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Sunset's guide to help you prepare for the next quake.

We run risks living in earthquake country. A reminder of the power-and fragility-of the Western landscape came roaring into our lives a year ago on the 17th at 5:04 Pm., with an event known as Loma Prieta.

Should we breathe a sigh of relief, figuring we faced a really big earthquake and survived? The opposite reaction would be more appropriate.

"The probability of an event of magnitude 7.5 to 8.0 (roughly equivalent in size to the great San Francisco quake of 1906) could be as great as 60 percent along the San Andreas fault in Southern California. Events of magnitude 7 or larger have a 30 percent probability of occurring within the next 30 years at six other locations in Southern California and three locations in northern California. A shock of this size on any one of these fault segments will likely cause considerably more damage than Loma Prieta." This is from a briefing given by the United States Geological Survey on October 25, 1989 only eight days after the 7.1 Loma Prieta quake.

On July 20, 1990, the USGS increased the odds to 67 percent for northern California, estimating the likelihood of a quake 7.0 or greater at one of four fault locations: Central San Andreas (Crystal Springs to State 17), North Hayward (San Pablo Bay to San Leandro), South Hayward (Fremont to Warm Springs), and Rodgers Creek (Santa Rosa to San Pablo Bay). At times, earthquake predictions may seem like the alarms of the boy who cried wolf. But the threat is very real; only the exact timing is difficult to call. "Loma Prieta was expected; it occurred along one of the six fault segments in California considered most likely to sustain a magnitude 6.5 or larger earthquake within the 30-year interval from 1988 to 2018," says Richard Eisner, executive director of the state- and federally funded Bay Area Regional Earthquake

Preparedness Project.

California isn't the only place in the West that's prone to shaking. Alaska has a long history of great quakes; 1964's 9.2 quake was one of the largest ever recorded. Oregon and Washington have the massive undersea Cascadia subduction zone to contend with, as well as many documented onshore faults. Nevada, Montana, and Utah have also had big shakes.

It's in everyone's best interest to get ready for a big quake. If one hits-when one hits-much of what you take for granted now may be damaged or destroyed; you'll We run risks, but we can also reduce risks. On these pages, we show how to prepare your house and your possessions. Next month, we'll show how to prepare yourself, your family, and your neighborhood for a quake; what to do during one; and what to do once the shaking stops.

What did we learn?

Following last year's quake, we conductcd a survey on earthquake preparedness. We received hundreds of responses, and the results were predictable. Some of you were prepared and, for the most part, fared well during and after the quake. But the vast majority of readers confessed to being ill prepared. For those of you who had your lives turned upside-down by the quake, thank you for sharing your astounding experiences.

Many of us were lucky last time. Next time ... ?

We learned a lot from Loma Prieta, your responses to it, and our interviews with seismic retrofitters, city planners, geologists, engineers, architects, government officials, and concerned citizens who have taken an active role in their communities.

We learned that preparedness pays off: it can significantly reduce the risk, the amount of damage incurred, and the amount of hardship we'll have to endure in a quake.

We learned that neighbors come to each other's aid in such a crisis, and that it's possible and highly advisable to get people aware and planning before the crisis occurs.

And we learned other lesson as well, which we describe in the following pages and in a continued report next month.

What's the ground like where you live?

Four out of five Californians live within the state's most active seismic areas. Large quakes have occurred near many of the West's other major population centers, too, including Seattle, Portland, and Salt Lake City.

The natural stability of the soil in these areas -and even in areas within these areas-differs vastly. San Francisco's Marina District, singularly hard-hit by Loma Prieta, was built on unstable fill much of it sand mixed with the debris from the 1906 quake.

Find out the earthquake potential for where you live: know where nearby faults are, and know the kind of soil your house is sitting on. (The soil under most houses is relatively stable; it's not bedrock, but it isn't likely to pose disastrous problems although the house will likely shake intensely.)

You can get a look at fault-zone maps and general soils maps at your city or county planning or engineer's office and some libraries and real estate offices. Find someone who can explain the maps to you. The person should also be able to alert you to other potential hazards, such as landslides and whether your property is in a flood or tidal plain.

