Did you feel an earthquake? Report it here!
What is it?
FEMA defines an earthquake as a sudden slipping or movement of a portion of the earth’s crust, accompanied and followed by a series of vibrations. This is a fairly innocuous description of what can be a traumatic event, to which anyone who has experienced an earthquake can surely testify.
The magnificent Teton range, although peaceful now, was formed through thousands of major earthquakes in the 7.0-7.5 magnitude range over 13 million years. Each of these earthquakes are estimated to have caused 3 to 6 feet of vertical ground movement (Windows Into the Earth; Smith and Siegel, 2000). There have not been any quakes of this magnitude along the Teton fault in recorded history, but it is still considered an active fault. In fact, there are many faults in Teton County, as shown by the colored lines below:
Click map for larger version
Click here for USGS Quaternary Fault Google Earth .kmz files
The main fault, the Teton Fault along the base of the Tetons, can produce a significant earthquake in the range of 7.0 to 7.5 according to Dr. Robert Smith of the University of Utah. The Teton fault is a normal fault, which means that the mountains rise and the valley drops during episodes of movement.
Below is a peak acceleration PDF map for Teton County generated by the USGS National Seismic Hazard Mapping Project of 2002. It does not show the chances of an earthquake occurring. What it does show is the peak acceleration of a theoretical particle on the ground during an earthquake. 
The entire map shows that in the next 50 years there is a 10% probability that the peak acceleration shown by the contour lines will be exceeded at any given point on the map. The unit of measurement (%g) for the contour lines represents the percentage of acceleration of gravity, which is 9.8 m/s² or 32 ft/s².
So for instance, the orange spot on the Yellowstone/Teton boundary says "30", which means that in this area, within the next 50 years, there is a 10% chance that an earthquake will cause an acceleration on the ground greater than 30% the rate of gravity which would be 30% x 32 ft/s²=9.6 ft/s². Remember, acceleration doesn't necessarily tell us how fast the ground is moving (velocity), but how much change there is in the velocity of the ground over a period of time. It is like accelerating in your car from 0 mph to 55 mph: it doesn't happen instantly. You need to build up to it, so at first you are moving at 5 mph, then a minute later 25 mph, then a minute later 45 mph, etc. If this were the case, you would be accelerating at 20 miles/hour/minute.
Click for larger view
How does this information help us? Well, if you are building a structure, you would want to know what the highest probable acceleration of your foundation might be during an earthquake so that you can take the proper precautions in construction. Planning and building departments also use this data to create building codes for safer structures in earthquake prone areas such as Teton County.
Earthquakes and geology are fascinating topics that cannot be completely covered here. If you would like to learn more, check out the USGS's "About Earthquakes" web page.
What are the risk factors?
There aren't any activities that you as a citizen can do to increase your risk of experiencing an earthquake. The main risk factor is in where you choose to reside:
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Living near an active fault.
If you live in Teton County, you live near an active fault. A look at the map at the top of the page shows the extensive fault lines throughout Teton County. The Teton Fault by itself is large enough that it can affect the entire county and beyond.
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The level of activity of the fault.
In theory, an active fault that has more frequent smaller earthquakes is less likely to have a major earthquake. The reasoning is that the pressure in the fault is being released in small doses more frequently, as opposed to being built up and finally releasing in a large earthquake. The Teton Fault is still considered active, and has not had a major earthquake in recorded human history, so it would fall into this category.
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Extensive mining.
Very extensive mining in some cases has been shown to cause earthquakes. Although artificial, they can still be destructive. Mining that has occurred in Teton County is unlikely to cause any significant earthquakes in and of themselves.
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Underground nuclear testing.
There have been cases of underground nuclear testing causing fault ruptures in areas of Nevada. Luckily, we don't have any nuclear testing in Teton County.
What should I do?
First off, you should have a family disaster plan in place. Then:
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Prepare before the earthquake occurs.
You should have flexible fittings for utilities such as hot water heaters, natural gas lines, and propane tanks to lessen the risk of line breakage. Make sure family members all know how to turn off utilities such as water, electricity, and gas. Keep a wrench near your gas shut-off valve so others can shut off your gas if necessary. Secure heavy items such as bookcases and hanging pictures. Move heavy items from top shelves to lower shelves. Also, strap in your hot water heater; if it remains upright following an earthquake you can use it as an emergency source of water if water lines are broken or contaminated.
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If inside, stay inside. If outside, stay outside.
Generally, it is safer to remain where you are than to try and move any significant distance during an earthquake. Many people are killed by falling bricks and debris just outside of buildings.
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Drop, cover, and hold on.
If inside, drop (a) to the ground. Next take cover (b) by getting under a sturdy table or other piece of furniture. Lastly, hold on (c) to the sturdy object you covered under and be prepared to move with it. If unable to get to a piece of furniture, crouch in an inside corner of the building and cover your head and face, or stand in a doorway and hold on (be aware that doors slam shut during an earthquake, so watch your fingers!). Avoid outside walls and stairways, as these are unstable and unsafe areas during an earthquake.
