Seismic imaging based on numerical simulations of seismic waves: from global to hydrocarbon-reservoir applications

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Understanding the geological evolution of the planet Earth has been one of the fundamental scientific questions that pique human curiosity. What are the tectonic processes and geological events in the past that shaped the topographic, geological and tectonic features observed on the Earth’s surface, what are the internal dynamical processes that drive the complex tectonic plate motions, and how do these plate motions and tectonic stress cause earthquakes? These intriguing questions have been the centre of solid geophysical research, in which seismology plays a leading role in illuminating the Earth’s interior and presents important clues to decipher the past, present and future of our planet. On another front, seismology engages in understanding earthquakes, one of the most damaging natural disasters to mankind, including their locations, source mechanisms, seismic wave propagation and the intensity of induced ground shaking. The collection of seismic catalogues and better understanding of the effect of heterogeneous internal structures provide us crucial guidance on long-term seismic hazard assessment and risk mitigation. The computational seismology group at University of Toronto is involved in seismological research that seeks answers and solutions to the above questions and subjects. In particular, we develop and apply well-maintained community spectral-element software packages that accurately simulate the propagation of seismic waves in 2D/3D heterogeneous media. In an effort to understand the tectonic processes associated with subduction zones, continental collision zones, cratons, etc., we use unique datasets from seismic array recordings, including regional earthquake data, noise cross-correlation functions (NCF), and teleseismic receiver functions (RF, i.e., converted/scattered/coda waves of teleseismic main phases), in combination with adjoint tomographic techniques to reveal detailed structures beneath seismic arrays as well as at continental and global scales. The methodology advancement in earthquake seismology also brings new insight into applied geophysical applications, in particular seismic imaging and microseismic monitoring for oil and gas exploration and mining. For example, microseismic events accompanying hydraulic fracturing processes in which fluid and proppants are injected at high pressure into relatively impermeable hydrocarbon reservoirs to create pathway for gas or/and oil to be drained efficiently can be more accurately located, monitored and interpreted through waveform modelling, source inversions as well as tomographic imaging. We apply full numerical simulations of wave propagation to model microseismic events in complex geological structures, and employ innovative seismic inversion methods to map detailed subsurface heterogeneities for both mining and hydraulic fracturing applications. Through the support of previous NSERC (individual) Discovery Grant and other sources of funding, I was able to establish an energetic research group composed of 2 postdocs, 8 graduate students (including 3 finished M.Sc.) and 7 undergraduates (including 2 B.Sc. theses) since I joined University of Toronto five years ago. Over the same period of time, our group published 13 papers (additionally 1 accepted, 2 under review) in peer reviewed journals. We are also co-authors on one book chapter and 2 expanded abstracts for conference proceedings. My postdocs, graduate students and I also made more than 50 conference and seminar presentations. Our research team expects to maintain a similar group size, plan for HQP training, and level of productivity for the next five years.