- EARTHQUAKES -

One of the most frightening and destructive phenomena of nature is a severe earthquake and its terrible after effects.

Earthquakes strike suddenly, violently, and without warning at any time of the day or night. If an earthquake occurs in a populated area, it may cause many deaths and injuries and extensive property damage.

Although there are no guarantees of safety during an earthquake, identifying potential hazards ahead of time and advance planning can save lives and significantly reduce injuries and property damage.

Earthquakes, also called temblors, can be so tremendously destructive, it’s hard to imagine they occur by the thousands every day around the world, usually in the form of small tremors.

Some 80 percent of all the planet's earthquakes occur along the rim of the Pacific Ocean, called the "Ring of Fire" because of the preponderance of volcanic activity there as well. Most earthquakes occur at fault zones, where tectonic plates—giant rock slabs that make up the Earth's upper layer—collide or slide against each other. These impacts are usually gradual and unnoticeable on the surface; however, immense stress can build up between plates. When this stress is released quickly, it sends massive vibrations, called seismic waves, often hundreds of miles through the rock and up to the surface. Other quakes can occur far from faults zones when plates are stretched or squeezed.

Scientists assign a magnitude rating to earthquakes based on the strength and duration of their seismic waves. A quake measuring 3 to 5 is considered minor or light; 5 to 7 is moderate to strong; 7 to 8 is major; and 8 or more is great.

On average, a magnitude 8 quake strikes somewhere every year and some 10,000 people die in earthquakes annually. Collapsing buildings claim by far the majority of lives, but the destruction is often compounded by mud slides, fires, floods, or tsunamis. Smaller temblors that usually occur in the days following a large earthquake can complicate rescue efforts and cause further death and destruction.

Loss of life can be avoided through emergency planning, education, and the construction of buildings that sway rather than break under the stress of an earthquake.

Fast Facts About Earthquakes

• Earthquakes strike suddenly, violently, and without warning at any time of the year and at any time of the day or night.

• Smaller earthquakes often follow the main shock.

• An earthquake is caused by the breaking and shifting of rock beneath the Earth's surface. Ground shaking from earthquakes can collapse buildings and bridges; disrupt gas, electric, and phone service; and sometimes trigger landslides, avalanches, flash floods, fires, and huge, destructive ocean waves (tsunamis).

• Most earthquake-related injuries result from collapsing walls, flying glass, and falling objects.

• In the United States, several thousand shocks of varying sizes occur annually and 70 to 75 damaging earthquakes occur throughout the world on an annual basis. All 50 states and all U.S. territories are vulnerable to earthquakes. Where earthquakes have occurred in the past, they will happen again.

• California experiences the most frequent damaging earthquakes; however, Alaska experiences the greatest number of large earthquakes—most located in uninhabited areas.

• Earthquakes occur most frequently west of the Rocky Mountains, although historically the most violent earthquakes have occurred in the central United States.

• The largest earthquakes felt in the United States were along the New Madrid Fault in Missouri, where a 3-month long series of quakes from 1811 to 1812 included three quakes larger than a magnitude of 8 on the Richter Scale. These earthquakes were felt over the entire Eastern United States (over 2 million square miles) with Missouri, Tennessee, Kentucky, Indiana, Illinois, Ohio, Alabama, Arkansas, and Mississippi experiencing the strongest ground shaking.

• The Richter Scale, developed by Charles F. Richter in 1935, is a logarithmic measurement of the amount of energy released by an earthquake. Earthquakes with a magnitude of at least 4.5 are strong enough to be recorded by sensitive seismographs all over the world.

• Estimates of losses from a future earthquake in the United States approach $200 billion.

What to Do Before an Earthquake

Earthquakes strike suddenly, violently and without warning. Identifying potential hazards ahead of time and advance planning can reduce the dangers of serious injury or loss of life from an earthquake. Repairing deep plaster cracks in ceilings and foundations, anchoring overhead lighting fixtures to the ceiling, and following local seismic building standards, will help reduce the impact of earthquakes.

