Nothing captures national attention like a natural disaster, and few disasters have the potential to wreak as much havoc as an earthquake. Although most injuries and fatalities associated with earthquakes don’t come from the actual shaking of the earth itself, side effects are vast and violent. Earthquakes can cause landslides, tsunamis, fire, and immense structural damage. This guide introduces the basic science of earthquakes and provides information on what to if you become caught in one.
Why Earthquakes Happen
Earthquakes occur when two large blocks of earth slip past each other or collide, creating destructive resonances called seismic waves. The earth is composed of four basic layers: the inner core, outer core, mantle, and the crust. The mantle and crust form the outer portion of the earth, like the skin on an apple, except this ‘skin’ is made of many pieces called tectonic plates. These plates are in slow but constant movement, and when they bump into one another faults form at the plate boundaries. Places with frequent earthquakes are often built along a fault; such is the case in California, where the San Andreas fault runs over 800 miles long. When two plates strike or scrape against one another, energy radiates outward in all directions like ripples on a pond, shaking the earth in waves that geologists measure with seismograph equipment.
The major shake in an earthquake is called its mainshock, which is followed by aftershocks. These smaller aftershocks are like mini quakes and can continue for weeks or even months past an earthquake’s initial rumble. The starting point of an earthquake deep in the planet is called the hypocenter. If you trace a line from the hypocenter to the surface of the earth, the point at which that line touches the surface is called the epicenter of the earthquake.
Earthquakes often appear suddenly and without warning. According to the Federal Emergency Management Agency (FEMA), every household should be prepared in the event of an earthquake, particularly if you live near a fault or in an area that is especially susceptible to quakes. FEMA recommends that everyone know what to do before an earthquake in order to stay safe during and after the disaster.
Check your home for hazards.
Shelves and heavy equipment like water heaters should be bolted or otherwise securely fastened to the wall, with large and weighty objects placed on the lower shelves to anchor them. Glass, china, and other objects that break easily should be placed inside low cabinets with locks or latches. Make sure to decorate intelligently: hang heavy objects away from places people might sit, like beds and couches. Repair any cracks in the walls, ceiling, or foundation of your hone, and check your electrical wiring and gas connections to minimize fire hazards.
Know what to do.
Before an earthquake ever has the chance to occur, you and your family should be educated about the procedures to follow in an emergency. Teach children how and when to call emergency services, and also show them the proper way to turn off gas, electricity, and water systems. Tell them how to identify safe places outside and inside. Contact your local Red Cross for educational materials about protecting your family and property from earthquakes.
Keep an Emergency Supply.
Your home emergency kit should include a flashlight, battery-operated radio, first aid kit, food and water, can opener (manual), any essential medication, cash and credit cards, and reliable shoes and clothing. Also, make sure to have extra batteries on hand.
Make an Emergency Plan.
You might become separated from family members during an earthquake. Create a plan so children and adults can reunite. You might ask an out-of-town friend or relative to be the family contact so children know who to call if they find themselves alone after an earthquake.
For even more ways to prepare for a quake, see 72 Hours, an emergency preparedness program endorsed by the city of San Francisco.
What to Do in an Earthquake
See what to do during an earthquake for detailed advice. The following tips will help you stay as safe as possible, but know that many earthquakes happen in phases and a second shock may be just around the corner after the initial mainshock. In general, you should minimize movements and stay where you are until you know you are safe.
- If you are inside, stay there. Drop to the ground and take cover under a sturdy piece of furniture. Hold on until the ground stops shaking. If there is no available cover, protect your head and arms and crouch near a corner of the building. Avoid windows and items that could fall on you. If you are near a doorway, stand under it for shelter. Do not move until the shaking stops. Do not attempt to use elevators.
- If you are outside, stay there until the shaking ceases. Move into an open space away from buildings and power lines. Stay away from tall structures, since they will have been compromised by the earthquake and may collapse or objects may fall from them.
- If you are in a moving vehicle, stay inside. Find an open space (away from bridges, trees, and power lines) and stop as soon as you can. When the earthquake stops, proceed cautiously.
- If you become trapped under debris, cover your mouth with cloth and tap on a pipe or wall so that rescue workers will find you. Do not light a match or move, as you will kick up dust. Avoid shouting as it can cause you to inhale too much dust.
The Public Earthquake Resource Center provides resources for teachers, children, and the public.
If you live in an area prone to earthquakes, see Living in Earthquake Country, a site that provides lesson plans with which to teach students how earthquakes start and how to stay safe when one happens.
Additionally, the USGS provides many valuable earthquake resources from a global earthquake search toseismic hazard maps and tools for engineers. Kids and students can learn more with interactive onlineearthquake games and activities.
Tremor is a service of FEMA with further educational activities.
*Image Credit: Wikimedia Commons