S027-0013
Shallow slow earthquakes and mechanical properties at the Guerrero seismic Gap, Mexico
Thursday, 10 December 2020
Poster
Raymundo Omar Plata Martinez1, Satoshi Ide2, Masanao Shinohara3, Emmanuel Garcia4, Naoto Mizuno5, Luis Antonio Dominguez Ramirez6, Taka'aki Taira7, Yusuke Yamashita4, Akiko Toh8, Tomoaki Yamada9, Jorge Arturo Real Sr.10, Victor M Cruz-Atienza11, Allen Leroy Husker Sr12 and Yoshihiro Ito4, (1)Kyoto University, Geophysics, Kyoto, Japan, (2)The University of Tokyo, Bunkyo-ku, Japan, (3)Univ Tokyo, Tokyo, Japan, (4)Disaster Prevention Research Institute, Kyoto University, Kyoto, Japan, (5)The University of Tokyo, Department of Earth and Planetary Science, Tokyo, Japan, (6)UNAM National Autonomous University of Mexico, Mexico City, Mexico, (7)Univ California Berkeley, Berkeley, CA, United States, (8)The University of Tokyo, Tokyo, Japan, (9)University of Tokyo, Bunkyo-ku, Japan, (10)Universidad Nacional Autonoma de Mexico, Sismilogia, Didtrito Federal, Mexico, (11)Universidad Nacional Autónoma de México, Instituto de Geofísica, Mexico, Mexico, (12)Universidad Nacional Autónoma de México, Institute of Geophysics, Mexico City, Mexico
Abstract:
Most of our knowledge regarding slow earthquakes comes from observations in the downdip portion of subduction zones at distances far from the trench, however, slow earthquakes are also present at shallow depths. For this reason, it is essential to include in our studies the near trench portions of subduction zones to understand its mechanical properties and asses the actual extent of seismogenic zones where tsunamigenic and devastating earthquakes may occur. For the past decades a proposed earthquake scenario for the Guerrero seismic gap, located along the Pacific coast of Mexico, has been one of a pending rupture of the entire gap capable of generating a large earthquake. The Guerrero subduction zone is also prone to slow earthquakes, unfortunately, these observations come only from onshore observations, limiting our knowledge of the shallow plate interface in the gap.
So far, shallow slow earthquakes have not been observed at the Mesoamerican trench, for that reason we deployed an array of ocean bottom seismometers inside the northwest Guerrero seismic gap. We seek to answer questions such as, if slow earthquakes happen near the trench, what are their characteristics and most importantly, we look to improve our understanding of future large earthquakes in Guerrero.
We searched for shallow tremors as first evidence of shallow slow earthquakes. Regular earthquakes and repeaters were also located and together with the residual gravity and residual bathymetry, where interpreted to infer mechanical properties at the plate interface. We found that subducted relief might contributed to produce highly heterogeneous frictional conditions that give rise to slow slip conveyed with episodic shallow tremor, repeaters and possible short-term slow slip events. Our observations indicate that the central portion of the Guerrero seismic gap is absent of a seismogenic zone and dominated by a low-coupling stable regime. This implies, that the initiation of a large earthquake is less likely to occur in the northwest Guerrero seismic gap. However, we cannot discard the possibility that the seismic gap could ruptured as the results of a M>8 earthquake propagating from an adjacent unstable domain.