If you find that your house is in both an active zone and an unstable geologic area (particularly if it's built on fill or other sandy soil prone to liquefaction during a quake), consult a geotechnical (soil) or foundation engineer about the risks involved.

If you're thinking of buying in such an area, don't do so without an engineer's verbal approval. Perhaps your best question for the engineer is, "What would you do if you were buying the house for yourself'?"

How do you secure your house?

Most of us live in single-story wood-frame houses the safest type of structures in which to ride out an earthquake. Wood-frame buildings are best for three reasons: they're lightweight (presenting a smaller inertial load), they're structurally redundant (with their multitude of wood framing members), and they're flexible-up to a point.

The key to riding out a quake is to make sure your house behaves as one continuous unit-and to make sure that during a quake it doesn't flex to the point of breaking either the supports or their connections. The building has to be able to absorb and evenly distribute the lateral forces; there shouldn't be a weak point that can fail.

Where the concrete meets the ground

With poured-concrete foundations, first check the "health" of the concrete (see the photograph on next page). Be somewhat wary of hybrid foundations that have an abrupt change in style or materials. If your foundation appears strange, or if you have any question about it, get advice-ideally, from an engineer. Slab foundations can be good-particularly on soft soil, fill, or other inferior ground where the slab can bridge gaps. In areas of "enduring seismicity," it's best to have well over the amount of embedded steel reinforcement that the code requires.

If a foundation in a pre-1935 house is soft or crumbly, immediately consult an engineer. An engineer should also check any foundation of brick, unreinforced concrete block, or wood; these have consistently failed in past quakes. Don't rule out necessity of wholesale replacement of the foundation.

Crawl space is critical: it's the likely weak link

All the walls in a house help absorb and dissipate the energy of a quake, but in houses not built on a slab, there's often only a perimeter wall-and perhaps an occasional short column on its own footing-between the first floor and the foundation.

Stiffening this perimeter "cripple wall" and bolting it to the foundation are the two key steps you can take to increase your house's chances of making it through a quake. These are also the most expensive and technically and physically difficult steps. Consult a professional if you're getting in over your head, and save your efforts for easier tasks described in later sections.

Bolting down your house. The board between the house and the foundation is called the mudsill. If bolts don't fix this sill to the foundation, even a moderate quake can cause your house to slip off its foundation. Houses built prior to 1940 weren't required to have sill bolts, and even some later houses don't have them. Several styles of retrofit bolts are available. All are forced into holes drilled through the sill and foundation with a rotary hammer. These rent for about $25 to $35 a day. You're best off buying a new bit, about $25 more; resharpened rental bits may have been reduced in diameter to the point where you'll never be able to force the bolts into the holes they drill. Before driving the bolt home, clean out the hole by sliding the bit up and down or blowing out the concrete dust with a plastic tube-and double-check the hole depth. If you can't get the nut tight and the bolts continue to climb out of their holes, you probably have weak or decomposing concrete; you'll need professional help (epoxy-set bolts might be a solution).

Retrofitted bolts should follow the same spacing as those in new construction. Place them 4 feet apart on center and within 12 inches of the end of any mudsill section. Any single stretch of mudsill needs at least two bolts. (You can space bolts up to 6 feet apart on a single-story house, but 4 feet is better.) Try to center them between the cripple studs if you're not using hold-downs (see section at right); there's more room to work there, and you'll know right where they are during subsequent nailing.

An average-size house usually requires 40 to 60 bolts. Cost per bolt ranges from about $3 for a 1/2- by 7-inch bolt up to about $6 for a by 10-inch one. The house's size and weight dictate the bolt size; the best general size is 1/8 by 8 1/2 inches. Stiffening the crawl space walls. Even bolted, a mudsill is of little use if the studs that rest on it are simply nailed into place. Cripple walls can easily buckle if not laterally braced. On these walls in some houses, you'll find let-in 1-by-4s or 1-by-6s, or steel-strap diagonal bracing. Don't count on either; their main purpose was to keep the house square during construction. Plywood shear paneling is necessary to stiffen cripple walls against damaging deformation. It's best to sheathe the whole wall, but at minimum, for cripple walls less than 4 feet tall, engineers recommend that you add 8 linear feet of plywood in each direction at every interior corner of the crawl space. Double the run to 16 feet for two-story houses.

