Thursday, May 29, 2014

Seismic Readings From #MCMudslide

#MCMudslide Likely Captured On Seismic Readings

Mesa County, Colo. -- In the Geology Department at Colorado Mesa University (CMU), their seismic stations (one station located in Palisade, the other in Orchard Mesa) captured readings on Sunday, May 25, 2014. The following information provides a breakdown of that significant seismic activity and is likely attributed to the #MCMudslide.

Two separate sources have provided the time of 5:44 p.m., on May 25, 2014, for the time of the largest portion of #MCMudslide occurring with a much smaller slide estimated to have occurred at 7:19 a.m., but barely recorded on the same two seismic sources that captured the later, much larger slide time.
The length of time recorded in the major event is a little over 2 minutes. That is not to say it took 2 minutes for the landslide to come down. Rather, the major portion of the mudslide may have come down in much less time than that and it is also possible it continued for 2 minutes, or more. Also, the seismometers are too far away to record what may have been continuous movement of the slide beyond that initial large movement. We also can't detect creep of the landslide, which may be continuing at this time. Times are almost always exact on seismic equipment when it comes to an earthquakes, because the movement of the quake is defined.  This information has been provided by Dave Wolny, of the Geology Department at Colorado Mesa University.

Two seismic stations on the Grand Mesa, within the CMU seismic network, captured the following readings:

Distance from landslide is 24 miles (or 39.7 km)

Distance from landslide is 37 miles (or 60.3 km)

To show the difference between an earthquake and the data gathered from the likely #MCMudslide event, a seismic reading from an known and actual earthquake event is posted here on the right. In the earthquake example, notice the very sharp P wave arrival. P arrival time is used to help determine time of origin and ultimately epicenter location. Compare it to the other 2 seismograms of the landslide and note the apparent lack of distinct P arrivals. That is why placing a time of origin on this event is difficult and gives a an error range in seconds rather than milliseconds.

Special Note: All seismic readings associated with this post are provided courtesy of Colorado Mesa University, Geology Department Adjunct Professor Dave Wolny. Any media reproduction of these images should give proper credit to CMU/Geology Dept. Dave can be reached by email at: