Exploring the slow slip cycle in Guerrero, Mexico through
low-frequency earthquakes

William B. Frank, IPGP
in collaboration with Nikolai M. Shapiro, Allen L. Husker, Vladimir
Kostoglodov, Baptiste Rousset, Mathilde Radiguet, Nathalie Cotte,
Harsha S. Bhat, and Michel Campillo.

The transient aseismic release of stress, frequently called slow slip
events, that occurs along the deep roots of plate interfaces has been
a hot topic since their discovery more than 15 years ago. Given the
proximity of slow slip events to the seismogenic megathrust zone, an
understanding of the interactions between aseismic and seismic slip is
essential to better estimate seismic hazard. We investigate the slow
slip cycle in Guerrero, Mexico through the systematic detection of
small seismic events called low-frequency earthquakes (LFEs) that are
collocated with transient aseismic slip. We first develop novel
automatic detection techniques that take advantage of the repeating
nature of LFEs to create a catalog that contains almost two million
events over the analyzed 2.5 year dataset and are regrouped into 1120
unique LFE sources. We observe two source regions that have distinctly
different activity regimes, similar to previously observed tectonic
tremor.  Thanks to our catalog? unprecedented high event density in
time and space, we are able to push our analysis to a finer
scale. Looking at the LFE activity through time along different
portions of the subduction interface, we show evidence that there is
an evolution of pore-pressure during the six month-long 2006 slow slip
event. Then using episodes of high LFE activity as a guide, we show
that there are in fact multiple small slow slip events that generate
displacement at the surface well below the cGPS noise level both
before and after the large 2006 event, indicating that there are in
fact two periodicities of slow slip in Guerrero. Finally, we present
evidence that strong slow slip at depth can influence the stress field
near the surface and enhance superficial repeating seismicity.