MMI
Value |
Description
of Shaking Severity |
Summary
Damage Description Used on 1995 Maps |
Full
Description
|
|
I. |
. |
. |
Not
felt. Marginal and long period effects of large earthquakes. |
|
II. |
. |
. |
Felt
by persons at rest, on upper floors, or favorably placed. |
|
III. |
. |
. |
Felt
indoors. Hanging objects swing. Vibration like passing of light trucks.
Duration estimated. May not be recognized as an earthquake. |
|
IV. |
. |
. |
Hanging
objects swing. Vibration like passing of heavy trucks; or sensation of a
jolt like a heavy ball striking the walls. Standing motor cars rock. Windows,
dishes, doors rattle. Glasses clink. Crockery clashes. In the upper range
of IV, wooden walls and frame creak. |
|
V. |
Light |
Pictures
Move |
Felt
outdoors; direction estimated. Sleepers wakened. Liquids disturbed, some
spilled. Small unstable objects displaced or upset. Doors swing, close,
open. Shutters, pictures move. Pendulum clocks stop, start, change rate. |
|
VI. |
Moderate |
Objects
Fall |
Felt
by all. Many frightened and run outdoors. Persons walk unsteadily. Windows,
dishes, glassware broken. Knickknacks, books, etc., off shelves. Pictures
off walls. Furniture moved or overturned. Weak plaster and masonry D cracked.
Small bells ring (church, school). Trees, bushes shaken (visibly, or heard
to rustle). |
|
VII. |
Strong |
Nonstructural
Damage |
Difficult
to stand. Noticed by drivers of motor cars. Hanging objects quiver. Furniture
broken. Damage to masonry D, including cracks. Weak chimneys broken at roof
line. Fall of plaster, loose bricks, stones, tiles, cornices (also unbraced
parapets and architectural ornaments). Some cracks in masonry C. Waves on
ponds; water turbid with mud. Small slides and caving in along sand or gravel
banks. Large bells ring. Concrete irrigation ditches damaged. |
|
VIII. |
Very
Strong |
Moderate
Damage |
Steering
of motor cars affected. Damage to masonry C; partial collapse. Some damage
to masonry B; none to masonry A. Fall of stucco and some masonry walls.
Twisting, fall of chimneys, factory stacks, monuments, towers, elevated
tanks. Frame houses moved on foundations if not bolted down; loose panel
walls thrown out. Decayed piling broken off. Branches broken from trees.
Changes in flow or temperature of springs and wells. Cracks in wet ground
and on steep slopes. |
|
IX. |
Violent |
Heavy
Damage |
General
panic. Masonry D destroyed; masonry C heavily damaged, sometimes with complete
collapse; masonry B seriously damaged. (General damage to foundations.)
Frame structures, if not bolted, shifted off foundations. Frames racked.
Serious damage to reservoirs. Underground pipes broken. Conspicuous cracks
in ground. In alluvial areas sand and mud ejected, earthquake fountains,
sand craters. |
|
X. |
Very
Violent |
Extreme
Damage |
Most
masonry and frame structures destroyed with their foundations. Some well-built
wooden structures and bridges destroyed. Serious damage to dams, dikes,
embankments. Large landslides. Water thrown on banks of canals, rivers,
lakes, etc. Sand and mud shifted horizontally on beaches and flat land.
Rails bent slightly. |
|
XI. |
. |
. |
Rails
bent greatly. Underground pipelines completely out of service. |
|
XII. |
. |
. |
Damage
nearly total. Large rock masses displaced. Lines of sight and level distorted.
Objects thrown into the air. |
ABAG, the Association of Bay Area Governments, is the
regional planning and services agency for the nine-county San Francisco Bay
Area.
Source - 2003 "On Shaky Ground" documentation prepared by ABAG.
jbp 10/15/03