Household seismic safety is an issue for areas of the world with a high risk of having earthquakes, and is concerned with the following:
- Securing furniture and appliances so they don't move around and hurt somebody.
- Preparations that will help anybody trapped inside the house survive until help arrives.
- Immediate emergency responses appropriate to a very large earthquake..
Seismic and seismic event refer to earthquakes, motions of the ground that can be hazardous to the occupants of buildings and the security and utility of structures such as bridges and tunnels. Methods to reduce hazards to structures (presently including low rise houses) are described in seismic retrofit.
There remains much that can be done to enhance home safety by the occupants, even if they are inexperienced mechanically, and some of these methods (such as securing water heaters) may be shown in some detail. Pamphlets showing application of these methods in greater detail are also available from public agencies, but often these show only a minimal and simplistic installation. Effective securing of household equipment and furnishings may require some thought - mostly along the lines of "what could happen", "how heavy is this", and "where are the strong points to secure to". It does little good to screw the back of a bookcase to a wall if the back is (as is common) weakly attached to the bookcase structure. Similarly, an expansion bolt through drywall may simply pull through if the load is heavy - one must locate and use stout screws into the underlying wood stud structure.
In order to be properly prepared, however, you must go beyond making sure your house is quakeproof. In a major catastrophe, there is a very good chance that police, firefighting, and medical assistance will be overwhelmed, and many hospitals may be so damaged, they may no longer be safe. A house should have sufficient water and preserved food for three days, and all household members should be trained in first aid. In some places, there are shops specializing in providing emergency equipment, supplies and containers.
There is also considerable neglect at the community level :
- Are you and your neighbors prepared to assist one another? Do you know who has first aid skills?
- Can you do CPR?
- Do you know emergency treatment for broken bones, burns, and bleeding?
- Do you know how to shut off your gas supply (and have an appropriate wrench nearby the valve)?
- Do you know what to do about a downed and live high voltage line touching an occupied vehicle?
- Do you have several fire extinguishers available?
There are many levels of detail in approach to securing a residence, ranging from providing large steel beams to reinforce a large garage door opening down to putting small dots of "earthquake" wax under small valuable items.
Objects within buildingsEdit
Any massive or tall object should be securely fastened to that structure, through bolts, screws, or strap hinges, so that the object does not move around during an earthquake.
Securing appliances and wood stovesEdit
Usually, appliances using natural gas are connected to the ductile iron supply pipes with a flexible corrugated tubing made from a relatively soft material, such as brass. It is important that the appliance be properly secured, or at least restrained in its maximum motion, so that it cannot extend and tear the flexible connection.
Free standing natural gas stoves — which in older homes may not be surrounded by cabinetry, but are simply set down upon the kitchen floor — require some form of restraint. If necessary to move the stove small distances for cleaning, such restraint may be provided by sturdy cables which must be attached to strong locations on both the stove and the wall of the kitchen. Stoves attached within cabinets may be a hazard if the cabinets themselves are weakly attached to the building structure.
Gas fireplace inserts, both decorative and functional, must also be restrained. Some form of restraining clip should be installed that may be easily removed when necessary.
Wood Franklin stoves and pellet stoves, often placed upon a hearth in front of a fireplace or with a separate pipe, are often quite heavy, and must be secured to a substantial member of the flooring system using fire safe methods.
Water heaters of any type, gas or electric, must be rigidly attached to the building structure, as when filled with water they are all quite heavy. When the building moves, the inertia of the water mass is sufficient to break the connecting water pipes, or to slide the bottom of the tank about, with the gas or electrical connections at risk. All water heaters should be secured in every horizontal direction and at the top and bottom with wood or metal blocking and corrosion-resistant steel straps.
Items permanently bolted to the building structure are technically considered to be part of the structure (as would be a built-in bookcase), so if the house is sold such items should be noted as exceptions. Renters should also obtain written permission to both secure the furnishings and a waiver allowing their removal at the termination of tenancy.
The china hutchEdit
These will often be composed of two units - a drawer unit as a base and a cabinet on top. If only the top is secured to the wall the attachments must be capable of holding the entire weight of the upper portion. Security of the doors from opening is also required, using a method suitable for kitchen cabinets. The cabinet will usually have glass panels, so it is not appropriate to store or display items within (such as a stone sculpture) that have enough mass to break the front glass or glass shelves inside of the cabinet.
One method of security allows the removal of the unit for cleaning or painting the wall behind or the floor underneath. Heavy hinges may be easily obtained that have a removable pin. To compensate for minor errors in location a new pin should be fabricated that is slightly smaller than the original pin. Additional means of preventing the pin from sliding out must be provided.
If the wall structure behind the hutch is wood frame with plaster or plasterboard (drywall) overlay, then at each location it is necessary to accurately locate the wall studs, in order to avoid splitting the stud. If the wall uses metal studs then it will be necessary to use appropriate toggle bolts through holes in the studs, or to open the wall and insert wood filler blocks, while masonry will require specialized expansion bolts or epoxied threaded stock (all-thread). Positioning vertically is also critical, and should be done by using the full hinge and the hutch as a guide for the vertical positioning. The hinges must also have (or be drilled for) bolt locations aligned with the studs. The hinges are then disassembled and mounted to the wall. The remaining portion of the hinge is mounted to the top of the hutch. If the hutch top not thick enough to receive appropriately large wood screws, then bolts with large washers should be used. Other methods may be required if the hutch has a very thin top, or a decorative barrel top, unsuitable for direct mounting. It may instead be necessary to add internal braces to the furnishing, which can then be through-bolted to the wall.
Bookcases need not only to be secured, it is also necessary to secure also each shelf and its contents. Each shelf should be secured from sliding out as a unit, and the shelf, if used for book storage, should have a lip at the lower edge. The space between shelves should be such that the books will not tip forward off of the shelf (pivoting about the lip), but rather should first strike the shelf above (which itself must be securely fastened). A book is easily removed by lifting it up slightly so that it will slide over the lip. Most shelving units have very thin backs that are not capable of restraining the unit. Instead, the top part of the case should be fastened to studs in the wall using angle brackets. Additional brackets may be required internally to secure the top to the sides.
Small decorative items should be secured using Velcro or a putty known as "earthquake wax". It may be necessary to remove felt padding from the bottom of the object in order to apply either substance.
Larger mobile itemsEdit
Specialty suppliers can provide a rubber-like mat that increases the friction between an object and the surface upon which it rests. This does not assure security of the item but will protect it in minor events.
Most modern cabinets are factory built, or custom built to specification, and then installed within the kitchen. These will often have poorly attached backs, being held only by staples, but will usually have a cross brace through which screws are attached to the building structure. Older buildings or some modern custom work may have "built in place" cabinetry. Even if the cabinets have a modern appearance, they may be a simple "reface" of this older type. Security is important and it may be necessary to add additional blocking above, below, or to the interior of cabinet structure so that the cabinet may be well affixed to a structural member of the wall.
Child proof latches are also useful to retain the contents within the cabinets. While very old cabinets were sometimes made with a mechanical latch that had to be manually operated, more modern cabinets typically use gravity, friction, or magnetism to keep the cabinet door lightly closed. The child proof latch allows the door to be partially opened but prevents complete opening until operated by hand. Of course, caution must be used when opening such cabinets after a seismic event.
- Earthquake Valve - automatic gas shut-off devices
- A BAG Steps for Making Your Home Safer (not concerning structural modification) by the Association of Bay Area Governments.
- University of California, Berkeley. Earthquake Engineering Research Center (1993), Abstract Journal in Earthquake Engineering 17,