APPENDIX A (updated 09/04/97)
MODIFIED MERCALLI INTENSITY SCALE OF 1931
(Abridged)
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 objecs may swing.
III. Felt quite noticeably indoors, especially on upper floors of buildings,
but many people do not recognize it as an earthquake. Standing motorcars
may rock slightly. Vibration like passing truck. Duration estimated.
IV. 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
rocked noticeably.
V. 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.
VI. Felt by all; many frightened and run outdoors. Some heavy furniture
moved; a few instances of fallen plaster or damaged chimneys. Damage
slight.
VII. 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 motorcars.
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 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 motorcars 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 surfaces. Lines of sight and level
distorted. Objects thrownn upward into the air.