Evidence for Transient Slip Events and Non-Volcanic Tremor on the Rivera Plate Subduction Interface, Northern Middle America Subduction Zone
Monday, 22 February 2016: 3:45 PM
Charles DeMets1, Bertha Marquez-Azua2, Enrique Cabral-Cano3, Michael Brudzinski4, Kristen M Schlanser4 and Osvaldo Sanchez-Zamora5, (1)University of Wisconsin Madison, Madison, WI, United States, (2)Universidad de Guadalajara, Guadalajara, Mexico, (3)UNAM National Autonomous University of Mexico, Departamento de Geomagnetismo y Exploración, Instituto de Geofísica, Mexico City, Mexico, (4)Miami University, Oxford, OH, United States, (5)UNAM National Autonomous University of Mexico, Mexico City, Mexico
Abstract:
As of late 2015, deformation above the Rivera plate subduction interface along the northern ~300 km of the Middle America trench has been measured continuously with GPS for nearly 23 years. During this time, no silent slip events (SSE) have been recorded that are comparable in magnitude to the numerous SSEs that have been observed along the Guerrero and Oaxaca segments. Although this might indicate that none of the Rivera plate subduction interface presently has the right frictional properties for spawning SSE, such a possibility seems unlikely given the many similarities between the Rivera subduction zone and the remainder of the Middle America trench, where SSE occurs frequently. We use continuous GPS measurements from the Jalisco-Colima region to present evidence for possible, nearly-annual small-magnitude SSE on the Rivera subduction interface and discuss the challenge of separating these tectonic events from non-tectonic, periodic signals. We compare our results to a space-time history of non-volcanic tremor from the Rivera plate subduction interface, as determined from the dense, 18-month-long MARS seismic deployment. Tremor bursts located using relative times in envelope waveforms indicate that episodes tend to occur in 50-km-wide swaths along-strike, downdip from the rupture zones of the 1995 and 2003 earthquakes, with a gap that appears to mark the subducted Rivera-Cocos plate boundary. Using spectral analysis to enhance tremor detection, episodes typically last for only a few days and recur as frequently as monthly in some locations. The lack of annual periodicity in the tremor episodes suggests tremor and GPS-detected slow slip are not temporally correlated in this area, consistent with some other areas of the Middle America Subduction Zone.
