USGS, Science for a Changing World, Earthquake Hazards Program, Ground Motion

Nisqually Earthquake - Strong Motion Data

Seattle Seismic Hazard Mapping Task

These are uncorrected accelerograms from Seattle for the M6.8 Feb 28, 2001 Nisqually Earthquake.

The data are from the urban seismic array in Seattle deployed and operated by the Geologic Hazards Team of the USGS, stationed in Golden, CO. These data were collected for the Seattle Seismic Hazard Mapping Task, with task leader Art Frankel. The field deployment and operation are led by Dave Carver, who sites, installs, maintains, and downloads the instruments. Tom Bice and Bob Norris also maintain and download the instruments. Edward Cranswick, Mark Meremonte, and Dee Overturf installed some of the sites in the initial phase of this experiment.

The Seattle Urban Hazards Seismic Array configuration table includes locations, orientations, site descriptions and other pertinent information about the individual recording sites. William et al. have determined shallow Vp and Vs profiles for many of the sites.

These files may be viewed and/or downloaded
HTML file
Formatted Text (Space Delimited) (*.prn)
Microsoft Excel Workbook (*.xls)

The first line of each data file below is the start time of the record in year, day, hour, min, sec, millisec. This is followed by the data. The left column is time in seconds and the right column is the amplitude in units of g.

Data for all of the earthquakes that our Seattle array has recorded up to October of 2004 may be found at

All of our stations have Kinemetrics K2 2g accelerographs. The data headers indicate whether the sensor is the older FBA-24 or the Episensor. Some stations also have Mark L-22 velocity sensors on channels 4, 5, and 6 (as indicated in the event headers.)

The event data is available in ASCII, the original evt, and SAC formats. The file, k2autoed.cfg, contains station configuration data that has been used to correct event data headers (such as orientation) for each of the formats. You will also find files that give ANSS Catalog Locations for all of the events for which we have data. The AssociatedEvent list can be used to easily determine the accuracy of timing. The column after ".evt" gives the number of hours since the last GPS clock correction. Generally speaking, if the GPS at a station has not locked within 12 hours we do not trust the accuracy of the timing for the data. For the Nisqually event, station MAR was not receiving GPS timing signals and so the clock correction is unknown. All of the other station's clocks were accurate to within .002 seconds for Nisqually.

If you have questions, contact Art Frankel ( or Dave Carver ( logo