TABLE -- MODIFIED MERCALLI INTENSITY SCALE
Summary Damage
MMI Description
Value Used on 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. Pictures Felt outdoors; direction estimated. Sleepers wakened. Liquids
Move disturbed, some spilled. Small unstable objects displaced or
upset. Doors swing, close, open. Shutters, pictures move.
Pendulum clocks stop, start, change rate.
VI. Objects Felt by all. Many frightened and run outdoors. Persons walk
Fall 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. Nonstruct Difficult to stand. Noticed by drivers of motor cars. Hanging
ural objects quiver. Furniture broken. Damage to masonry D,
Damage 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. Moderate Steering of motor cars affected. Damage to masonry C; partial
Damage 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. Heavy General panic. Masonry D destroyed; masonry C heavily damaged,
Damage 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. Extreme Most masonry and frame structures destroyed with their
Damage 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.