Seismometers showed no earthquake triggered Saturday's landslide at Oso, but seismic signals show there were two major slides during the event, about four minutes apart.
Information about the landslide readings was posted Wednesday on the Pacific Northwest Seismic Network blog by Kate Allstadt, a researcher at the University of Washington.
She writes the landslide was detected on 17 seismic stations up to 170 miles away. The closest was seven miles away.
They show the biggest slide started at 10:37 a.m. and lasted more than two minutes. This is the slide that hit the town of Oso. There was a second slide at 10:41 a.m. This may have been slumping onto the debris. They were followed by more than a dozen smaller slides for more than an hour.