DENVER - Sunday's slide on the Grand Mesa caused an earthquake that registered 2.8 on the Richter scale, the U.S. Geological Survey office in Golden reported Wednesday.
Two separate seismic monitoring stations registered a two minute event beginning at 5:44 p.m. Graphs from the Colorado Mesa University Geology Department seismometers in Palisade and Orchard Mesa chart the violent event in a gradual, curving shape.
In comparison to the seismic reading of an earthquake, Mesa County and CMU say the mudslides arrived very gradually. Earthquakes typically arrive with a spike on the chart, instead of the gradual increase seen with the mudslide.
The gradual arrival of the "P Wave" makes it difficult for geologists to place a precise time of origin on Sunday's slide.
Clancy Nichols, 51, his son Danny, 24, and Wes Hawkins, 46, are missing and presumed dead in the mudslide. Officials believe they were investigating a water flow problem that could have been caused by a small slide earlier in the day.
Mesa County and CMU report the seismic monitoring stations registered that much smaller slide around 7:19 a.m., but say it barely registered.
Because of ongoing fears of another landslide, incident commanders in Mesa County said they are looking to place remote cameras, GPS equipment and seismometers in the area to gather better information. For now, however, experts are primarily monitoring the area visually with manned or unmanned flights and two USGS satellites.
"The instability and current water saturation levels, along with the water pooling in the area behind the slide near its origin, are indicators that a further or additional slide and earth movement could happen any time," the county wrote in a May 29 blog post about the incident.
The goal, Mesa County said, is to build a warning system focused on these three tiers:
- Salt Creek Road residents from Highway 330 to the toe of the mudslide
- From Salt Creek Road to the town of Collbran
- Below the town of Collbran
*Editors Note: An earlier version of this article was provided by our partners at The Denver Post: http://ch7ne.ws/SSjgAk