{"id":2927,"date":"2020-08-07T11:59:16","date_gmt":"2020-08-07T02:59:16","guid":{"rendered":"http:\/\/www.eri.u-tokyo.ac.jp\/en\/?p=2927"},"modified":"2020-08-07T12:00:29","modified_gmt":"2020-08-07T03:00:29","slug":"overpressured-underthrust-sediment-in-the-nankai-trough-forearc-inferred-from-transdimensional-inversion-of-high%e2%80%90frequency-teleseismic-waveforms","status":"publish","type":"post","link":"https:\/\/www.eri.u-tokyo.ac.jp\/en\/research\/2927\/","title":{"rendered":"Overpressured Underthrust Sediment in the Nankai Trough Forearc Inferred From Transdimensional Inversion of High\u2010Frequency Teleseismic Waveforms"},"content":{"rendered":"\n<p style=\"text-align:center\"><a href=\"https:\/\/doi.org\/10.1029\/2020GL088280\">https:\/\/doi.org\/10.1029\/2020GL088280<\/a><\/p>\n\n\n\n<p style=\"text-align:center\">\u00b9Takeshi Akuhara\u3000\u00b2Takeshi Tsuji\u3000\u00b3Takashi Tonegawa<\/p>\n\n\n\n<p style=\"text-align:center\">\u00b9Earthquake Research Institute, University of Tokyo\u3000\u00b2 Department of Earth Resources Engineering, Kyushu University  \u00b3JAMSTEC  <\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"d4889184\">Abstract<\/h2>\n\n\n\n<p>Active\u2010source seismic surveys have resolved the fine\u2010scale\u00a0<em>P<\/em>\u2010wave velocity (<em>V\u00a0<\/em><sub>p<\/sub>) of the subsurface structure in subduction forearcs. In contrast, the\u00a0<em>S<\/em>\u2010wave velocity (<em>V\u00a0<\/em><sub>s<\/sub>) structure is poorly resolved despite its usefulness in understanding rock properties. This study estimates\u00a0<em>V\u00a0<\/em><sub>p<\/sub>\u00a0and\u00a0<em>V\u00a0<\/em><sub>s<\/sub>\u00a0structures of the Nankai Trough forearc, by applying transdimensional inversion to high\u2010frequency teleseismic waveforms. As a result, a thin (\u223c1\u00a0km) low\u2010velocity zone (LVZ) is evident at\u00a0\u223c6\u00a0km depth beneath the sea level, which is located ~3\u00a0km seaward from the outer ridge. Based on its high\u00a0<em>V\u00a0<\/em><sub>p<\/sub>\/<em>V\u00a0<\/em><sub>s<\/sub>\u00a0ratio (\u223c2.5) and comparison to an existing seismic reflection profile, we conclude that this LVZ reflects a high pore pressure zone at the upper portion of the underthrust sediment. We infer that this overpressured underthrust sediment hosts slow earthquake activities and that accompanied strain release helps impede coseismic rupture propagation further updip.<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img loading=\"lazy\" decoding=\"async\" width=\"837\" height=\"786\" src=\"http:\/\/www.eri.u-tokyo.ac.jp\/en\/wp-content\/uploads\/sites\/2\/2020\/08\/1.png\" alt=\"\" class=\"wp-image-2928\" srcset=\"https:\/\/www.eri.u-tokyo.ac.jp\/en\/wp-content\/uploads\/sites\/2\/2020\/08\/1.png 837w, https:\/\/www.eri.u-tokyo.ac.jp\/en\/wp-content\/uploads\/sites\/2\/2020\/08\/1-300x282.png 300w, https:\/\/www.eri.u-tokyo.ac.jp\/en\/wp-content\/uploads\/sites\/2\/2020\/08\/1-768x721.png 768w, https:\/\/www.eri.u-tokyo.ac.jp\/en\/wp-content\/uploads\/sites\/2\/2020\/08\/1-500x470.png 500w\" sizes=\"(max-width: 709px) 85vw, (max-width: 909px) 67vw, (max-width: 984px) 61vw, (max-width: 1362px) 45vw, 600px\" \/><\/figure>\n","protected":false},"excerpt":{"rendered":"<p>https:\/\/doi.org\/10.1029\/2020GL088280 \u00b9Takeshi Akuhara\u3000\u00b2Takeshi Tsuji\u3000\u00b3Takashi Tonegawa \u00b9Earthquake Research In &hellip; <a href=\"https:\/\/www.eri.u-tokyo.ac.jp\/en\/research\/2927\/\" class=\"more-link\">Continue reading<span class=\"screen-reader-text\"> &#8220;Overpressured Underthrust Sediment in the Nankai Trough Forearc Inferred From Transdimensional Inversion of High\u2010Frequency Teleseismic Waveforms&#8221;<\/span><\/a><\/p>\n","protected":false},"author":9,"featured_media":2928,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[11],"tags":[],"class_list":["post-2927","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-research"],"_links":{"self":[{"href":"https:\/\/www.eri.u-tokyo.ac.jp\/en\/wp-json\/wp\/v2\/posts\/2927"}],"collection":[{"href":"https:\/\/www.eri.u-tokyo.ac.jp\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.eri.u-tokyo.ac.jp\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.eri.u-tokyo.ac.jp\/en\/wp-json\/wp\/v2\/users\/9"}],"replies":[{"embeddable":true,"href":"https:\/\/www.eri.u-tokyo.ac.jp\/en\/wp-json\/wp\/v2\/comments?post=2927"}],"version-history":[{"count":2,"href":"https:\/\/www.eri.u-tokyo.ac.jp\/en\/wp-json\/wp\/v2\/posts\/2927\/revisions"}],"predecessor-version":[{"id":2930,"href":"https:\/\/www.eri.u-tokyo.ac.jp\/en\/wp-json\/wp\/v2\/posts\/2927\/revisions\/2930"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.eri.u-tokyo.ac.jp\/en\/wp-json\/wp\/v2\/media\/2928"}],"wp:attachment":[{"href":"https:\/\/www.eri.u-tokyo.ac.jp\/en\/wp-json\/wp\/v2\/media?parent=2927"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.eri.u-tokyo.ac.jp\/en\/wp-json\/wp\/v2\/categories?post=2927"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.eri.u-tokyo.ac.jp\/en\/wp-json\/wp\/v2\/tags?post=2927"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}