1. Check for Hazards in the Home

◦ Fasten shelves securely to walls.
◦ Place large or heavy objects on lower shelves.
◦ Store breakable items such as bottled foods, glass, and china in low, closed cabinets with latches.
◦ Hang heavy items such as pictures and mirrors away from beds, couches, and anywhere people sit.
◦ Brace overhead light fixtures.
◦ Repair defective electrical wiring and leaky gas connections. These are potential fire risks.
◦ Secure a water heater by strapping it to the wall studs and bolting it to the floor.
◦ Repair any deep cracks in ceilings or foundations. Get expert advice if there are signs of structural defects.
◦ Store weed killers, pesticides, and flammable products securely in closed cabinets with latches and on bottom shelves.

2. Identify Safe Places Indoors and Outdoors

◦ Under sturdy furniture such as a heavy desk or table.
◦ Against an inside wall.
◦ Away from where glass could shatter around windows, mirrors, pictures, or where heavy bookcases or other heavy furniture could fall over.
◦ In the open, away from buildings, trees, telephone and electrical lines, overpasses, or elevated expressways.


3. Educate Yourself and Family Members

◦ Contact your local emergency management office or American Red Cross chapter for more information on earthquakes. Also read the "How-To Series" for information on how to protect your property from earthquakes.
◦ Teach children how and when to call 9-1-1, police, or fire department and which radio station to tune to for emergency information.
◦ Teach all family members how and when to turn off gas, electricity, and water.

4. Have Disaster Supplies on Hand

◦ Flashlight and extra batteries.
◦ Portable battery-operated radio and extra batteries.
◦ First aid kit and manual.
◦ Emergency food and water.
◦ Nonelectric can opener.
◦ Essential medicines.
◦ Cash and credit cards.
◦ Sturdy shoes.

5. Develop an Emergency Communication Plan

◦ In case family members are separated from one another during an earthquake (a real possibility during the day when adults are at work and children are at school), develop a plan for reuniting after the disaster.
◦ Ask an out-of-state relative or friend to serve as the "family contact." After a disaster, it's often easier to call long distance. Make sure everyone in the family knows the name, address, and phone number of the contact person.

6. Help Your Community Get Ready

◦ Publish a special section in your local newspaper with emergency information on earthquakes. Localize the information by printing the phone numbers of local emergency services offices, the American Red Cross, and hospitals.
◦ Conduct a week-long series on locating hazards in the home.
◦ Work with local emergency services and American Red Cross officials to prepare special reports for people with mobility impairments on what to do during an earthquake.
◦ Provide tips on conducting earthquake drills in the home.
◦ Interview representatives of the gas, electric, and water companies about shutting off utilities.
◦ Work together in your community to apply your knowledge to building codes, retrofitting programs, hazard hunts, and neighborhood and family emergency plans.

What to Do During an Earthquake

Stay as safe as possible during an earthquake. Be aware that some earthquakes are actually foreshocks and a larger earthquake might occur. Minimize your movements to a few steps to a nearby safe place and stay indoors until the shaking has stopped and you are sure exiting is safe.

If indoors

• DROP to the ground; take COVER by getting under a sturdy table or other piece of furniture; and HOLD ON on until the shaking stops. If there isn’t a table or desk near you, cover your face and head with your arms and crouch in an inside corner of the building.

• Stay away from glass, windows, outside doors and walls, and anything that could fall, such as lighting fixtures or furniture.

• Stay in bed if you are there when the earthquake strikes. Hold on and protect your head with a pillow, unless you are under a heavy light fixture that could fall. In that case, move to the nearest safe place.

• Use a doorway for shelter only if it is in close proximity to you and if you know it is a strongly supported, loadbearing doorway.

• Stay inside until shaking stops and it is safe to go outside. Research has shown that most injuries occur when people inside buildings attempt to move to a different location inside the building or try to leave.

