1D VELOCITY MODEL FOR NORTHERN PERU USING LOCAL EARTHQUAKE DATA

We compute a new 1D velocity model for northern Peru by inverting the  arrival times of P and S waves. We follow the methodology based on the non-linear inversion using the Veslest algorithm. We use 1593 local earthquakes recorded during six years (1996-2001) by a local seismic network. The inversion was carried out using 2897 arrivals of P and S waves, corresponding to 547 earthquakes. We evaluated several models considering different velocities and thicknesses layer, this process allowed us to obtain 12 well-defined models that were re-evaluated through the earthquakes relocation. We selected a model that which showed reduction in the location and the root mean square (rms).
The 1D velocity model that we propose consists of six layers with velocities of Vp = 5.66 km/s for the first layer, to 7.92 km/s for the last one. This model defines the boundary between the crust and mantle (Mohorovicic) at a depth of 45 km below our study area. The earthquake relocation shows a better distribution of hypocenters in surface and depth and also shows a reduction of 35% in the rms values. This model constitutes a major contribution to the knowledge of the structure velocity in northern Peru and can be used as a reference in software for earthquake location, as well as in seismicity, tectonics and seismic risk studies in northern Peru.
Published in: Boletín de la Sociedad Geologica del Perú