Earthquakes and Nevada - Is There Fault to be Found in the Truckee Meadows?
Sunday, March 13, 2011 at 13:26 My neighbor and friend, Peg O’Malley sent this to me toay in an email, saying “Remember when we did this? Maybe it’s time to redistribute the info?” Yup. She and I put this together for the South Hills homeowners association, back in the day. Thanks for finding this and reminding me, Peg!
This is exactly what I was talking about in my recent Friday Fish Wrap when I suggested that folks use the Japan earthquake as a damn good reason to initiate conversations among their own families - in addition to their schools, work places and neighborhoods. I’m going to work on distributing this to folks around here in the neighborhood again.
Peg’s seimic information is timeless. Some of the contact and reference information - especially in the sections I authored - needed updating, and I have done that.
Please, take the time to sit down with your familes, friends and co-workers. Don’t wait for somebody else. Be the person who initiates the conversation to prepare!
- Lt Col Cynthia S. Ryan, Nevada Wing, Civil Air Patrol
AKA maven
EARTHQUAKE AWARENESS
Is There Fault to be Found in the Truckee Meadows?
By Peg O’Malley
The recent earthquake in the Pacific Northwest finally prodded me to write about an issue that I’ve been meaning to address for years. A number of neighbors have asked whether South Hills is in an “earthquake zone”; what the chances of an earthquake occurring in this area might be; and if they should be concerned about this possibility. These are difficult questions to answer given the nature of earthquake faults and how the probability of their future movement is estimated.
Western Nevada is one of the more active areas in the United States when it comes to earthquakes. Everyone knows about California and the San Andreas Fault because of the Great San Francisco Earthquake of 1906 and, more recently, the Loma Prieta and San Fernando Earthquakes of the 1980s and 1990s, among others. Washington State has also been the site of several very large earthquakes in the past 50+ years; the Olympia Earthquake of 1949, Seattle Earthquake of 1965, and now the Nisqually Event of 2001. But what about Nevada? Nevada and adjacent areas of east-central California have experienced a number of very large earthquakes (around magnitude 7.0).
1845 Stillwater area of Nevada, magnitude unknown. In 1845 Nevada was sparsely populated. Reporting is limited.
1872 Owens Valley, California - the Lone Pine Earthquake, magnitude 8.0. Height of fault scarp = approx. 25 feet. Surface rupture = approx. 45 miles. This earthquake was devastating and caused many deaths in the Lone Pine area.
1915 Pleasant Valley, Nevada, magnitude 7.6. Height of fault scarp = approx. 6 to 15 feet. Surface rupture = approx. 25 miles.
1932 Cedar Mountains, Nevada, magnitude 7.3. Height of fault scarp = inches. Surface rupture = 40 miles.
1954 Fairview Peak, Nevada, magnitude 7.1. Height of fault scarp = 15 feet. Surface rupture = 30 miles.
1954 Dixie Valley, Nevada, magnitude 6.8 (equivalent to the Nisqually Event in magnitude). Height of fault scarp = approx. 6 feet. Surface rupture = 25 miles.
Looking at the dates of these events, a recurrence interval of approximately 30 years can be estimated for an earthquake of magnitude 7.0 or greater for this region. This estimate is for western Nevada as a whole.
But what about probability of an earthquake on a particular fault? What is the chance that a fault in your own back yard will rupture and cause an earthquake? That chance is about once in about 2,000 years. To show how we calculate this probability, let’s look at where we live in the Truckee Meadows.
The South Hills community is situated on the edge of what is known to geologists as the Mt. Rose alluvial fan. The “fan” is a large accumulation of sediment (sand, gravel, cobbles and boulders) deposited primarily by the streams that have crisscrossed this area over the past several million years. If you have attempted to dig a hole in your yard to any depth, you know exactly what the rocky composition of this fan is like. The rounded shape of the rocks in the fan are an indication of their transport by water.
