Array analysis using circular-wave-front geometry: an application to locate the nearby seismo-volcanic source

The zero-lag cross-correlation technique, used for array analysis in the hy pothesis of plane waves, has been modified to allow the wave front to be ci rcular. Synthetic tests have been performed to check the capability of the method, which returns the input test data when the source-array distances a re not greater than two or three times the array aperture. For this distanc e range the method furnishes an estimate of the apparent velocity and the e picentral coordinates of the source. For more distant sources the method be comes equivalent to that based on the planar-wave approximation, which give s an estimate of the backazimuth to the source and the apparent velocity. T he method has been applied to seismic data recorded at the active volcano l ocated at Deception Island, Antarctica. 35 volcanic long-period events occu rring in a small swarm were selected. Results show that the epicentres are close to the array (between 0.4 and 2 km) and aligned in a SW direction, in agreement with one of the main directions of the fracture system of Decept ion volcano.