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Title: Origin of crustal anisotropy: Shear wave splitting studies in Japan

Abstract

Shear wave splitting manifested as leading shear wave polarization, that is, parallel alignment of leading shear wave particle motions from a variety of sources, has been observed at a number of seismograph stations in Japan. Detected on shear wave seismograms from crustal earthquakes over a wide range of source zones and source-receiver azimuths, the shear wave splitting can be attributed to crustal anisotropy. This paper discusses the relation between leading shear wave polarization directions and tectonic features of Japan. To explain the observed shear wave splitting, the author proposes that at least three phenomena should be taken into account: stress-induced microcracks primarily aligned in vertical or subvertical planes; cracks or fractures in the vicinity of active faults having their orientation parallel to the fault planes; and intrinsic rock anisotropy resulting from preferred orientation of minerals. Travel time differences between leading and slower split shear waves from crustal and upper mantle earthquakes analyzed for about one third of the stations suggest that the crustal anisotropy which causes the observed shear wave splitting may be limited to the upper 15-25 km. This implies that the density of nonhorizontally aligned cracks or fractures below 15-25 km and into the upper mantle is muchmore » smaller than that in the crust above 15-25 km.« less

Authors:
 [1]
  1. Univ. of Tokyo (Japan)
Publication Date:
OSTI Identifier:
5446740
Report Number(s):
CONF-880531-
Journal ID: ISSN 0148-0227; CODEN: JGREA
Resource Type:
Conference
Journal Name:
Journal of Geophysical Research; (United States)
Additional Journal Information:
Journal Volume: 95:B7; Conference: 3. international workshop on seismic anisotropy, Berkeley, CA (United States), 31 May - 4 Jun 1988; Journal ID: ISSN 0148-0227
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; CONTINENTAL CRUST; ANISOTROPY; JAPAN; SEISMIC S WAVES; BIREFRINGENCE; DEPTH; DISTRIBUTION; EARTH MANTLE; EARTHQUAKES; GEOLOGIC FAULTS; GEOLOGIC FRACTURES; GEOLOGIC STRUCTURES; MINERALS; ORIENTATION; POLARIZATION; ROCK MECHANICS; SEISMIC DETECTION; SEISMIC SURVEYS; TECTONICS; TIME DEPENDENCE; TOMOGRAPHY; WAVE PROPAGATION; ASIA; DETECTION; DEVELOPED COUNTRIES; DIAGNOSTIC TECHNIQUES; DIMENSIONS; EARTH CRUST; GEOPHYSICAL SURVEYS; MECHANICS; REFRACTION; SEISMIC EVENTS; SEISMIC WAVES; SURVEYS; 580000* - Geosciences

Citation Formats

Kaneshima, Satoshi. Origin of crustal anisotropy: Shear wave splitting studies in Japan. United States: N. p., 1990. Web.
Kaneshima, Satoshi. Origin of crustal anisotropy: Shear wave splitting studies in Japan. United States.
Kaneshima, Satoshi. Tue . "Origin of crustal anisotropy: Shear wave splitting studies in Japan". United States.
@article{osti_5446740,
title = {Origin of crustal anisotropy: Shear wave splitting studies in Japan},
author = {Kaneshima, Satoshi},
abstractNote = {Shear wave splitting manifested as leading shear wave polarization, that is, parallel alignment of leading shear wave particle motions from a variety of sources, has been observed at a number of seismograph stations in Japan. Detected on shear wave seismograms from crustal earthquakes over a wide range of source zones and source-receiver azimuths, the shear wave splitting can be attributed to crustal anisotropy. This paper discusses the relation between leading shear wave polarization directions and tectonic features of Japan. To explain the observed shear wave splitting, the author proposes that at least three phenomena should be taken into account: stress-induced microcracks primarily aligned in vertical or subvertical planes; cracks or fractures in the vicinity of active faults having their orientation parallel to the fault planes; and intrinsic rock anisotropy resulting from preferred orientation of minerals. Travel time differences between leading and slower split shear waves from crustal and upper mantle earthquakes analyzed for about one third of the stations suggest that the crustal anisotropy which causes the observed shear wave splitting may be limited to the upper 15-25 km. This implies that the density of nonhorizontally aligned cracks or fractures below 15-25 km and into the upper mantle is much smaller than that in the crust above 15-25 km.},
doi = {},
journal = {Journal of Geophysical Research; (United States)},
issn = {0148-0227},
number = ,
volume = 95:B7,
place = {United States},
year = {1990},
month = {7}
}

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