The inner workings of the earthquake cycle: New insight from integrating Quaternary fault activity, microstructures, and geophysics

Fault activity is now known to be highly dynamic, with observable spatial and temporal variability in earthquake recurrence and the style of fault slip. This exciting project explores the underlying physical processes that lie at the core of dynamic fault behaviour by probing the rock and Quaternary records of fault slip. In this multi-disciplinary project, you will integrate knowledge obtained from high resolution laser scanning (LiDAR), quantitative microstructural work, and Quaternary fault studies to gain an in-depth understanding of the physical processes acting on a fault and/or fault zone. Results will be far reaching in fundamental science with direct implications for applied science in terms of earthquake hazard evaluation and forecasting. Earthquakes are one of the main hazards that humanity faces, and improving our ability to anticipate how fault zones behave through time is of major importance. However, we have very little understanding of why some faults appear to accommodate different slip modes and others do not, how different slip processes are represented in the rock record, and why faults cycle between different modes. This project is novel in its cross-disciplinary nature integrating earthquake cycle analysis on real rocks including information on the time-averaged fault activity using isotopic age dating on fault rocks, patterns of fault surface roughness, and their link to microstructures from natural and experimental fault rocks. In Leeds we have the rare opportunity of this integration as experts in the respective fields are within the same school. In addition, strong personal links to collaborators at other universities (Dr Bora Uzel, Dokuz Eylul University, Turkey and Prof Ken McCaffrey, Durham University) strengthen this project. In this project you will collect a set of fault breccia samples “caught in the act” from active fault zones in several potential field areas. One area of focus will be from the Apennines in central Italy, which in 2016 experienced a devastating earthquake sequence that began with an Mw 6.2 resulting in nearly 300 deaths and relocation of tens of thousands of people (Walters et al., 2018). This regions hosts normal faults that are at varying stages of maturity that have been shown to demonstrate slip rate variability (Cowie et al., 2017). You will also have the opportunity to investigate normal faults in southwest Turkey, and other potential regions depending on your interest and progress. Target faults in Central Italy and Turkey have been researched in terms of their seismic activity and their average Quaternary slip behaviour, and the location of ideal field sites is already known. You will have the unique opportunity to combine knowledge gained through microscopic studies with mesoscale features on these faults, using terrestrial laser scanning datasets detailing the metre-scale fault surface, in collaboration with co-supervisor Prof Ken McCaffrey, from Durham University. These faults provide the opportunity to investigate structures from the outcrop to the nanoscale, allowing for a process-oriented analysis of fault rock structure. Finally, observations of the fault rocks will be paired with cosmogenic isotope analyses from the same faults, to reveal the multi-earthquake cycle behaviour of each fault. Active tectonics and the resulting earthquake hazard is a pressing issue facing many countries. We are in a unique position at Leeds to bring together a range of observational, modelling and field approaches to answer important unresolved questions about the earthquake cycles. The research topic has immediate relevance to improving our understanding of the link between faulting and timescale and nature of seismic hazard. There will be ample opportunities to deliver the results of the project at international conferences in addition to UK meetings. Through in-country collaborators, there will be the opportunity to communicate the earthquake hazard to local authorities and ci