Unified Structural Representation of the southern California crust and upper mantle

We present a new, 3D description of crust and upper mantle velocity structure in southern California implemented as a Unified Structural Representation (USR). The USR is comprised of detailed basin velocity descriptions that are based on tens of thousands of direct velocity (Vp, Vs) measurements and incorporates the locations and displacement of major fault zones that influence basin structure. These basin descriptions were used to developed tomographic models of crust and upper mantle velocity and density structure, which were subsequently iterated and improved using 3D waveform adjoint tomography. A geotechnical layer (GTL) based on Vs30 measurements and consistent with the underlying velocity descriptions was also developed as an optional model component. The resulting model provides a detailed description of the structure of the southern California crust and upper mantle that reflects the complex tectonic history of the region. The crust thickens eastward as Moho depth varies from 10 to 40 km reflecting the transition from oceanic to continental crust. Deep sedimentary basins and underlying areas of thin crust reflect Neogene extensional tectonics overprinted by transpressional deformation and rapid sediment deposition since the late Pliocene. To illustrate the impact of this complex structure on strong ground motion forecasting, we simulate rupture of a proposed M 7.9 earthquake source in the Western Transverse Ranges. The results show distinct basin amplification and focusing of energy that reflects crustal structure described by the USR that is not captured by simpler velocity descriptions. We anticipate that the USR will be useful for a broad range of simulation and modeling efforts, including strong ground motion forecasting, dynamic rupture simulations, and fault system modeling. The USR is available through the Southern California Earthquake Center (SCEC) website (http://www.scec.org)

Investigating the variation in CO[subscript 2] sequestration supply curves

CCS projects that can bring together all pieces of the system—capture, transport, and storage—at the lowest cost will likely be the first to become operational. We have modeled the cost per tonne of CO[subscript 2] of a geologic sequestration system that stores CO[subscript 2] in saline aquifers in the United States. The model includes aspects of capture, transport, storage, and finance, and we present the sensitivity of the model to various source- and sink-specific parameters. From our cost model we developed CO[subscript 2] sequestration supply curves for CO[subscript 2] sources within 100 miles of nine identified CO2 sinks in the Illinois Basin. The supply curves present the amount of CO[subscript 2] that can be sequestered under current economic and technical conditions at a given CO[subscript 2] price, and can and should be used by policy makers and commercial organizations to determine the most economical combinations of sources and sinks for CCS on national, regional, and local levels