Name ________________________________________ Block _______ NB __________
Measuring Earthquake Intensity
Directions: Use the scales below to answer the following questions.
Rossi Forel Scale of Earthquake Intensity
The Rossi-Forel Scale ranges in intensity from I to X. (or 1 to 10)
Earthquakes with an intensity of I would be least noticeable while
earthquakes with an intensity of X would be most noticeable. When
assigning intensities to areas on a map, note that the area “inside” the
number is the area experiencing that intensity.
o
o
o
I. Recorded by a single
seismograph or by
some seismographs of
the same pattern, but
not by several
seismographs of
different kinds; the
shock felt by an
experienced observer.
II. Recorded by
seismographs of
different kinds; felt by a
small number of
persons at rest.
III. Felt by several
persons at rest; strong
enough for the duration
or direction to be
appreciable.
o
IV. Felt by several
persons in motion;
disturbance of
moveable objects,
doors, windows,
creaking of floors.
o
VII. Overthrow of
moveable objects, fall
of plaster, ringing of
church bells, general
panic, without damage
to buildings
o
V. Felt generally by
everyone; disturbance
of furniture and beds;
ringing of some bells.
o
VIII. Fall of chimneys,
cracks in the walls of
buildings.
o
o
VI. General awakening
of those asleep;
general ringing of bells;
oscillation of
chandeliers, stopping
of clocks; visible
disturbance of trees
and shrubs; some
startled persons leave
their dwellings.
IX. Partial or total
destruction of some
buildings.
o
X. Great disasters,
ruins, disturbance of
strata, fissures in the
earth's crust, rockfalls
from mountains.
1. Describe what people in Charlotte, North Carolina
would have felt during this earthquake.
2. What intensity number can be assigned to
Syracuse, New York for this earthquake?
3. How far is New York, New York from the
epicenter?
4. What city would have felt the following: the
earthquake was felt only by people at rest?
Modified Mercalli Scale
The Modified Mercalli Scale is similar to the Rossi-Forel Scale
because it also provides descriptions of events or damage to gauge the
intensity of an earthquake. The Mercalli Scale ranges from I to IIX (or 1 to
12).
I. Not felt except by a very few under
especially favorable circumstances.
II. Felt only by a few persons at rest,
especially on upper floors of buildings.
Delicately suspended objects may swing.
III. Felt quite noticeably by persons indoors,
especially on upper floors of buildings. Many
people do not recognize it as an earthquake.
Standing motor cars may rock slightly.
Vibration similar to the passing of truck.
Duration estimated.
IV. Felt indoors by many, outdoors by few
during the day. At night, some awakened.
Dishes, windows, doors disturbed; walls
make cracking sound. Sensation like heavy
truck striking building. Standing motor cars
rocked noticeably.
V. Felt by nearly everyone; many awakened.
Some dishes, windows broken. unstable
objects overturned. Pendulum clocks may
stop.
VI. Felt by all; many frightened. Some heavy
furniture moved; a few instances of fallen
plaster. Damage slight.
VII. Damage negligible in building of good
design and construction; slight to moderate in
well-built ordinary structures; considerable
damage in poorly built or badly designed
structures; some chimneys broken. Noticed
by persons driving motor cars.
VIII. Damage slight in specially designed
structures; considerable in ordinary
substantial buildings with partial collapse.
Damage great in poorly built structures. Fall
of chimneys, factory stacks, columns,
monuments, walls. Heavy furniture
overturned.
IX. Damage considerable in specially
designed structures; well-designed frame
structures thrown out of plumb. Damage
great in substantial buildings, with partial
collapse. Buildings shifted off foundations.
X. Some well-built wooden structures
destroyed; most masonry and frame
structures destroyed with foundations. Rails
bent.
XI. Few, if any (masonry) structures remain
standing. Bridges destroyed. Rails bent
greatly.
XII. Damage total. Lines of sight and level
distorted. Objects thrown into the air.
1. What intensity level would be assigned to the following scenario:
You hear a rumble like a freight train or a big truck passing by. The sound
is so low that it is more felt than heard. But instead of fading away, the
sound changes into a shuddering sound. Panes of glass in the windows
rattle. Glass in cabinets clink. A fern in a hanging planter sways a little.
Richter Scale
The Richter Scale is most commonly used by seismologists (people who
study earthquakes) to describe the intensity of earthquake. Unlike the Rossi-Forel
and Mercalli Scales, the Richter Scale is not based on observations of events or
damage but an actual measure of the energy released during the earthquake.
There are two pieces of information provided from the magnitude number
assigned to the earthquake. First, is the height of the earthquake waves. Consider
this example:
A magnitude 1 earthquake has waves that are one unit high. A
magnitude 2 earthquake has waves that are 10 times higher than the magnitude 1
earthquake (or 1 x 10 = 10). A magnitude 3 earthquake has waves that are 10 times
higher than the magnitude 2 earthquake and 100 times higher than the magnitude
1 earthquake (or 10 x 10 x 1 = 100)
The second piece of information to consider is the energy released.
Consider this example:
A magnitude 1 earthquake releases energy equivalent to 170g of
TNT. A magnitude 2 earthquake releases 33 times the energy of a magnitude 1
earthquake (or 6ounces x 33 = 13 pounds TNT) A magnitude 3 earthquake releases
33 times the energy of a magnitude 2 earthquake and 1089 (or 33 x33) times the
energy of a magnitude 1 earthquake (or 33 x 33 x 6 ounces= 397 pounds) NOTE:
Pounds of TNT in the above examples are approximate.
1. How many times higher are the waves of a magnitude 6 earthquake than
a magnitude 2 earthquake?
2. How much more energy is released by a magnitude 8 earthquake than a
magnitude 3 earthquake?