Seismic stations pick up earthquake swarm near Gilchrist, Oregon.

Beginning the afternoon of October 22, 2015, a swarm of mostly small earthquakes occurred about 10 km (6 miles) NW of the towns of Crescent and Gilchrist, Oregon. Through the morning of October 23, the Pacific Northwest Seismic Network (PNSN) located 29 events (maximum magnitude M 2.6) and a number of additional events are too small to locate. The PNSN locations are spread out over a 5 by 10 km (3 by 6 miles) area in the vicinity of Ringo and Cryder Buttes, with depths ranging from 1 to 15 km (0.6 to 9 miles). Since the nearest network station is about 40 km (25 miles) to the northeast, location and depth determinations have a high degree of uncertainty and it is quite possible that events are occurring over a much smaller area.

This area has experienced periods of elevated seismicity in the past. In June-August 2001, the PNSN located 6 events (maximum magnitude M 2.6), and in July-August 2012 the PNSN located 20 events (maximum magnitude M 1.1). Prior to the expansion of the Newberry seismic network in 2012 earthquakes were much harder to detect and locate in central Oregon in general and in this area in particular, so it is conceivable that other Crescent-area swarms could have occurred prior to 2012 that were not detected by CVO or the PNSN.