The Modified Mercalli earthquake intensity scale

Revisions arising from recent studies of New Zealand earthquakes

  • D. J. Dowrick GNS Science, Lower Hutt, New Zealand


The 1992 New Zealand version of the Modified Mercalli (MM) intensity scale, was the result of a major multi-disciplinary review, and comments were invited. This paper results from considerable use of the 1992 scale in recent studies of twenty two New Zealand earthquakes including two of magnitude Ms7.8, and insights into the scale gained from studies of the well-documented Mw6.6 1987 Edgecumbe earthquake. Improvements to the 1992 New Zealand MM intensity scale are offered, including criteria for chimney damage at MM6 to MM8, and also criteria for MM10 to MM12 based on a simple matrix procedure of logical extrapolation from lower intensities, and the use of new construction categories. Discussions of the influence of ground conditions at high intensities, and on definitions of the key terms "partial collapse", "collapse" and "destroyed", are included.


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How to Cite
Dowrick, D. J. (1996). The Modified Mercalli earthquake intensity scale. Bulletin of the New Zealand Society for Earthquake Engineering, 29(2), 92-106.

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