A methodological workflow for the identification of earthquake sources from macroseismic data

Macroseismic intensity data are a fundamental source of information for characterising historical earthquakes. This study presents a methodology to constrain the sources of large earthquakes through the analysis and modelling of macroseismic intensity data. The proposed workflow consists of three main stages: (1) the identification and removal of outlier intensity data points; (2) the revision of macroseismic earthquake parameters (epicentral location and magnitude); and (3) the construction of three-dimensional (3D) seismogenic sources, simulation of ground shaking including site effects, and a subsequent residual analysis. The key novelty lies in the detection of intensity outliers through residual analysis between observed and predicted macroseismic intensities using an intensity prediction equation (IPE). The application of this workflow to a set of case studies from the parametric catalogue of Italian earthquakes demonstrates that the implemented approach allows the identification of seismogenic sources for large to moderate magnitude events, which are consistent with macroseismic data, geological structures and ground motion data, when available. The results of this study can have direct implications for seismic hazard assessment and shaking scenario modelling. The proposed workflow can be systematically applied to reconstruct the seismogenic sources of the strongest Italian historical earthquakes ( M w ≥ 5.5).