Earthquakes are vibrations of the ground that happen when bodies of rock break releasing energy.
The point beneath earth’s surface where the earthquake actually occurs is called the focus.
The point on the surface directly above the focus is called the epicenter.
This energy travels in the form of waves, like waves made when you drop a rock in a calm pond.
3 kinds of waves
1. Primary waves (p-waves)-
· travel through solid, liquids and gases
· travel the fastest
· first to reach a location
· move side to side in the direction the wave is traveling
2. Secondary waves (s-waves)-
· travel through solids only
· slower than p-waves
· second to arrive at a location
· move at right angles(up and down) to the direction wave is traveling
3. Long waves (l-waves)-
· Travel across the surface
· Produced only in a very powerful earthquake
· travel outward in a circle from point of origin
· are measured using a seismograph
· can be used to determine what the structure of the earth’s interior is like
Scientists believe the earth’s interior is made up of distinct layers.
They have theories about what the layers are made of thanks to earthquake waves.
S-waves can’t travel through liquids so when they disappear while traveling through the earth where the outer core may start, scientists use that to prove the outer core is liquid.
P-waves don’t show up on seismographs in some places on the earth because as they travel through the earth, they are bent with each change in material they pass through. Where they don’t show up is called a shadow zone.
This measures the size of an earthquake based on the amount of ground movement caused by the earthquake waves.
With every increase on the scale of 1, the earthquake becomes ten times more powerful as the number before it.
Ex-an earthquake of 3 on the Richter scale is 100x greater than an earthquake of 1 on the scale.
1=1
2=10x1=10
3=10x10=100 and so on
This measures the intensity of the earthquake based on how much damage it does to buildings etc.
The most damage done by earthquakes is at the epicenter of the quake.
Damage amount depends on
Power of the earthquake
Location or type of ground earthquake moves through
Type of structures
Dangers associated with earthquakes
Tsunamis-if quake is under water
Firestorms-from ruptured gas lines
Collapsing buildings and highways
Liquefaction of ground-ground turns to quicksand
Mud and landslides