Quantifying the variability and migration of active normal faulting during the Late Pleistocene-Holocene using 36Cl cosmogenic nuclide techniques

Much of the Earth is prone to damaging earthquakes. Earthquakes cannot be predicted, and the variability of earthquake occurrence makes this natural hazard difficult to anticipate. There are many fault lines that have not had an earthquake during human history, and whilst these faults are indeed active and capable of having big seismic events, they are often not realised to be a threat. This is particularly true on the continents, where the strain that results from the collision of tectonic plates is distributed such that faults occur over huge areas and in complex networks, which may interact. The interaction of faults, and how they behave on prehistoric timescales, is poorly understood due to difficulties in measuring the past fault motion.

During my fellowship, I will investigate the brittle faults that cause earthquakes on timescales longer than human history. During my fellowship, I will aim to measure how earthquake occurrence is variable over the last several tens of thousands of years. Some scientists have suggested that faults may have periods of intense earthquake activity, interspersed in quiet intervals, and I aim to quantify whether this occurs on faults in western Turkey. I will also produce models of this behaviour that will help to understand the fundamental variability of earthquakes.

Each time a fault has a large earthquake, a portion of the ground along the fault line is moved relative to the ground next to it. On extensional faults, the fault plane is uplifted and preserved for many thousands of years. As the fault plane is uplifted, it is exposed to the cosmogenic radiation that is constantly bombarding the earth's surface. This high-energy radiation produces isotopes that are otherwise not found on Earth; the result is akin to sunburn of the fault plane. The longer the plane has been exposed to cosmogenic rays, the higher the concentration of isotopes (the darker the tan). I will measure profiles of cosmogenic isotope concentrations on exposed fault planes in order to determine the history of fault exposure due to earthquakes. My results will quantify how long periods of intense seismicity last, how frequently they occur, whether they occur on every fault in a network, and whether faults in the network switch on and off relative to one another. I will also incorporate my data into models of fault behaviour. Many models assume that earthquakes occur in regular intervals, but it is important to model what is driving irregular recurrence. The models will also help to understand the physical interaction between faults in complex networks.

My research will have impact on understanding earthquake hazard both locally, in western Turkey, and worldwide. During my fellowship whilst conducting field work in Turkey, I will conduct a ShakeOut drill in local communities, in collaboration with Prof Hasan Sozbilir. This drill is already practised in earthquake prone regions across the globe, including in the USA and Japan (www.shakeout.org). By having a mock earthquake once per year, the drill helps to increase disaster preparedness by encouraging participants to go through an earthquake checklist that includes building an earthquake-ready kit with essential survival items, practicing how to take cover during an earthquake, and determining what to do after the event. The greater impact of my research will be realised by communication of my results with scientists and policy makers alike, and efforts to increase the uptake of new understanding of fundamental earthquake behaviour.

Direct benefits

My fellowship will directly benefit the people who must live with the earthquake hazard present in SW Turkey. There is a long historical record of earthquake damage in the region and much of the population is at risk for casualties and economic losses that occur as a result of earthquakes. I will engage with both the public and government officials by initiating a ShakeOut drill (www.shakeout.org) and by creating a digitised map of active faults in SW Turkey with useful information for each fault.

The ShakeOut drill will benefit the earthquake-vulnerable community of western Turkey. This drill involves having a mock earthquake once a year; during which participants consider what to do to prepare for the potential effects of seismic events. The drill helps to increase disaster preparedness by encouraging participants to go through an earthquake checklist that includes building an earthquake-ready kit with essential survival items, practicing how to take cover during an earthquake, and determining what to do after the event. By disseminating established and reliable ShakeOut materials during field work, I will be able to affect a general audience that would be difficult to reach through anything other than a grassroots campaign.

Government officials charged with the task of mitigating earthquake hazard will benefit from the creation of a digitised map of active faults and key diagrams useful for explaining the parameters presented in the map database. The academics who work with government officials will also benefit from this efficient method of sharing information. The Google Earth (GE) database of active faults will include useful information such as field photos and imagery overlays that explain visible fault features. This will enable non-specialists, and particularly local council members, to understand the hazard of surrounding faults. Details will include any known information on the key parameters used to mitigate risk- such as typical earthquake size, long term slip rates, and the variability of these rates. Simple diagrams explaining faults and the effect of earthquake shaking will be available in order to help policy makers and the public understand the data in terms of region-specific earthquake risks.

Long-term benefits

My research will indirectly benefit the general public in the UK, Turkey, and elsewhere who are at risk for the setbacks that are incurred by the global economy when destructive earthquakes occur in regions that are underprepared. The cost of earthquakes comes not only in lives lost and thoroughly disrupted, but also in billions spent repairing the damage. The need to deal with hazard is directly highlighted by the theme of resilience to natural hazards within the NERC remit. My research will contribute to this theme by quantifying fault behaviour on a time scale that is currently poorly understood, which I will integrate into geodynamic models of fault behaviour that will be used by the earthquake community as a whole.

Long term benefits will be enabled through an AGU session on incorporating fault slip data measured on long time scales with earthquake hazard assessment. The earthquake hazard community will benefit from this session because it will allow for the dissemination of my research through the academic community to geological surveys and the risk and disaster reduction industries. I will also work with the Global Earthquake Model (GEM), which is a collaborative effort between scientists and stakeholders focused on improving seismic hazard assessment and mitigation. By incorporating my research into their global earthquake model, end users will effectively benefit from the results of my fellowship.