3D gEology-constrained seismic rupture dynamic models: a new interdisciplinary strategy For Earthquake forecastiNg and reSilience

Italy faces a critical challenge due to seismic hazard. Fault systems are capable of triggering earthquakes (EQs) up to approximately magnitude (M) 7. In the 20th and 21st centuries, EQ-related fatalities in Italy have exceeded 125,000, and over the last fifty years, the costs incurred by the Italian government due to EQs have exceeded 150 billion €, not taking into account the losses in terms of human lives, cultural heritage and lost business income or the burdens on the health system. Despite extensive efforts, our readiness for such events remains insufficient. The key to enhancing our understanding of future seismic events is to unlock insights from past EQs. To address this, the DEFENS project adopts a groundbreaking and interdisciplinary approach that draws upon structural geology, geochemistry, paleoseismology and modeling, to analyze seismic potential, provide constrained dynamic seismic rupture scenarios and engage communities. The primary objective of DEFENS is to develop a worldwide-first toolkit spanning from field geology to finite element modeling (FEM) of EQ processes, combining, for the first time, multicycle with the dynamic rupture modeling. The national-scale, geologically-constrained FEMs replicate EQ cycles since the last glacial maximum (~18 kyr) to the present. Data input from detailed fault segmentation, mechanical factors, extensive fieldwork for geological, geochemical, and paleoseismological well-constrained information on past EQs, help forecast the character and preferred epicentral zones of future events. Focusing on 12 major seismogenic fault systems of the Apennines of Italy, DEFENS aims to significantly advance our understanding of surface faulting, emphasizing the role of fault complexities, such as bends, stepovers, and gaps, in enabling or impeding rupture propagation, contributing to multi-fault and multi-segment ruptures that can lead to larger EQs. DEFENS has the potential to impact the scientific-social-economic fabric of the country, offering a multi-pronged approach to enhance EQ forecasting capabilities,
improving seismic risk management and public safety, and contributes significantly to understanding the dynamics of surficial effects of EQs.