One of the first jobs that came my way 25 years ago, when I was a student of the seismic risk evaluation, was to fly over the Mt. Rose fan and take photographs of faults. To do this, flights are scheduled at times when the sun is low in the sky and shadows are long. This enhances the appearance of any surface features (hills, ridges, depressions, etc.). Topographic irregularities stand out in shaded relief like zebra stripes. To say that the faults on the Mt. Rose “fan” were striking is an understatement. There are literally dozens of these structures running in a northerly-southerly direction, roughly parallel to the Sierra Nevada range front. These faults mark lines where the surface has broken when earthquakes occurred in times past.
The type displacement on these faults is what is referred to as “normal” faulting. Normal faults are caused when the crust is being pulled apart and the block on one side of the fault slides down relative to the other side. The movement along the fault is predominantly vertical but there is often a significant amount of lateral (sideways) movement as well. Normal faults are the kind that we find here in South Hills and in many of the foothill communities throughout the Truckee Meadows.
One of the more charming characteristics of this neighborhood is its rolling topography. Driving or walking through South Hills, you are always encountered with a dip or hill if you are going in a roughly easterly-westerly direction. The little dips or valleys are actually what geologists call “grabens” and the hills are known geologically as “horsts”. Horsts and grabens are up-lifted and down-dropped fault blocks, respectively.
As was said at the beginning of this article, the chance of any one of these neighborhood faults experiencing movement during a person’s lifetime is extremely low, but it is not zero. An earthquake anywhere in the Truckee Meadows would probably be felt in South Hills as well, so the following suggestions are meant serve as a general precaution. There are things you can do to help safeguard your home in the event of an earthquake to protect your heirlooms and other valuables.
Earthquake insurance is expensive and has a high deductible, but it may serve to give you peace of mind. Most homeowner’s policies do not include coverage for earthquake damage (an act of God) unless it is purchased as a separate rider. The price of this coverage varies considerably (anywhere from a few hundred to several thousand dollars annually) and depends on the value of your home and its contents, where your home is situated in the seismic scheme of things, and how and from what materials the home is constructed.
One of the most common sights in a community after an earthquake is chimney damage. Non-reinforced construction with brick, stone and block is particularly vulnerable to seismic damage. Each individual brick or stone has its own unique frequency of resonance, each slightly different from its neighbor. For this reason, adjacent bricks will “vibrate” to earthquake shock waves at differing frequencies, increasing the discordant resonance within the overall structure. Mortar between these vibrating bricks, particularly if it is degraded, weathered, or of poor original quality, will then be susceptible to breaking apart, causing the structure to fail.
Preparing Your Home with Earthquakes in Mind
By Capt. Cynthia S. Ryan
Integrated Emergency Mgt. Liaison, Nevada Wing, Civil Air Patrol
Here are some things you can do to make your home safer in case of an earthquake:
Bolt all the tall,heavy furniture (especially in the bedrooms) into the wall studs with simple big heavy screw eyes and ‘clips’ (heavy duty dog leash kind). Use “Quakewax” (used by conservators and museums) under any valuable breakables, and also behind all pictures and plaques on the walls.
Put toe pressure open/close release clips on cabinets such as an amoire, bar or china closet. You can also put them on kitchen cabinets but they can be annoying. Secure the water heater to the wall studs with a metal strap.
Those of you with computer equipment in your home know its value. Therefore, secure your computer components, especially the monitor. You should also consider backup up your information and critical data. You can least expensively do this with a 4 GB flash drive or external hard drive that you would grab and run with. Another, perhaps, more sophisticated alternative would be to back up your data to ‘the cloud’. This entails backing up data much like you back up photos to web sharing sites. Carbonite is a consumer oriented back up site, with a reasonable annual fee ($54.95). Backing up to the ‘cloud’ enables you to have access to secured data anytime, from any computer hooked to the internet.
Secure tall filing cabinets (or even the low horizontal ones, preferably with some sort of drawer locking mechanism.
Keep 5-gallon jugs of water in a central location of the house and two fire extinguishers at each end of the house.
Check the fire extinguishers annually and be sure that you know how to use them. Know the location of the main gas shutoff and where/which wrench to use. Do not use any electrical devices, AND THAT INCLUDES THE TELEPHONE, until you are sure your house is clear of gas leaks or buildups.
Remember the duck-and-cover routine; protect yourself under stable, heavy furniture if at all possible. Talk with your family about survival scenarios (make plans) Have a central meeting place or contact points if you are separated at the time of an earthquake.