• Be aware that the electricity may go out or the sprinkler systems or fire alarms may turn on.

• DO NOT use the elevators.

If outdoors

• Stay there.

• Move away from buildings, streetlights, and utility wires. • Once in the open, stay there until the shaking stops. The greatest danger exists directly outside buildings, at exits, and alongside exterior walls. Many of the 120 fatalities from the 1933 Long Beach earthquake occurred when people ran outside of buildings only to be killed by falling debris from collapsing walls. Ground movement during an earthquake is seldom the direct cause of death or injury. Most earthquake-related casualties result from collapsing walls, flying glass, and falling objects.

If in a moving vehicle

• Stop as quickly as safety permits and stay in the vehicle. Avoid stopping near or under buildings, trees, overpasses, and utility wires.

• Proceed cautiously once the earthquake has stopped. Avoid roads, bridges, or ramps that might have been damaged by the earthquake.

If trapped under debris

• Do not light a match.

• Do not move about or kick up dust.

• Cover your mouth with a handkerchief or clothing.

• Tap on a pipe or wall so rescuers can locate you. Use a whistle if one is available. Shout only as a last resort. Shouting can cause you to inhale dangerous amounts of dust.

What to Do After an Earthquake

• Expect aftershocks. These secondary shockwaves are usually less violent than the main quake but can be strong enough to do additional damage to weakened structures and can occur in the first hours, days, weeks, or even months after the quake.

• Listen to a battery-operated radio or television. Listen for the latest emergency information.

• Use the telephone only for emergency calls.

• Open cabinets cautiously. Beware of objects that can fall off shelves.

• Stay away from damaged areas. Stay away unless your assistance has been specifically requested by police, fire, or relief organizations. Return home only when authorities say it is safe.

• Be aware of possible tsunamis if you live in coastal areas. These are also known as seismic sea waves (mistakenly called "tidal waves"). When local authorities issue a tsunami warning, assume that a series of dangerous waves is on the way. Stay away from the beach.

• Help injured or trapped persons. Remember to help your neighbors who may require special assistance such as infants, the elderly, and people with disabilities. Give first aid where appropriate. Do not move seriously injured persons unless they are in immediate danger of further injury. Call for help.

• Clean up spilled medicines, bleaches, gasoline or other flammable liquids immediately. Leave the area if you smell gas or fumes from other chemicals.

• Inspect the entire length of chimneys for damage. Unnoticed damage could lead to a fire.

• Inspect utilities.

◦ Check for gas leaks. If you smell gas or hear blowing or hissing noise, open a window and quickly leave the building. Turn off the gas at the outside main valve if you can and call the gas company from a neighbor's home. If you turn off the gas for any reason, it must be turned back on by a professional.

◦ Look for electrical system damage. If you see sparks or broken or frayed wires, or if you smell hot insulation, turn off the electricity at the main fuse box or circuit breaker. If you have to step in water to get to the fuse box or circuit breaker, call an electrician first for advice.

◦ Check for sewage and water lines damage. If you suspect sewage lines are damaged, avoid using the toilets and call a plumber. If water pipes are damaged, contact the water company and avoid using water from the tap. You can obtain safe water by melting ice cubes.

An Overview of Earthquakes

Earthquakes are one of the most powerful natural forces on earth and regularly affect people around the world. Unlike often equally damaging severe weather events such as hurricanes and tornadoes, earthquakes can hit at anytime. Earthquakes can also have a range of magnitudes with the strongest having devastating consequences for the areas where they are centered, nearby areas, and even some far away in the case of earthquake-generated tsunamis. Until relatively recently, geologists and other scientists were not entirely sure what caused earthquakes. Now with increasing technology, the resultant better monitoring, and an enhanced understanding of plate tectonics, they are able to give more solid reasons for them.

Earthquakes are defined as a vibration of the earth's surface that occurs after a release of energy in the earth's crust.

