Earthquake Intensity Database
Earthquake Intensity Database Introduction
Table 1.--Modified Mercalli Intensity Scale of 1931
||Not felt except by a very few under especially
||Felt only by a few persons at rest, especially
on upper floors of buildings. Delicately suspended objects may swing.
||Felt quite noticeably indoors, especially on
upper floors of buildings, but many people do not recognize it as an
earthquake. Standing motor cars may rock slightly. Vibration like passing
truck. Duration estimated.
||During the day felt indoors by many, outdoors by
few. At night some awakened. Dishes, windows, and doors disturbed; walls make
creaking sound. Sensation like heavy truck striking building. Standing
motorcars rock noticeably.
||Felt by nearly everyone; many awakened. Some
dishes, windows, etc., broken; a few instances of cracked plaster; unstable
objects overturned. Disturbance of trees, poles, and other tall objects
sometimes noticed. Pendulum clocks may stop.
||Felt by all; many frightened and run outdoors.
Some heavy furniture moved; a few instances of fallen plaster or damaged
chimneys. Damage slight.
||Everybody runs outdoors. Damage negligible in
buildings of good design and construction slight to moderate in well built
ordinary structures; considerable in poorly built or badly designed structures.
Some chimneys broken. Noticed by persons driving motor cars.
||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 structures. Fall
of chimneys, factory stacks, columns, monuments, walls. Heavy furniture
overturned. Sand and mud ejected in small amounts. Changes in well water.
Persons driving motor cars disturbed.
||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.
||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 over banks.
||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.
||Damage total. Waves seen on ground surfaces. Lines
of sight and level distorted. Objects thrown upward into the air.
Reference: Harry O. Wood and Frank Neumann, in Bulletin of the
Seismological Society of America, Vol. 21, No. 4, December 1931.
es Geophysicae, 4B, (6), Paris, France, 1986, pp. 679-702.