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Estimation of S-wave velocity structures in and around the Sendai Basin, Japan, using array records of microtremors

Toshimi Satoh, Hiroshi Kawase and Shin'ichi Matsushima
Estimation of S-wave velocity structures in and around the Sendai Basin, Japan, using array records of microtremors
Bulletin of the Seismological Society of America (April 2001) 91 (2): 206-218

Abstract

We conducted array measurements of microtremors at six sites in and around the Sendai basin to estimate deep S-wave velocity structures above the seismological bedrock (pre-Tertiary bedrock). After estimating phase velocities of microtremors in the frequency range from about 0.5 to 3 Hz, we succeeded to estimate the deep structures above the pre-Tertiary bedrock at four soil sites (KATA, OKIN, ARAH, and MYG15) and only the upper part just beneath the Pliocene layer at the other soil site (TRMA) using a Rayleigh-wave inversion technique. At TRMA and a rock site TAMA, we roughly estimate the deep S-wave velocity structures using empirical site amplification factors derived from strong-motion records. The deepest bedrock depth is 1 km, and the shallowest depth is 200 m among these six sites. The difference of the bedrock depth between the eastern side and the western side of an active thrust fault, the Nagamachi-Rifu line, is only 120 m. The difference of the bedrock depth between two sites in the east of the basin reaches about 500 m, although any geological boundaries or buried faults have not been mapped. Since the deep S-wave velocity structure of the Sendai basin had been basically unknown, we delineate it for the first time in this article using array measurement of microtremors.


ISSN: 0037-1106
EISSN: 1943-3573
Coden: BSSAAP
Serial Title: Bulletin of the Seismological Society of America
Serial Volume: 91
Serial Issue: 2
Title: Estimation of S-wave velocity structures in and around the Sendai Basin, Japan, using array records of microtremors
Affiliation: Shimizu Corporation, Izumi Research Institute, Tokyo, Japan
Pages: 206-218
Published: 200104
Text Language: English
Publisher: Seismological Society of America, Berkeley, CA, United States
References: 33
Accession Number: 2001-049456
Categories: Seismology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables, geol. sketch maps
N38°16'00" - N38°16'00", E140°52'00" - E140°52'00"
Secondary Affiliation: Kyushu University, JPN, Japan
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute.
Update Code: 200115
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