Earthquakes - Geotechnical Engineering Investigation - page 910

TABLE 11.4
Modified Mercalli Scale, 1956 Version a

Intensity Effects V b (cm/sec.) g c

M d I Not felt. Marginal and long-period effects of large earthquakes

(for details see text)

3 II Felt by persons at rest, on upper floors, or favorably placed

III Felt indoors. Hanging objects swing. Vibration like passing 0.0035-0.007

of light trucks. Duration estimated. May not be recognized
as an earthquake

4 IV Hanging objects swing. Vibration like passing of heavy trucks; 0.007-0.015

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 Felt outdoors; direction estimated. Sleepers wakened. 1-3 0.015-0.035

Liquids disturbed, some spilled. Small unstable
objects displaced or upset. Doors swing, close,
open. Shutters, pictures move. Pendulum clocks stop,
start, change rate

VI Felt by all. Many frightened and run outdoors. Persons 3-7 0.035-0.07

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)

6 VII Difficult to stand. Noticed by drivers of motor cars. 7-20 0.07-0.15

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; 20-60 0.15-0.35

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

7 IX General panic. Masonry D destroyed; masonry C heavily 60-200 0.35-0.7

damaged, sometimes with complete collapse; masonry B
seriously damaged. (General damage to foundations — CFR.)
Frame structures, if not bolted, shifted off foundations.
Frames racked. 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 200-500 0.7-1.2

foundations. Some well-built wooden structures and
bridges destroyed. Serious damage to dam, 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

( Continued )