Ball-and-socket tectonic rotation during the 2013 Mw7.7 Balochistan earthquake
Earth and Planetary Science Letters
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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.
Suggested Citation
Barnhart, W.D., Hayes, G., Briggs, R., Gold, R.D., and Bilham, R., 2014, Ball-and-socket tectonic rotation during the 2013 Mw7.7 Balochistan earthquake: Earth and Planetary Science Letters, v. 403, p. 210-216, https://doi.org/10.1016/j.epsl.2014.07.001.
| 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 |