Gran Desierto de Altar - Tectonics

Tectonics

The Gran Desierto is located adjacent to a rapidly subsiding tectonic basin, the Salton Trough, which is a northern extension of the Gulf of California, an embayment created by rifting initiated during the Pliocene along the East Pacific Rise and the San Andreas fault system . Regional subsidence has propagated to the northwest as rifting and strike-slip faulting continues into the present-day. The central portion of the nearby Salton Trough is more than 70 m below sea level; it is protected from marine embayment only by the natural dike of the Colorado River Delta.

Ongoing tectonic activity modifies the Gran Desierto today. The southernmost extension of the San Andreas fault system, the Cerro Prieto Fault, passes directly through the area before continuing offshore into the Gulf of California . Strike-slip movement in the area is as high as 60 mm/yr. .

Since 1900, one magnitude 6.3 and two magnitude 7.1 earthquakes have originated within the erg. Most seismicity within the Gran Desierto originates at depths of five to six kilometers, corresponding to the transition between deltaic deposits and basement crystalline rocks (Von der Haar and Howard, 1981). Local uplift is still occurring along the Mesa Arenosa, a drag folded fault block forming the coastal boundary.