Descr: We request equipment from PASSCAL to acquire seismic reflection data in the Spokane Valley to better understand the geology surrounding the recent swarm of earthquakes near Spokane, Washington. Beginning in June of 2001, a series of magnitude 4.0 earthquakes rocked the metropolitan area of Spokane Washington. Seismicity continued sporadically until November of that year before slowly tapering off. Fault plane solutions suggest that the fault responsible for the earthquakes is a northwest trending normal fault, but there is no identified seismogenic structure that can be linked directly to the earthquakes. Recent mapping, however, by Derkey and Hamilton (1999) identified several northwest trending structures to the southwest and southeast of Spokane. The largest of these is the Latah Creek Fault, which appears to occupy the Latah Creek Lineament, a 40 km long northwest trending linear valley that hosts Latah Creek. Derkey and Hamilton (1999) interpret the Latah Creek Fa! ult as a west side down normal fault, which suggests that the structure could be the one that spawned the recent swarm of earthquakes. However, there are no known exposures of the Latah Creek Fault or the other faults to the southeast, nor any detailed geophysical data with which to evaluate the geologic structure of these faults and their potential seismic risk. We propose to collect three seismic reflection surveys across the Latah Creek Lineament and the Spokane Valley. The results of the seismic survey will be used to identify possible seismogenic structures and the timing of their latest movement.
