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Earth, Planets and Space

, Volume 55, Issue 5, pp 277–282 | Cite as

Shear-wave splitting analysis of later phases in southwest Japan —A lineament structure detector inside the crust—

Open Access
Article

Abstract

We attempt to detect the lineament structure inside the crust using a shear-wave splitting analysis. A seismicity map suggests several lineaments in southwest Japan. No clear active fault was found to support the lineaments. We researched shear-wave splitting in southwest Japan using two later phases: PpPms and PpSms. The PpPms is a later S-phase, which is reflected at the surface as a P wave, dives again, and reflected and converted from P to S at the Moho boundary. The PpSms is a later arriving S-phase, which is converted from P at the Earth’s surface, and is reflected at the Moho discontinuity before arriving at a seismic station. The PpPms and PpSms phases are used to detect lineament structures inside the crust. The observed polarization directions obtained are ENE-WSW, NE-SW, and N-S with a lateral variation. The directions are not consistent with that of maximum principal stress in the area. The results of shear-wave splitting in southwest Japan could not be explained by crack-induced anisotropy caused by maximum principal stress. The direction NE-SW is consistent with that of the geological lineament structure in this area. The shear-wave splitting is probably caused by the lineament structure inside the crust.

Key words

Shear-wave splitting southwest Japan later phase anisotropy 

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Copyright information

© The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences. 2003

Authors and Affiliations

  1. 1.Earthquake Research InstituteUniversity of TokyoTokyoJapan

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