PNSN Strong Motion Network PNSN > Strong Motion > Operations

Strong Motion Program Status Report

February 9, 2000

The strong-motion subnetwork began in 1996 with the installation of 3 high-dynamic range, digital instruments. The models selected were the IDS-24 manufacured by Terra Technologies of Redmond, Washington. These instruments successfully recorded on-scale waveform data from regional earthquakes such as the the M=4.9 Bremerton earthquake of June 23, 1997.

Data recovery in the initial phase was via dial-up modems. Taking about 5 minutes per station to recover data it became apparent that real time data acquisition was the only option for an expanding network. Real time acquisition of strong motion data began in 1998, via either dedicated phone lines or via the internet. Some stations also retained their dial-up access for station maintenance and as backup to the real time link.

The PNSN currently operates 15 strong motion stations all with real time telemetry. Three stations use the internet for data telemetry. Three stations in the Portland area use a hybrid of of dedicated phone lines for data collection to a central point and then exportation to the UW via the internet. The remaining nine stations use dedicated phone lines. Microwave communications systems form part of the telemetry link for some of these stations. All of the strong motion stations can record ground motions up to 2g with their 3-component accelerometers. Four stations have additional 3-component broadband seismometers, especially useful in seismic research.

Station locations, sensor types, and telemetry are summarized in a station list.

The primary data product from the strong motion network are summary, or parametric data such as peak acceleration, ground motion duration, and spectrum intensity. After a quality review of the waveforms these summary data are made available on PNSN Web pages (www.ess.washington.edu/SEIS/PNSN) within a few hours after a significant earthquake. The summary data are presented in a table and peak accelerations are also shown in automatically generated maps. An example is the information for the Mc=5.1 (mb=5.5) Satsop earthquake of July 3, 1999.

An additional benefit of the strong motion network is the increased capabilities of the PNSN to accurately and rapidly determine locations and magnitudes for earthquakes in the Puget Sound region. Several methods are used to provide earthquake information within minutes of an event. The PNSN automated alert system sends messages by e-mail, fax, and pager systems. Another method is the Rapid Alert for Cascadia Earthquakes (RACE) system. In this system, remote computers receive earthquake location and magnitude via pagers and display this information on maps. In the future, summary parameters from the strong motion network will be included in RACE displays. Information on RACE is available at www.ess.washington.edu/SEIS/PNSN/race.html.

Time series from all PNSN stations, including the strong motion stations, are archived on a quarterly basis at IRIS. These time series data, as well as station response information, are available through automated request methods.

The PNSN is developing a partnership program called the Pacific Northwest Earthquake Research Affiliates (PERA). Partners in this program will participate in development on the strong motion network. They will assist with such efforts as site selection, telemetry, operational support, and research using strong motion data. PNSN data products can be tailored to meet specific needs of the research affiliates. Potential affiliates include organizations such as local utilities, industries, emergency management offices, and other public and private organizations.

If interested in participating in the RACE project or in any aspect of the the strong-motion program such as instrument siting. please contact:

Updated October 18, 2000