HR: 1400h
AN: S33A-05    [Abstracts]
TI: Non-Volcanic Seismic Tremor in the Chile Triple Junction Region: Active Subducted Transform Faults?
AU: * Gallego, A
EM: agallego75@gmail.com
AF: Dept. of Geological Sciences University of Florida, P.O. Box 112120, 241 Williamson Hall, Gainesville, FL 32611, United States
AU: Russo, R M
EM: rrusso@ufl.edu
AF: Dept. of Geological Sciences University of Florida, P.O. Box 112120, 241 Williamson Hall, Gainesville, FL 32611, United States
AU: Comte, D
EM: dcomte@dgf.uchile.cl
AF: Depto. de Geofisica Universidad de Chile, Blanco Encalada 2002, Santiago, 837-0449, Chile
AU: Mocanu, V I
EM: mocanu@gg.unibuc.ro
AF: Dept. of Geophysics University of Bucharest, 6 Traian Vuia Str., Bucharest, RO-70139, Romania
AU: Murdie, R E
EM: ruth.murdie@ctbto.org
AF: CTBTO, P.O. Box 1200 Vienna International Centre, Vienna, A-1400, Austria
AU: VanDecar, J C
EM: jvandecar@hotmail.com
AF: DTM, Carnegie Inst. of Washington, 5241 Broad Branch Rd. NW, Washington, DC 20015, United States
AB: We present analyses of episodic non-volcanic seismic tremor recorded at the Chile Ridge Subduction Project temporary seismic network, operated jointly by the University of Florida and the Universidad de Chile, Santiago. The 57 station network was deployed to study subduction of the Chile Ridge spreading center in the Chile Triple Junction region. Tremor activity during the first project year (2004-5) includes 4 or 5 peaks of high activity with a maximum duration of 48 hours. We observe progressive increases and decreases of activity before and after the high activity peaks, the frequency content of tremor signals is less than 15 Hz, and we observe low magnitude earthquakes within the tremors on rare occasions, as has been seen in Cascadia and Japan. Tremor source regions were determined using the source scanning algorithm of Kao and Shan (2004). The tremors are mainly concentrated in the northern Taitao Peninsula, in the neighborhood of the now-subducted Taitao transform fault, which is the subsurface Nazca-Antarctica plate boundary east of the Chile Triple Junction. At depth, the tremors are distributed between the surface and around 40 km depth, and thus occur mainly in overriding South America. The Taitao transform fault was the site of an unusual slow seismic event around one month after the great 1960 Chile earthquake. Kanamori and Stewart (1979) observed 1.5-2 hours of continuous Rayleigh wave radiation consistent with strike-slip motions on the transform fault, but without associated body wave radiation. We speculate that the tremors are also a result of quasi-continuous slow strike-slip events on the subducted Taitao transform fault and associated deformation and fluid flow in overriding South America.
UR: http:seismology.geology.ufl.edu/chile
DE: 1207 Transient deformation (6924, 7230, 7240)
DE: 7218 Lithosphere (1236)
DE: 7240 Subduction zones (1207, 1219, 1240)
DE: 7250 Transform faults
DE: 8120 Dynamics of lithosphere and mantle: general (1213)
SC: Seismology [S]
MN: 2007 Joint Assembly