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Abstract:
Macroseismology plays a crucial role in earthquake hazard and risk analyses, tying earthquake occurrences and impacts from the past with those of the present and future. The use of macroseismic intensity has grown as the hazard layer within essential USGS and others’ real-time information products and even in presenting hazard maps in a form friendlier to nontechnical users. However, even with best practices, there are limitations to modern macroseismic data collection approaches. Whereas crowd-sourced intensities are robust for lower levels, they are poorly defined above intensity VII, where damage assessment requires knowledge of each building’s structural system. Likewise, the United States, New Zealand, and others employ the Modified Mercalli Intensity (MMI) scale, which is consistent with—yet inferior to—the more recently developed European Macroseismic Scale (EMS-98). We report on an IMS Working Group meeting held in October 2022 at the USGS Powell Center to address these and other issues and to work towards an IMS. Workshop goals were, first, to harmonize the MMI scale with EMS-98 for the US and NZ—which share several similar building types—by considering those structures and associated damage grades not well represented in the current EMS-98 building vulnerability table. Second, formalize the process of augmenting EMS-98 with vulnerability classes appropriate for building types in other countries, thus promoting a scale that can be employed globally. Such efforts require expanding the EMS-98 explanatory documents. Lastly, we discuss how standardized earthquake-damage data collection worldwide—as part of an IMS—could facilitate hazard and risk analyses.
