Crustal characteristics beneath the Tien Shan belt, Central Asia, using the seismic receiver function

Abstract

The crustal structure beneath Tien Shan belt was evaluated using teleseismic waveforms from 20 broadband stations and gravity modeling as well. The crustal thickness varies from 36 km to 68 km where the crust thickens due north and the southwest of Tien Shan, while the central part has a thin crust. The area of interest has Vp/Vs ratio of 1.81 ± 0.025, indicating a mafic crust, detached by Moho from the mantle. Additionally, collision zone between Tien Shan and the Tarim Basin has the thickest crust and highest Φ values. The average Moho sharpness, R (0.17), is comparable to that of the typical crust and decreases due northwest. Stations east of the Talas-Fergana strike-slip fault show low Vp/Vs ratios and anomalously thin crust of about 42 km, probably suggesting delamination of the lower crust. The average Bouguer anomalies are large and negative, particularly near the stations in the southern part of Tien Shan where the elevations are the highest. The study suggests these large negative values beneath Tien Shan are a result of thickening of the lithosphere. Keywords: Crustal structure, Moho, Vp/Vs ratio, Receiver function, Tien Shan