Marine geophysical data—Point Arena to Cape Mendocino

Dates

Start Date: 2010-08-09
End Date: 2012-09-25
Publication Date: 2016-06-06

Citation

Beeson, J.W., Johnson, S.Y., Goldfinger, C., and Hartwell, S.R., 2016, Marine geophysical data—Point Arena to Cape Mendocino: U.S. Geological Survey data release, https://doi.org/10.5066/F7GT5K8R.

Summary

This data release includes marine geophysical data collected on three research cruises conducted in 2010 and 2012 between Point Arena and Cape Mendocino. The overall goal of this research is to better understandthe northernmost section of the San Andreas Fault (SAF). In 2010, the USGS collected seismic-reflection profiles crossing the SAF at 1 km spacing from Point Arena to Fort Bragg (survey B-5-10-NC). Then, Oregon State University (OSU) and U.S. Geological Survey (USGS) jointly collected seismic-reflection data crossing the SAF at 1 km spacing from offshore Fort Bragg to Point Delgada (survey C-1-10-NC). In 2012, OSU and USGS jointly collected additional seismic-reflection and marine magnetic data west of the SAF between Point Delgada [...]

Summary

This data release includes marine geophysical data collected on three research cruises conducted in 2010 and 2012 between Point Arena and Cape Mendocino. The overall goal of this research is to better understandthe northernmost section of the San Andreas Fault (SAF). In 2010, the USGS collected seismic-reflection profiles crossing the SAF at 1 km spacing from Point Arena to Fort Bragg (survey B-5-10-NC). Then, Oregon State University (OSU) and U.S. Geological Survey (USGS) jointly collected seismic-reflection data crossing the SAF at 1 km spacing from offshore Fort Bragg to Point Delgada (survey C-1-10-NC). In 2012, OSU and USGS jointly collected additional seismic-reflection and marine magnetic data west of the SAF between Point Delgada and Punta Gorda, and east of the SAF between Point Delgada and Fort Bragg (survey B-04-12-NC).

Approximately 1,605 km of single-channel, seismic-reflection data between Point Arena and Punta Gorda were collected during the three cruises. This dataset includes 120 crossings of the SAF at 1 km spacing. Seismic-reflection data were collected using a minisparker system that creates an acoustic signal by discharging an electrical pulse between electrodes and a ground that generates a frequency spectrum roughly between 200 and 1600 Hz. At boat speeds of 4 to 4.5 nm/hour, seismic traces were collected roughly every 1 to 2 meters. Water depths were generally between 50 m and 150 m, but as shallow as 10 meters near the shoreline and as deep as 500 m within Noyo submarine canyon. Acoustic pulses were generated at 0.5-second intervals on most profiles; a 1-second interval was used on the few deeper water profiles acquired around the head of Noyo submarine canyon. Standard SEG-Y files were generated using a Triton Subbottom Logger (SBL). Seismic data processing was accomplished using Sioseis, a public-domain software developed at Scripps Institute of Oceanography (part of the University of California at San Diego), and SeismicUnix developed at the Colorado School of Mines. The processing of these data consisted of a bandpass filter, mute function, automatic gain control, water bottom detect, swell correction, and scaling/plotting. Both raw data in SEG-Y format and processed data (“Corrected SEG-Y”) are provided here.

Marine magnetic data were also collected during the 2012 survey using a Geometrix G882 cesium vapor magnetometer at a 10Hz sample rate. Magnetic data were collected simultaneously with seismic-reflection data at 1 km line spacing. Additional magnetic profiles were run midway between seismic lines, resulting in a uniform line spacing of 500 m. Preliminary processing of the magnetic data included corrections to remove periodic noise from the seismic source, diurnal field variations, and the reference field defined by the International Geomagnetic Reference Field (IGRF). Further processing included line leveling and decorrugation in the Fourier domain.

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Contacts

Point of Contact :: PCMSC Science Data Coordinator
Originator :: Jeffrey W. Beeson, Samuel Y Johnson, Christopher Goldfinger, Stephen Hartwell
Associate Project Chief :: Samuel Y Johnson
Metadata Contact :: PCMSC Science Data Coordinator
Publisher :: U.S. Geological Survey
SDC Data Owner :: Pacific Coastal and Marine Science Center
USGS Mission Area :: Natural Hazards
Distributor :: U.S. Geological Survey - ScienceBase

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PtArena_thumb.png “Map showing navigation lines for three surveys in the study area”		93.07 KB	image/png

Marine geophysical data—Point Arena to Cape Mendocino

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