HR: 0800h
AN: T21A-0358 [Abstracts]
TI: Tidal Variation in Non Volcanic Seismic Tremor Activity at the Chile Triple Junction
AU: * Gallego, A
EM: agallego75@gmail.com
AF: Dept. of Geological Sciences University of Florida, P.O. Box 112120, 241 Williamson Hall,
Gainseville, 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,
Gainseville, 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 evidence that non volcanic seismic tremor detected at Chile Ridge Subduction Project (CRSP)
seismic network correlates with the semidiurnal (M2) tidal amplitude variation, enhanced by the lunar monthly
(Mm) orbital cycle. Tremors were detected at 14 broadband seismic stations in the Los Chonos Archipelago and
Taitao Peninsula by two methods: simple visual inspection of correlated tremor on seismograms at CRSP
stations, and an automated search of the tremor frequency band (5-10 Hz). The two methods yield similar
results. Analysis of two years of data (2005-2006) reveals a positive correlation (R = 0.76) between daily tremor
duration and daily tidal variations, with a lag of 2.5 days between maximum tidal amplitude difference and tremor
activity. The 28 day tidal cycle is produced by conjunction (New Moon), generating the highest and lowest tide
amplitudes of the orbital cycle. Gravitational traction due to tidal acceleration is maximum near the latitude of the
study region, and is enhanced by the ocean loading. At least two hypotheses could explain the correlation: stress
cycling on the subducted Taitao and Darwin transform faults due to solid earth tide and ocean loading, leading to
tremor generation; or enhanced hydrothermal activity during fluid release in the subducted Chile ridge structure.
UR: http://www.clas.ufl.edu/users/russo/
DE: 8111 Continental tectonics: strike-slip and transform
DE: 8118 Dynamics and mechanics of faulting (8004)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting