INL Strong Motion Accelerographs
The INL started an accelerograph network in 1973 when 11 analog strong-motion accelerographs were installed in buildings at INL. Additional analog strong motion accelerographs were installed at INL following the 1983 surface-wave magnitude (Ms) 7.3 Borah Peak, Idaho earthquake. All analog accelerographs were replaced with digital accelerographs in 2003. Beginning in 2002, accelerometers were added to INL seismic stations. Accelerographs at INL recorded acceleration data from the 1983 Borah Peak earthquake and several small to moderate size earthquakes (such as the 2005 moment magnitude (Mw) 5.6 Dillon, Montana and the 2008 Mw 6.0 Wells, NV earthquakes).
Currently, there are 25 strong-motion accelerographs located within buildings and free-field sites at INL and seven tri-axial accelerometers located at INL seismic stations. Self-contained strong motion accelerographs consist of DAQSystems NetDAS four-channel recorders that contain Applied MEMs Inc. model SF1500A tri-axial accelerometers. The NetDAS has an embedded LINUX computer, a Symmetric Research 24-bit digitizer, and its own GPS clock. The accelerographs are set to trigger accelerations of approximately 0.005 g. Several strong motion accelerographs are connected to phone lines, providing quick access to acceleration data in the event of a large earthquake. Other accelerographs save the data on memory cards for INL Seismic Monitoring Program personnel to retrieve. Seismic stations with acceleration sensors have Applied MEMs Inc. model SF1500A, SF2500A, or SF3000L tri-axial accelerometers. The acceleration data are digitized by eight-channel NetDAS recorders and transmitted along with the seismic data from seismic stations to Idaho Falls.