Dr. Frank Vernon, research geophysicist at Scripps Institution of Oceanography, University of California at San Diego (UCSD), will head a team and project that will install seismic monitoring stations at a number of locations on the Hill to measure San Jacinto Fault activity. Two of the stations will be in Idyllwild. The others will be at Rouse Ridge Road in Anza, and Blackburn Canyon. 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.
The purpose of the Hill installations, said Vernon, is to better understand earthquake activity on this section of the San Jacinto Fault Network (SJFN). The SJFN is considered by seismologists to be one of the most active fault networks in Southern California, with regular quakes in the 2 to 3 magnitude range with larger quakes, in the 7 magnitude range, happening every 100 to 200 years. It is not a continuous fault but a series of faults that follow a north-south axis. “There has not been a rupture between two sections, from the top of Bautista Canyon down to Borrego Mountain, in over 200 years,” said Vernon. “The last major [mountain] quake was in 1800, in Anza.” Vernon said the Hill seismic project is designed to fill information gaps for activity in the immediate Anza-Idyllwild area. “This will give us better measurements in this area and show precise patterns of activity,” he said. Vernon noted that given the 200 years since the large Anza quake, and that major quakes in the 7 magnitude range occur roughly every 200 years on the mountain, this area is due.
When asked the perennial question of whether these stations would help predict the next major quake, Vernon demurred. “We’re not able to predict at this in time,” he said. When asked if the Idyllwild area would get less shaking than off-Hill areas because we’re on bedrock granite, he offered a different opinion than some seismologists the Town Crier has talked to in the past. “You’re only six miles from the San Jacinto fault section that’s nearest you,” he said. “That’s a lot closer than to Palm Springs. You can definitely get strong shaking where you are.”
Vernon pointed out a strong earthquake near Idyllwild would carry the strongest energy upward toward ridgelines. “The energy travels upward,” he noted.
Vernon is still waiting for Forest Service approval before beginning installation of the monitoring units. “We’ve been trying to do this experiment for many years,” he noted. “Once we have the go ahead, I’ll get the team organized and move forward with the installations. Some of the installations will go in in short order.”
Vernon advocated preparedness, making homes and businesses in this area earthquake safe. “It [a large quake on the SJFN] may not happen in your lifetime,” he said. “But it is due.”