Ball-and-socket tectonic rotation during the 2013 Mw7.7 Balochistan earthquake

Earth and Planetary Science Letters
By: , and 

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Abstract

The September 2013 Mw7.7 Balochistan earthquake ruptured a ∼200-km-long segment of the curved Hoshab fault in southern Pakistan with 10±0.2 m of peak sinistral and ∼1.7±0.8 m of dip slip. This rupture is unusual because the fault dips 60±15° towards the focus of a small circle centered in northwest Pakistan, and, despite a 30° increase in obliquity along strike, the ratios of strike and dip slip remain relatively uniform. Surface displacements and geodetic and teleseismic source inversions quantify a bilateral rupture that propagated rapidly at shallow depths from a transtensional jog near the northern end of the rupture. Static friction prior to rupture was unusually weak (μ<0.05), and friction may have approached zero during dynamic rupture. Here we show that the inward-dipping Hoshab fault defines the northern rim of a structural unit in southeast Makran that rotates – akin to a 2-D ball-and-socket joint – counter-clockwise in response to India's penetration into the Eurasian plate. This rotation accounts for complexity in the Chaman fault system and, in principle, reduces seismic potential near Karachi; nonetheless, these findings highlight deficiencies in strong ground motion equations and tectonic models that invoke Anderson–Byerlee faulting predictions.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Ball-and-socket tectonic rotation during the 2013 Mw7.7 Balochistan earthquake
Series title Earth and Planetary Science Letters
DOI 10.1016/j.epsl.2014.07.001
Volume 403
Year Published 2014
Language English
Publisher Elsevier
Contributing office(s) Geologic Hazards Science Center
Description 7 p.
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Earth and Planetary Science Letters
First page 210
Last page 216
Country Pakistan
State Balochistan