Natural variability of faults and earthquakes, and the implications for seismic hazard

Observations of field exposures of active faults and historical or instrumental records of earthquakes all point towards earthquakes being complex phenomena, which makes quantifying probabilistic seismic hazard a challenge. We cannot simply wait for more earthquake to happen to be able to understand them better, but instead we can utilise a range of geological observations to quantify earthquake variability, fault interaction and the geometry of active faults. In this talk, I will present results from the tectonically active central Apennines of Italy and discuss how these results highlight the natural variability of earthquakes and faults. These observations led to the development of my current UKRI Future Leaders Fellowship project Quake4D, where we will combine geological observations with physics-based numerical modelling to explore a wider range of earthquake scenarios than would be possible using observations alone. In addition to using observations of active faults, inactive faults are being studied using seismic reflection data to look at how individual faults and networks evolve over geological timescales – which are factors rarely considered in current seismic hazard approaches.