A new P-velocity model for the Tethyan margin from a scaled S-velocity model and the inversion of P- and PKP-delay times

Abstract

We estimate a 3D P-velocity model for the Tethyan margin by inverting P- and PKP-delay times. The inversion is relative to a 3D reference model, which is a scaled S-velocity model for the same region. This S-velocity model was derived by jointly inverting regional S and Rayleigh waveform fits, teleseismic arrival times, Rayleigh-wave group velocities, and independent Moho constraints. Thus, our 3D reference model includes structures resolved over a larger depth range as well as more information on aseismic regions with few stations than is typically obtained from traditional teleseismic delay time inversions. We then inverted P- and PKP-delay times to obtain perturbations relative to the scaled 3D reference model. Comparing our P-velocity model (EAPV11) with P-velocity models derived from P data only, we find a model with more uniform and better depth resolution, including velocity anomalies for aseismic regions with few stations such as North Africa, southeastern Arabia, and the East European platform. Using EAPV11 to predict arrival times for relatively accurately located events that were not used in the inversion shows that our model produces significant variance reductions for these data as well. Therefore, our approach to build P-velocity models based on 3D reference S-velocity models may provide a practical way to better estimate P-velocity anomalies in the uppermost mantle and beneath aseismic regions with few stations.