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Multi‐fault rupture and successive triggering during the 2012 Mw 8.6 Sumatra offshore earthquake
Author(s) -
Zhang Hao,
Chen Jiawei,
Ge Zengxi
Publication year - 2012
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 - 10.1029/2012gl053805
Subject(s) - seismology , geology , intraplate earthquake , fault (geology) , strike slip tectonics , submarine pipeline , transform fault , earthquake rupture , seismic gap , tectonics , geotechnical engineering
On April 11, 2012 a Mw 8.6 strike‐slip earthquake struck the northern Sumatra offshore region, and became the largest intraplate event ever recorded there. Preliminary study results show a remarkably complex rupture pattern, on a fault system manifested by north‐south trending paleo‐transform faults and east‐west striking abyssal hill fabric. To image the rupture pattern of the earthquake, we back‐projected teleseismic P wave recordings observed at three regional seismic networks (EU, AU, and F‐net). Our results indicate that the earthquake ruptured on a conjugate fault system, composed of two subparallel WNW‐ESE trending faults, and a NNE‐SSW striking fault in between, for a duration of at least 120 s. The rupture started at the WNW end of the first WNW‐ESE trending fault located at the east of the conjugate fault system, and propagated toward ESE. It then jumped to the second NNE‐SSW trending fault located west of the first fault, and first extended SSWward and 15 s later NNEward. After its end on the second fault, the rupture jumped onto the third WNW‐ESE trending fault and continued WNWward. The static Coulomb stress changes calculated from the rupture of the first and then the second faults, based on simplified uniform slip models, suggest that initiation of the rupture on the second fault could be statically and dynamically triggered by the first fault. However, the third fault was primarily dynamically triggered by S or even Love waves radiated from the southern branch of the second fault.