AGU journal highlights -- April 22, 2008

Nonvolcanic tremors are episodes of seismic radiation (mostly in the 1–10 Hertz range) likely associated with aseismic slow slip events within the transition zone between the seismogenic coupled and deep free-slipping segments of a fault. Such tremors have been observed on the San Andreas Fault and on some subduction thrust faults in Japan, the United States, and Costa Rica. To learn more about the phenomenon, Payero et al. study data from a transect across a subduction zone in central Mexico that is overdue for a major earthquake and has been well monitored with Global Positioning System (GPS) networks and broadband seismic stations from the Mesoamerican Subduction Experiment (MACE). GPS data show that two large slow slip events occurred in the Guerrero-Oaxaca region, one in 2001–2002 and the other in 2006. Seismological analyses revealed that nonvolcanic tremor activity was higher during those two slow slip events compared with that for the “quiet” period of 2003–2005. Models suggest that the tremors might be related to low-temperature metamorphic processes and dehydration of the subducted oceanic crust.

Title: Nonvolcanic tremor observed in the Mexican subduction zone

Authors: Juan S. Payero: Posgrado en Ciencias de la Tierra, Instituto de Geofísica, Universidad Nacional Autónoma de México, Mexico City, Mexico; also at Instituto Sismológico Universitario, Facultad de Ciencias, Universidad Autónoma de Santo Domingo, Santo Domingo, Dominican Republic;

Vladimir Kostoglodov, Takeshi Mikumo, Arturo Igelsias and Xyoli Pérez-Campos: Instituto de Geofísica, Universidad Nacional Autónoma de México, Mexico City, Mexico;

Nikolai Shapiro: Institut de Physique du Globe de Paris, Paris, France;

Robert W. Clayton: Seismological Laboratory, California Institute of Technology, Pasadena, California, U.S.A.

Source: Geophysical Research Letters (GRL) paper 10.1029/2007GL032877, 2008; http://dx.doi.org/10.1029/2007GL032877

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