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Making the Case for Implementing the International Macroseismic Scale (IMS) in the United States

Macroseismology plays a crucial role in earthquake analysis, tying occurrences and impacts from the past with those of the present and future while continuing to serve a valuable role in earthquake response and mitigation. Here, we report on efforts to facilitate the uptake of the International Macroseismic Scale (IMS) framework in the United States (US), superseding the Modified Mercalli Intensity (MMI) scale. European countries, long accustomed to the European Macroseismic Scale (EMS-98), will have few updates to consider with IMS. However, the US and others will require additional considerations, none insurmountable. The elegance of IMS over MMI is its consistent approach to structural vulnerabilities, damage grades, and quantitative intensity assignments, which are essential for characterizing damaging intensity levels. Lower intensities can continue via crowdsourcing without modification. Conversely, there is a greater role for engineering expertise at higher intensities, requiring practitioners to collect building damage data systematically. We aim to use current inspection and survey protocols already in use for post-earthquake safety, reconnaissance, and insurance and add the capability to assign intensities by employing consistent building taxonomies and damage grades. Working with the Applied Technology Council, Global Earthquake Model Foundation, and California Office of Emergency Services, we intend to modify existing inspection forms, such as ATC-20, to use building damage data for their primary safety tagging purposes, yet also allow aggregation into sharable datasets for IMS assignments and more. Lastly, just as “Richter Scale” magnitudes are now referred to simply as “magnitudes,” MMI values could be referred to as macroseismic “intensity” values, allowing seamless IMS adoption among the scientific and public domains given their practical equivalent. As with magnitudes, the underlying metadata must reflect the scale employed. In the long run, utilizing the IMS will lead to better characterization of damage and risks in the US and compatibility with the macroseismic and damage datasets worldwide.

Session: Macroseismic Intensity: Past, Present and Future [Poster]

Type: Poster

Room: Exhibit Hall

Date: 4/17/2025

Presentation Time: 08:00 AM (local time)

Presenting Author: David Wald

Student Presenter: No

Invited Presentation: 

Poster Number: 16

Additional Authors