Modified Mercalli Intensity (abbreviated description)
The approximate values of acceleration
shown are not part of the definition of MM intensity
The values are from Richter, C., Elementary Seismology, WH
Freeman, 1958
|
MM
Intensity
|
Accel.
%g
|
Description
of Intensity Level
|
|
I
|
0.1
|
Not felt except by a very few
under especially favorable circumstances. |
|
II
|
0.2
|
Felt only by a few persons at
rest, especially on upper floors of buildings. Delicately suspended
objects may swing. |
|
III
|
0.3
|
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 a truck. Duration estimated. |
| IV
|
0.7
|
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
|
1.5
|
Felt by nearly everyone; many
awakened. Some dishes, windows broken. Unstable objects overturned.
Pendulum clocks may stop.
|
| VI
|
3
|
Felt by all; many frightened.
Some heavy furniture moved; a few instances of fallen plaster. Damage
slight.
|
| VII
|
7 |
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 |
15 |
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 |
32 |
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 |
70 |
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. |
