HR: 1340h
AN: T53A-1406    [Abstracts]
TI: Earthquake Swarms Detected by the Mariana SUBFAC Seismograph Deployment: Submarine Volcanic Activity and Tectonic Deformation of the Mariana Microplate
AU: * Heeszel, D S
EM: davidh@seismo.wustl.edu
AF: Department of Earth and Planetary Sciences Washington University in St. Louis, Box 1169, EPSc 110, St. Louis, MO 63130 United States
AU: Wiens, D A
T53A-1406 AF: Department of Earth and Planetary Sciences Washington University in St. Louis, Box 1169, EPSc 110, St. Louis, MO 63130 United States
AU: Shore, P J
T53A-1406 AF: Department of Earth and Planetary Sciences Washington University in St. Louis, Box 1169, EPSc 110, St. Louis, MO 63130 United States
AU: Shiobara, H
T53A-1406 AF: Earthquake Research Institute, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-0032 Japan
AU: Sugioka, H
T53A-1406 AF: IFREE, JAMSTEC, 2-15 Natsushima-Cho, Yokosuka, 237-0061 Japan
AB: The 48 ocean bottom seismographs (OBS) and 20 land seismographs deployed from June 2003 to May, 2004 for the Mariana Subduction Factory Imaging Experiment recorded four significant swarms of seismicity in the Central Mariana Arc. Earthquakes were detected using the Antelope database and located using the dbgenloc program. A large swarm of 128 events occurred between East and West Diamente Seamounts from mid-July to mid-August of 2003. The best-located earthquakes form an east-west trending feature on the western slope of East Diamente seamount extending to mid-Diamente seamount. Active hydrothermal activity was observed on East Diamente during an April, 2004 NOAA cruise. The location of these earthquakes and their tight temporal grouping indicates a possible submarine eruption or magma movement associated with East Diamente submarine volcano. Another possibly volcanogenic swarm consisting of 44 events was located on the northwest slope of West Sarigan seamount from December, 2003 to January, 2004. West Sarigan is a submarine volcanic cone and the location of this swarm ~ 10 km northwest of the summit suggests possible volcanic activity. Two other swarms are located away from regions of known volcanism and probably reflect recurrent seismicity associated with deformation of the Mariana arc. A strong swarm composed of 25 events occurred in the Mariana backarc in a region of relatively featureless bathymetry between Sarigan Island and the backarc spreading center during August, 2003. The swarm earthquakes define an E-W lineation that is not due to earthquake mis-location. An August, 2005 Mw 5.4 earthquake at this location has a CMT solution indicating N-S compression on E-W trending faults. The final swarm, during October, 2003, is located on the forearc rise to the east of Sarigan and consists of 45 events. The earthquake locations suggest a southwest-northeast trending fault. A Mw 5.2 event occurred at this location in 1990; its CMT solution shows northeast-southwest extension. These final two swarms indicate a high rate and complex pattern of internal deformation of the Mariana microplate between the Mariana trench and the backarc spreading center.
DE: 3001 Back-arc basin processes
DE: 8104 Continental margins: convergent
SC: Tectonophysics [T]
MN: Fall Meeting 2005