By K. Lords Earthquakes & Earthquake Safety

What is an earthquake anyway? An earthquake by definition is a sudden movement of the Earth's lithosphere. They are natural geologic phenomena causing the sudden and rapid movement of a large volume of rock. Due to rupture and slippage along faults, or fractures in Earth’s crust, violent shaking and many times destruction occur. Earthquakes originate at the focus or hypocenter which occurs at any depth between 5 and 700 kilometers (3.1 and miles) below the Earth’s surface. Directly above the hypocenter, on the surface is the epicenter. This is the point on the Earth’s surface where the earthquake begins.

How do earthquakes cause damage? Ground shaking is the cause for damage done by earthquakes. The magnitude or size (energy release) of an earthquake, distance to the epicenter, depth of the hypocenter, type of faulting, and type of rock and mass material are important factors in determining the amount of ground shaking that might be produced at any particular site /messina.htm

How do we measure earthquakes? During an earthquake, large amounts of energy are released in the form of heat and seismic waves. Sensitive instruments, seismographs, located around the world can quickly pick up on the rapidly dissipating seismic waves and energy. We take the measure the magnitude of an earthquake by using the Richter Scale, with 1 being We measure the intensity of an earthquake by using the modified Mercalli scale, which starts with I being the lowest intensity and XII being the most intense.

Mercalli Scale

Liquefaction Liquefaction occurs when earthquake vibrations cause the loose or saturated soil particles to lose contact with one another. As a result, the soil behaves like a liquid, has an inability to support weight and can flow down very gentle slopes. Causing a lot of significant damage in many earthquakes.

Can Earthquakes be predicted? There are no definite ways of predicting earthquakes in either the short term or long term. The movement of tectonic plates and faults is so unpredictable, that there is no sure way of knowing exactly when and where an earthquake will strike. Many factors contribute to how large and devastating an earthquake will be, depending on what type of fault it is, how much energy is released, how structurally sound the buildings and structures are in the surrounding area, how prepared the cities surrounding are prepared to deal with the earthquake, etc.

Earthquake Safety It is important in the event of an earthquake to be prepared, and since we are unable to predict earthquakes, it is necessary to be prepared at all times… The following slides show how FEMA suggests we prepare ourselves when faced with an unpredictable natural disaster, in this case earthquakes.

FEMA’s 7 Steps to Earthquake Preparedness  PREPARE (before) 1. Secure your spaces 2. Create a plan 3. Prepare disaster kits 4. Strengthen your home  SURVIVE (during) 5. Drop, cover, and hold on  RECOVER (after) 6. Check for injuries and damage 7. Follow your plan

STEP 1: Secure your space 1) Hang plants in lightweight pots with closed hooks, well secured to a joist or stud and far away from windows. 2) Install strong latches on kitchen cabinets. 3) Use flexible connections where gas lines meet appliances. 4) Remove or lock refrigerator wheels, secure to studs. 5) Secure valuable electronics items such as computers and televisions. 6) Keep breakables in low or secure cabinets with latches. 7) Move heavy plants and other large items to floor or low shelves. 8) Hang mirrors and pictures and pictures on closed hooks. 9) Secure free-standing woodstove or fireplace insert. 10) Keep heavy unstable objects away from doors and exit routes. 11) Place bed away from windows or items that may fall. 12) Secure knick knacks and other small valuables with museum putty. 13) Brace overhead light fixtures. 14) Place only light weight/soft items over bed. 15) Secure top-heavy furniture to studs. 16) Secure water heater with metal straps attached to studs. 17) Trim hazardous tree limbs.

STEP 2:Create a plan 18) Store fire extinguisher (type ABC) in easily accessible location. 19) Keep several flashlights in easily accessible places around the house. 20) Keep wrench or turn-off tool in water proof wrap near gas meter. 21) Know the location of your main electrical switch (fuse box or circuit breaker). 22) Have your emergency plan accessible and discuss with all family members. 23) Know whether you live, work, or play in a tsunami hazard zone. 24) Obtain a NOAA Weather Radio with the Public Alert feature to notify you of tsunamis and other hazards. 25) Keep flashlight, slippers and gloves next to beds. 26) Keep gas tank at least half full. STEP 3: Prepare disaster kits 27) Keep an emergency backpack with copies of important documents near the door to grab and go. 28) Store emergency food and water supplies in a dry accessible area. Include first aid kit, extra cash, portable radio, extra batteries, medications and other necessary supplies. STEP 4: Strengthen your home 29) Use anchor bolts every 4 to 6 feet to secure home to foundation. 30) Reinforce brick chimneys.

During an Earthquake It’s important to properly protect yourself by…  Dropping to the floor  Covering yourself under or parallel to a large stable object  Hold on, and ride out the earthquakes vibrations

A Few Famous Earthquakes San Francisco, California: April 18, 1906 (Magnitude: About 8) Tokyo, Japan: September 1, 1923 (Magnitude: About 8.25) Chile: May 22, 1960 (Magnitude: About 9) Anchorage, Alaska: March 27, 1964 (Magnitude: About 8.5) Tangshan, China: July 27, 1976 (Magnitude: About 7.5) Sumatra, Indonesia, Dec. 26, (Magnitude: About 9.0)

Sources Earth: An Introduction to Physical Geology, 10 th Edition by Edward J. Trabuck, Frederick K. Lutgens, and Dennis Tasa.  2011