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Intermittence of Transient Slow Slip in the Mexican Subduction Zone, as Seen by Tectonic Tremors

Description: 

The Mexican subduction zone hosts a variety of slow slip events, both in the states of Guerrero and Oaxaca, favored by the flat geometry of the plate interface. Previous studies using GNSS data revealed Mw 7-7.5 Long-term Transient (LT) accompanied by a microseismic activity of Tectonic Tremors (TT) and/or Low Frequency Earthquakes (LFEs), highly clustered in time. Short-term Transients (ST) of smaller amplitude were also identified in Guerrero between 2005 and 2007 using approaches combining GNSS data and LFEs catalogs.

In this study, we used the TT catalog published by Husker et al. [2019] to investigate, over a 10-year time period, how TT activity can help to characterize the dynamic of transient events over shorter time scales than accessible with GNSS data only. We analyzed separately the periods corresponding to LTs, and periods inter-LTs during which Short-Transients (ST) can be detected.

From the TT catalog (covering 2009-2019), we extracted TT bursts (events clustered in time). We decomposed the GNSS time series using the timing of TT bursts, providing for each GNSS time series a surface velocity during and in-between TT bursts. These velocities are then inverted to locate the associated source on the plate interface.

Our decomposition results during LTs reveal that, 80% of the surface motion during LTs is occurring during TT times, which represent only 30% of the LTs duration. These results highlight the intermittence of slip during long-transients, as most of the slip occurs during TT activity.

The decomposition during inter-LTs periods unveiled the occurrence of 29 STs in the Guerrero area, with a source at the location of previously identified STs. In Oaxaca, our result reveals for the first time the occurrence of 18, with a source located in the tremor zone. Our joint analysis of TT and GNSS data reveals that STs of small amplitudes occur regularly in Guerrero and Oaxaca. Consequently, short-term plate coupling is higher than previously estimated.

Session: Deciphering Earthquake Clustering for the Better Understanding of Crustal Deformation Mechanisms [Poster]

Type: Poster

Date: 4/20/2023

Presentation Time: 08:00 AM (local time)

Presenting Author: Zaccaria El Yousfi

Student Presenter: Yes

Invited Presentation: 

Authors