arXiv subjects

Davide Zaccagnino

Publications and source records attributed to Davide Zaccagnino.

3 recordsLinked to original sources

arXiv2026

Critical slip distance on rough faults

The critical slip distance $D_c$ - the characteristic displacement over which a fault dynamically weakens from peak to residual strength - is a key parameter in earthquake rupture dynamics, controlling the nucleation process and slip evolution. Nevertheless, its physical origin and scaling remain debated: Dc is observed to span from micrometers in lab experiments to meters on natural faults, a scaling which cannot be explained within the standard friction framework, which interprets Dc as a material constant related to the contact population and provides no mechanism linking it to fault structure or event size. Here, we propose a first-principles derivation showing that Dc is a structural property of faults, governed by their self-affine roughness belonging to the Kardar-Parisi-Zhang universality class. We further demonstrate that rate-and-state friction emerges as the mean-field limit of the underlying fractal asperity dynamics and provide analytical formulas for its parameters: the state variable represents the population-averaged contact age, while the critical distance identifies the geometric unlocking of the dominant pinning bumps. Rate-and-state friction is therefore an emergent phenomenology whose mathematical form reflects the statistical mechanics of the underlying contact population, and its parameter values are strictly scale-dependent. This allows us to better characterize fault stability from a multiscale perspective; hence, we introduce a new concept named "fault retentivity'': the ability of a fault to arrest a nucleated rupture before it degenerates into run-away via the multiscale barrier population encoded in the fault structure. Retentivity determines whether a fault hosts only small earthquakes or can occasionally nucleate large ones. The key implication is that assessing fault stability requires to understand the hierarchical architecture of the fault system.

physics.geo-ph↗

arXiv2026

Accelerating unrest at Campi Flegrei signals a critical transition within the next decade

Campi Flegrei, a large caldera in southern Italy, is among the most hazardous volcanic systems on Earth, directly threatening over one million people. Since 2005, it has entered a phase of accelerating uplift accompanied by intensified seismicity, raising the key question of whether this evolution will culminate in eruption, a bradyseismic peak, or another regime change. Here, we show that the acceleration of seismicity and geodetic deformation is better described by a regularised finite-time singularity than by exponential growth, implying not just a better empirical representation but a different underlying process with potentially dire consequences for the system's subsequent evolution. Independent analyses converge on a critical time $t_c \approx 2030-2034$, with uplift projected to reach about 4 metres by the early 2030s. Geochemical and statistical evidence indicates that deep magmatic volatile input drives this evolution by progressively pressurising the crust. Although no evidence of imminent eruption is found, the system appears to be approaching a critical mechanical threshold whose outcome remains uncertain, requiring sustained high-resolution monitoring and continuously updated forecasts.

physics.geo-ph↗

arXiv2026

Physics-Based Seismic Hazard and Risk Assessment: A New Paradigm for Earthquake Forecasting

Epistemic uncertainty in probabilistic seismic hazard assessment (PSHA) is commonly addressed through a logic-tree framework that combines weighted alternative models to characterize the range of plausible hazard outcomes. Implicit in this approach is a critical assumption: that the available model class provides an adequate representation of the underlying physics governing fault networks. Yet current formulations remain highly simplified, neglecting nonlinear interactions, diverse fault slip modes, multi-scale coupling, and the emergent dynamics that govern the nucleation and evolution of large earthquakes. As a result, the standard treatment of epistemic uncertainty may introduce systematic hazard bias and substantially underestimate forecast uncertainty. To formalize this limitation, we introduce SHARP (Seismic Hazard Assessment and Risks with Physics), a new framework that shifts the focus from selecting among imperfect models to quantifying their collective distance from physical and observational constraints. Central to SHARP is the Model Adequacy Distance (MAD), a quantitative metric of model inadequacy. MAD combines (i) a moment-weighted scoring function scaling with seismic moment to reflect the disproportionate social and economic impact of large events and (ii) compatibility measures derived from geodetic observations and statistical properties of seismicity. We illustrate the approach with an application to the frequency-magnitude distribution of Southern California seismicity. SHARP establishes a rigorous foundation for moving beyond conventional epistemic uncertainty toward a physics-grounded framework for seismic hazard and risk assessment.

physics.geo-ph↗