M A S T E R P A G E
Modified Mercalli Intensity Scale
3.3a
Intensity Value & Description
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 indoors, especially on upper floors of buildings, but many people do not recognize it as
an earthquake. Standing automobiles may rock slightly. Vibration like passing of truck. Duration estimated.
IV.
During the day felt indoors by many, outdoors by few. At night some awakened. Dishes, windows, doors
disturbed; walls make creaking sound. Sensation like heavy truck striking building. Standing automobiles
rocked noticeably.
V.
Felt by nearly everyone, many awakened. Some dishes, windows, and so on broken; cracked plaster in a few
places; unstable objects overturned. Disturbances of trees, poles, and other tall objects sometimes noticed.
Pendulum clocks may stop.
VI.
Felt by all, many frightened and run outdoors. Some heavy furniture moved; a few instances of fallen plaster
and damaged chimneys. Damage slight.
VII.
Everybody runs outdoors. Damage negligible in buildings of good design and construction; slight to
moderate damage in well-built ordinary structures; considerable in poorly built or badly designed structures;
some chimneys broken. Noticed by persons driving cars.
VIII.
Damage slight in specially designed structures; considerable in ordinary substantial buildings, with partial
collapse; great in poorly built structures. Panel walls thrown out of frame structure. Chimneys, factory stacks,
columns, monuments, walls may fall. Heavy furniture overturned. Sand and mud ejected in small amounts.
Changes in well water. Persons driving cars disturbed.
IX.
Damage considerable in specially designed structures; well-designed frame structures thrown out
of plumb; great in substantial buildings, with partial collapse. Buildings shifted off foundations. Ground cracked
conspicuously. Underground pipes broken.
X.
Some well-built wooden structures destroyed; most masonry and frame structures destroyed with
foundations; ground badly cracked. Rails bent. Landslides considerable from river banks and steep slopes.
Shifted sand and mud. Water splashed, slopped over banks.
XI.
Few, if any (masonry) structures remain standing. Bridges destroyed. Broad fissures in ground.
Underground pipelines completely out of service. Earth slumps and land slips in soft ground. Rails bent greatly.
XII.
Damage total. Waves seen on ground surface. Lines of sight and level distorted. Objects thrown into the
air.
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