Geophysical studies of plate boundary zone processes in western North America and lithospheric structure of terrestrial planets

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Over the next five years my research program will focus on two key problems in geophysics, one in observational seismology and the other in the rheology of the lithosphere on Earth and terrestrial planets. The first project concerns the structure of the crust and mantle around major plate boundary zones and faults in western North America, from the San Andreas Fault in California to the northern Canadian Cordillera in the Yukon and Northwest Territories, and their influence on earthquake and crustal deformation. A number of different styles of earthquake, each with its own significance for seismic hazard, occur along major fault lines in this region. In addition to large destructive earthquakes (like the 1906 San Adreas earthquake or the 2011 Tohoku-Oki earthquake in Japan), these faults harbor a wide variety of slip modes, including the recently discovered "slow slip" and associated "non-volcanic tremors". Although not a direct threat, there is growing evidence that these slow slip earthquakes are associated with regular earthquake occurrence through structural properties (e.g., fluids) of the fault, as imaged using seismological data. This research aims to clarify the role played by such structural attributes in the faulting and earthquakes processes.The second project addresses a long-standing problem in solid-Earth geophysics, namely the global rheology and strength of the lithosphere of the Earth and terrestrial planets. The solid Earth's response to geological loads (e.g., ice sheets, river deltas) is determined by its rigidity, or long-term strength, which is obtained by comparing the Earth's gravitational field anomalies with the topography. Knowledge of lithospheric strength is a useful parameter to understand crustal evolution and heat transport in the Earth and planets. Following major revisions of models and techniques used to estimate this parameter, this research will focus on the application of the new methods to Earth and other terrestrial planets (e.g., Mars, Venus, Mercury) to establish a classification of planetary rheology for the inner solar system.