2017 seismic imaging of the West Napa Fault Zone, St. Helena, California

Dates

Publication Date: 2018-07-25
Time Period: 2017-04-11

Citation

Chan, J.C., Catchings, R.D., Philibosian, B., Goldman, M.R., Criley, C.J., Sickler, R.R., and DeLong, S.B., 2018, 2017 seismic imaging of the West Napa Fault Zone, St. Helena, California: U.S. Geological Survey data release, https://doi.org/10.5066/P9LKXZKP.

Summary

In April 2017, the U.S. Geological Survey acquired high resolution P- and S-wave seismic data across the suspected trace of the West Napa Fault zone in St. Helena, California. We acquired seismic reflection, refraction, and guided-wave data along a 215-m-long profile across the expected trend of the West Napa Fault zone. To acquire the reflection and refraction data, we co-located shots and geophones, spaced every 2 m along the profile. We used 109 SercelTM L40A P-wave (40-Hz vertical-component) geophones with a sensitivity of 22.34 volts/meter/second to record 108 P-wave shots, and 109 SercelTM L28-LBH S-wave (4.5-Hz horizontal-component) geophones with a sensitivity of 31.3 volts/meter/second to record 108 S-wave shots. We generated [...]

Summary

In April 2017, the U.S. Geological Survey acquired high resolution P- and S-wave seismic data across the suspected trace of the West Napa Fault zone in St. Helena, California. We acquired seismic reflection, refraction, and guided-wave data along a 215-m-long profile across the expected trend of the West Napa Fault zone. To acquire the reflection and refraction data, we co-located shots and geophones, spaced every 2 m along the profile. We used 109 Sercel^TM L40A P-wave (40-Hz vertical-component) geophones with a sensitivity of 22.34 volts/meter/second to record 108 P-wave shots, and 109 Sercel^TM L28-LBH S-wave (4.5-Hz horizontal-component) geophones with a sensitivity of 31.3 volts/meter/second to record 108 S-wave shots. We generated P-wave data using one of two active sources depending on site accessibility: a 226-kg accelerated weight drop (AWD) and a 3.5-kg sledgehammer and steel plate combination. S-wave sources were generated by horizontally striking an aluminum block with a 3.5-kg sledgehammer. We acquired fault zone guided wave data by generating P- (AWD) and S-wave (angle AWD) energy approximately 225 m north of the P- and S-wave recording arrays. All data were recorded using two 60-channel Geometrics Stratavisor NX-60^TM seismographs with a 24-bit analog-to-digital converter with a roll-along descaling factor (Subcommittee of the SEG Engineering and Groundwater Geophysics Committee, 1990); the seismographs were connected to the P- and S-wave geophones via refraction cables. Each shot was recorded for two seconds, with data recording starting 100 ms before the actual time of the shot. Data were recorded at a sampling rate of 0.5 ms, or 2000 samples per second. This report provides the metadata needed to utilize the seismic data.

Reference: Subcommittee of the SEG Engineering and Groundwater Geophysics Committee, Pullan, S.E., Chairman, 1990, Recommended standard for seismic (/radar) data files in the personal computer environment: Geophysics, v. 55, n. 9, p. 1,260-1,271.

Contacts

Point of Contact :: Joanne H Chan, Rufus D Catchings
Process Contact :: Mark R Goldman
Originator :: Joanne H Chan, Rufus D Catchings, Belle E Philibosian, Mark R Goldman, Coyn J Criley, Robert R Sickler, Stephen B DeLong
Metadata Contact :: Joanne H Chan, Mark R Goldman
Publisher :: U.S. Geological Survey
Participant :: Carolyn Stieban, Keith Galvin, Shuai Zhao, Ryota Kiuchi
Distributor :: U.S. Geological Survey - ScienceBase
USGS Mission Area :: Natural Hazards
SDC Data Owner :: Office of the Southwest Regional Director

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StHelena_4_2017_metadata.xml Original FGDC Metadata	View	19.19 KB	application/fgdc+xml
StH17Map.jpg “Map of study area”		140.25 KB	image/jpeg
StHelena_4_2017_locations.csv “Station locations”		7.98 KB	text/csv
StHelena_4_2017_shots.csv “Shot locations”		33.36 KB	text/csv
StHelena_4_2017_SEG2.tar “SEG2 seismic data”		765.9 MB	application/x-tar

Purpose

The primary goal of the seismic survey was to precisely locate the trace of the West Napa Fault in St. Helena to assist in a paleoseismic trenching investigation.

2017 seismic imaging of the West Napa Fault Zone, St. Helena, California

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