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Intensity is
a measure of how severe the shaking was at a particular location and
is determined by classifying the
degree of shaking severity as measured by an intensity
scale.
Modified Mercalli (MM) Scale Categories:
I. Felt only by a very few people under especially favorable circumstances
II. Felt only by a few people at rest, especially on the upper floors of
buildings. Suspended objects may swing.
III. Felt quite noticeably indoors.
Standing motor vehicles may rock slightly.
Vibration like the passing of a truck.
IV. Felt indoors by many, outdoors by a few.
At night, some awakened.
Crockery, glassware, windows, doors
rattle.
V. Felt by nearly everyone; damage to contents and structures uncommon but
possible.
VI. Felt by all; many frightened and run outdoors; damage slight.
VII. Everybody runs outdoors; damage negligible to buildings seismically
well-designed and constructed; slight to
moderate to ordinary structures; considerable damage to
poorly built or badly designed structures.
VIII. Damage slight in well-designed, considerable in ordinary, and great
in poorly built structures; chimneys,
monuments, walls, etc., fall.
IX. Damage considerable to well-designed structures, and great (including
partial or complete collapse) in other
buildings; buildings shifted off foundations;
underground pipelines disrupted.
X. Some well-built wooden structures destroyed; most masonry and ordinary
structures destroyed; railroad tracks
bent; landslides common; water spills over banks of
streams, lakes, etc.
XI. Few, if any, masonry structures remain standing; bridges are
destroyed; broad fissures open in the ground;
underground pipelines are completely out of service;
earth subsides.
XII. Damage is total; waves are seen propagating along surface of the
ground; nearly impossible to stand; objects
thrown up into the air.
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