HR: 1400h
AN: G33A-07    [Abstracts]
TI: Nonvolcanic tremors in the Mexican subduction zone
AU: * Payero, J S
EM: payero@ollin.igeofcu.unam.mx
AF: Instituto Sismológico UASD, Juan Sanchez Ramirez esq Alma Mater, Santo Domingo, DN 1355, Dominican Republic
AU: Kostoglodov, V
EM: vladi@servidor.unam.mx
AF: Instituto de Geofísica UNAM, Av. Universidad 3000, México, DF 04510, Mexico
AU: Mikumo, T
AF: Instituto de Geofísica UNAM, Av. Universidad 3000, México, DF 04510, Mexico
AU: Perez-Campos, X
AF: Instituto de Geofísica UNAM, Av. Universidad 3000, México, DF 04510, Mexico
AU: Iglesias, A
AF: Instituto de Geofísica UNAM, Av. Universidad 3000, México, DF 04510, Mexico
AU: Clayton, R
AF: Caltech, California, San Francisco, CA , United States
AB: Nonvolcanic low frequency tremors (NVT) have been discovered and studied recently in Japan and Cascadia subduction zones and deep beneath the San Andreas Fault. The tremors activity is increasing during so-called silent earthquakes (SQ) in Japan and Cascadia. NVT clusters also migrate following the propagation of the SQ. The origin of the NVT is still unclear. The studies of NVT and SQ in different subduction zones are required to understand the cause for these phenomena. We discovered a number of NVT from daily spectrograms of continuous broad band records at seismic stations of Servicio Seismológico Nacional (SSN) an MASE project. The analyzed data cover a period of 2001-2004 (SSN) when in 2002 a large SQ has occurred in the Guerrero- Oaxaca region, and a steady-state interseismic epoch of 2005 and a new large SQ in 2006 (MASE). NVT occurred in the central part of the Mexican subduction zone (Guerrero) at approximately 200 km from the coast. We can not accurately localize the tremors because of sparse station coverage in 2001-2004. The MASE data of 2005-2006 show that NVT records in Mexico are very similar to those obtained in Cascadia subduction zone. The tremors duration is of 10-60 min, and they appear to travel at S-wave velocities. More than 100 strong NVT were recorded by most of the MASE stations with the epicenters clustered in the narrow band of ~40x150 km to the south of Iguala city and parallel to the coast line. NVT depths are poorly constrained but seem to be less than 40 km deep. We noticed a some increase of NVT activity during the 2001-2002 and 2006 SQs compared with an NVT activity for the "SQ quiet" period of 2003-2004 nevertheless. A lack of NVT for the period of 2-3 months after the SQ is apparent in 2002 and 2006.
DE: 6924 Interferometry (1207, 1209, 1242)
DE: 7209 Earthquake dynamics (1242)
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
SC: Geodesy [G]
MN: 2007 Joint Assembly