Lithospheric seismic structure of the West Alborz - Talesh ranges, Iran

We compute models for lithospheric P- and S-wave velocity structure beneath a transect extending from the South Caspian Basin shoreline, crossing the West Alborz-Talesh ranges to the north of Central Iran block assemblage. The models were derived from regional and teleseismic travel times of compressional and shear seismic phases recorded by a dense temporary array of 17 seismic stations. In contrast to usual teleseismic tomograms, the models have good resolution in the crust due to small interstation spacing (similar to 9 km in average) and Pn constraints employed in the inversion. Two shallow low-velocity anomalies are resolved as evidence of thick sedimentary depocentres in the South Caspian Basin and in the northern edge of Central Iran. Two sharp lateral velocity contrasts in the crust and the upper mantle are observed beneath the Gilan plain and the northern flank of the south Talesh range which we interpret as the boundary between the lithospheric structure of the South Caspian Basin, and that of the south Talesh and Central Iran. The results do not favour underthrusting of the South Caspian Basin beneath Central Iran.