What is an earthquake?
- Earthquakes are the shaking, rolling or sudden shock of the earth’s surface.
- They are the Earth’s natural means of releasing stress.
- Earthquakes can be felt over large areas although they usually last less than one minute.
- Earthquakes cannot be predicted, although scientists are working on it.
What causes an earthquake?
- There are about 20 plates along the surface of the earth that move continuously and slowly past each other. When the plates squeeze or stretch, huge rocks form at their edges and the rocks shift with great force, causing an earthquake.
- Ex: pencil test
- As the plates move they put forces on themselves and each other. When the force is large enough, the crust is forced to break. When the break occurs, the stress is released as energy, which moves through the Earth in the form of waves, which we feel and call an earthquake.
What is a fault?
- A fault is an area of stress in the earth where broken rocks slide past each other, causing a crack in the Earth’s surface.
- There are 4 major types of faults which are as follows: dip-slip normal, dip-slip reverse, strike-slip, and oblique-slip.
4. Major Types of Fault
Dip-Slip Normal Fault
Dip-Slip Reverse Fault
Strike – Slip Fault
Oblique – Slip Fault
What are plate tectonics?
- The plate tectonic theory is supported by a wide range of evidence that considers the earth’s crust and upper mantle to be composed of several large, thin, relatively rigid plates that move relative to one another.
- The plates are all moving in different directions and at different speeds. Sometimes the plates crash together pull apart or sideswipe each other. When this happens, it commonly results in earthquakes.
What is a seismograph?
- A seismograph is an instrument used for recording the intensity and duration of an earthquake.
What is a tsunami?
- A tsunami is a large ocean wave usually caused by an underwater earthquake or a volcanic explosion.
- Tsunamis are NOT tidal waves.
- Tidal waves are caused by the forces of the moon, sun, and planets upon the tides, as well as the wind as it moves over the water.
- With typical waves, water flows in circles, but with a tsunami, water flows straight. This is why tsunamis cause so much damage.
Tidal waves vs. Tsunamis
– The point on the earth’s surface directly above the source of the earthquake.
- SEISMIC WAVES
– The energy created by the quake that travels in waves from the epicenter, where they are the strongest.
- RICHTER SCALE
– A measurement of an earthquake’s intensity.
– Each one-point increase on the scale indicates ten times the amount of shaking and 33 times the amount of energy.
– The energy released by a large earthquake may be equal to 10,000 times the energy of the first atomic bomb.
- 4 – Minor Earthquake
- 5 – Moderate Earthquake
- 6 – Strong Earthquake
- 7 – Major Earthquake
- 8 – Great Earthquake
Earthquake Safety Tips
- BEFORE AN EARTHQUAKE:
- Choose a safe place in every room such as under a sturdy piece of furniture like a table or a desk where nothing can fall on you.
- Practice DROP, COVER AND HOLD ON!
– Drop under something sturdy, hold on, and protect your eyes by pressing your face against your arm.
- Prepare a disaster supplies kit for your home and car. Include a first aid kit, canned food and a can opener, bottled water, battery-operated radio, flashlight, protective clothing and written instructions on how to turn off electricity, gas, and water.
DURING AN EARTHQUAKE:
- DROP, COVER AND HOLD ON!
- Stay indoors until the shaking stops.
- Stay away from windows.
- If you’re in bed, hold on and stay there, protecting your head with a pillow.
- If you’re outdoors, find a clear spot away from buildings, trees and power lines. Then, drop to the ground.
- If you’re in a car, slow down and drive to a safe place. Stay in the car until the shaking stops.
AFTER THE SHAKING STOPS:
- Check for injuries.
- Inspect your home for damage.
- Eliminate fire hazards, so turn off the gas if you think its leaking.
- Expect aftershocks.
- Each time you feel one, DROP, COVER AND HOLD ON.