Paul A Selvadurai

ETH Zurich | ETH Zürich · Department of Earth Sciences

Recent laboratory tests and large-scale observations have revealed the complex interplays between aseismic and seismic deformation, as well as the progressive localization of the rock failure process. To investigate these processes, we conducted triaxial tests that combined distributed strain sensing (DSS) with acoustic emission (AE) sensors. Progr...

We performed a series of hydraulic stimulations at 1.1 km depth in the Bedretto underground laboratory, Switzerland, as part of an overall research strategy attempting to understand induced seismicity on different scales. Using an ultra‐high frequency seismic network we detect seismic events as small as Mw < −4, revealing intricate details of a com...

The application of machine learning techniques in seismology has greatly advanced seismological analysis, especially for earthquake detection and seismic phase picking. However, machine learning approaches still face challenges in generalizing to data sets that differ from their original training setting. Previous studies focused on retraining or t...

We combined novel laboratory techniques and numerical modeling to investigate (a)seismic preparatory processes associated with deformation localization during a triaxial failure test on a dry sample of Berea sandstone. Laboratory observations were quantified by measuring strain localization on the sample surface with a distributed strain sensing (D...

Earthquakes are rupture-like processes that propagate along tectonic faults and cause seismic waves. The propagation speed and final area of the rupture, which determine an earthquake’s potential impact, are directly related to the nature and quantity of the energy dissipation involved in the rupture process. Here, we present the challenges associa...

Clay‐rich rocks are integral to subduction zone dynamics and of practical importance, for example, as barriers in nuclear waste and CO2 repositories. While the effects of swelling strain on the self‐sealing capabilities of these rocks are relatively well‐established, the implications of polar fluids interacting with charged clay particles on the fr...

Water infiltration into fractures is ubiquitous in crustal rocks. However, little is known about how such a progressive wetting process affects fracture stiffness and seismic wave propagation, which are highly relevant for characterizing fracture systems in situ. We study the acousto‐mechanical behavior of a free‐standing fractured granite subjecte...

The water adsorption into pore spaces in brittle rocks affects wave velocity and transmitted amplitude of elastic waves. Experimental and theoretical studies have been performed to characterize moisture-induced elastodynamic variations due to macroporous effects; however, little attention has been paid to the manner in which wetting of nanopores af...

In this study, we examine numerical models that employ the rate-and-state frictional (RSF) framework to investigate earthquake sequences using laboratory driven descriptions of heterogeneous frictional properties. Using previously obtained experimental measurement of roughness, we observed that wear produced a bimodal Gaussian distribution of surfa...

Plain Language Summary The motion of glaciers is often assumed to be smooth and slow. But this is not always true. During hot summer days, the ice of alpine glaciers melts. The meltwater runs through the ice down to the boundary between ice and rock, and builds up pressure. At a Swiss mountain glacier, our measurements show that during times of hig...

Physical mechanisms governing natural and induced earthquakes are still poorly understood and, despite the relevance, this lack of knowledge limits the usefulness of Geoenergy projects and severely undermines their societal acceptance. Due to the difficulty in retrieving direct measurements and observations to understand these important processes,...

During the failure of geomaterials, quasi-static (aseismic) and dynamic (seismic) deformation have been observed in laboratory and field experiences. The measurement of both is required for in-depth understanding into the progressive failure of rocks, and to reduce the risk associated with induced seismicity. The study of acoustic emission (AE) in...

We investigated the force produced by a conical piezoelectric (PZT, lead zirconate titanate) transducer actuated by high voltage pulses (HVP) in contact with a steel transfer plate. Using elastic wave propagation theory in a semi-infinite plate, we aimed to quantify the magnitude and estimate the shape of the force–time function via the body waves...

Plain Language Summary Glaciers mostly move smoothly and slowly. But regularly at specific locations at the glacier bed, the ice suddenly slips forward. This slip causes an “icequake” which is similar to a small earthquake, but so weak, that one cannot feel it. However, electronic sensors on the ice surface can measure it but lots of information ge...

The application of absolutely calibrated piezoelectric (PZT) sensors is increasingly used to help interpret the information carried by radiated elastic waves of laboratory/in situs acoustic emissions (AEs) in nondestructive evaluation. In this paper, we present the methodology based on the finite element method (FEM) to characterize PZT sensors. Th...

Slow slip events (SSEs) represent a slow faulting process leading to aseismic strain release often accompanied by seismic tremor or earthquake swarms. The larger SSEs last longer and are often associated with intense and energetic tremor activity, suggesting that aseismic slip controls tremor genesis. A similar pattern has been observed for SSEs th...

Modified version: Main text, figures, authorship, conclusions have been revised

Granitic rock from the western part of the Canadian Shield is considered as a potential host rock for the siting of a deep geological repository for the storage of heat-emitting high-level nuclear fuel waste. The research program focused on the use of surface permeability measurements conducted at 54 locations on a 300 mm cuboid of granite, obtaine...

We performed a series of 12 hydraulic stimulation experiments in a 20m×20m×20m foliated, crystalline rock volume intersected by two distinct fault sets at the Grimsel Test Site, Switzerland. The goal of these experiments was to improve our understanding of stimulation processes associated with high-pressure fluid injection used for reservoir creati...

