S-wave velocity zones at the Irazú Volcano (Costa Rica)

Abstract

The Irazú Volcano (83°51′09″ W, 9°58′45″ N) is located in the middle portion of Costa Rica, close to a highly populated area, and is one of the largest volcanoes in Central America. The knowledge of the nature and characteristics of the crust under a volcano like this is important in order to interpret the roots of the volcano and its reservoirs. Based on the data from two seismic monitoring stations located at the Irazú edifice, the analysis of receiver functions obtained, and the study of the calculated S-wave velocity models by inversion of P-wave receiver functions of teleseismic events, we interpret the existence of low-velocity layers under the Irazú volcano, located at a depth between 10 and 30 km. In the same way, we interpret high velocity zones as caused by intrusive bodies related to the ancient Irazú volcanic cycles. We confirm these interpretations based on the petrogenetic results from previous scientific sources and their integration with the models presented here. In order to get information about the nature and dimensions of the low- and high-velocity layers, we correlate velocity profiles and results show irregular and tilted shapes in agreement with present and ancient magma reservoirs.