Central Italy has a long record of devastating earthquakes, including most recently the August – October 2016 Amatrice sequence of 3 M>5.9 earthquakes which led to the loss of ~300 lives and €200 billion damages. The causative normal faults are well exposed at the surface as limestone fault scarps which can be used, along with modelling, to understand how past earthquakes can influence where future earthquakes might occur and to give insights into how continental deformation occurs.
The frequency and spatial distribution of earthquakes varies over time within fault systems. It is important to quantify and understand such variation for use in seismic hazard assessment, but this is currently difficult because historical and instrumental records of earthquakes are too short to capture the full variability of seismic cycles. My research focusses on using models of static stress transfer from movement along faults over a range of timescales to investigate how nearby faults interact with each other. Using historical earthquake record over many centuries, I’ve shown how the static stress from earthquakes and interseismic loading builds up on faults and potentially controls the location of subsequent or future earthquakes. Studying fault slip rate over many millennia (derived from cosmogenic isotope analysis) shows that the slip rate is not constant. This leads to periods of quiescence on faults with low earthquake activity and long recurrence intervals, and other periods of relatively accelerated earthquake activity. Why do these faults experience temporal earthquake clustering? And what are the implications for seismic hazard studies that typically rely on using the recurrence intervals?