EARTHQUAKES – ASSISTED NOTES
Deadliest Earthquakes


The earthquake that caused the most destruction in history occurred in the Shansi province of China on January
23,1556. An estimated ____________________________________________________.
The second most destructive earthquake also occurred in China--in July, 1976--and killed 255,000 people.
What is an Earthquake?


The definition of an earthquake is… ______________________________________________________.
These vibrations move in all directions through the earth. They begin at a point along a
____________________________________.
How do faults form?

The earth’s crust is constantly experiencing pressure from forces within and around it. This pressure builds up
over time, and eventually causes the crust to break. This becomes a __________________________________
What is an Earthquake?


An earthquake begins along a fault (a crack in the earth’s surface) at a point called the
_____________________________.
Directly above the focus is a point on the earth’s surface called the
______________________________________.
Why is the epicenter important?


Seismologists have stations all over the world that continuously
____________________________________________________ about earthquakes. This kind of information
can help scientists figure out where larger, more destructive earthquakes may strike by mapping out the
location of smaller ‘quakes. They also get a greater understanding of the changes the earth’s crust makes as the
earthquakes occur.
How do they do this???
What is an Earthquake?


When the fault ruptures with a sudden movement energy is released that has built up over the years. This
energy is released in the form of vibrations called __________________________________... earthquakes!
It is actually when these seismic waves reach the surface of the earth that most of the destruction occurs, which
we associate with earthquakes.
What Kind of Damage Do They Do?

Earthquakes can cause _________________________________________, sudden eruptions as in the case of a
hot lava flow from a ___________________________________________ or giant waves called
__________________________________________. Sometimes new land mass are also formed. Such
earthquakes are attributed with the creation of the greatest undersea mountain range and the longest land
mountain range.
How are earthquakes measured?

Earthquakes are measured using the _____________________________________________. The strongest
earthquake ever measured was a 9.5 on the Richter Scale. This is a measurement of the amount of energy
released from the earthquake.
 ___________________________________is a number that characterizes the relative size of earthquakes & is
proportional to energy released
...and in the 48 states

In the lower 48 states, there is a tie between the February 1812, New Madrid, Missouri earthquake and the
January 1857, Fort Tejon, California earthquake--both ___________________________________--for the
strongest earthquake recorded.
What Does an Earthquake Feel Like?

Generally, during an earthquake you first will feel a ______________________________________ or
________________________________________________, then a slight pause, followed by a more intense
rolling or jerking motion. The duration of the shaking you feel depends on the earthquake's magnitude, your
distance from the epicenter, and the geology of the ground under your feet.
How Long Does an Earthquake Last?




For minor earthquakes, ground shaking usually lasts only _________________________________________.
Strong shaking from a major earthquake usually lasts __________________________________________. For
example, shaking in the 1989 magnitude 7.1 Loma Prieta (San Francisco) earthquake lasted
__________________________________________;
For the 1906 magnitude 8.3 San Francisco earthquake it lasted about
______________________________________.
Shaking for the 1964 magnitude 9.2 Alaska earthquake, however, lasted
___________________________________.
What is an aftershock?

Aftershocks are smaller earthquakes which occur in the same general area during the
_______________________________________________ following a larger event or
"_________________________________________". As a general rule, aftershocks represent minor
readjustments along the portion of a fault that slipped at the time of the main shock. The frequency of these
aftershocks decreases with time.