The Seismological Search for Magma

Abstract

Seismological methods provide the highest resolution exploration tools in the search for magma in volcanic and geothermal areas. Active techniques such as refraction and reflection use man made controlled sources to illuminate the absolute velocity structure of the upper crust. Recently, multiple explosions coupled with dense seismic arrays have provided detailed three dimensional images of the upper crust from inversion of P wave travel times. Passive techniques such as teleseiscmic P wave residual inversion image the deeper velocity structure of the crust and upper mantle beneath volcanic and geothermal areas. Local earthquakes within or very near such areas provide energy sources that can be used effectively to illuminate in detail two or three dimensional variations in velocity and attenuation structure. In combination, all of these seismic techniques can contribute to our understanding of the crust beneath volcanic and geothermal areas and of the structural setting of the associated geothermal systems. In several cases, the geometry of underlying magma bodies has been delineated successfully.