Publication Date:
2013-02-13
Description:
ABSTRACT [1] We located continuous seismic tremorwith coherent amplitude wavetrainsin the Chile Ridge subduction region (~46.5°S)in two clusters north and south of the Chonos Archipelago, between the Chile trench and the North Patagonian forearc. Tremor persisted from December 2004 to February 2007 (the entire period of the Chile Ridge Subduction Project temporary seismic deployment), and lasted 〉 17 hours on six occasions. Tremor in the more active southern cluster reached a maximum duration of 48 hours, and we observed no more than 3 continuous days without tremor activity. The cluster locations coincide with the surface projections of subducted transform faultsformed atthe Chile ridge. We also detected simultaneous, co-located low-frequency microearthquakes with well-defined impulsive waves within the tremor signals distributed from the surface to 40 km depth, suggesting tremors and earthquakes are part of the same process. The periodicity of tremor duration is strongly correlated with semi-diurnal, diurnal, and long period tides, M2, N2, K1, O1, P1, and Mm (12.421, 12.000, 23.934, 25.819, 24.066 hrs and 27.555 days, respectively). We found a significant correlation between tremor occurrence and earth tides when tidal stressis calculated forthe slip plane of a right-lateral strike-slip fault withstrikeN95 0 E, which isnear parallelto subducted transform faults (N78 0 E) of the Chile Ridge,indicatingthat the very small stresses resulting from the combination of ocean loading and solid earth tides (~1kPa) are sufficient to facilitate or suppress tremor production; tremors occur when shear stressesare maximum and wane or are low whenshear stresses are minimum.
Electronic ISSN:
1525-2027
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
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