You wake up during the night, or you’re walking outside, and the earth starts to tremble and shake. Have you ever wondered what causes earthquakes or how to stay safe during an earthquake? Here are the answers.
What Is An Earthquake?
A tectonic earthquake is an earthquake that results from sudden movements of rock under the surface. These are the most common type of earthquakes. Volcanic earthquakes occur with volcanic activity; collapse earthquakes are small earthquakes in caverns or mines; and explosion earthquakes occur from the explosion of nuclear and chemical devices. [1]
Tremors, Aftershocks, and Foreshocks
Tremors are weak earthquakes. Aftershocks are tremors that follow an earthquake for days or months. Foreshocks are smaller earthquakes occurring before the main earthquake.
Earthquake Zones
Their are multiple earthquake zones around the earth. The most active zone is the circum-Pacific Belt, also known as the Ring of Fire. The Ring of Fire borders North, Central, and South America, Japan, the Philippines, New Zealand, and the island in the South Pacific.
Another belt, the Alpide Belt, extends from southern Europe into Asia. The other belts are the Mid-Atlantic Ridge, East African Rift Zone, and the Indian Ocean Belt.
Waves
There are three types of waves: P waves, S waves, and surface waves. P waves, or primary waves, arrive first and are felt first, but they do little damage. P waves are also the fastest type of wave. S waves, or secondary waves, arrive second and creates a lot of damage. Surface waves are produced from P waves and S waves. Surface waves cause the most damage to buildings.
Where It Starts
The hypocenter is the are in the earth where the earthquake first generates from. The hypocenter is also know as the focus. The epicenter is the place on the surface directly above the hypocenter.
Instruments Used
Seismologists, scientists who study earthquakes, use a seismograph to study and record the vibrations. A seismometer is in the seismograph and detects the earth’s movements. A seismogram is the record of the vibrations.
Knowing The Hit Spot
Seismologists have a way to finding out where earthquakes will hit. At least three separate seismographs have to be in different places. They will calculate a circle and where all three seismographs meet is where the epicenter is.
Earthquake Intensity
There are multiple scales used to measure an earthquakes intensity. The modified Mercalli scale is based on the effect of an earthquake on man, man’s structures, and the earth’s surface. The Richter magnitude scale is used to measure an earthquakes strength. The Richter scale is the most famous scale used to measure an earthquake’s strength. The moment magnitude scale is also used to measure an earthquake’s strength. It is considered the most reliable method for measuring an earthquake’s strength.
How To Stay Safe
Places prone to earthquakes should keep emergency supplies at home. You should also keep flammable things kept away so they won’t spill. You can also use lower shelves instead of higher shelves.
If an earthquake hits the first rule is to stay calm. If you’re indoors, stay indoors; if you’re outside, stay outside. If you are inside, don’t stand next to windows, but find something sturdy you can hide underneath, such as a table or desk. When you’re in relative safety, 1. drop, 2. cover, and 3. hold on. Protect your head once in safety. If you’re outside, stay away from buildings, trees, and electrical lines.
Notes:
- ^http://scecinfo.usc.edu/education/k12/learn/eq2.htm (go back ↩)
