Source processes of 15 September 1998 M 5.0 Sendai, Northeastern Japan, earthquake and its M 3.8 foreshock by waveform inversion

Tomomi Okada, Norihito Umino, Yoshihiro Ito, Toru Matsuzawa, Akira Hasegawa, Makoto Kamiyama

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)

Abstract

A moderate earthquake (M 5.0) occurred on 15 September 1998 in Sendai City, northeastern Japan, causing slight damage in a portion of the city. It was located at about 12-km depth on the Nagamachi-Rifu fault, an active reverse fault passing through the center of the city. We investigate rupture processes of the earthquake and its largest foreshock (M 3.8) by an empirical Green's-function method. We use waveform data recorded by nearby dense strong-motion arrays and by short-period and broadband stations. Waveform inversion results for the mainshock show that the spatial extent of its rupture area is about 3 × 3 km2, which is roughly consistent with that of the aftershock area. Most of the moment release was contained in two asperities. Aftershocks precisely relocated by a homogeneous-station method show that their activity is high in areas with a relatively small amount of moment release of the mainshock. Rupture of the largest foreshock (M 3.8) that occurred 6 min before the mainshock started approximately at the mainshock hypocenter. Its rupture area, with a radius of about 300 m, does not strongly overlap with the asperities of the mainshock.

Original languageEnglish
Pages (from-to)1607-1618
Number of pages12
JournalBulletin of the Seismological Society of America
Volume91
Issue number6
DOIs
Publication statusPublished - 2001 Dec 1

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

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