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Crustal Velocity Structure in Italy from Analysis of Regional Seismic Waveforms

Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata, 605, Rome 00143, Italy

Lupei Zhu

Department of Earth and Atmospheric Sciences, Saint Louis University, St. Louis, Missouri 63103-2097

Fabrizio Bernardi

Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata, 605, Rome 00143, Italy

Matteo Spada

Institute of Geophysics, ETH-Honggerberg, CH-8093 Zurich, Switzerland

^* Current address: School of Geophysics and Geo-information Systems, China University of Geosciences, Beijing, China; lih{at}cugb.edu.cn.

In this article, we use regional seismic waveforms recorded by the recently installed Istituto Nazionale di Geofisica e Vulcanologia (INGV) national network and the Mediterranean Very Broadband Seismographic Network (MedNet) stations to develop 1D crustal velocity models for the Italian peninsula. About 55,000 P-wave and 35,000 S-wave arrival times from 4727 events are used to derive average seismic parameters in the crust and uppermost mantle. We define four regions, according to geological constraints and recent travel-time tomography results. Based on the average seismic parameters, we combine broadband seismic waveforms and travel times of regional phases to model crustal structures for the four regions by applying the genetic algorithm. Our results indicate smooth velocity gradients with a depth beneath the Apennines and a deep Moho beneath the central Alps. Green’s functions from the regionalized 1D velocity models are used to determine source depths and focal mechanisms for 37 events with a magnitude larger than 3.5 by a grid search technique. Our results show that normal and strike-slip faulting source mechanisms dominate the Apenninic belt and that most thrust faulting events occur in the Adriatic Sea and the outer margin of the northern Apennines.