from Th* Mini Page by B*tty D*bcum * 1990 Univerwl Pret* SyndiC4le
MORE ABOUTEARTHQUAKES
Our Earth
What happens
Seismic waves
D
A. Inner core of solid iron and
nickel
B. Outer core of melted iron and
nickel
C. Mantle of solid rock
D. Hard crust, from 5 miles to 40
miles deep
. The force of most earthquakes
is centered in the crust (D) and in
the upper part of the mantle (C).
Mantle
The focus is where the
earthquake starts.
The epicenter is the point on the
Earth's surface just above the
focus.
calli scale
Scientists have ways
to record how big
earthquakes are. The
Mercalli scale is based
on what people see. It
measures the effect of
*
earthquakes on people, landscape
and buildings, roads and bridges.
It uses Roman numerals from I
to XII.
Below are just a few of the steps.
I. Not felt except by a few.
V. Felt by practically all and
frightened a few.
XII. Damage nearly total.
Tsunamis (soo-NAHM-ees) are
huge waves caused by earthquakes in the ocean. The waves
can be 100 feet high and travel
at speeds up to 600 miles per hour.
A geophysicist points to the zigzag lines
recorded at a seismograph station. A
geophysicist (je-o-FIZ-i-cist) is a scientist
who studies the behavior and makeup of the Earth.
During a quake, the Earth's
crust may first bend and then
snap into position.
While it's bending and breaking,
vibrations called "seismic waves"
travel from the source of the
quake to faraway places.
Seismographs (SIZE-mohgraphs) are instruments that
measure seismic waves. They can
measure earthquakes thousands of
miles away.
The instruments make zigzag
records on special paper.
^ f ^ ^ A ^ \ V
A
' ^ ^ ^ —
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This is how the Oct. 17, 1989,
quake looked. It was rated 7.1 on
the Richter scale. It was a major
quake.
The Richter scale
The Richter scale measures how
much energy is released in an
earthquake.
It uses a special math formula.
1.0 to 2.0 — Usually only
detected by instruments
3.0 to 4.0 — Can hardly be felt
4.0 to 5.0 — Generally felt,
slight damage
6.0 — Moderately destructive
7.0 — Major earthquake
8.0 — Great earthquake
4 - Special Supplement to the Savanna* Morning News, Tuesday, February 13, 1990
An earthquake is the sudden
release of energy caused by the
movement of the Earth's crust.
During an earthquake:
• the Earth shakes and cracks.
• there are landslides.
• sandy areas with a lot of
water might turn to liquid for a
matter of seconds up to a few
minutes. The liquid can be forced
upward as high as 20 feet. It blasts
through cracks and holes much
like a volcano erupts. The holes it
makes are called "sand boils" or
"sand blows."
The Charleston, S.C., Earthquake of 1886
caused this sand boil.
Earthquake safety
Inside: Learn the
safe spots in each
room.
• under supported
archways
• against inside
walls
• under heavy pieces of
f u r n i t u r e such as a desk or heavy
table
• Stay away from things that
could break or fall on you.
• Stay where you are. If
outdoors, stay outdoors. If
indoors, stay indoors. Most people
get h u r t when they are entering
or leaving buildings.
Outside: Move away from
buildings, telephone and electric
wires. Once in the open, stay
there until the shaking stops.