USGS: No earthquake to blame for mudslide

USGS: No earthquake to blame for mudslide
The U.S. Geological Survey has released dramatic new aerial images of the area devastated by the Mar. 22 landslide near Oso. The photos were taken Mar. 24 during a joint survey with the Washington State Department of Transportation, the Washington State Department of Natural Resources and the King County Sheriff's Office. (Courtesy: U.S. Geological Survey/King County Sheriff's Office - Air Support Unit)
U.S. GEOLOGIC SURVEY NEWS RELEASE -- Seismograph readings show no indication of an earthquake in association with the landslide near Oso, Washington, on March 22, 2014.

The readings show two wave signals, the first is the landslide at 17:37 UTC and a second is a slide that occurred at 17:41 UTC. There are no earthquakes or other local seismic events on the records around the time of the landslide. The seismic signals are of long period surface waves, with no clear high-frequency P or S phases that we would expect to see if a local earthquake occurred at the time of the event. The landslides generated elevated levels of local ground shaking for over an hour.

Seismic readings are from the University of Washington Pacific Northwest Seismic Network, operated in cooperation with the USGS.