






















EARTHQUAKES
Earthquakes can happen at any type of plate boundary. They can happen at
divergent, convergent, and transform boundaries.
The most common boundaries for earthquakes are transform boundaries.
The most violent earthquakes happen at convergent boundaries
The mildest earthquakes happen at divergent boundaries
At convergent boundaries with subduction zones, the more dense plate will
subduct under the less dense plate
An earthquake is a sudden shaking of the ground caused by breaking rock.
Earthquakes generate (make or produce) seismic waves
A seismograph is the apparatus (machine) that measures seismic waves and
arrival times
There are 3 types of seismic waves: P waves, S waves, Surface waves
P waves are PRIMARY waves; they are a compression type wave, and they are
the fastest
S waves are SECONDARY waves; they are a shear type wave, and they are
slower than primary waves
SURFACE waves are the slowest, and they case a rolling wave motion on the
surface of the earth. They cause the most damage and shaking of the surface
Divergent boundary = normal fault = tension stress
Convergent boundary = reverse fault = compression stress
Transform boundary = strike-slip fault = shear stress
The area or boundary that surrounds the Pacific plate where most earthquakes and
volcanoes occur is called the Ring of Fire
In order to locate an earthquake, 3 seismic stations are needed.
The place ON the earths SURFACE where an earthquake originates (starts) is
called the epicenter
The place DIRECTLY below the epicenter (inside the crust) where the earthquake
starts and the rock actually breaks is called the focus
There are three common ways (or scales) to measure an earthquake
Richter scale, Mercalli scale, and the Moment Magnitude scale
Richter scale- measures size and MAGNITUDE (strength) of the earthquake. It
has no limit; it starts from 1 and can go up without ending. 1 would be the
smallest size and strength. The greatest one on record is about a 9.7on the Richter
scale
Mercalli scale-measures the DAMAGE an earthquake causes; it has a scale from
1 to12. 1 being nearly no damage, and 12 being total destruction.
Moment Magnitude scale- This is basically a combination of the Richter scale
and the Mercalli scale