Reflection imaging of deep structure beneath Montserrat using microearthquake sources

[1] The SEA-CALIPSO experiment was designed to image structure related to active volcanism beneath the island of Montserrat in the Caribbean. As part of that experiment, over 200 Texan recorders with 5 Hz geophones were deployed in 3 linear arrays at a nominal spacing of 100m, primarily to record an airgun source towed offshore around the island. Because the recorders were operating in continuous mode for three days, a number of shallow microearthquakes under the active summit of Soufriere Hills Volcano (SHV) were also recorded. 20 events were sufficiently well recorded and located that they could be used to identify and map reflections from deep subsurface structure. Here we report on the processing of those recordings as multichannel CMP reflection sources, with emphasis on careful statics correction and coherency enhancement. The resulting reflection images indicate subhorizontal layering at depths between 6 and 19km which we interpret as sills.