Earthquake environmental effects and intensity assessment: the INQUA scale project

Earthquake Environmental Effects (EEEs) are any phenomena generated in the natural environment by a seismic event. An earthquake intensity scale (INQUA scale) based on EEEs was presented in MICHETTI et alii (2004). The use of this new scale, combined and integrated with traditional macroseismic scales, is recommended for many reasons including: i) the EEE sizes are the only reliable tool for the intensity estimates of strong earthquakes (I≥X) as they do not suffer from saturation; ii) they are independent from cultural and technological aspects and so they are able to give homogeneous earthquake intensity assessments at global scale; iii) they provide the most long-term picture of seismicity (recent, historical and paleo earthquakes). The ongoing worldwide testing of the INQUA’s EEE intensity scale is based on standardized data formats and procedures, to reduce subjectivity. The archive developed to store information regarding EEEs and corresponding intensities is based on three spatial levels: site, locality, and total affected area. Two case studies (historical and recent) from different geotectonic environments are used here to show the power of the EEE scale, able, depending on completeness of dataset, to provide a detailed spatial distribution of intensity, or, with the limited data available for old earthquakes, at least an intensity for the epicentral area. Though the EEE intensity scale itself does not take into account damage distribution, the comprehensive earthquake study requires analysis of all observed effects on environment and constructions. The use of both traditional macroseismic and EEE scales can ensure the most complete image of the earthquake; the INQUA scale is not intended to replace previous macroseismic scales, but rather to integrate them. The project is in progress and open issues listed in the conclusions still can be solved based on further application of the scale to case studies.