William Frank : "Exploring the slow slip cycle in Guerrero, Mexico through low-frequency earthquakes"

Séminaire de l'IPGS le 7 avril à 13h45.

Intervenant : William Frank William Frank, post-doctorant à l'Institut de Physique du Globe de Paris, qui rejoindra en novembre le Massachusetts Institute of Technology. William Frank s'intéresse aux évènements de glissement lent et aux trémors non-volcaniques dans la région de Guerrero (Mexique).

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

Lieu : EOST, 5 rue Descartes, amphi. Rothé

Résumé :
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 infact 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.