ZOOM WEBINAR PRESENTATION
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Abstract: The assumption that the strength of the Earth's upper crust is bounded by its frictional limit (i.e., the frictional equilibrium) is plausibly supported by in situ stress characterizations already made in deep boreholes worldwide. In this context, the simple Coulomb frictional failure theory, employing the laboratory-derived frictional coefficient values, has enabled the estimation of in situ stress and fault criticality, albeit with some degree of uncertainty. The applicability of the simple Coulomb theory and the laboratory-derived frictional coefficient values to the natural variabilities such as the crustal rock masses has often been questioned. This talk explores this issue from two independent perspectives: the source of such uncertainty and how to harness such uncertainty. A stochastic Coulomb model has been proposed to explicitly study the variations of frictional coefficient and consequently the in-situ stress heterogeneity. Further on the stress heterogeneity, an innovative methodology to invert the in-situ stress, via data analytics, is presented. Both aspects corroborate the applicability of the Coulomb theory and the laboratory-derived frictional coefficient values.
Biography: Dr. Xiaodong Ma is a lecturer and senior researcher at ETH Zürich. He is affiliated with the Department of Earth Sciences and the Bedretto Underground Laboratory for Geosciences and Geoenergies ('Bedretto Lab'). He is leading the geomechanics efforts at the Bedretto Lab for field experiments related to enhanced geothermal system and induced seismicity. He received education in Earth sciences and geological engineering on three continents (Asia, Europe and North America). He obtained his PhD degree in Geological Engineering (2014) from the University of Wisconsin-Madison, and subsequently conducted post-Doctoral research at Stanford University, Department of Geophysics. He is interested to connect rock mechanics fundamentals (e.g., friction, poroelasticity, time-dependency) with geo-engineering applications (e.g., geo-structures, geo-resources and geo-hazards), through the main research theme related to crustal stress and its spatio-temporal variations. He combines laboratory and field observations, physics-based models and data analytics to tackle modern challenges of geomechanics. He is the recipient of American Rock Mechanics Association (ARMA) Future Leader honor (2018) and its inaugural Distinguished Service Award in 2020.