Idyllwild Water District (IWD) General Manager Terry Lyons confirmed that his district is in discussion with the United States Geological Survey (USGS) to install two seismic monitoring units on IWD property — one at the district’s wastewater and percolation pond site and the other near Foster Lake. Forest Service (FS) approval would be required for the wastewater site, since that is FS land IWD uses with a permit. The IWD board would also need to approve the plan and then structure an agreement with USGS. Lyons presented the plan to his board at its Tuesday, Sept. 20 meeting.
Dr. Frank Vernon, research seismologist with the Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, UC San Diego, would lead the project. Vernon is the current director of the U.S. Array Network Facility for the National Science Foundation’s EarthScope program, which deploys thousands of seismic, GPS and other geophysical instruments to study the structure and evolution of the North American continent and the processes that trigger earthquakes.
Once FS and IWD board approval is obtained, Vernon would have his team study the sites to choose optimal installation points that best provide line-of-sight access with existing USGS telemetry equipment at Torro Peak in the Santa Rosa Mountains between Idyllwild and Palm Springs. Two methods of installation would likely be used in Idyllwild, according to Vernon — a simple burial of the device at the Foster Lake site and a posthole installation at the wastewater facility.
Basically, according to Vernon, monitoring devices measure developing strain along or near faults using high-precision GPS measurements and/or shallow borehole strainmeters. “Using the history of earthquakes on a fault, both from observed earthquakes as well as results from paleoseismology, we can develop models of where future earthquakes may be likely to occur,” he said. “The timing of the events is still unpredictable.”
Lyons noted the addition of seismic monitors in the Idyllwild area would help seismologists better understand how this area would be affected in a major quake. Idyllwild sits on granite, a dense material through which destructive energy waves generated by a quake move more quickly than through less dense material. Also, with a granite base there is little danger of liquefaction, the sudden mixing of high ground water with sand causing the collapse of buildings.
Lyons could offer no date by which the proper agreements with the Forest Service and the IWD board could be reached, even though Vernon had indicated a desire to start at the earliest opportunity.