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Stay away from windows and glass doors
Falling objects, or simply the shifting of the building, can cause glass to shatter and form dangerous shrapnel.
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Stay away from heavy standing objects such as bookcases, refrigerators, filing cabinets, or entertainment centers.
These items can easily cause serious harm to you if they fall.
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Don't try to keep large items from falling over.
During an earthquake, your primary concern should be to duck, cover, and hold. If you are trying to prevent something from falling over, you are exposing yourself to danger. Also, your chances of keeping your balance and preventing a heavy object from falling are almost impossible.
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If outside, stay away from buildings, chimneys, fences, trees, and power lines.
All of these objects present a falling debris hazard that can seriously injure or kill you.
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If you are in your vehicle, stay inside of it.
Pull over and stop, away from high structures, power lines, overpasses, trees, etc. and wait for the shaking to stop.
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After the earthquake, expect aftershocks.
Although aftershocks are usually less intense than the actual earthquake, weakened structures and loose debris can be more susceptible to shaking so caution must be used. React to the aftershocks just as you do to the main earthquake.
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After the quake, check for broken gas, water, and electric lines.
Turn off utilities that have broken lines, especially gas. Never turn gas back on. If you need to turn gas back on, contact your utility company for they will need to send out a technician. Click the following links for contact information on local utility companies:
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Do not use elevators following an earthquake.
Not only could the elevator have been damaged during the quake, there is an increased probability of more earthquakes in the form of aftershocks following the mainshock (earthquake).
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Stay tuned to EAS broadcasts for instruction before, during, and following the disaster.
Listen to your NOAA All-Hazards Weather Radio or another Emergency Alert System (EAS) broadcaster for instructions from emergency services before, during, and following a disaster.
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Learn more.
To learn more about what to do before, during, and after an earthquake, check out FEMA's Earthquake Page.
If you would like to get email notifications of earthquakes, you can sign up for the USGS's Earthquake Notification Service. This service allows you to select a geographic area, then get emails whenever the USGS registers an earthquake in that area. If you just choose the intermountain west with a low threshold (below magnitude 5.0), you will be getting a lot of emails. Narrow down the geographic area, and also set a threshold of at least 3.0, but if you only want to know of significant earthquakes you can safely set it at 4.0.
What are the impacts?
A major earthquake on the Teton Fault would have many serious impacts here in Teton County:
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Serious injury and death.
Most importantly, there are going to be people who are injured or killed during the earthquake. The shaking itself does not usually cause injuries, but rather falling objects, shattering glass, and collapsing structures are the culprit.
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Cascading events.
When a large earthquake occurs, usually it is after the shaking stops that the major problems occur. Earthquakes are a type of disaster that can cause what are known as cascading events. Examples of cascading events would be broken gas lines fueling fires, loss of electricity, disrupted routes of transportation, landslides, dam ruptures, or any other secondary disaster caused initially by the earthquake. Now, in addition to the damage caused by the earthquake, emergency services have to deal with these cascading events as well. With limited resources and damaged roadways, you can see how these cascading events can compound an already difficult situation.
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Isolated communities within Teton County.
In Emergency Management, we refer to this as Teton County's "islands". An earthquake can collapse bridges, cause both landslides and avalanches, and damage roads making them impassable. This can easily isolate communities within Teton County not allowing the people already there to leave, and more importantly blocking emergency services from reaching them. Teton County has taken steps to alleviate the "island effect" by spreading out our emergency apparatus such as ambulances and fire trucks throughout the county. Emergency Management and Jackson Hole Fire/EMS have also placed mass casualty equipment caches in all of the firestations located throughout the county so that major first aid supplies are available to communities even if routes are shut down to Jackson.
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Limited resources available for response and recovery.
Due to Teton County's remote location, and the fact that an earthquake of the 7.0 magnitude range would be a regional event, there may be limited outside resources initially available to assist us. Major emergency response teams from Idaho Falls, Salt Lake City, or 
Denver can generally mobilize within half a day to a day. They may not be able to reach Teton County for days, however, due to collapsed bridges, damaged airstrips, or ruptured roadways. That is why Teton County Emergency Management stresses that every family has at least a 72 hour preparedness kit, and preferably one that will last a week.
These damaged roads and bridges will also make it difficult for local emergency responders to report for duty. During a widespread disaster such as a major earthquake, you will need to band together with your neighbors to do the most good for the most people, all the while keeping your personal safety in mind. If you are interested in learning more about helping your community during a disaster, check this link to our CERT page.
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Economic impacts to local business.
According to a 2006 Small Business Administration study, up to 25% of small businesses fail to reopen following a disaster. Most of this is due to lack of planning, but some disasters are just too great to overcome. In our community we depend on small businesses, and if 25% of them failed to reopen it would be catastrophic for our economy.
