HR: 0800h
AN: S31A-05    [Abstracts]
TI: Structure of the Wagner Basin in the Northern Gulf of California From Interpretation of Seismic Reflexion Data
AU: * Gonzalez, M
EM: mgonzale@cicese.mx
AF: Division Ciencias de la Tierra, CICESE, Km 107, Carretera Tijuana-Ensenada, Ensenada, BC 22860, Mexico
AU: Aguilar, C
EM: aguilar@cicese.mx
AF: Division Ciencias de la Tierra, CICESE, Km 107, Carretera Tijuana-Ensenada, Ensenada, BC 22860, Mexico
AU: Martin, A
EM: amartin@cicese.mx
AF: Division Ciencias de la Tierra, CICESE, Km 107, Carretera Tijuana-Ensenada, Ensenada, BC 22860, Mexico
AB: The northern Gulf of California straddles the transition in the style of deformation along the Pacific-North America plate boundary, from distributed deformation in the Upper Delfin and Wagner basins to localized dextral shear along the Cerro Prieto transform fault. Processing and interpretation of industry seismic data adquired by Petroleos Mexicanos (PEMEX) allow us to map the main fault structures and depocenters in the Wagner basin and to unravel the way strain is transferred northward into the Cerro Prieto fault system. Seismic data records from 0.5 to 5 TWTT. Data stacking and time-migration were performed using semblance coefficient method. Subsidence in the Wagner basin is controlled by two large N-S trending sub-parallel faults that intersect the NNW-trending Cerro Prieto transform fault. The Wagner fault bounds the eastern margin of the basin for more than 75 km. This fault dips ~50° to the west (up to 2 seconds) with distinctive reflectors displaced more than 1 km across the fault zone. The strata define a fanning pattern towards the Wagner fault. Northward the Wagner fault intersects the Cerro Prieto fault at 130° on map view and one depocenter of the Wagner basin bends to the NW adjacent to the Cerro Prieto fault zone. The eastern boundary of the modern depocenter is the Consag fault, which extends over 100 km in a N-S direction with an average dip of ~50° (up to 2s) to the east. The northern segment of the Consag fault bends 25° and intersects the Cerro Prieto fault zone at an angle of 110° on map view. The acoustic basement was not imaged in the northwest, but the stratigraphic succession increases its thickness towards the depocenter of the Wagner basin. Another important structure is El Chinero fault, which runs parallel to the Consag fault along 60 km and possibly intersects the Cerro Prieto fault to the north beneath the delta of the Colorado River. El Chinero fault dips at low-angle (~30°) to the east and has a vertical offset of about 0.5 seconds (TWTT). Seismic imaging indicates that the Wagner and Consag faults transfer most of their slip to the Cerro Prieto fault. Moreover, the 130° intersection between the Wagner and Cerro Prieto faults suggests that the Wagner fault has a significant strike-slip component. Our results indicate that most of the strain in this plate boundary is transferred along two main sub-parallel oblique faults in a narrow zone 35 km-wide.
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 7250 Transform faults
DE: 8105 Continental margins: divergent (1212, 8124)
DE: 8123 Dynamics: seismotectonics
DE: 8150 Plate boundary: general (3040)
SC: Seismology [S]
MN: 2007 Joint Assembly