In this study, a new quantitative index for multi-hazard risk assessment, the GEological-geotechnical Index (GETI), is applied to a selected case study to determine its effectiveness. The GETI aims to address the limitations of existing methods by accounting for the cascading effects of a primary hazard and providing a quantitative assessment tool for decision-makers.

The workflow is composed by two stages: first, a thorough literature review is performed to establish the geological context, followed by an evaluation of morphological, stratigraphic, and tectonic features, including field investigations, to determine potential instability conditions. This stage includes remote analysis, such as utilizing high-resolution Digital Terrain Models (DTM) derived from LiDAR data, to identify ground deformations and factors that predispose an area to seismic hazards.

The second stage involves developing a geological and geotechnical model using on-site and laboratory geotechnical evaluations, along with non-invasive geophysical techniques. This process facilitates the identification of natural hazards, which are then quantified using both simplified and advanced methods documented in existing literature.

Thus, the effects of the occurrence of hazards on the subsoil were quantified, and used as input parameters to calculate the probability of damage for each event and the total probability of damage using fragility curves.

The index primarily concentrates on earthquake-related risks and their secondary effects, such as ground motion amplification, soil liquefaction, and landslides or rockfalls. This method uses conditional probability to mathematically represent the concept of cascading effects. The GETI is designed as the total probability of damage from an earthquake, considering a range of damage intensities from minor to severe.