3.3
VOCABULARY
Epicenter:
the point on
Earth’s surface directly
above the focus of an
earthquake.
ACTIVITY ONE
T
HE
M
ERCALLI
S
CALE
: C
ALLING
S
TATION
KWAT
RA T I ONA L E
Students need to know how seismologists establish earthquake
intensity in order to understand how much damage earthquakes can
cause and how building codes are developed.
F OCU S QU E S T I ON S
How do seismologists determine the intensity of an earthquake?
OB J E C T I V E S
Students will:
1. Interpret the Modified Mercalli scale and assign values on the basis
of descriptions by citizen observers during and after a quake.
2. Use the assigned values to construct an isoseismal map.
MA T E R I A L S
Q
Overhead projector
Q
Student copies of Master 3.3a, Modified Mercalli Intensity Scale
Q
Transparency made fromMaster 3.3a, Modified Mercalli Intensity Scale
Q
Back of Master 3.3a, Teacher Background Reading: Richter vs. Mercalli
Q
Student copies of Master 3.3b, Wattsville Map
Q
Transparency made from Back of Master 3.3b, Wattsville Map Key
Q
One copy of Master 3.3c, KWAT Television Script, cut into strips
Q
Student copies of Master 3.3c, KWAT Television Script
Q
Colored pencils and lead pencils
Focus (pl. foci):
the point within the
Earth that is the origin of an
earthquake where stored energy is
first released as wave energy.
Intensity:
a subjective measure of
the amount of ground shaking an
earthquake produces at a particular
site, based on geologic effects,
impact on human structures, and
other human observations. Mercalli
intensity is expressed in Roman
numerals.
Isoseismal line:
a line on a map
that encloses areas of equal
earthquake intensity.
Magnitude:
a number that
characterizes the size of an
earthquake by measuring the
motions on a seismograph and
correcting for the distance to the
epicenter of the earthquake.
Magnitude is expressed in Arabic
numbers.
A G U
/
F E M A
162
S
E I S M I C
S
L E U T H S
