Plumbing System of Pacaya Volcano, Guatemala Revealed by 3D P-wave Tomography

Abstract:

Pacaya volcano, in Guatemala, is a basaltic stratovolcano that has been persistently active since 1961. Both effusive and explosive eruptions have built a young cone on the west side of the older volcanic complex and over an ancestral collapse scarp on the western flanks. Over the last two years Pacaya has experienced increased volcanic activity, including energetic strombolian eruptions, lava flows and continuous passive degassing. In January 2015, we installed a temporary seismic network consisting of 19 three-component, short-period sensors, and 2 three-element triangular infrasound arrays. During the two weeks of network operation, the volcano was constantly degassing, and incandescence at the summit was reported by local guides. In addition to seismic tremor, about 300 local events were detected. Spectrograms show a high frequency content, up to 10 Hz. Initial locations suggest the data are suitable for tomographic imaging of the cone. Tomographic modeling of the 3D P-wave structure is underway and results will be presented. The tomographic model will delineate the boundary between the older volcanic complex and the overlying cone, which is thought to represent a zone of weakness susceptible to failure. In addition, the velocity model will provide insight into the sources of deformation observed with GPS data since 2009.