Rupture process at the beginning of the 2007 Chuetsu-oki, Niigata, Japan, earthquake

Hiroshi Takenaka, Yosuke Yamamoto, Hirokazu Yamasaki

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

The rupture process at the beginning stage of the 2007 Chuetsu-oki, Niigata, Japan, earthquake (Mw 6.6) is investigated by analyzing P-wave records from local strong-motion stations. The P-wave portion of the near-source strong-motion records shows about 2 s of small but increasing amplitude arrival (so-called "initial rupture phase") followed by the onset of the main energy release ("main rupture phase"). Two issues are addressed in this paper: (1) where the initial rupture process occurred and (2) where the seismic energy corresponding to the main rupture phase was released at the primary stage of the main rupture. The first issue is addressed by locating the main rupture onset position, and the second issue is then approached by introducing a method for mapping the wave energy onto plausible fault planes. Eventually, the following were revealed. The rupture initiated and propagated on the NW-dipping plane, which is a nodal plane of the focal mechanism solution. At 2.1 s after rupture initiation the subsequent main rupture started at a position of approximately 4 km away, southwestward and updipward from the hypocenter. The main rupture at this stage has two possible rupture planes: the same plane as the initial rupture plane, and the conjugated plane, which shares the main rupture onset point with the initial rupture plane. Although it is difficult to determine which plane was actually ruptured at the primary stage of the main rupture, we found that the possible areas radiating strong wave energy on the two possible planes, which could correspond to the first asperity of this earthquake, are located between the hypocenter and the Kashiwazaki-Kariwa nuclear power plant.

Original languageEnglish
Pages (from-to)279-283
Number of pages5
JournalEarth, Planets and Space
Volume61
Issue number2
DOIs
Publication statusPublished - Jan 1 2009
Externally publishedYes

Keywords

  • 2007 Chuetsu-oki earthquake
  • Asperity
  • Fault plane
  • Initial rupture
  • Source process

ASJC Scopus subject areas

  • Geology
  • Space and Planetary Science

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