Fault zone properties affecting the rupture evolution of the 2009 (Mw 6.1) L’Aquila earthquake (central Italy): Insights from seismic tomography

Abstract

We have inverted P‐ and S‐wave travel times from seismograms recorded by a dense local network to infer the velocity structure in the crustal volume where the April 6th 2009 main shock nucleated. The goal is to image local variations of P‐wave velocity and Poisson ratio along the main shock fault zone for interpreting the complexity of the rupture history. The initial stages of the mainshock rupture are characterized by an emergent phase (EP) followed by an impulsive phase (IP) 0.87 s later. The EP phase is located in a very high VP and relatively low Poisson ratio (n) region. The IP phase marks the beginning of the large moment release and is located outside the low n volume. The comparison between the spatial variations of VP and Poisson ratio within the main shock nucleation volume inferred in this study with the rupture history imaged by inverting geophysical data allows us to interpret the delayed along strike propagation in terms of heterogeneity of lithology and material properties