The International Macroseismic Scale (IMS-25) represents a revision and extension of parts of the European Macroseismic Scale of 1998 (EMS-98). The IMS-25 was developed by the IMS working group and published as Vol. 33 of the Cahiers du Centre Européen de Géodynamique et de Séismologie, where the EMS-98 and its related issues were also released, as, e.g., the translations.
Since the EMS-98 has proven itself over decades thanks to its innovations, large parts thereof are unchanged or practically unchanged in the IMS-25, e.g., the definitions of intensity degrees, the short form of the scale and largely unchanged the damage grades of masonry buildings and those of reinforced concrete included so far as well as parts of the Guidelines. Therefore, and as noted in the introduction, the IMS-25 is not actually a new macroseismic scale - rather, its extensions allow for a macroseismic damage classification of both traditional and modern building types constructed using Earthquake Resistant Design (ERD).
The new features of IMS-25 include (i) an extension of the vulnerability table, whose six established vulnerability classes now cover 26 building types, (ii) illustrated tables for classifying damage grades for additional building types, (iii) the extension of the former photo series to include additional examples of damaged buildings, which serve as aids in assigning vulnerability classes and damage levels, and (iv) supporting materials for the macroseismic assessment of buildings using ERD.
In the long period since the introduction of EMS-98 (respectively EMS-92 in 1993), it was never intended to limit their application to Europe, and in fact its scope extends far beyond. With the new title, i.e., IMS, the authors better capture the factual reach of macroseismic intensity assignments based on that tool.
The IMS-25 provides the possibility of being supplemented by National Annexes. These additional documents are intended to facilitate macroseismic studies in regions of the world where certain types of buildings are found that are not described, or are described only to a limited extent, in the corresponding sections of the scale.
In the text of the scale, following the introductory chapter, there is Part I, the Core Scale, supplemented by Part II, the Guidelines for applying the scale. Part I includes the essential Vulnerability Table, the definitions of the five damage grades for the considered main building types including related damage drawings, the definitions of the intensity grades as well as the short form of the scale. Part II comprises of four chapters. Chapter 1 and 2 provide guidance on assigning intensity as well as general background information on the use of the scale. Chapter 3 outlines the basic elements of the Core Scale (buildings, vulnerability and damage) as well as the types of structures included in the Vulnerability Table and how to assign appropriate vulnerability classes. In chapter 4, the series of photos of damaged buildings with assigned vulnerability classes and damage grades is presented to facilitate damage classification.
Chapters 1 and 2 are sufficient for analysing only low intensities or written (historical) descriptions. Field studies involving higher, damaging intensities require consideration of chapters 3 and 4.
Cite the IMS-25 as: Grünthal, G., Musson, R.M.W., Schwarz, J., Spence, R., Wald, D.J., Wenk, T. (2026) International Macroseismic Scale 2025 (IMS-25). Cahiers du Centre Européen de Géodynamique et de Séismologie, Vol. 33. Centre Européen de Géodynamique et de Séismologie, Luxembourg, 152pp. https://doi.org/10.48440/w22j-df09