Because the earth's crust is made up of numerous segments or "plates" that are constantly moving slowly, vibrations can occur and result in small earthquakes. Most earthquakes are quite small but are not readily felt. Larger and more violent earthquakes are those that occur in a release of energy as the plates slide past or collide into one another.

Large earthquakes can focus on the boundaries where two plates meet, but they are not limited to these areas. As the plates move, fractures in the earth's crust develop and earthquakes are often located on them. These fractures are referred to as faults, of which there are three types and all generate earthquakes when they move.

The first type of fault is called a normal fault. These are described as being nearly vertical and occur in areas where earth's plates are pulled apart because of a divergent plate boundary nearby. On this fault, the hanging wall pushes down on the footwall. For reference, the hanging wall is the rock pushed above the fault plane and the footwall is the rock below the plane. The fault plane is the flat surface representing the fracture line of the fault.

Another nearly vertical fault is a reverse fault. These are created when the earth's crust is compressed when two plates collide. Here the hanging wall pushes up and the footwall pushes down.

Finally, the strike-slip fault is a horizontal fault where the areas of rock slide past one another. These occur in areas where there is a transform plate boundary. The San Andreas fault in California is an example of a strike-slip fault.

In all of these faults, the most damaging earthquakes happen when the blocks of rock become locked together due to the intense friction created when they move. As they continue attempting to move once they are locked, pressure continues to build until it has enough energy to move the rock and the blocks move, creating an earthquake.

The point where the energy is released is called the focus and the focal depth is the depth beneath the earth's surface where the energy release originates. The epicenter is another term used in studying earthquakes and this is the point on the earth's surface directly above the focus. From here, the energy released spreads out in rings moving across the surface - not unlike those caused when a rock hits still water.

In addition to the main shaking created by an earthquake, there are often foreshocks and aftershocks. Foreshocks generally increase in magnitude leading to the main earthquake, whereas aftershocks happen after the main event and decrease in strength.

Once an earthquake finishes its movement, its magnitude (strength) is determined with the Richter and/or Mercalli Scale. The Richter scale measures the energy released by an earthquake while the Mercalli scale measures the felt or observed intensity at a particular location.

The impacts of earthquakes vary based on their energy and intensity. The strongest earthquakes that occur can result in ground rupture, causing damage to bridges, dams, roads, railroad tracks, and the foundations of buildings. They can also cause landslides and avalanches as a result of the shaking. Intense shaking can also cause liquification of ground built on landfill when water mains break. The shaking of an earthquake is increased in areas of landfill.

Another major cause of damage is the fires that ignite when power lines fall and gas lines rupture. In addition, undersea earthquakes can generate tsunamis that are capable of traveling great distances from the epicenter and cause significant damage to coastal communities.

One of the strongest earthquakes to occur in the 20th Century was in San Francisco, California in 1906. It was measured to have a magnitude between 7.7 and 8.3 and caused $400 million in damage. Most of the damage was caused by the fires that resulted after the earthquake.

On March 27, 1964, Alaska (the U.S. state with the most earthquakes) experienced a quake measuring 9.2 which generated several tsunamis in the Pacific Ocean. Trees were said to have been snapped apart near the epicenter, but because Alaska is not heavily populated, fortunately only 114 people died.

Both of these earthquakes occurred on faults near plate boundaries, as do most. More recent events such as the 1989 Loma Preita, the 1994 Northridge, and the Pacific Northwest's Nisqually in 2001 all have a similar status and were equally damaging. Many other large earthquakes have struck similar areas around the globe.

In an effort to reduce the impacts of such earthquakes, areas prone to them have taken steps to retrofit buildings and educate citizens (in schools and the media for example) on what they should do when an earthquake occurs.

Scientists at universities around the world and organizations such as the United States Geological Survey (USGS) also work hard in monitoring such earthquakes in hopes of being able to one day predict them to alert people. However, until then, knowledge of what to do and always being prepared for an earthquake is the best way to reduce injuries, deaths, and damage to cities and towns when they occur.