Monday, January 19, 2009

Quake update: Geologists of Jackson Hole: 'Just be prudent'

An earthquake was felt at 9:15 pm on Thursday, January 15th in Jackson, Alpine, Etna and Thayne, Wyoming, and Idaho Falls, Idaho. According to the US Geological Survey, it was a magnitude 4.0 event located just north of Alpine Junction at a depth of 3 miles.

This earthquake occurred at the south end of the extended Teton Fault zone along the eastern base of the Teton Mountain Range. Geologists call this area the “Seismic Gap” because of the lack of recorded earthquakes—a linear area along the large Teton Fault, which is unusually seismically quiet. The recent swarm of hundreds of earthquakes in Yellowstone National Park lie near the northern end of this “seismic gap”.

This seemingly quiet seismic zone centered along the Teton Fault has been the site of magnitude 7. plus earthquakes in pre-historic times. The Faults have created the Grand Teton Mountains and shaped western Wyoming. Another magnitude 7. plus earthquake will fill this gap sometime within the next several hundred years. Some earthquakes are preceded by a perceptible increase in seismicity at one or both ends of the “seismic gap”. There is currently no reliable way to know in advance which small earthquakes are foreshocks to large earthquakes. There is no scientific basis to predict that a large earthquake is imminent.

But this is a reminder to dust off your earthquake response plans. There are precautions that can be taken, just like fastening the seatbelt in your car, to increase safety just in case a bigger earthquake should happen:

1. Revise or develop an earthquake plan. How will your family get back together if roads are blocked, bridges are down, and telephones do not work? Discuss with family, neighbors, and friends how everyone might respond to such an emergency. Employ a "buddy system" so that you can confirm that your neighbors are not trapped, and visa-versa.
2. Have some emergency medical supplies, food, fuel, and cold-weather clothes/sleeping bags on hand.
3. Be sure your gas appliances (especially stoves, hot water heaters and furnaces) are fastened down and use flexible connections to the gas supply.
4. Know how to shut off water, gas, and electric inputs to your home and office.
5. Think how your belonging would respond to a sharp vertical and slightly horizontal motion.
6. Be sure fragile glassware, pieces of art, valuable equipment such as computers are fastened down or enclosed in latched cabinets.
7. Remove or fasten down large heavy items that could fall from high places, especially from shelves over your bed. Secure book shelves.
8. Be sure to have a neighborhood evacuation plan for river-bottom and other low-lying areas. Get to know your neighbors and share knowledge of resources before emergencies.
9. Have access to portable power generators and be ready to take care of yourself and others for extended periods of time.

There is no reason to be overly concerned at this time. Just be prudent.