Seismic tomography of the Gulf of Corinth: a comparison of methods

摘要: At a local scale, travel-time tomography requires simultaneous inversion of earthquake positions and velocity structure. We applied joint iterative scheme where medium parameters hypocenter were inverted simultaneously. each step the inversion, rays between hypocenters stations traced, new partial derivatives estimated scaling was performed as well. The large sparse linear system modified by solved LSQR method at iteration. compared performances two different forward techniques. Our first approach fast ray tracing based on paraxial to solve two-point boundary value problem. connect sources in structure described 3D B-spline interpolation over regular grid. second is finite-difference solution eikonal equation with are differently depending method. reconstructed images sensitive spatial variation shown synthetic examples. aldo found that involved be important recovering accurate amplitudes anomalies. This five through examples real configuration sources. also it necessary scale Pand S velocities order recover better anomaly. crustal 50X50X20 km domain near Patras Gulf Corinth (Greece) recovered using microearthquake data. These data recorded during field experiment 1991 dense network 60 digital deployed. microearthquakes widely distributed under enabled us perform reliable arrival P travel-times. obtained this seismically active zone show south/north asymmetry agreement tectonic context. transition high lies 6 9 indicating very thin crust related extension regime.At regime.