HR: 13:40h
AN: G43A-01 INVITED     [Abstracts]
TI: (Nearly) Silent Earthquakes on Volcanoes
AU: Segall, P
EM: segall@stanford.edu
AF: Geophysics, Stanford University, Stanford, CA 94305 United States
AU: * Desmarais, E
EM: emilyd@pangea.stanford.edu
AF: Geophysics, Stanford University, Stanford, CA 94305 United States
AU: Miklus, A
EM: asta@usgs.gov
AF: Hawaiian Volcano Observatory, U.S. Geological Survey, Volcano, HI 96718 United States
AU: Okubo, P
EM: pokubo@usgs.gov
AF: Hawaiian Volcano Observatory, U.S. Geological Survey, Volcano, HI 96718 United States
AB: Slow, or silent, earthquakes are not restricted to plate boundary zones. Cervellli et al. (Nature, 2002) discovered a slow slip event on Kilauea Volcano, Hawaii that occurred in November 2000. This event, with a moment magnitude of ~ 5.7, had a duration of roughly 36 hours, and slipped a subhorizontal thrust fault at a depth of ~ 5 km. Since that publication, four additional slow earthquakes have been discovered using the Kilauea continuous GPS network. These events are nearly identical to the 2000 event, in pattern of deformation, amplitude, and duration. Inversions for source geometry using simulated annealing place the causative fault in precisely the same location as the 2000 event. In comparison to slow slip events in subduction zones in Cascadia, Japan, Mexico, and elsewhere, the volcanic slow slip events are smaller M_w 5.7 compared to M_w 7 for the larger subduction events, shorter in duration, 1-2 days compared to several years for the Tokai slow slip event, shallower, 5 km as opposed to 30-50 km for most subduction events, and have faster slip rates, ~ 20 m/yr compared to ~ 1 m/yr in Cascadia. The lateral position of the imaged slow event dislocations is directly seaward (updip?) of a prominent, and persistent band of microseismicity on Kilauea. Remarkably, there is a clear increase in seismicity within this region accompanying the slow slip events, although the events (M<3) are far too small to account for the GPS displacements. The temporal and spatial association suggests that the earthquakes are triggered by the otherwise silent slip. We are currently investigating whether non-volcanic tremor also accompanies these slip events.
DE: 1207 Transient deformation (6924, 7230, 7240)
DE: 7280 Volcano seismology (8419)
DE: 8118 Dynamics and mechanics of faulting (8004)
SC: Geodesy [G]
MN: Fall Meeting 2005