Is Your Home Protected From Earthquake Disaster?

Earthquakes: What, When, Where and Why Did you know that the ground beneath you is constantly moving? The Earth’s surface is broken into many different plates, which float on top of the Earth’s quasi-liquid mantle. Typically, one plate interacts with another by either colliding with it, sliding past it or pushing itself underneath it.

These areas along which plates interact are known as geological faults. As plates move over time, the edge of one plate often catches itself on another, forcing that portion of the fault to remain motionless while stress builds. Eventually, the fault reaches a breaking point and slips suddenly, sometimes by yards or sometimes only by inches. This sudden vertical or lateral (sideways) movement releases seismic waves, which we feel as an earthquake. The point where the fault first slips is located deep within the earth and is called the hypocenter. Directly above that, on the earth’s surface, is the epicenter.

Measuring an Earthquake’s Size Seismologists estimate the size, or magnitude, of an earthquake in several different ways. The Richter scale measures the size of the earthquake’s waves (amplitude); whereas, the moment magnitude scale estimates the total energy released during the slip of a fault. Because the moment magnitude scale is more objective than the Richter scale, it is now more commonly used.

What You Feel and Why You Feel It
The amount of movement you experience during an earthquake doesn’t depend just upon its magnitude. Where you’re located in relation to the earthquake’s epicenter also has an effect. The farther away you are, the less shaking you feel, since the seismic waves lose energy as they travel through the earth. Imagine a drop of water hitting the surface of a pond. As the circular waves travel away from the impact, they lose energy and reduce in size and frequency. In time, they disappear altogether.

Also, the kind of soil underneath and around you plays a large role in how much of the earthquake you experience. Unlike water, soil is not uniform throughout. The soil type can have a dramatic effect on the way seismic waves travel through the earth. For instance softer, less compact soil can actually increase the forces. More stable soils, such as bedrock or compacted fill, dissipate an earthquake’s energy more quickly.

Three major factors – an earthquake’s magnitude, your proximity to the epicenter and the condition of the soil around you – determine the amount of shaking you feel. The Modified Mercalli Intensity scale measures this intensity by evaluating the earthquake’s effect on you and your home.

What Your Home Experiences
Imagine that a strong earthquake strikes where you live. Loose items fall and break. Cabinets and bookcases tip over, blocking exits. Dust billows everywhere. Gas and water lines break, and phone and electrical service are interrupted for days. Your home may collapse, slide off its foundation or simply come apart at the seams.

What You Can Do
You can protect your home by modifying it, or retrofitting it, in two different ways: Nonstructural retrofits protect your home’s contents against damage with little cost and effort. Examples of retrofits include: securing water heaters, large appliances, bookcases, pictures and bulletin boards; latching cabinet doors; and using safety film on windows.

To complete these improvements simply follow the instructions in this brochure. In most cases, you won’t need a building permit. It’s a good idea, however, to contact your local building department to make sure. Structural retrofits strengthen your home’s structure or skeleton so it can better withstand the force of an earthquake. Your home’s structure is made up of many different parts, or components, which must work together in order to resist an earthquake. Modifications to your home’s structure tend to be quite involved and generally require the expertise of a registered design professional (engineer, architect or building contractor) and your local building department’s approval.

Use this brochure to identify potential problem areas in your own home. If you have any questions or concerns about what you see, contact a professional engineer or architect.

Nonstructural Retrofits
In this section, you will learn inexpensive and easy ways to protect yourself against some of the damage earthquakes can cause inside your home. Start by looking for objects that could fall and break during an earthquake. Consider items such as water heaters, bookcases and light fixtures,as well as items that are difficult to replace because they have monetary or sentimental value. As you conduct your inspection, think about ways in which you can protect them from damage. If you have any questions about the changes you should make, contact a professional engineer, architect or contractor.

More: | 1 | 2 | 3 | 4 |