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Time for an Updated Macroseismic Scale

Year: 2026

Type: article

Abstract: We believe that macroseismic scales are not static, but they should instead be updated based on new experimental observations."-Tosi et al. (2015) Macroseismology plays a crucial role in earthquake hazard and risk analyses, linking past earthquake occurrences and impacts with those of the present and future.The popularity of internet-based community contributions and the use of intensities for communicating seismic hazards, early warning, and impacts to the public have all bolstered the use of macroseismology beyond its traditional utility in characterizing sources and shaking from historical and modern earthquakes (Wald et al., 2023).Nevertheless, many modern approaches for collecting building damage data and assigning macroseismic intensities suffer limitations.Many countries do not or no longer routinely collect such data, and even after significant and catastrophic earthquakes, building damage data are often not collected or shared systematically, nor are field-based macroseismic intensities professionally assigned.Here, we describe how the International Macroseismic Scale of 2025 (IMS-25, Grünthal et al., 2026) could be used to replace other macroseismic intensity scales.For example, the United States, Canada, and other nations still use variations of the modified Mercalli intensity (MMI) scale (Wood and Neumann, 1931) for assigning macroseismic intensities.At nearly 100 yr old, the MMI scale predates most modern building types.It says nothing about single-or multiunit wood-frame buildings, the predominant type of residential structure in the United States and Canada, whose damage is a particularly important indicator of shaking intensity.Reliance on the U.S. Geological Survey (USGS) "Did You Feel It?" (DYFI; Quitoriano and Wald, 2020) for domestic intensity data collection limits its accuracy at higher, damaging intensity levels, where attention to building type is requisite.The MMI and some of its widely used variants are often poorly documented; there is neither an official version, nor is it even clear which version of the scale was employed in many studies (Musson et al., 2010;Musson and Cecić, 2002).The MMI scale is consistent with-but is more limited than-the 1998 European Macroseismic Scale (EMS-98, Grünthal, 1998).The new IMS-25 (Grünthal et al., 2026) builds on EMS-98-a well-documented, modern scale already widely used in Europe and well beyond.Those currently employing EMS-98 need not 1.U.

Source: Seismological Research Letters

DOI: 10.1785/0220260196

Authors: David J. Wald, Ayse Hortacsu, Tiegan E. Hobbs, Keith Porter, Vitor Silva, Lindsay Davis