HR: 17:00h
AN: V14B-05    [Abstracts]
TI: Precise Hypocenter Location of High-Frequency-Onset Earthquakes, Tomography, and Changing Stress Conditions Beneath Soufriere Hills Volcano, Montserrat
AU: * Miller, V
EM: vmiller@geosc.psu.edu
AF: Dept of Geosciences, Pennsylvania State University, University Park, State College, PA 16802 United States
AU: Thompson, G
AF: British Geological Survey, Kingsley Dunham Centre, Nicker Hill, Keyworth, NG12 5GG United Kingdom
AU: Voight, B
EM: voight@essc.psu.edu
AF: Dept of Geosciences, Pennsylvania State University, University Park, State College, PA 16802 United States
AU: Ammon, C
EM: cammon@geosc.psu.edu
AF: Dept of Geosciences, Pennsylvania State University, University Park, State College, PA 16802 United States
AB: The andesite stratovolcano of Soufriere Hills (SHV), Montserrat, has been intermittently erupting now for 9 years. Previous work (Aspinall et al., 1998) has examined hypocenter locations for events 1995 - 1997 to map possible magma migration pathways and domains sensitive to stress redistributions caused by magmatic processes. This indicated a NE-SW alignment of epicenters under the NE flank, and nests occurring under the volcano, and 3 km W of SHV. Recent instrumentation at SHV with hardware by the CALIPSO Project (Voight et al., 2003; Mattioli et al., 2003) have made it desirable to re-examine the seismic database to more precisely constrain the magma storage and transport system, and stress changes which have occurred during eruption activity. Recent developments have allowed more precise hypocenter relocations using relative positioning techniques. Studies using such methods (e.g., Prejean et al., 2002) have demonstrated improvements in location precision, with distinct lineaments emerging where previous techniques had merely identified earthquake clusters. Therefore we have examined seismic data at SHV utilizing the Waldhauser and Ellsworth (2000) precise relocation technique. The aim of the study is to provide clarification of distinct structures that may have influenced magmatic processes, and which might influence the modeling of crustal strains as deduced by CALIPSO data. Velocity structure is examined, and fault plane solutions are also explored to detect any stress changes that have occurred in concert with pulsatory magmatic pressure episodes. Examination of the data for both spatial and temporal patterns provides constraints on magma storage and transport dynamics at SHV.
DE: 8400 VOLCANOLOGY
DE: 8419 Eruption monitoring (7280)
DE: 7280 Volcano seismology (8419)
DE: 1749 Volcanology, geochemistry, and petrology
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting