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April 8, 2012, earthquake swarm ~20 km south of Mount Hood

April 9, 2012

The swarm is consistent with a tectonic, rather than magmatic, origin.

According to the Pacific Northwest Seismic Network (PNSN), a short-lived swarm of small earthquakes (maximum magnitude 2.7) occurred ~20 km south of Mount Hood near Clear Lake on the morning of April 8, 2012. The swarm featured 25 locatable events occurring between 0500-1030 PDT, with most depths ranging from 3-8 km. Although locations appear to be aligned in an east-west direction, most events are quite small and station coverage is sparse, so it is possible that the east-west alignment is an artifact of poor station coverage. The swarm occurred in an area with relatively sparse historical seismicity; outside of a M 3.2 earthquake in July of 1980, very few earthquakes have been recorded within 10 km of the April 8 swarm. The characteristics of the swarm are most consistent with a tectonic, rather than magmatic, origin. The graphic is a webicorder record from station VFP showing most of the swarm events