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Open-File Report 2006-1373

High-resolution boomer seismic-reflection profiles of the shelf off southern California from cruise A-1-00-SC: Santa Monica Bay to San Diego

Introduction

Seismic-reflection data from the California Continental Borderland were collected during 5 cruises beginning in 1997, in support of the southern California Earthquake Hazards Task of the Southern California Coastal and Marine Geology Regional Investigations Project (see the Tierra component of the CABRILLO Project, and Other Resources). These data were acquired to identify the active fault systems in the southern California offshore area. An important aspect of the effort was to map the connectivity of faults from onshore to offshore, because the length of the faults has a direct bearing on the size earthquake it might produce (e.g. Wells and Coppersmith, 1994), see Figure 1. By 2000, the yearly surveys had covered a large part of the designated study area, with the exception of a nearshore swath that lies within California state waters, which extend to three nautical miles from the coast. Under the regulations of the California State Lands Commission, we were limited in our choice of sound sources to use for this critical part of the study; total power had to be less than 2 kJoules. In addition, the survey had to be permitted under the Marine Mammal Protection Act e.g., an Incidental Harassment Authorization permit, in order to be allowed to collect any data using acoustic sources. Related to issues central to the Marine Mammal Protection Act, we also had to apply to the California Coastal Commission for a “consistency determination” to work offshore California with any acoustic sound source. For information on the permitting process, see Childs and others (1999); for details on the permitting for the cruise A-1-00-SC, see Gutmacher and others (2000).

Multichannel seismic-reflection data collected on cruises from 1997-2000 have been released in Sliter and others (2005). Single-channel sleeve-gun profiles collected in 1992, which have proven useful to this project, have been recently released (Normark and others, 2006). The present publication continues the process of making data from this project available to the public for their use.

The following sections present information about the collection and processing of the Geopulse data. Readers may locate and download these data using the static map and table, or via the Google Earth presentation. Images of the data are available in both PDF and JPEG formats, and the SEG-Y formatted data can be downloaded as well.

For more information contact: Ray Sliter

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