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Constructing subsurface structures of the Chelungpu fault to investigate mechanisms leading to abnormally large ruptures during the 1999 Chi‐Chi earthquake, Taiwan
Author(s) -
Wang ChienYing,
Li ChienLi,
Lee HsiangChun
Publication year - 2004
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2003gl018323
Subject(s) - geology , seismology , fault (geology) , thrust fault , reflection (computer programming) , far east , active fault , seismic gap , computer science , political science , law , programming language
The Chelungpu fault, a NS oriented thrust fault, was activated by the 1999 Chi‐Chi earthquake (Mw = 7.6), Taiwan. At its northern end, the fault turned east causing an extra 15 km EW branch, which experienced abnormal 9 m surface rupturing. In this paper, we used shallow reflection seismics to investigate the subsurface structure, attempting to find the relationship between the structure and large ruptures. Over 90 short seismic lines were distributed throughout a 10 km × 20 km area. Approximate 3D subsurface structures can be constructed by carefully compiling all seismic profiles with well data. The revealed structural pattern shows that the Chinshui shale, the key‐bed layer on which the Chelungpu fault slips, arises toward the north and becomes quite shallow under the EW branch. This structural variation is believed to be the main factor causing the abnormal rupturing of the Chelungpu fault.