HR: 1340h
AN: T23B-1418    [Abstracts]
TI: Microseismicity in the Lau Basin from T-phases recorded by the LABATTS ocean bottom seismograph experiment
AU: * Conder, J A
EM: conder@seismo.wustl.edu
AF: Washington University, Department of Earth and Planetary Sciences Campus Box 1169, St. Louis, MO 63132, United States
AU: Wiens, D A
EM: doug@kermadec.wustl.edu
AF: Washington University, Department of Earth and Planetary Sciences Campus Box 1169, St. Louis, MO 63132, United States
AU: Heath, S
EM: simon@mantle.wustl.edu
AF: Washington University, Department of Earth and Planetary Sciences Campus Box 1169, St. Louis, MO 63132, United States
AB: We use the 1994 LABATTS Ocean Bottom Seismograph (OBS) array to locate microseismicity within the Lau Basin, delineating intrabasin tectonic, volcanic, and hydrothermal sources. The main line of OBSs was deployed across the Central Lau Spreading Center (CLSC), stretching from the Lau ridge to past the Tonga trench, and several OBSs were deployed off -line. Although the array was not optimally designed for microseismicity studies, a large number of T-phases, were recorded at multiple stations, allowing for hypocenter determination. The OBSs were 4-component broadband stations, and recorded at 32sps for three months in late 1994. Body waves were often recorded for these smaller events at a couple of stations, which are included in the location algorithm, but the larger number of T-phases recorded on the hydrophones typically govern the location hypocenter determinations. Given the large number of T-wave arrivals and the difficulty in precisely picking these largely non-impulsive seismic signals, we automate the picking by performing a gridsearch over the basin and stacking the envelopes of the time-shifted data, for predicted relative arrival times at each station in the experiment layout. After initial hypocenter determination, we re-locate each of the hypocenters in a weighted least-squares fashion. A few patterns are apparent in the data. A significant percentage of located events are to the north of the CLSC and associated with the Peggy Ridge extensional relay zone, possibly the most seismically active feature within the Lau basin. Another significant concentration of seismicity occurs near the northern extension of the ELSC, with some scattered off-axis events as well. Many of these events occur in swarms with dozens of events occurring over the space of a few hours.
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 8120 Dynamics of lithosphere and mantle: general (1213)
DE: 8123 Dynamics: seismotectonics
SC: Tectonophysics [T]
MN: 2007 Fall Meeting