Seismic activity in the Gulf of Mexico. A preliminary analysis

Resumen

The southwestern corner
of the Gulf of Mexico (around the Isthmus of Tehuantepec) is exposed
to intense deep (> 100 km) seismic activity caused by the subduction
of the Cocos Plate. Aside from this, the gulf has been considered a
zone of low or no-seismicity. However, a sparse shallow seismic
activity is observed across the Gulf of Mexico, even in the most
distant areas from the plate boundaries. Some of these earthquakes
have been strongly felt (e.g. 23/05/2007 and 10/09/2006), and the
Jaltipan 1959 earthquake caused fatalities and severe destruction in
central and southern Veracruz. In this study we analyze five
relevant earthquakes that occurred since 2001. At the central Gulf
of Mexico, focal mechanisms show inverse faults oriented
approximately NW−SE with dip ~45o, suggesting a link to sediment
loading and/or to salt tectonics. On the other hand, we analyzed in
the southwestern corner of the gulf some clear examples of
strike-slip faults and activity probably related to the Veracruz
Fault. One anomalous earthquake, recorded in 2007 in the western
margin of the gulf, shows a strike-slip mechanism indicating a
transform regime probably related with the East Mexican Fault.

The
recent improvements of the Mexican Seismological broadband network
have allowed the recording of small earthquakes distributed in the
Gulf of Mexico. Although intermediate and large earthquakes in the
region are infrequent, historic evidence indicates that magnitudes
could reach Mw ~6.4. This fact should be taken in consideration to
reassess the seismic hazard for industrial oil infrastructure in the
region.