Open-File Report 02-203
The U.S. Geological Survey (USGS), as part of an ongoing program to acquire seismic velocity and geologic data at locations that recorded strong-ground motions during earthquakes, has investigated five sites in the Fortuna, California region (Figure 1). We selected drill sites at strong-motion stations that recorded high accelerations (Table 1) from the Cape Mendocino earthquake (M 7.0) of 25 April 1992 (Oppenheimer et al., 1993). The boreholes were drilled to a nominal depth of 95 meters (310 ft) and cased with schedule 80 pvc-casing grouted in place at each location. S-wave and P-wave data were acquired at each site using a surface source and a borehole three-component geophone. This report contains the velocity models interpreted from the borehole data and gives reference to locations and peak accelerations at the selected strong-motion stations.
First posted May 29, 2002
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Gibbs, James F., Tinsley, John C., Boore, David M., 2002, Borehole Velocity Measurements at Five Sites That Recorded the Cape Mendocino, California Earthquake of 25 April, 1992: U.S. Geological Survey Open-File Report 02-203, 48 pp., https://pubs.usgs.gov/of/2002/0203/.
P- and S-Wave Travel-Time Data
Summary Velocity Profiles