Fifteen years of Environmental Seismic Intensity (ESI-07) scale: Dataset compilation and insights from empirical regressions

Abstract

The Environmental Seismic Intensity scale (ESI-07), published 15 years ago under the umbrella of INQUA (International Union for Quaternary Research), is solely based on earthquake effects on the natural environment. ESI-07 provides complementary information with respect to other macroseismic scales, in particular those stemming from the original Mercalli scale, which are mainly based on effects on manmade structures. We collect information on 157 earthquakes, occurred between 300 AD and 2020, that have been studied using the ESI-07 scale. The ESI-07 epicentral intensity can be assigned based on linear or areal features (e.g., length of surface rupture, area affected by environmental effects); this value is generally in good agreement, or slightly larger, than estimates provided using other macroseismic scales. Higher discrepancies are found for earthquakes with ESI-07 epicentral intensity above X, where other scales tend to saturate, as expected based on the original definition of the Mercalli-family intensity scales. We develop scaling relations among ESI-07 epicentral intensity and moment magnitude, surface rupture length and affected area. After critically evaluating the scientific literature, we argue that the ESI-07 reached its original goals and proved to be particularly useful for the documentation of earthquake damage i) in remote regions, ii) in the case of strong events, where other scales saturate, and iii) in the region closer to the epicenter. Finally, we identify gaps where to focus future efforts, such as the integration of remote sensed datasets in ESI-07 assignment and the refinement of empirical regressions.