Further Studies on Three Large Earthquakes in the Makran Subduction Zone Region: The Crustal Velocity and Source Rupture Models

Abstract

Three large earthquakes (2011-01-18 Pakistan Mw 7.2; 2013-04-16 IRAN Mw 7.7; and 2013-09-24 Pakistan Mw 7.8) occurred in the Makran subduction zone north region. This chapter introduces an average crustal model retrieved using Rayleigh wave dispersion data in the three earthquake region and their vicinity, the source rupture modeling results, and some geological background features. The centers of the major ruptures of the 2011 Mw 7.2 and the 2013 Mw 7.7 earthquakes were at depth about 65 km; the major rupture of the shallow 2013 Mw 7.8 earthquake was within the upper crust. The focal mechanisms of the two deep earthquakes were normal type; while the shallow earthquake was a left-lateral strike–slip type with a thrust component. The dipping directions of all the three earthquakes were at northwest directions. The rupture process of the Mw 7.2 earthquake was simple; the Mw 7.7 became complex; while the shallow one was the most complex among the three. The sources of the two deep earthquakes were farther than that of the shallow earthquake to the Makran subduction front. All three earthquakes were in the interception region of the Arabian plate, Indian Plate, and the Eur-Asian Plate. The shallow earthquake occurred along a known fault; while the deeper two may occur along a deep, large, potent fault.