Crustal Thickness of Iran Inferred from Converted Waves

Abstract

The Iranian plate is part of the Alpine-Himalayan orogenic belt, which has been formed by the continental collision between the Arabian and Eurasian plates. The present-day Iranian plate is characterized by diverse tectonic domains including mountain belts (e.g. Zagros and Alborz, Kopeh-Dagh) and oceanic plate subduction (e.g. Makran). Here we present the lateral variations of the Moho discontinuity beneath Iran using a detailed P receiver function study. Our results allow for more precise estimations of the crustal thickness and enable us to provide a detailed Moho depth map for all of Iran for the first time. We used the teleseismic events recorded from 1995 to 2011 at 77 national permanent stations (24 broadband and 53 short period stations). Our results show significant variations in the crustal thickness, which are related to the different geological features within Iran. In general, the average crustal thickness beneath Iran is about 40–45 km. A relatively thick crust of about 54 ± 2 km due to the shortening is observed beneath the Alborz mountain ranges. The crust beneath the Alborz zone shows a thickness changing from 47 ± 2 to 45 ± 2 km from west to east and reaches a thickness of about 50 ± 2 km beneath the Kopeh-Dagh mountain range. We find the thinnest crust of about 33 ± 2 km beneath the Makran subduction zone in southeast Iran showing a normal continental crust, which has not been influenced by collisional processes. The thickest crust (~66 ± 2 km) is locally observed beneath the Sanandaj-Sirjan Zone, which is considered the suture zone of the collision between the Arabian and Eurasian plates.