Boyd Deep Canyon Desert Research Center

28 Feb, 04 PM - 30 Mar, 05 PM

This project addresses the processes of rupturing a continent through a seismic reflection and refraction survey at the Salton Trough in southern California. The Salton Trough is the northernmost part of the Gulf of California extensional province that rifted the North American continent and transferred Baja California and the Peninsular Ranges to the Pacific plate. Despite similar total extension along the province, very different extensional structures have been produced, from seafloor spreading in the southern Gulf to 14-20 km thick continental or transitional crust in the northern Gulf and Salton Trough. The southern and central Gulf were the target of a recent MARGINS project, and significant differences in rifted continental margins were observed in adjacent rift segments. Seismic refraction and reflection studies in the northern Gulf indicate that stretched continental crust still underlies the rift. In the Salton Trough, however, the 20-22 km thick crust is composed entirely of new material added by magmatism from below and Colorado River sedimentation from above. A combination of driving forces, thermal regime, inherited structure, magmatism, and sedimentation produce a range of rheological responses to extension. At rifted continental margins, narrow or broad areas of new crust, transitional between continental and oceanic, are created through lithospheric stretching (normal faulting, detachment faulting, and/or lower crustal flow), magmatism, and sedimentation. In the Salton Trough, low-angle faulting has been observed at the surface, but the central rift appears to have been completely ruptured and new, thick crust has been created. It is an excellent place to study the effects of magmatism and sedimentation on continental extension, and the partitioning of strain vertically in the lithosphere. As a highly oblique rift, it also provides the opportunity to study the lateral partitioning of strain into rifting, transform faults, and zones of oblique extension. Our scientific goals are to investigate: i) the nature of transitional crust at rifted continental margins, ii) the role and mode of magmatism in the final stages of continental breakup, iii) the effect of rapid syn-rift sedimentation on magmatism and extension mechanism, iv) the partitioning of displacement in highly oblique continental rifting, and v) 3-D structure for earthquake hazards evaluation. These will be constrained by densely sampled seismic refraction/wide-angle reflection and by seismic reflection imaging of the crust and upper mantle. Our results will be combined with those of recent MARGINS studies in the Gulf of California, and a new USGS earthquake hazards initiative on the southern San Andreas Fault.

Visit #23915 @Boyd Deep Canyon Desert Research Center

Approved

Under Project # 23020 | Research

Salton Seismic Imaging Project

faculty - California Institute of Technology

Reservation Members(s)

Group of 2 Graduate Student Feb 28 - Mar 30, 2011 (31 days)
Group of 2 Volunteer Feb 28 - Mar 30, 2011 (31 days)

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Day use 4 Feb 28 - Mar 30, 2011