INEL (Idaho National Engineering Laboratory) Microearthquake Survey Near the Western Edge of the Eastern Snake River Plain, 1988.

摘要

A network of seventeen analog recording seismograph, spaced approximately 2 km apart, were operated from May to November, 1988 near the western edge of the eastern Snake River Plain (ESRP) to record small magnitude microearthquakes. Two three-component digital seismographs were also installed to record the microearthquake activity for analysis of earthquake source parameters and any regional earthquakes for possible analysis of the localized site and crustal effects of the ESRP on earthquake ground motions. We determined near-surface crustal velocities for this area that were slightly lower than the near-surface crustal velocities presently used in routine locations of events recorded by the INEL Seismic Network from five 100 lb surface blasts. During the survey period, only two earthquakes were located near the network area. One of the events occurred in May and was recorded by four of the portable seismic stations and two of the permanent INEL Seismic Network stations. It had a coda magnitude (M(sub c)) of approximately 0.3. The other event was recorded by seventeen portable analog stations and three of the permanent INEL Seismic Network stations. We located this microearthquake, M(sub c)=0.5, about 2 km west of Howe, Idaho, off of the ESRP. We determined an unconstrained focal mechanism for this event, which could be interpreted as normal faulting striking N 44(degree) W or strike-slip faulting on a plane striking either N 44(degree) W or N 47(degree) E. 26 refs., 10 figs., 3 tabs.