Subsidence and strike-slip tectonism of the upper continental slope off Manzanillo, Mexico

Abstract-On 22 January 2003, the M w = 7.6 Tecomán earthquake struck offshore of the state of Colima, Mexico, near the diffuse triple junction between the Cocos, Rivera, and North American plates. Three-hundred and fifty aftershocks of the Tecomán earthquake with magnitudes between 2.6 and 5.8, each recorded by at least 7 stations, are relocated using the double difference method. Initial locations are determined using P and S readings from the Red Sismológica Telemétrica del Estado de Colima (RESCO) and a 1-D velocity model. Because only eight RESCO stations were operating immediately following the Tecomán earthquake, uncertainties in the initial locations and depths are fairly large, with average uncertainties of 8.0 km in depth and 1.4 km in the north-south and east-west directions. Events occurring between 24 January and 31 January were located using not only RESCO phase readings but also additional P and S readings from 11 temporary stations. Average uncertainties decrease to 0.8 km in depth, 0.3 km in the east-west direction, and 0.7 km in the north-south direction for events occurring while the temporary stations were deployed. While some preliminary studies of the early aftershocks suggested that they were dominated by shallow events above the plate interface, our results place the majority of aftershocks along the plate interface, for a slab dipping between approximately 20°and 30°. This is consistent with the slab positions inferred from geodetic studies. We do see some upper plate aftershocks that may correspond to forearc fault zones, and faults inland in the upper plate, particularly among events occurring more than 3 months after the mainshock.

Section: Resultsmentioning

confidence: 99%

Double-difference Relocation of the Aftershocks of the Tecomán, Colima, Mexico Earthquake of 22 January 2003

Andrews

Stock

Vázquez

et al. 2010

“…Plate motion studies indicate the direction of convergence between the Rivera and North American plates as northwestward along the Mexican subduction zone (BANDY et al, 2005). The EGG zone is characterized by NE-SW oriented structures.…”

Section: General Characteristics Of the Rivera-cocos Platementioning

confidence: 98%

“…The Rivera-Cocos plate boundary zone is a complicated across-trench tectonic structure (Fig. 2) consisting of a few grabens and horsts (BANDY et al, 2005). It run across the Middle American trench (El Gordo graben) and has its continental continuation within the Colima rift.…”

Section: General Characteristics Of the Rivera-cocos Platementioning

confidence: 99%

Influence of Rivera-Cocos Plate Boundary Geodynamics on Earthquake Intensity Patterns: the 9 October 1995 (Mw 8.0) and 21 (22) January 2003 (Mw 7.5) Earthquakes

Zobin

2010

This study examines two large thrust subduction earthquakes occurring within the Rivera-Cocos plate boundary which struck the western coast of México on 9 October 1995, Mw 8.0, and 21 (22 GMT) January 2003, Mw 7.5. The Modified Mercalli (MM) earthquake intensities observed during these earthquakes were surprising for some towns located in the Mexican coastal zone. During the smaller Mw 7.5 2003 earthquake, MM intensity VII was observed for towns of Colima, Villa de Alvarez and Ixtlahuacán, while during the larger Mw 8.0 1995 earthquake, their MM intensities were only IV-V, V and V-VI, respectively. We construct the macroseismic patterns for these two earthquakes and discuss the possible reasons for the significant difference in the outline of the MM VII isoseismals, such as the tectonic setting of epicentral zones and the directivity of rupture processes along and across the coastal line.

“…Moreover, not only do earthquakes associated with subduction processes occur in the region, but also large intraplate earthquakes take place, such as the historical events of December 27, 1568 and (BOURGOIS and MICHAUD 1991;KHUTORSKOY et al 1994;MICHAUD et al 1996), one threefold profile (BANDY et al 2005), several threefold profiles acquired in the Rivera transform zone (BANDY et al 2011), and five multichannel analog seismic data acquired in 1996 during the CORTES project (BARTOLOME et al 2011;DAÑ OBEITIA et al 1997, Fig. 3) are available in the literature.…”

Section: Earthquake History Of the Jalisco Regionmentioning

confidence: 99%

Multichannel Seismic Imaging of the Rivera Plate Subduction at the Seismogenic Jalisco Block Area (Western Mexican Margin)

Bartolomé

Gorriz

Dañobeitia

et al. 2016

Self Cite

Abstract-During the TSUJAL marine geophysical survey, conducted in February and March 2014, Spanish, Mexican and British scientists and technicians explored the western margin of Mexico, considered one of the most active seismic zones in America. This work aims to characterize the internal structure of the subduction zone of the Rivera plate beneath the North American plate in the offshore part of the Jalisco Block, to link the geodynamic and the recent tectonic deformation occurring there with the possible generation of tsunamis and earthquakes. For this purpose, it has been carried out acquisition, processing and geological interpretation of a multichannel seismic reflection profile running perpendicular to the margin. Crustal images show an oceanic domain, dominated by subduction-accretion along the lower slope of the margin with a subparallel sediment thickness of up to 1.6 s two-way travel time (approx. 2 km) in the Middle American Trench. Further, from these data the region appears to be prone to giant earthquake production. The top of the oceanic crust (intraplate reflector) is very well imaged. It is almost continuous along the profile with a gentle dip (\10°); however, it is disrupted by normal faulting resulting from the bending of the plate during subduction. The continental crust presents a well-developed accretionary prism consisting of highly deformed sediments with prominent slumping towards the trench that may be the result of past tsunamis. Also, a bottom simulating reflector (BSR) is identified in the first half a second (twtt) of the section. High amplitude reflections at around 7-8 s twtt clearly image a discontinuous Moho, defining a very gentle dipping subduction plane.