Panels should run from the mudsill to the top plate. Use 1/2-inch plywood 1/8-inch if you're using a nail gun). Anchor the panels with 8d nails 4 inches apart around the perimeter of each panel and 6 inches apart on every interior stud. As you nail, proceed from an upper corner to the opposite lower one in order to work out any warps in the plywood. Every plywood joint should be nailed on a stud. You can substitute self-tapping screws if that's easier for you than driving nails. Drill a vent hole at least 1 inch in diameter at the top and bottom of each bay; these help prevent moisture buildup and rot (also pretreat plywood with a preservative).

Heavier houses with a more complicated perimeter configuration need heavier plywood and larger, more tightly spaced nails. All nailing points should be on the same plane; you may need to add blocking in places. If the mudsill is wider than the cripple studs, you bolt through the added blocking (resting on top of the sill plate) and the existing sill plate into the foundation-add 1 1/2 inches to your bolt length. If you're blocking along an entire mudsill, run your bolts at the same 4-foot spacing; for the blocks between the bolts, nail with 16d nails.

Also in the arsenal: hold-downs, structural steel angles

Where shear sheathing falls short of being twice as long as it is tall, reinforce the studs with hold-downs. These anchors bolt into the foundation and into corner posts or other supporting columns that immediately benefit from the additional bracing.

Hold-downs connect support columns directly to the foundation; they are your best solution where the 2-to-1 width-to-height ratio is unachievable. Hold-downs are an excellent reinforcement for corner posts; many retrofitting situations call for hold-downs on intermediate columns as well. You can also use pairs of hold-downs to hold two floors together: bolt brackets at the tops of the studs on the lower floor and at the bottoms of the studs of the upper one; drill through the floor, run a length of threaded rod between the hold-downs, and bolt it in place. In cases where a house's floor joists sit on the sill or where the cripple wall is very short, you can use 1/4-inch structural steel angle instead of anchor bolts (see photograph below left). Holes are drilled into the sides of the foundation for two expansion bolts (typically 5/8-by 6-inch size) and into the sides of the floor joists for machine bolts sized to the width of the joists (typically, a single 3/4-by 3-inch bolt or a pair of 5/8-by 3-inch bolts). Space them as you do sill bolts. Make sure all blocking is in place between floor joists, both along the perimeter walls and at least every 8 feet along the joists' span.

Seismic retrofitting: it's not for the timid

Figure on spending at least $600 to do the necessary bolting and sheathing yourself, not counting tool rental. Contractors charge $25 or more per installed bolt. A complete retrofit will generally cost $2,000 to $6,000. Depending on what's necessary for the installation, even spending 10 times what it would cost to do it yourself can still be a bargain.

"Take a good common-sense look at your house. If it's anything other than a really simple house (1 in 100); or if there are any special problems relating to soil, structure, or design; or if there's anything other than a perimeter foundation, then bring in a specialist," recommends Greg Prinsze of Earthquake Safety, Inc., a Berkeley retrofitter.

David Helfant, another retrofitter, writes, "Seismic retrofitting takes place in dark, dusty, and suffocatingly small crawl spaces. Quite often the work is done in crouching or reclining positions, or on your knees. Often the installer must lie on his side or stomach for hours while doing the work which is noisy, involves powerful, heavy, hand-held equipment, and is physically demanding. It is not work for the weak, the meek, or the claustrophobic. Running a powerful rotary hammer while wedged between floor joists and the ground makes for deafening noise and very sore elbows and knees. The risk of injury is relatively great, and properly worn protective equipment is essential."

If you decide to look for professional help, be cautious. All it takes to designate yourself a seismic retrofitter is a contractor's license. Find an experienced contractor who specializes in this kind of work, and ask for affiliations and references. You can call your state license board to see if any complaints have been filed against any contractor you're considering.

