Large earthquakes in the Tehuantepec subduction zone: evidence of a locked plate interface and large-scale deformation of the slab
Por:
SUAREZ, GERARDO
Publicada:
1 abr 2021
Ahead of Print:
1 nov 2020
Resumen:
The Tehuantepec subduction zone was identified as a seismic gap by
several authors. The presence of three large earthquakes at the turn of
the twentieth century, in temporal and spatial proximity, poses
questions on the extent of the seismic gap and on the type of tectonic
deformation in this region. On 19 April 1902, a large earthquake
occurred in Guatemala. The macroseismic data and recent relocations
suggest that it is not a subduction event but an intraplate earthquake
within the subducted Cocos plate. The recent relocations and the
macroseismic data of the 23 September 1902 earthquake, which is
frequently interpreted as an interplate subduction event, show that it
is an intermediate-depth earthquake located inland in central Mexico.
The 14 January 1903 earthquake, located in the Gulf of Tehuantepec, may
be interpreted as an intraplate event, similar to the 8 September 2017
earthquake (M-w 8.2) or a subduction earthquake. Thus, there is no clear
evidence of large subduction earthquakes (M-w > 7) in Tehuantepec at
least in the last 250 years. Geodetic data suggest that the subduction
zone is highly coupled and, therefore, a considerable amount of plate
motion has not been released. The length of the presumed seismic gap is
equivalent to a M-w similar to 8.5 earthquake. In contrast, the
September 1902 (M-w 7.8), 1903 (M-w 7.4), 1931 (M-w 7.8), 1999 (M-w 7.5)
and the great 8 September 2017 events (M-w 8.2) are all down-dip
tensional earthquakes in the slab, reflecting a complex state of stress
in the downgoing Cocos plate. These frequent and large tensional
earthquakes may reflect a large-scale deformation of the slab that
locked at the plate interface is under tensional stress under its own
gravitational weight. As a result, seismic hazard in the Isthmus of
Tehuantepec stems from both subduction and intraplate earthquakes.
Filiaciones:
SUAREZ, GERARDO:
Suarez, G (Corresponding Author), Univ Nacl Autonoma Mexico, Inst Geofis, Cd Univ, Mexico City 04510, DF, Mexico
Univ Nacl Autonoma Mexico, Inst Geofis, Cd Univ, Mexico City 04510, DF, Mexico
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