Figure 3. Draft map of peak ground accelerations for the July, 3, 1999 Satsop earthquake that occurred at a depth of 42 kilometers. The focus of this earthquake was in the subducting Juan de Fuca plate, not in the overlying North America plate. The map shows recorded ground accelerations in percent of g (1 g = 9.8 m/sec**2). The measured accelerations were determined from a combination of the PNSN's digital real-time accelerographs and broad band seismic stations, plus information from old-style USGS accelerometers. Some of the stations used to contour the data lie off the map in Oregon, Canada, and eastern Washington.
The star shows the epicenter of the earthquake. The contours show a smoothed version
of the expected ground accelerations modified by the actual observations.