The attenuation structure in the source region of 2007 Noto-Hanto earthquake, northern part of central Japan
Abstract
On March 2007, a shallow inland earthquake of M6.7 struck on the west coast of Noto Peninsula, northern part of central Japan. Temporary seismic observation was deployed by members of universities and research institutes after the main shock. Tsumura et al.(2012) mapped a seismic attenuation (Qp) structure in the source region of the 2007 Noto Hanto earthquake using seismic data from such dense observation network. The results show low-Qp zone in the northwestern part of the main shock fault and high Qp zone in the southeastern part beneath the western coast of the Noto Peninsula. The aftershock hypocenters are located on the plane of the boundary between high and low Qp zones. Beneath the inland area, estimated Qp becomes lower than that of the western coast area. Especially low Qp zone is seen at the main shock fault, where aftershocks' activity is high. The values of the low Qp zone become half of those of surrounding area. In the deeper part, where another seismic activity is seen outside of the main shock fault, Qp values become low. Next we made Qp/Qs estimation for several ray paths by using spectral ratio method. Obtained Qp/Qs for the low Qp zone in the main shock fault is higher than that of the surrounding area. In conjunction with other geophysical data, these attenuation features might be caused by the rupture of the Noto Hanto Earthquake. To detect the temporal change of subsurface structure in and around the source region, we made the other temporary seismic observations in the study area in 2011 and in 2012. In 2011 and 2012 observations, we set 5 or 10 seismic stations, which were located at the same position of 2007 observation. A tentative result for 2012 observation data shows that ray paths having high Qp/Qs concentrated on the west coast area of Noto Peninsula in which estimated Qp/Qs also was high in the 2007 observation.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.S31C2370T
- Keywords:
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- 7230 SEISMOLOGY Seismicity and tectonics;
- 7270 SEISMOLOGY Tomography