Other spots needing shear strengthening

Many buildings that failed in San Francisco's Marina District were "soft story" buildings-wide-open ground floors (usually garages) supporting multiple stories above. If you have living space over your garage, make sure the wall surrounding the garage door-as well as the back wall of the garage is sheathed with 1/2-inch plywood, nailed as cripple walls are, provided there's plenty of space on both sides of the door. Use hold-downs to anchor the posts supporting the garage's header beam. For extreme loads (several stories), you may need a fabricated steel frame surrounding the garage opening.

Think about shear strengthening any time your walls are opened up during remodeling, for instance. Sheathing should completely surround any large opening (picture windows, double doors), Ideally, sheathing on each side should be at least as wide as the opening and extend from top plate to sole plate. Existing plywood siding doesn't guarantee shear strength; the original nailing pattern is likely to be inadequate.

Stucco can be a fine seismic stiffener if it's applied to strong wire mesh carefully lapped and securely nailed to plywood sheathing, not just to wired gypsum board backing. Don't count on stucco with an unknown installation history.

When the walls aren't wood

Unreinforced masonry walls are extremely dangerous and are increasingly rare in houses in earthquake territory. If you want to improve such walls (especially recommended if your house was built before 1930), consult a structural engineer.

These days, brick or other masonry is more commonly used as veneer. If inadequately tied to supporting walls, the veneer will consistently topple, although this isn't likely to cause structural damage. You can easily check the inside of a masonry wall to see if the stuff is veneer or not, but knowing how well it's tied to its supporting frame is another matter. Private building inspectors or a structural engineer can determine that for you. Another thing to check (besides looking for major cracks) is the shape the mortar is in. If you can scrape it off easily between bricks, it's likely to fail during a quake; see an engineer.

A few other key connection points

In general, make sure all connection points you can gain access to (plates between stories, ceiling plates to rafters, and so on) are tied together well, You can find a metal connector for every conceivable joint- from simple L- and T-straps for any exposed columns or girders, to threaded-rod hold-downs for floor-to-floor tension connections.

Also make sure all gas and plumbing lines and vent pipes are supported at least every 4 feet; strap them to floor joists or to walls.

Pay particular attention to peripheral, nonstructural connections, making sure everything is well anchored to everything else. In Hollister, Santa Cruz, and Los Gatos, we saw numerous examples of porches that were ripped off the sides of the houses because the connections between the two were so minimal.

The roof and the chimney

Keep your roof in good shape, particularly if it's tile or some other heavy material. If you're reroofing, consider the weight of the roof. A clay tile roof on a 1,500-square-foot house weighs tons more than a composition or wood roof. During reroofing is also an excellent time to add solid plywood shear panels over the rafters. This solid sheathing-now required in many applications anyway will also provide protection for your roof if the chimney falls (most snap at the roof line).

If you have skip-sheathing on your roof and a brick chimney, at least brace the-roof around the chimney. You can feed sheets of plywood up into the attic (ripped to fit through the access hatch) and screw them to the joists around the chimney don't nail or you'll knock plaster off old ceilings or pop nails in newer ones. Lay down plywood from the chimney to a distance 1 1/2 times its height (measure from the joist to the top). The farther a chimney rises above the roof line, the farther and consequently harder-it can fall. At 5 feet tall, if it collapses, it can come through the roof (the likelihood increases as the slope of the roof decreases).

If the chimney poses a major threat, take it down; if the risk is minimal, leave it alone. The older your house, the greater a liability your masonry chimney is. As with any masonry, you should check the mortar for deterioration.

Only recent codes require internal and external bracing adequate to keep most chimneys intact during a quake. Some masonry chimneys can be made safer with bracing and strapping, but realize that your fireplace and its chimney are probably the heaviest things in your house. If it falls, an improperly strapped chimney could bring the wall down with it. Check with local building inspectors; rules about reinforcing chimneys are based on zones of seismic vulnerability and vary widely from community to community. if you're thinking of adding a fireplace, your most earthquake-safe choices are lightweight, prefab metal fireplaces.

