutions were characterized as normal-fault mechanisms. The joint use of the offshore and onshore networks reduced the estimation errors of the CMT solutions compared with the only use of the onshore network, although the optimal solutions were consistent. The dip angles for the thrust earthquakes determined by our analysis were more consistent with the dip angle of the plate boundary than those determined by conventional CMT analyses. Additionally, we found that the conventional CMT analysis could introduce a systematic bias in depth and magnitude determinations. This finding highlights the importance of an offshore seismograph network and a reliable seismic velocity structure model for CMT inversions.\",\"PeriodicalId\":15864,\"journal\":{\"name\":\"Journal of Geophysical Research: Solid Earth\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":3.9000,\"publicationDate\":\"2024-11-08\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Journal of Geophysical Research: Solid Earth\",\"FirstCategoryId\":\"89\",\"ListUrlMain\":\"https://doi.org/10.1029/2024jb029944\",\"RegionNum\":2,\"RegionCategory\":\"地球科学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q1\",\"JCRName\":\"GEOCHEMISTRY & GEOPHYSICS\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Geophysical Research: Solid Earth","FirstCategoryId":"89","ListUrlMain":"https://doi.org/10.1029/2024jb029944","RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"GEOCHEMISTRY & GEOPHYSICS","Score":null,"Total":0}
Impact of the Offshore Seismograph Network and 3-D Seismic Velocity Structure Model on Centroid Moment Tensor Analysis for Offshore Earthquakes: Application to the Japan Trench Subduction Zone
Recently, a widespread and densely continuous-recording ocean-bottom seismograph network has been deployed in the Japan Trench subduction zone. Utilizing the offshore network data improves azimuthal station coverage for offshore earthquakes in the Japan Trench subduction zone. It has a potential to obtain centroid moment tensor (CMT) solutions more accurately than conventional analyses using onshore networks and a simple one-dimensional seismic velocity structure model. In this study, we conducted CMT inversion for subduction zone earthquakes that occurred between 1 April 2017, and 31 March 2024, with a moment magnitude range of 5.2–7.0. We used seismograms obtained from both the offshore and onshore networks. We calculated Green's functions using a three-dimensional seismic velocity structure model. Our CMT solutions with thrust-type mechanisms mostly indicated depths and dip angles consistent with the plate interface. For earthquakes in the outer-rise region, our CMT solutions were characterized as normal-fault mechanisms. The joint use of the offshore and onshore networks reduced the estimation errors of the CMT solutions compared with the only use of the onshore network, although the optimal solutions were consistent. The dip angles for the thrust earthquakes determined by our analysis were more consistent with the dip angle of the plate boundary than those determined by conventional CMT analyses. Additionally, we found that the conventional CMT analysis could introduce a systematic bias in depth and magnitude determinations. This finding highlights the importance of an offshore seismograph network and a reliable seismic velocity structure model for CMT inversions.
期刊介绍:
The Journal of Geophysical Research: Solid Earth serves as the premier publication for the breadth of solid Earth geophysics including (in alphabetical order): electromagnetic methods; exploration geophysics; geodesy and gravity; geodynamics, rheology, and plate kinematics; geomagnetism and paleomagnetism; hydrogeophysics; Instruments, techniques, and models; solid Earth interactions with the cryosphere, atmosphere, oceans, and climate; marine geology and geophysics; natural and anthropogenic hazards; near surface geophysics; petrology, geochemistry, and mineralogy; planet Earth physics and chemistry; rock mechanics and deformation; seismology; tectonophysics; and volcanology.
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