Structure of the Western Jaz Murian Forearc Basin, Southeast Iran, Revealed by Autocorrelation and Polarization Analysis of Teleseismic P and S Waves

Abstract

The Jaz Murian Basin in Southeast Iran is a forearc basin that sits on top of the western Makran subduction zone. A recent seismic deployment inside the western Jaz Murian Basin documents extremely strong reverberations between the free surface and the top of the basement. These strong multiples, which hamper studies of deeper structures, carry precious information on the structure of the basin. Here we combine three independent measurements, including teleseismic P/S‐wave coda autocorrelations, P‐wave polarization analysis and receiver functions, to image the architecture of the western Jaz Murian Basin. The S‐wave velocity structure beneath each station is constrained by teleseismic P‐wave polarization analysis and a simple grid search method. In addition, both P‐ and S‐wave reflections are extracted to measure the Poisson's ratio and the thickness of sediments, in addition to P‐ and/or S‐wave velocities. We find that the sedimentary cover has an average thickness of ∼3 km with very low S‐wave velocities around 1.2 km/s. The estimated Vp/Vs ratios are relatively high between 2.23 and 2.52, suggesting that the western Jaz Murian Basin contains unconsolidated recently deposited sediments.