A tsunami in your back yard?

In an earthquake, smaller versions of oceanic tidal waves (tsunamis) occur in lakes; these are called seiches. Your swimming pool is a lake, and it's liable to encounter such rhythmic sloshing.

Evidence from previous quakes has shown that pools can lose 25 percent or more of their water this way; many readers told us of just such things happening resulting in flooded family rooms, permanent covers being torn right off pools, and other accidents. There's not much you can do with existing pools, but if you're considering putting in a new pool, you might want to consider where the water will go during a quake-and locate the pool accordingly.

Securing your possessions: a few rules of thumb

Once you've secured the house itself, you can turn to its contents. There are two requirements here: protecting your possessions, and protecting yourself from your possessions.

Take a walk with your family through your house and play "spot the hazard." Most rooms are full of them. In an earthquake, falling objects are the prime danger; that's how most people are hurt. Mentally shake every room in your house to see what could fall.

Identify and list the risks, then begin correcting them. Eliminate the most glaring hazards first, then work your way down.

Do the same with your possessions, figuring out how to protect the "good stuff" first.

It's important to remember that you can't completely quake-proof your possessions; you can just improve your odds. One reader in Watsonville (4 miles from Loma Prieta's epicenter) had taken many precautions, and saw many of them fail: a strapped water heater still twisted enough to break water lines, eye screws pulled out of wood cabinet doors, pictures fastened securely to walls fell because the hanging wire broke.

Place heavy things low, place breakables in secured spaces, and keep caustic chemicals in secure cabinets at floor level.

Anything top-heavy, from a water cooler to a drill press to a bunk bed, should be secured. If your furnace is top-heavy, anchor it as you do your water heater.

Bookcases, armoires, and entertainment centers should all be secured to the wall. Once you've done that, you can worry about securing objects you store in them. Objects on tables and open shelves tend to slide or "walk" during earthquake shaking. Barriers will keep them from falling off, putties, tapes, and other adhesives will keep items from moving at all. Top-heavy small objects, such as vases or lamps, can be weighted with beanbags filled with sand or lead shot.

Restrain all electronic gear either by fastening it directly or tethering it to secured shelves or desktops.

Things that hang from the ceiling need to be secured to joists or beams. To check the security of anything on your ceiling, the simplest test is to give it a tug. You should be able to tell right away whether it's secure. With plants, you can keep weight down by using plastic pots; hang only on closed hooks. Fans and lights should be hung from electrical boxes securely fastened to the ceiling joists; check fixture attachments from the attic above if possible. If you can't, you may be able to see evidence of a secure connection inside the box if you remove the fixture.

Divide hanging artwork into two categories: things that can be damaged, and things that could damage what they fall on.

Hang heavy art or mirrors on double hooks, and pad the backs to minimize damage from banging. Ideally, hooks should be driven into studs. This is less critical with lighter objects, but don't just rely on a nail; use an appropriate anchor. Make sure to bend hooks closed so art can't bounce or slip out.

You can hang paintings from wires that run up the wall to the ceiling plate, but leave empty wall space--at least 10 percent of the wire length on both sides of the art as swing space.

The water heater

The water heater is your most unstable appliance. Make sure it's secured to the wall with loops of plumber's tape (tape should wrap entirely around the heater, then be bolted to studs on two sides). Or use ready-made brackets or some other positive supports. If you have a zero-clearance water heater that sits out from the wall, brace it from behind with 2-by-4s so it won't bang against the wall. If the wall is concrete, install heavy eye screws in lead anchors, then run light steel cable through the eye screws and around the heater. Make sure the gas line in and the water lines in and out connect with at least a foot of flexible line.

In the kitchen

The kitchen is potentially the most dangerous room in the house. But it's also the easiest to make safe. Cabinets should latch positively and securely. You can retrofit cabinets with heavy spring-loaded hasp or touch latches, or replace the pulls with latches or catches that lock to the cabinet frame. Don't count on magnetic catches; they often shake free.

