The recent strong earthquake near Anchorage, Alaska underscores the importance of family earthquake readiness. Thankfully, we live in a country with modern building standards. This is not in the case of many Third World nations, where unreinforced masonry construction is the norm. In the Third World, folks tend to be very stingy with reinforcing bar (“rebar”). So its seems that every time there is a large earthquake in those regions, there are building collapses, with large loss of life.
By far, the safest houses for earthquakes are of wood frame construction. This is because such structures can flex and sway, when an earthquake rolls through. If you look at recent history of fairly large earthquakes in California, the three things that suffer the most are: 1.) Bridges and overpasses, 2.) Brick fireplace chimneys attached to wood frame houses, and 3.) Water mains. Again, we can be thankful that wood frame construction is the norm, and that most masonry buildings in the U.S. and Canada have sufficient rebar reinforcement. But even reinforced concrete and brick is inherently more vulnerable that wood frame, in the most severe earthquakes. (Magnitude 7.0, or higher, on the Richter scale.) By the way, the Richter scale is logarithmic. That means that a Magnitude 7.0 is 10 time more powerful that a Magnitude 6.
For those of you reading this who live in a wood frame house or apartment, you should have two concerns: A.) Seismic retrofitting, if needed, and B.) Securing furniture, water heaters, wall hangings, and fragile items from falling, in the event of an earthquake. In this article, I will be discussing both of these.
Seismic Retrofitting Standards
To become earthquake safe, many wood frame houses that were built on typical concrete “ring and pier” foundations before the 1980s may require additional sill bolts. These are the large bolts that attach the wooden bottom sill plate (also known as the “sole plate”) of your house frame to the concrete foundation. To be safe from most earthquakes (under 7 magnitude), your house should have sill lag bolts spaced at no less than six foot intervals. Grab a flashlight, and check your house, to see!
Note: Unless you already own a large, high-torque 90-degree masonry drill and have the requisite experience to use it, then you should probably hire a contractor to handle the job of retrofitting sill bolts. According to the 2088 FEMA advisory on seismic retrofitting:
“Having a contractor bolt the sill plates to the foundation will cost approximately $50 to $75 per bolt, depending on the type of foundation you have. For example, a structure measuring 60 feet by 30 feet would have a perimeter of 180 feet and would therefore require a minimum of 30 bolts (if the bolts are placed no more than 6 feet apart). So the cost for that structure would be about $1,500 to $2,250.”
Also see: FEMA 232, Homebuilders’ Guide to Earthquake-Resistant Design and Construction, dated June 2006.
Strap That Down!
After you have made sure that your house structure is earthquake safe, you should look closely at the contents of your house. Walk through, room-by-room, and do a mental exercise: Imagine a magnitude 6.5 earthquake hitting your house. What items are vulnerable to tipping or coming loose? Look particularly at attachment for shelves, lockers, tall cabinets, televisions, aquariums, and armoires. Ditto for any large framed pictures or mirrors. Examine their current attachments (or lack thereof), and beef them up. When you consider the potential risk of injury and the high cost replacing damaged items in your house, then the time required and cost of adding protective straps is negligible.
I want to make special mention of flat screen televisions and computer monitors. These have become ubiquitous in the past 15 years. Not only are they inherently more prone to tipping than traditional “box” CRTs, but both their number and their sizes have steadily grown, because their cost has quickly come down, in recent years. The good news is that most televisions and monitors have one or more threaded bolt holes in the back. You can use these to insert an appropriate size eye bolt (or eye bolts). This eye bolt can be chained, roped, or cable-tied to a wall anchor bolt. Don’t leave more than two inches of free play in that attachment.
Preventing a Huge Mess
Retaining straps for shelf contents are also important. If anything heavy or breakable is on a shelf, then it needs protection! In her great Rural Revolution blog, our friend Patrice Lewis illustrated a simple yet effective method of installing plastic lattice to prevent glass food canning jars from sliding off of shelves, in the event of an earthquake.
Another quite important upgrade for earthquake readiness is a hot water heater retaining strap. If you have a traditional free-standing tank water heater, it can be at considerable risk in an earthquake if it were to tip over. Not only would it dump its contents, but it its also very likely to break its inlet water line, and break its natural gas, propane, or electric service line. Those are huge risks that could badly damage or destroy your house by either flooding or fire. But there is a simple solution: Attaching a galvanized steel retaining strap to the nearest wall(s). These straps will stop a hot water heater from tipping over, in all but the most severe earthquakes. Their cost is quite low: Under $25, assuming that you do the installation yourself. That is cheap insurance!
Plan B Evacuation
No matter how well you plan, prepare, construct, and retrofit to be ready for an earthquake, there is always that dreaded ‘worst case.” Here, I’m talking about an earthquake of such great magnitude that it makes even stout woodframe houses uninhabitable. One “Plan B” fallback would be to pre-position clothing, bedding, tentage, fuel, weapons, field gear, first aid supplies, a fire extinguisher, and so forth in a free-standing shed, in a car trunk, or in a camping trailer that will survive even a high magnitude earthquake. Obviously, the trunk of a car is only an option if the car is parked out in a safe location away from large trees and buildings.
In a severe earthquake, many windows will be broken. So I also recommend buying some rolls of 6 mil (or thicker) translucent sheet plastic keep on hand. A house with broken windows would be at least habitable, with ersatz plastic windows tacked up in place, while you await proper replacements.
All of the preceding advice is of course already of great concern to folks living along the Pacific Rim and in the New Madrid Seismic Zone. The regions along the edges of the North American Craton are also at considerable risk. But everyone in America needs to prepare for earthquakes. Earthquakes can occur in places where they have never been reported before. In August, there was a magnitude 6.4 earthquake in a locale where quakes were not even expected. This was on Alaska’s North Slope. Luckily, that was a very lightly-populated region. But this illustrates that the earthquakes in the “diverse places” mentioned in the Bible, really are at risk. Read Luke 21:5-8, and pray:
For many shall come in my name, saying, I am Christ; and shall deceive many. And ye shall hear of wars and rumours of wars: see that ye be not troubled: for all these things must come to pass, but the end is not yet. For nation shall rise against nation, and kingdom against kingdom: and there shall be famines, and pestilences, and earthquakes, in divers places. All these are the beginning of sorrows.
Be ready, folks. – JWR