How Many? A Dictionary of Units of Measurement
© Russ Rowlett and the University of North Carolina at Chapel Hill

Table of Contents
About the Dictionary
Using the Dictionary

Modified Mercalli Earthquake Intensity Scale

This description of the Mercalli scale is from the U.S. Geological Survey pamphlet The Severity of an Earthquake (1986).

Mercalli
magnitude
Effects
observed
I

Not felt except by a very few under especially favorable conditions.

II

Felt only by a few persons at rest, especially on upper floors of buildings. Delicately suspended objects may swing.

III

Felt quite noticeably by persons indoors, especially on the upper floors of buildings. Many do not recognize it as an earthquake. Standing motor cars may rock slightly. Vibration similar to the passing of a truck. Duration estimated.

IV

Felt indoors by many, outdoors by few during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck striking building. Standing motor cars rocked noticeably.

V

Felt by nearly everyone; many awakened. Some dishes and windows broken. Unstable objects overturned. Pendulum clocks may stop.

VI

Felt by all; many frightened and run outdoors, walk unsteadily. Windows, dishes, glassware broken, books off shelves, some heavy furniture moved or overturned; a few instances of fallen plaster. Damage slight.

VII

Difficult to stand. Furniture broken. Damage negligible in building of good design and construction; slight to moderate in well-built ordinary structures; considerable damage in poorly built or badly designed structures; some chimneys broken. Noticed by persons driving motor cars.

VIII

Damage slight in specially designed structures; considerable in ordinary substantial buildings with partial collapse. Damage great in poorly built structures. Fall of chimneys, factory stacks, columns, monuments, walls. Heavy furniture moved.

IX

General panic... Damage considerable in specially designed structures, well designed frame structures thrown out of plumb. Damage great even in substantial buildings, with partial collapse. Buildings shifted off foundations.

X

Some well built wooden structures destroyed; most masonry and frame structures destroyed with foundations. Rails bent.

XI

Few, if any masonry structures remain standing. Bridges destroyed. Rails bent greatly.

XII

Damage total. Lines of sight and level distorted. Objects thrown into the air.

 

Return to the Dictionary Contents page.

You are welcome to email the author (rowlett@email.unc.edu) with comments and suggestions.

All material in this folder is copyright © 2000 by Russ Rowlett and the University of North Carolina at Chapel Hill. Permission is granted for personal use and for use by individual teachers in conducting their own classes. All other rights reserved. You are welcome to make links to this page, but please do not copy the contents of any page in this folder to another site. The material at this site will be updated from time to time.

January 10, 2000