Project funded by
NSF
through both the
MARGINS Program
and the
EarthScope Program
and funded by the
U. S. Geological Survey
through the
Multi-Hazards Demonstration Project.
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.
Recent MARGINS studies in the Gulf of California, the current EarthScope-USArray deployment, and a new USGS earthquake hazards initiative on the southern San Andreas Fault (see below) currently provide a synergy for new studies in the Salton Trough.
Broader Impacts
The proposed work addresses the goals of the Rupturing Continental Lithosphere initiative of MARGINS and lies in an identified focus site. It also addresses the goals of EarthScope to study the evolution of the North American continent and lies within an identified focus region of the integrative GeoSwath initiative. It uses EarthScope instrumentation.
The southernmost San Andreas Fault is considered at high risk of producing a damaging earthquake. For this reason, the U. S. Geological Survey is a partner on this proposal and will contribute a substantial portion of the funds for fieldwork. Structure of the faults, sedimentary basins, and underlying crust will be incorporated into community models for simulation of strong ground motion and earthquake hazards in southern California.
Collaboration will be created with earthquake networks and with scientists in Mexico. The proposed work would be the subject of graduate student research, undergraduate student internships, and a formal graduate/undergraduate field and data analysis course.
Two collaborating projects are also shown:
Wet-SSIP controlled-source seismic reflection/refraction lines are shown schematically in the Salton Sea. Wet-SSIP is led by Neal Driscoll, Graham Kent, and Alistair Harding from Scripps Inst. Oceanography and U. Nevada Reno, and funded by the NSF Marine Geology & Geophysics Program.
BB-SSIP broadband stations (stars) will be deployed at close spacing across the Salton Trough to image structures at greater depth. BB-SSIP is led by Simon Klemperer from Stanford U., and funded by the NSF Geophysics Program.
Note that this map is schematic: actual field plans will depend upon logistics and scientific re-tuning, which are underway. Your input is welcome!
[November 2009 version of this figure]
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