Do you have pets? Go to the FEMA site that addresses emergency pet care: http://www.fema.gov/individual/animals.shtm .
Do not immediately run outdoors and endanger yourself with falling architecture, window glass or power lines, unless you are sure you are in imminent danger of fire or explosion indoors. Know which of your walls are load-bearing.
Keep an emergency kit or two (in your house and car).
Items to have on hand in an emergency supply box: Blankets. extra sturdy shoes (boots and/or sneakers), heavy sox, sweater or sweats, sturdy pants, flashlights and at least one radio with extra batteries, ‘light sticks’ (cyalumn sticks), a sterno or other heat source. For fire-starting, I also have baggies with cotton batting wrapped around wooden matchsticks, dipped in oil and then wax and also cotton balls dipped in a little oil.
Have a complete first aid kit. This kit could include: the Red Cross approved mouth to mouth resuscitation kit that keeps you from getting AIDS or other pathogens (including expelled stomach contents); medical gloves; all types of bandages; gauze wrappings; antibiotics; pain relievers; sedatives (if necessary); Pepto Bismol or something similar; and a book on first aid and survival.
Have at least 10 days’ worth of extra up-to-date medications for folks that have to have them on a daily basis. Your survival kit should include simple, cheap rain panchos and “space blankets” in the little packages and a simple folding saw and shovel (for extrication). If you want a complete kit, you should also have compasses, signal mirrors, hand held radios, etc. Have some fresh power bars or similar food to get you by until you can safely go back into your house.
EARTHQUAKE AWARENESS
Where to go for Information
By Capt. Cynthia S. Ryan Integrated Emergency Mgmt. Liaison, Nevada Wing, Civil Air Patrol
Last month we told you about how to prepare your home in case of an earthquake. This month, I’d like to give you some names and websites where you can go to access more information on this important topic.
Remember, when preparing your family for dealing with a potential disaster, above all:
HAVE A PLAN, HAVE A PLAN, HAVE A PLAN!
Here are some excellent websites:
FEMA Project Impact - Building a Disaster Resistant Community
FEMA Community Emergency Response Teams (and Washoe Country has a CERT Team)
FEMA Emergency Services Preparedness Checklist
FEMA Emergency Guide for Business and Industry (now may be the time to show your employer how much you care?)
This might be the time you want to become involved in Emergency Management as a volunteer. It was a really worthwhile education for me, as an Emergency Management Liaison for the Civil Air Patrol. I attended the FEMA Institute in Maryland, for advanced training, and earned certification in every level of emergency management training/ Incident Command System up to and including the 700 and 800 Levels (National Incident Management, and National Response Framework). There are training modules specific to medical professionals and others. You need to be connected to an emergency services agency to participate in some, but not all, of these courses.
Nevada Department of Public Safety Emergency Management
Volunteer Organizations Active in Disaster VOAD
NOTE: Between Nevada Division of Emergency Management (NVDEM) and Civil Air Patrol (CAP), a first class presentation emergency preparedness can be made available for many groups. This presentation includes folks from CAP, NVDEM, the UNR Seismology Lab, NOAA, etc.
National Headquarters Civil Air Patrol: www.capnhq.gov/ Membership in the Civil Air Patrol (CAP) is not limited to pilots. The CAP always needs ground-based personnel to train in communications (we have our own repeater station net for the entire state), air and group SAR/DR operations, administration, Public Information Officer, etc. The Air Force offers many relevant ECI courses that qualify for college credits, as well as offering the specialized CAP training.
People should learn what to do when disaster strikes to minimize damage and personal injury, how to mitigate additional damage or injury potential, and to learn just how the entire local, state, regional, federal emergency management system works.
Being prepared enables citizens to know what kind of help they can expect to receive, and when and from whom the help will be provided. Calling hysterically to the wrong people or agencies just wastes time and can cost lives and property. Learning about how disaster response operates, enables you to be specific in your requests to emergency responders, and to get the most from them.
If you have any questions about this material, just contact me:
Ladybird53@sbcglobal.net or through the mavenandmeddler.com blog