Earthquake Catalog for the Eastern Snake River Plain, Idaho (430 N, 1115 - 1140 W) October 1972 - June 1982

King, J; Doyle, T

Ten years of earthquake data, gathered by the Idaho National Engineering Laboratory, presented. Results and mechanisms discussed. Geographic location: Regional, Idaho National Engineering Laboratory site and surrounding areas. The Idaho National Engineering Laboratory (INEL) has deployed a network of short-period high-gain vertical seismograph since December 1971 to monitor earthquake activity on and about the eastern Snake River Plain (ESRP), Idaho. This report summarizes the earthquakes located within a designated Special Study Area (43.0’ – 44.5’N, 11.5’ – 114.0’W) from October 1972 to June 1982. Seventy-eight events were located within the Special Study Area, with a Richter Local Magnitude (ML) range of 0.8 ≤ ML ≤ 2.7. The mean ML for these microearthquakes was 1.4. Only three small microearthquakes (ML ~ 1.0) were detected on the ESRP. Fifty-nine microearthquakes were located northwest of the ESRP, primarily in the Birch Creek Valley – Beaverhead Range region. Sixteen microearthquakes were located southeast of the ESRP within the Special Study Area. The aseismicity within the ESRP can possibly be attributed to high crustal heat flow which allows aseismic creep to occur in response to regional tectonic forces, rather than earthquakes. The aseismic behavior of the Lost River, Lemhi, and Beaverhead Ranges northwest of the ESRP may also be associated with aseismic creep or possibly small strain accumulation rates. The very low seismic activity reported in this study is in agreement with the historical record of seismicity for the ESRP region.