Project Abstract
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This report summarizes work supported by grant #09094 which consisted of constructing high-resolution bathymetry, gravity, and magnetic field maps of offshore southern California from existing databases. This research activity was in preparation for an NSF-funded marine seismic deployment scheduled for August, 2010 to deploy ocean bottom seismometers off the southern California coast in the Continental Borderland and on the Pacific plate further west. The data compilations produced here served as guides during the planning of the marine experiment by complementing additional research activities during the cruise, and by avoiding the duplication of previously collected ship board underway data. The existing data are scattered among several databases and it was necessary to compile the required data for our marine deployment in one place. The overarching goals for the work were to contribute surface geomorphology, seismicity, fault structure, and lithospheric data of the western side of the wide, diffuse, transpressional Pacific-North America plate boundary.
There have been many ship tracks passing over this region either coming or going from more distant research projects, or for bathymetric, magnetic field, or gravity studies. Most academic cruises will report marine underway data sets to the NOAA NGDC (National Geophysical Data Center) from which we accessed data online. Other data repositories included MBARI, the USGS, and private geophysical firms in southern California. Although publicly available, raw data are often stored with different degrees of processing and had to be analyzed for data gaps, offsets between cruises and/or ships, corrected for individual experiment settings, navigation (especially turns and sharp direction changes which affect continuous data collection), as well as sea state which can produce apparent but false anomalies in the final maps. We explored all known sources of ship track data available either publicly or otherwise to provide an inclusive data collection. We present our final maps showing high resolution ship board multibeam bathymetry, gravity data, and magnetic field data for the region.
The compiled information is available to the SCEC scientific community, and aided in planning the marine experiment that took place in August 2010. Specifically, the data and maps were used to optimize the ship track plan for both deployment and recovery legs, and to project the need for additional gravity and magnetic field data collection during the 2010 cruise. This reconnaissance study was comprehensive and it was crucial to finish it by the ocean bottom seismometer deployment dates. |
