County prepares for big one at Tahoe

Scripps Institution report suggests fault may rupture
By: Gus Thomson Journal Staff Writer
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Scientists say the Lake Tahoe area is overdue for a major earthquake. But a quake won’t catch Placer County flat-footed. It’s something the county’s emergency services division has very recently been rehearsing for. Scientists at the Scripps Institution of Oceanography at the University of California San Diego reported this week that earthquakes with a magnitude-7 occur every 2,000 to 3,000 years in the Tahoe basin but the largest fault there last ruptured more than 4,100 years ago. The fault runs along the west shore of the lake before passing west of South Lake Tahoe. Waves from the shaking would run the length of the lake onto the north shore, which is part of Placer County. Placer County’s Office of Emergency Services conducted a training exercise in November, using a major earthquake and the subsequent tsunami-like seiche as the starting point for a dress rehearsal for disaster. Rui Cunha, Placer emergency services program manager, said Wednesday that while there has been nothing in recent memory that has produced significant damage, the threat is serious enough to have it identified as one of several hazards included in safety plans for the Tahoe area. The November exercise included El Dorado County and state emergency personnel in a scenario that started with a quake and then saw a freshwater wave – technically defined as a Seiche (pronounced “saysh”) slosh back and forth from shore to shore four times. Wave height was calculated and estimates were extrapolated using assessor’s parcel map data to determine how far onshore they would go. With damage to the shoreline, boats and homes, the exercise added unexpected emergencies for the team to work with. They included a landslide on Highway 89 and damage to Fanny Bridge, at the intersection of highways 28 and 89. Cunha said the idea was to overwhelm local resources and gauge the time it would take to bring in help from the outside. With ground transportation links cut off, exercise participants found a way to evacuate victims using boats from the shoreline, he said. The November exercise provided emergency personnel with valuable training for an emergency Cunha said he hopes the area will never see. But there was a series of tremors in 2003 and 2004. And in 2005, a magnitude-5 temblor was felt widely in the Reno and Lake Tahoe region. Residents can prepare for an earthquake or other emergency by keeping a battery-, solar- or crank-powered radio on hand, as well as other staples to used during a 72-hour power outage and disruption to the drinking water supply. The list includes bottled water, canned food and blankets. The Journal’s Gus Thomson can be reached at