Bathymetry and active geological structures in the Upper Gulf of California

Resumen

Bathymetric surveys
made between 1994 and 1998 in the Upper Gulf of California revealed
that the bottom relief is dominated by narrow, up to 50 km long,
tidal ridges and intervening troughs. These sedimentary linear
features are oriented NW-SE, and run across the shallow shelf to the
edge of Wagner Basin. Shallow tidal ridges near the Colorado River
mouth are proposed to be active, while segments in deeper water are
considered as either moribund or in burial stage. Superposition of
seismic swarm epicenters and a seismic reflection section on
bathymetric features indicate that two major ridge-troughs
structures may be related to tectonic activity in the region. Off
the Sonora coast the alignment and gradient of the isobaths matches
the extension of the Cerro Prieto Fault into the Gulf. A similar
gradient can be seen over the west margin of the Wagner Basin, where
in 1970 a seismic swarm took place (Thatcher and Brune, 1971)
overlapping with a prominent ridge-trough structure in the middle of
the Upper Gulf. It is believed that these major elongated features
can be linked to active geological structures reflecting the
geometry of the deep basement in the Wagner Basin.