Poster of the Southwestern Iran Earthquake of of 09 April 2013 - Magnitude 6.3

Tectonic Summary

The April 9, 2013 M6.3 earthquake in southern Iran occurred as result of northeast-southwest oriented thrust-type motion in the shallow crust of the Arabian plate. The depth and style of faulting in this event are consistent with shortening of the shallow Arabian crust within the Zagros Mountains in response to active convergence between the Arabian and Eurasian plates. Because this event is an intraplate event, occurring almost 300 km south of the main plate boundary, and since the event likely did not break the surface, precise identification of the causative fault is difficult at this time. On a broad scale, the seismotectonics of southern Iran are controlled by active convergence between the Arabian and Eurasian tectonic plates. This motion manifests in two ways: subduction in the Makran which stretches from the mouth of the Persian Gulf eastward into Pakistan, and continental collision in the Zagros Mountains, which stretch from the Makran northward into Iraq and Turkey. The April 9 event occurred within the Zagros fold-and-thrust belt - the portion of the Zagros Mountains that border the north shore of the Persian Gulf. At the latitude of the event, convergence rates between Arabia and Eurasia are approximately 30 mm/yr. The Zagros Mountains experience high rates of seismicity, with thrust-type events similar to the April 9 earthquake and right-lateral strike slip events common. Recent thrust-type events as large as M6 have occurred south of the April 9 epicentral area in the Bandar-e-Abbas region. Highly damaging events such as the 2003 M6.6 Bam earthquake occurred outside of the Zagros Mountains, north of the Makran subduction zone, 660 km to the east of the April 9 event. While the Zagros region experiences high rates of seismicity, large (>M7) surface rupturing earthquakes here are rare. Over the past 40 years, 5 events of M6 or greater have occurred with 300 km of the April 9 earthquake. The closest was an M6.1 right-lateral strike slip event on March 1, 1994, which killed approximately 50 people.

Earthquake Report

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