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Borderland Working Group
Chair: Craig Nicholson
2004 Annual Report
The offshore California Continental Borderland is a critical element in terms of understanding the tectonic evolution, active fault systems, and seismic hazard of Southern California. As a result, SCEC created the Borderland Working Group and made it an official part of the organizational structure of SCEC in June 2002. Its purpose is to focus and integrate research activities within the offshore Continental Borderland that relate to the scientific mission and objectives of SCEC. This includes the coordination of cooperative and collaborative research projects, helping to assess, archive and analyze existing offshore geologic and geophysical data, and helping to plan new research activities including future experiments within the Continental Borderland. An extended white paper on the objectives, goals, and research priorities of the SCEC Borderland Working Group is based largely on the results of a workshop held in March 2002 on Santa Catalina Island.
The Borderland Working Group recognizes that much of the support, data and facilities needed for offshore research must come from external sources and funding agencies, such as NOAA, NSF, NURP and ONR. The Borderland Working Group has thus been working to identify fundable research problems for which the offshore Borderland provides a particularly useful, unusual or outstanding natural laboratory to study.
In 2004, various Borderland projects were conducted or initiated, of which two received some support from SCEC. NSF funded Kennett, Nicholson, and Sorlien (UCSB)—in collaboration with Normark and Fisher (USGS)—to test the viability of extending the high-resolution climate record in Santa Barbara Basin. The project uses high-resolution seismic stratigraphy to map 3D structure and the location of where older stratigraphic sequences crop out along the Mid-Channel Trend (Hopkins et al., 2004). These older sequences will then be sampled by piston core in August 2005. In addition to climate studies, this project will help to quantify patterns and rates of offshore late-Quaternary faulting and folding in the Santa Barbara Channel.
In 2004, SCEC helped support Sorlien (UCSB) to conduct continued analysis of active fault systems in Santa Monica Bay (Figure III-23-1). This includes the Palos Verdes, San Pedro Basin and Shelf Projection Blind faults of the inner Borderland that interact with and terminate against the more east-west-striking, north-dipping Malibu Coast and Santa Monica-Dume faults (Sorlien et al., 2004a). This work led to the identification and preliminary mapping of the low-angle Shelf Projection blind fault beneath the Palos Verdes anticlinorium (Sorlien et al., 2004b) that may be the offshore extension of the Compton blind fault in the Los Angeles basin. This project, in collaboration with colleagues at USGS and LDEO, mapped stratigraphic reference horizons to document amounts of deformation absorbed by fault slip, folding and rotation (Figure III-23-1b), and contributed several new 3D fault surfaces to the SCEC Community Fault Model.
In 2003 and 2004, as part of a tectonic and marine habitat program, NOAA and NURP funded Goldfinger (OSU) to conduct high-resolution multibeam, chirp, and submersible dive studies of submerged marine terraces and Pleistocene lowstand shorelines (Meiner et al., 2004) around the Northern Channel Islands and Pilgrim Banks. SCEC partially supported this program by providing funds to date recovered marine fossils, thereby helping to quantify rates of offshore vertical motion associated with the deformation of these paleo-sealevel reference surfaces.
In 2004, USGS personnel continued work on offshore stratigraphy (Normark et al., 2004) and the analysis of high-resolution multibeam, Huntec, chirp and multichannel seismic data to document the location, geometry, and timing of near-shore faulting (Ryan et al., 2004) and submarine landslide (Fisher et al., 2004) hazards.
Besides these major on-going projects, progress continues on obtaining extensive grids of existing high-quality multichannel seismic (MCS) reflection data collected by the industry for hydrocarbon exploration. Much of these data are high-quality and, in some cases, irreplaceable as the data extend into areas (National Marine Sanctuaries, State Water, etc.) where such marine seismic acquisition is now precluded by law. Several of these industry data sets, including data from Western GeCo and Chevron-Texaco, extend along the entire western margin of the continental Unites States, making them excellent data resources for use by both SCEC and EarthScope. Negotiations with Chevron-Texaco, Western GeCo, Venoco, and Heck-Ogle Petroleum have begun and preliminary agreements made to transfer and archive the offshore MCS data with USGS, IRIS, and SCEC, if funding sources for the tape transcription costs can be found. Jon Childs (USGS) has negotiated contracts for the data transfer and tape transcription with Western GeCo, and the USGS has some initial funding to begin this data rescue and archiving process. Members of the Borderland Working Group are currently working with NSF, IRIS and industry to identify and provide matching support for the USGS effort, and to support initial analyses of the MCS data. If these additional necessary funds are found, substantial progress can be made in investigating the active deformation and hazard potential of the offshore Continental Borderland.
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