Interaction between fluid flow and stress fields from seismicity

Project Rationale:

The flow of high-pressure fluids in the Earth’s crust commonly causes rocks to fracture, thereby causing measurable small magnitude earthquakes (micro-seismicity) to occur. Capturing the microseismicity at high resolution is therefore a powerful tool for mapping out the spatial and temporal migration of fluids. In addition, earthquake source parameters such as focal mechanisms, as well as properties of the rock sampled by the earthquake rays such as anisotropy, provide valuable clues regarding the state of stress of the fracturing rock. There is however, ongoing controversy regarding how and where fluids are focused and migrate in natural settings such as volcanoes [1] and fault zones [2], as well as in settings of human-induced seismicity such as wastewater disposal and fracking [3] . It also remains unclear how migrating fluids modify the stress state of the Earth [1], and what conditions are required to generate fluid related earthquakes [3]. Answering these questions are important for understanding the behavior of volcanoes and geothermal systems, and also for evaluating the spatial and temporal link between of human sourced geofluids and induced earthquakes, and the causal mechanisms.

Methodology:

This project will use the principles in the project rationale to better understand the interaction between fluid flow and rock stresses. The student will use both legacy and new datasets from human-induced settings and from active volcanic settings Specifically, legacy data available on the IRIS Data Management system from Oklahoma and Alberta will be used to investigate human induced seismicity [3]. Legacy data from the Afar diking episode [2] and new data from recent projects in Ethiopia and Tanzania will explore both magmatic, and hydrothermal systems [1]. The evolution of earthquake swarms will be determined using cutting edge techniques of waveform cross correlation, frequency analysis, and waveform matching. Source mechanisms will also be determined. Newly developed automated techniques for measuring shear(S)-wave splitting will be tested and used to measure seismic anisotropy. Source mechanisms and S-wave splitting will be used to invert for the stress state of the rocks [2].

Training:

The INSPIRE DTP programme provides comprehensive personal and professional development training alongside extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial/policy partners. The student will be registered and hosted at the University of Southampton. Specific training will include relevant programming skills in Python and Matlab, and the use of cutting-edge techniques in earthquake location, shear-wave splitting, and source mechanism inversion. The student will also receive training on the handling and deployment of seismometers, and also the management and numerical treatment of large seismic datasets. The student will have the opportunity to participate in seismic fieldwork, likely in East Africa, and/or Italy.