ShakeOut encourages earthquake preparedness, safety
Deep below the patchwork of soil and water that provides life to the people, livestock, crops and wildlife that call the Mission Valley home, the Mission Fault runs along the base of the Mission Mountains. The minor geological fault line presents a constant threat of earthquakes and secondary hazards that can follow a seismic event.
At 10:23 a.m. on October 23, government agencies, schools, families, and businesses across the state of Montana will participate in the Rocky Mountain ShakeOut. The ShakeOut is a two-week long event held across Colorado, Wyoming and Montana in an effort to raise earthquake awareness.
Local entities registered to participate, as of press time, were: Valley View School, Dayton Elementary, Salmon Prairie Elementary, K. William Harvey Elementary, and the Valley Journal. During the drill, people will be asked to “drop, cover, and hold on,” underneath a sturdy table or desk until the simulated shaking stops. The method has been deemed the safest way to ride out a quake. The drill is also a good time to think about what shelving and hanging objects might fall or become projectiles during an earthquake.
Lake County Superintendent of Schools, Michelle Wood, said that she wanted the small rural schools to take part in the ShakeOut because the state requires schools to hold eight drills every year. Four must be fire drills, the other four are left up to the district’s discretion.
“I thought it would be great for the kids to know that people across Montana, Colorado and Wyoming were learning the same things they were,” Wood said.
Other than schools, no other agencies on the Flathead Reservation were planning to participate in the drill, according to tribal emergency management coordinator Dale Nelson.
“A lot of people here are used to severe weather,” Nelson said. “They have the ‘survivor’ mentality already. It’s hard to convince people they need to be prepared.”
In the event of a major earthquake, people should plan to sustain their families for at least three days.
“Because of our location in between Kalispell and Missoula, the bottom line is it will be at least 72 hours before we see any kind of help,” said Lake County Emergency Management director Steve Stanley.
The county and tribe have identical preparedness plans that put a very detailed recovery protocol into place if an earthquake of a 6.0 magnitude or greater strikes the area. A quake that large could cause significant structural damage, but other hazards might also result in the aftermath. Just as earthquakes can set off devastating tsunamis when they occur underneath the floors of oceans, earthquakes that occur beneath or near large bodies of water can trigger seismic seiches. This phenomenon results in oscillation within bodies of water, much like a basin of water sloshes back and forth when shaken by a person. Seiches five feet high have been reported to the U.S. Geologic survey before. Seiches can cause hundreds of thousands of dollars in damage to harbors and boats and are sometimes powerful enough to pull people into the water from the shore.
Earthquakes can also trigger another water-related hazard. Approximately 5,900 people live downstream of 17 dams or reservoirs that could be susceptible to failure after an earthquake, according to Lake County’s Emergency Operations Plan.
“Dams that could have the greatest impact to life and property include Kerr, Tabor, Mission, McDonald, Ninepipe, Pablo, Crow, Kicking Horse, Jocko, Black Lake, Upper Dry Fork, and Lower Dry Fork, followed by Hillside Lake, Turtle Lake, and Hell Roaring Dams,” the plan reads.
Nelson said the tribe has a control room dedicated to monitoring the dams all day, every day.
Loose sediments on mountainsides can trigger landslides. A landslide triggered by the magnitude 7.3 Hebgen Lake earthquake in 1959 killed 28 people. It is the state’s strongest and deadliest earthquake on record, according to the U.S. Geological Survey.
Earthquakes can also create sanitation and utility crises. Fires can result from downed power lines or broken gas lines. Water lines can break. Wells may be muddied by the shaking. Gravesites can be disturbed so much that bodies have to be reinterred.
The tribal and county plans have detailed instructions on what to do in all of these situations.
“We have had small quakes, but haven’t been hit by the big one so far,” Nelson said. “We hope it never does.”
A magnitude 4.7 earthquake in the Flathead Lake area on April 1, 1969, caused damage at Big Arm, Dayton, Proctor and in the Lake Mary Ronan area. The quake also caused a water well near Polson to go dry, and muddied others in Proctor, according to the USGS.
According to Lake County planning documents the last major earthquake that occurred an estimated 7,000 years ago along the Mission Fault is estimated to have been a 7.5 magnitude event. The Jocko Fault also runs along the southern border of the county, but the U.S. Geologic Survey has relatively little data about it recorded.
Small earthquakes occur regularly in Lake County. The most recent was of a 1.2 magnitude that was recorded six miles southeast of Ronan on Oct. 3.
In the event of a more damaging quake that triggers emergency response, tribal members enrolled in the emergency alert system will receive updates electronically, Nelson said. The program is not currently open to non-tribal members. Updates may also be sent out via the tribe’s Twitter and other social media accounts.
The American Red Cross has an earthquake app available via iTunes and Google Play.