Babyproof catches are inexpensive and will keep doors and drawers closed during a quake. They're simple to use, invisible from outside, and can be used on any type of cabinet.

At the very least, install secure catches on the cabinets that hold your precious dishes and stemware, and on other cabinets that hold breakable glass. To minimize breakage, also pay attention to how items are stored within cabinets. Put cushioning layers of foam or paper between seldom-used heirloom plates. Install nonskid shelf padding (see photograph on page 172).

"Built-in" appliances-stoves, dishwashers, microwave ovens-aren't necessarily secured to surrounding cabinets; many simply rest on a trim strip, held only by gravity. Check to see how yours are secured. Also make sure all gas appliances have flexible connectors. If possible, block the rollers on your refrigerator or use a tether to secure the appliance to the wall. You can also "lock" the door with hook-and-loop fastener (such as Velcro), or with a babyproof slide latch.

In the bathroom, in the bedroom

The bathroom is like a miniature version of the kitchen. Secure cabinets to keep objects from falling. Check the nuts holding down the toilet to make sure it's secure.

Statistically, you're most likely to be in your bedroom when a quake hits. Make sure nothing can fall onto any beds or cribs in the house. Remove or block casters. Keep beds away from windows, and use window coverings to deflect flying glass. Security film will strengthen glass and keep windows from shattering into the room.

Make sure bunk-bed sections are strapped, screwed, or otherwise secured to each other and to the wall. Make sure mirrors are securely fastened to dressers or walls.

Beyond the walls: don't forget to look outside Look under windows that may serve as emergency exits; make sure there aren't any hazards underneath. Check surrounding big trees to see if they could pose a threat if they fell or lost limbs; correct as necessary.

On the roof, attach antennas securely to the middle of the roof or along a wall-not to the chimney or a fragile cornice. Make sure all solar heating equipment is extremely well connected.

In next month's Sunset. how to secure yourself your family, and your neighborhood,- what to do during and after,- and further readings.

How to shut off a gas valve: manually or automatically If your gas line breaks in a quake, you must shut the gas off quickly. Learn where your shutoff valve is, and check it now to make sure it's not frozen. To check, turn it 1/8 turn (no farther; turn is the closed position). If it's frozen, call your utility company.

Keep a wrench near the shutoff, and make sure everybody in your family (and your immediate neighbors) knows how to use it.

For about $400 to $600, you can have an automatic shutoff valve installed on the line. This "seismic-actuated" valve, typically installed between the meter and the house, shuts off the gas when low-level vibrations shake a ball or cylinder off a perch within the valve and it drops to seal the line.

Older models had problems with being set off by other vibrations, such as heavy trucks driving by or jackhammers used on nearby concrete. Standards for valves sold after 1987 are stricter; in theory, these newer valves ignore such higher-frequency industrial vibrations. Most valves are easily reset anyway, although if you don't know how to turn your gas on yourself and relight all your appliances, you'll have to call a plumber or the gas company to do it.

Are the valves a good idea? Fire departments think they're great; gas companies are ambivalent. The valve will trigger in a big quake, whether the service is damaged or not. Once the gas is off, you won't be able to know if you do have a leak. It could be weeks before the utility company restores your service, given the more pressing problems it will probably be encountering. Of the 160,000 households who shut off their gas during Loma Prieta, only 20,000 had actual damage.

Among our readers, several praised the valves after Loma Prieta, and some contractors swear by them. Others say that if you're home most of the time and your neighborhood is organized to take this step, then your preparedness dollar can be better spent elsewhere in the house. If you live in an isolated house, aren't home that much, or are otherwise unable to turn off the gas, an automatic shutoff could be a good idea.

New codes for earthquake safety?

"Our history has been, if we have an earthquake, we have legislation," said Paula Schulz, deputy director of BAREPP (Bay Area Regional Earthquake Preparedness Project). The same is true this time around.

At our press time, AB 3561 is still pending before the California legislature. If passed, it will require foundation bolting and cripple-wall sheathing, or an acceptable variation, upon sale or other transfer of ownership (and on all houses no later than 1996) on all dwellings of one to four units.

