Complexity of the seismic cycle in Guerrero, Mexico : long term coupling modified by slow slip events, as inferred by cGPS

Abstract:

Since the first cGPS station has been installed in 1997 in Guerrero, Mexico, several large transient deformations have been observed, generating surface displacements up to 6 cm on the N-S component west of Acapulco city. These deformations are caused by Slow Slip Events (SSEs) occurring along the subduction interface, with slip at depth as large as 20 cm over a 6-9 months duration and a recurrence time of roughly 4 years.

The presence of these SSEs has strong implications in terms of seismic hazard in the Guerrero area. For the cGPS stations installed in this area, we determine the long term (secular) trend of the positioning time series, over several SSE cycles. The long term coupling is then determined by inversion and gives information about the slip budget over several SSE cycles.  Thanks to the dense cGPS network, lateral variability of long term coupling is observed. We show that the long term coupling is low in the area of the SSEs and estimate the slip released by the aseismic processes. This allows us to quantify the slip potentially available to generate earthquakes.