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Data report for line 8 of the 2011 USGS seismic imaging survey at San Andreas Lake, San Mateo County, California

March 19, 2020

In June of 2011, the U.S. Geological Survey acquired high-resolution P- and S-wave seismic data across the mapped (Schussler, 1906) trace of the San Andreas Fault zone at San Andreas Lake in unincorporated San Mateo County, California. Our seismic survey consisted of seismic reflection, refraction, and guided-wave data along a 60-m-long profile. To acquire the reflection and refraction data we co-located shots and geophones, spaced every meter along the profile. We used 59 SercelTM L40A, P-wave (40-Hz vertical-component) geophones (sensitivity of 22.34 volts/meter/second) to record 59 P-wave shots and 59 SercelTM L28-LBH, S-wave (4.5-Hz horizontal-component) geophones (sensitivity of 31.3 volts/meter/second)to record 59 S-wave shots. We generated P-wave data using a charge from a Betsy SeisgunTM, with the charge placed approximately 0.4 meters (16 inches) beneath the ground surface. The charge consisted of an 8-gauge, 400-grain, blank shotgun shell. S-wave sources were generated by horizontally striking an aluminum block with a 3.5-kg sledgehammer. We acquired fault-zone-guided-wave data using approximately one pound of explosives within a mapped trace of the San Andreas Fault, approximately 1.74 km NNW of the recording arrays. The explosives were placed in a 5-cm (2 inch) diameter borehole approximately 3-meter (10 feet) deep. All data were recorded using a 60-channel Geometrics Stratavisor NX-60TM seismograph with a 24-bit analog-to-digital converter and a roll-along descaling factor, and the output data are in SEG-Y format (Barry et al, 1975). Each in-line 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 analyze the seismic data. References Barry, K.M., Cavers, D.A. and Kneale, C.W., 1975, Recommended standards for digital tape formats: Geophysics, vol. 40, no. 2, p. 344-352. Schussler, H., 1906, The Water Supply of San Francisco, California, Before, During, and After the Earthquake of April 18, 1906 and the Subsequent Conflagration: Martin B. Brown Press, New York, 103 pp.