Until 1940 in California, most building codes did not require foundation anchor bolts. Even some later structures have connections deemed inadequate within the context of AB 3561.

The Long Beach quake of 1933 is considered the watershed. That's when building construction began to take earthquake resistance-specifically diagonal bracing and anchoring into consideration. Codes then began to reflect seismic issues-and, in general, every three-year revision of the Uniform Building Code has reflected higher standards. But don't rely on codes to give you an earthquake-safe house. Codes vary from region to region and, according to engineer and preparedness expert Peter Yanev, "are at best only minimally effective in meeting some earthquake hazards."

Codes are the minimum acceptable standards. If you live in a seismically active region, a thoughtful design should be well in excess of code requirements.

What do those numbers really mean?

The magnitude of an earthquake is an index of the energy it releases. This magnitude is recorded on a seismograph and measured on the Richter scale. Earthquake intensity indicates the damage caused by a quake; it's measured on an index known as the Mercalli scale.

The Richter scale is logarithmic; an increase of one full point (5.0 to 6.0) in magnitude indicates a tenfold increase in the size of the quake. That tenfold increase in size represents 31.6 times as much energy released. So a quake of Richter magnitude 8.0 has roughly 32 times the energy of a 7.0, and is nearly a thousand times more powerful than a 6.0 (31.6 x 31.6=998.6). The higher the Richter number, the longer and stronger the shaking.

The Mercalli scale is based on observation. It describes effects on people and buildings at a specific location. There are numerous Mercalli ratings for any given quake. People do not generally feel intensities below III or IV. Minor structural damage, such as cracks in walls and chimneys, usually begins with intensities of VI. Moderate damage occurs in the VII to VIII range, major damage at IX and X, and devastation at XI and XII. Mercalli ratings require the quantification of reliable observations; they usually come in long after Richter ratings.

What about insurance?

From the hundreds of surveys we received, we found that roughly two-thirds of you choose not to carry earthquake insurance (though many of you got some after October 17, 1989). Insurance protects you against things you can't know about, like unknown faults or poor construction. It provides protection from total loss in a major quake; it does not set out to reimburse on the lesser damage.

Typically you buy an amount of insurance based on the cost of rebuilding your house less a 10 percent deductible. So your $300,000 house may carry $125,000 worth of insurance, with a $12,500 deductible. You don't insure the full $300,000; you still own the land even if the house falls down. Premiums average between $1.50 and $4 per $1,000 of policy value. Location, type of structure, soil conditions, hazardous construction (like unreinforced masonry), and the like can push the rates up. Figure that the higher the risk is, the higher the rate will be. Shop around. The two policy types (addendum to existing homeowner's insurance, or separate) may offer different deductibles and different rates. Some coverages base the deductible on the total market value of the house at the time of the loss, not the value of the policy. Many policies also carry a 72-hour occurrence limit, which makes you liable for the deductible again on damage resulting from a late aftershock.

Check to make sure your fire insurance covers quake-related fire, including fires originating from outside forces-such as a neighbor's burning or collapsing house. Masonry (including fireplaces), masonry veneer, glass, and personal property are rarely covered. Get a separate rider on your policy for plate glass; the rider is usually inexpensive, most quake policies don't cover it, and broken glass is practically guaranteed in a big quake. Your regular homeowner's policy should pay for itemized possessions, your comprehensive auto policy for your car. Make sure that your agent explains all coverage details to your satisfaction. I f you live in a community that has association fees, you may be covered under a blanket policy. Check to see what the coverage is, then determine whether you can supplement it if you're not comfortable with it. Will your insurance company survive the quake, and the likely flood of claims? Good question. The National Committee on Property Insurance has projected losses from all insurance coverages in the event of a major a earthquake at about 50 billion. (Loma Prieta came in at about $1 billion). The ability of insurance companies to fund all those claims is at issue within the insurance industry itself.

Provided your insurer is sound and if you're in an active region, insurance is a good idea. It's your best second line of defense; the best insurance is carefully preparing your house and yourself.
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Date:Oct 1, 1990
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