{"id":644,"date":"2016-06-14T10:50:33","date_gmt":"2016-06-14T01:50:33","guid":{"rendered":"http:\/\/www.eri.u-tokyo.ac.jp\/en\/?p=644"},"modified":"2016-06-14T15:29:52","modified_gmt":"2016-06-14T06:29:52","slug":"ocean-influenced-rayleigh-waves-from-outer-rise-earthquakes-and-their-effects-on-durations-of-long-period-ground-motion","status":"publish","type":"post","link":"https:\/\/www.eri.u-tokyo.ac.jp\/en\/research\/644\/","title":{"rendered":"Ocean-influenced Rayleigh waves from outer-rise earthquakes and their effects on durations of long-period ground motion"},"content":{"rendered":"

Shinako Noguchi,1<\/sup> Takuto Maeda2<\/sup> and Takashi Furumura2<\/sup>
\n1<\/sup>Association for the Development of Earthquake Prediction (ADEP)
\n2<\/sup>Earthquake Research Institute, The University of Tokyo<\/p>\n

Geophys. J. Int., 205(2), 1099-1107,\u00a0doi:10.1093\/gji\/ggw074, 2016<\/p>\n

SUMMARY
\nWe investigate the cause of anomalously long duration (>100 s), long-period (T = 13\u201314 s)\u00a0phase packets following the Rayleigh wave, which are observed widely in eastern Japan during\u00a0outer-rise earthquakes. As this phase is not seen in records of interplate earthquakes, the late\u00a0long-period phase is assumed to develop as a result of propagation across the Japan Trench.
\nUsing 3-D finite-difference simulations of seismic wave propagation with a detailed structural\u00a0model that includes seafloor topography and water layers, we demonstrate that the late phase\u00a0could be generated by a fundamental-mode oceanic Rayleigh wave propagating in the deep
\nPacific (at a depth of 6 km), which converts to a fundamental-mode continental Rayleigh wave\u00a0as it crosses the Japan Trench. Our models suggest that the conversion is caused by the change\u00a0in bathymetry. Based on analysis of surface wave dispersion, we confirm that the first arrival of the Rayleigh wave on land can develop from the first higher mode oceanic Rayleigh wave.
\nThe successive arrivals of the two types of Rayleigh waves on land produce ground motions\u00a0with very long durations after outer-rise earthquakes.<\/p>\n

\"maeda_fig1\"<\/a>
Figure 1. Vertical-component displacement seismograms for: (b) an outer-rise event (B in Table 1 and Fig. 1) and (c) a deep interplate event (A in Table 1 and Fig. 1), along a profile from Tohoku to Kanto (straight black line in (a)), with Hi-net stations indicated by black triangles. All waveforms are bandpass filtered at 2\u201320 s and normalized by the maximum of all waves during each event. See Table 2 for additional information about each phase.<\/figcaption><\/figure>\n
\"Fig2.Snapshots
Fig2.Snapshots of vertical-component displacement motions at the surface and seafloor, taken from FDM simulations at times t = 70, 100, 150, 200 and 250 s from the earthquake origin time. Lower panels show cross-sections along the dashed line in the upper panels. (a)\u2013(e) are taken from a simulation with a model that includes water; (f)\u2013(j) are from the corresponding simulation whose model excludes water. Up- and downgoing motions are shown in red and blue, respectively. The yellow star in each plot shows the hypocentre. Phase labels are explained in Table 2. See also Animation S1 in Supplementary Information.<\/figcaption><\/figure>\n

(Click the figure to see animation)<\/p>\n

\nhttp:\/\/www.eri.u-tokyo.ac.jp\/en\/wp-content\/uploads\/sites\/2\/2016\/06\/resize_50_yuv.mp4<\/a><\/video><\/div>\n

 <\/p>\n","protected":false},"excerpt":{"rendered":"

Shinako Noguchi,1 Takuto Maeda2 and Takashi Furumura2 1Association for the Development of Earthquake Predictio … Continue reading “Ocean-influenced Rayleigh waves from outer-rise earthquakes and their effects on durations of long-period ground motion”<\/span><\/a><\/p>\n","protected":false},"author":9,"featured_media":645,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[11],"tags":[],"class_list":["post-644","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\/644"}],"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=644"}],"version-history":[{"count":6,"href":"https:\/\/www.eri.u-tokyo.ac.jp\/en\/wp-json\/wp\/v2\/posts\/644\/revisions"}],"predecessor-version":[{"id":655,"href":"https:\/\/www.eri.u-tokyo.ac.jp\/en\/wp-json\/wp\/v2\/posts\/644\/revisions\/655"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.eri.u-tokyo.ac.jp\/en\/wp-json\/wp\/v2\/media\/645"}],"wp:attachment":[{"href":"https:\/\/www.eri.u-tokyo.ac.jp\/en\/wp-json\/wp\/v2\/media?parent=644"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.eri.u-tokyo.ac.jp\/en\/wp-json\/wp\/v2\/categories?post=644"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.eri.u-tokyo.ac.jp\/en\/wp-json\/wp\/v2\/tags?post=644"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}