Environmental Engineering Reference
In-Depth Information
Table 12.1.
Modified Mercalli Scale, 1956 version (Richter, 1958; Hunt, 1984).
Intensity
Effects
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 wood walls
and frames creak.
V
Felt outdoors, duration estimated. Sleepers wakened. Liquids disturbed, some spilled.
Small unstable objects displaced or upset. Doors swings, close, open. Shutters,
pictures move. Pendulum clocks stop, start, change rate.
VI
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 - CFR).
VII
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 - CFR). 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
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; 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
General panic. Masonry D destroyed; masonry C heavily damaged, sometimes with
complete collapse; masonry B seriously damaged. (General damage to foundations -
CFR). Frame structures, if not bolted, shifted off foundations. Frames cracked.
Serious damage to reservoirs. Underground pipes broken. Conspicuous cracks in
ground. In alluviated areas sand and mud ejected, earthquake fountains, sand
craters.
X
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 beachheads 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.
Note: Masonry A, B, C, D. To avoid ambiguity of language, the quality of masonry, brick or otherwise,
is specified by the following lettering (which has no connection with the conventional Class A, B, C
construction).
- Masonry A: Good workmanship, mortar, and design; reinforced, especially laterally, and bound
together by using steel, concrete, etc.; designed to resist lateral forces;
- Masonry B: Good workmanship and mortar; reinforced, but not designed to resist lateral forces;
- Masonry C: Ordinary workmanship and mortar; no extreme weaknesses such as non-tied-in corners,
but masonry is neither reinforced nor designed against horizontal forces;
- Masonry D: Weak materials, such as adobe; poor mortar; low standards of workmanship; weak
horizontally;
- CFR indicates additions to classification system by Richter (1958).
