A new approach to construct 3-D crustal shear-wave velocity models: method description and application to the Central Alps

Abstract We develop a new inversion approach to construct 3-D structural and shear-wave velocity model of the crust based on teleseismic P-to-S converted waves. The proposed does not require local earthquakes such as body wave tomography, nor large aperture seismic network ambient noise but three-component station with spacing similar expected crustal thickness. main features method are: (1) novel parametrization mesh nodes that are fixed in horizontal directions can flexibly vary vertically; (2) implementation both sharp changes across discontinuities smooth gradients; (3) an accurate ray propagator respects Snell’s law at any interface geometry. Model parameters inverted using stochastic composed simulated annealing followed by pattern search algorithm. first application is carried out over Central Alps, where long-standing permanent temporary AlpArray Seismic Network stations provide ideal coverage. For this study we invert 4 independent parameters, which Moho discontinuity depth, Conrad P-velocity change average Vp/Vs crust. results clearly image roots Alpine orogen, including Ivrea Geophysical Body. lower crust's thickness appears fairly constant. Average ratios relatively higher beneath low-Vp/Vs area northern foreland seems correlate earthquakes, be related mechanical differences rock properties, probably inherited. Our agreement those found though our inherently performs better localizing discontinuities. Future developments technique incorporate joint inversions, well more efficient parameter space exploration.