This presentation provides an overview of the methods and some results detailed in the JGR manuscript: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018JB017194

This paper presents an alternative approach for estimating the Biot coefficient for the Grimsel granite, which appeals to the multi-phasic mineralogical composition of the rock. The modelling considers the transversely isotropic nature of the rock that is evident from both the visual appearance of the rock and determined from mechanical testing. Co...

We investigate energy partitioning using seismological methods of seismic ruptures with estimated submicron levels of slip in the laboratory. Estimates inferred from recorded seismic waves are founded on microscale phenomenological friction experiments in the laboratory and appear to be constrained by inherent assumptions. In this concerted study,...

We performed a series of 12 hydraulic stimulation experiments in a 20 x 20 x 20 m foliated, crystalline rock volume intersected by two distinct fault sets at the Grimsel Test Site, Switzerland. The goal of these experiments was to improve our understanding of stimulation processes associated with high-pressure fluid injection used for reservoir cre...

This paper presents an alternative approach for estimating the Biot coefficient for the Grimsel granite, which appeals to the multi-phasic mineralogical composition of the rock. The modelling considers the transversely isotropic nature of the rock that is evident from both the visual appearance of the rock and determined from mechanical testing. Co...

A better understanding of how slip accumulates along faults and its relation to the breakdown of shear stress is beneficial to many engineering disciplines, such as, hydraulic fracture and understanding induced seismicity (among others). Asperities forming along a preexisting fault resist the relative motion of the two sides of the interface and oc...

Reservoir core measurements can help guide seismic monitoring of fluid-induced pressure variations in tight fractured reservoirs , including those targeted for supercritical CO 2 injection. We have developed the first seismic-frequency " room-dry " measurements of fracture-specific shear stiffness, using artificially fractured standard granite samp...

Spatial variation in frictional properties on natural faults are believed to be a factor influencing the presence of slow slip events (SSE). This effect was tested on a laboratory frictional interface between two PMMA bodies. We studied the evolution of slip and slip rates that varied systematically based on the application of, both, high or low no...

Earthquake faults, and all frictional surfaces, establish contact through asperities. A detailed knowledge of how asperities form will enable a better understanding of the manner in which they communicate during foreshock failure sequences that are observed, leading to the larger main shock. We present results of experiments where a pressure sensit...

Summarizes findings in: Selvadurai, P. A., S. D. Glaser, and J. M. Parker (2017), On factors controlling precursor slip fronts in the laboratory and their relation to slow slip events in nature, Geophys. Res. Lett., 44, doi:10.1002/2017GL072538.

The paper examines the coupled thermo-hydro-mechanical (THM) processes that develop in a fractured rock region within a fluid-saturated rock mass due to loads imposed by an advancing glacier. This scenario needs to be examined in order to assess the suitability of potential sites for the location of deep geologic repositories for the storage of hig...

A pressure-sensitive film was used to characterize the asperity contacts along a polymethyl methacrylate (PMMA) interface in the laboratory. The film has structural health monitoring (SHM) applications for flanges and other precision fittings and train rail condition monitoring. To calibrate the film, simple spherical indentation tests were perform...

Laboratory experiments were performed on a polymethyl methacrylate (PMMA)‐PMMA frictional interface in a direct shear apparatus in order to gain understanding of fault dynamics leading to gross rupture. Actual asperity sizes and locations along the interface were characterized using a pressure‐sensitive film. Slow aseismic slip accumulated nonunifo...

Summarizes the findings in: Selvadurai, P. A., and S. D. Glaser (2015), Laboratory-developed contact models controlling instability on frictional faults, J. Geophys. Res. Solid Earth, 120, doi:10.1002/2014JB011690. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2014JB011690

The paper examines the coupled thermo-hydro-mechanical (THM) processes that develop in a fractured rock region within a fluid-saturated rock mass due to loads imposed by an advancing glacier. This scenario needs to be examined in order to assess the suitability of potential sites for the location of deep geologic repositories for the storage of hig...

This paper uses experimental data derived from surface permeability tests conducted on a bench-scale 508 mm cuboidal sample of Indiana Limestone. These results are used in combination with computational modelling to test the hypothesis that the geometric mean is a good proxy to represent permeability when the spatial distribution of the permeabilit...

Our current laboratory investigations quantified the local stress states on a laboratory fault which control the transition of sliding from stable (quasi-static) to unstable (dynamic), commonly referred to as rupture nucleation. A fault was experimentally modeled using two Poly(methyl methacrylate) samples in a direct shear configuration. A pressur...

Developing a mechanistic understanding of the nucleation of frictional rupture would help explain the behavior of rock masses, from earthquake mechanics to dam foundations to seismicity due to subsurface fluid injection. This paper presents a laboratory investigation aimed at quantifying localized stress conditions required for sliding to transitio...

Developing a mechanistic understanding of the nucleation of fault rupture would help explain many behaviors of rock masses, from earthquake mechanics to response of dam foundations subjected to subsurface fluid injection. This paper presents a contact model to quantify the localized stress conditions required for a sliding block to transition from...

Seismic stress drop is an important metric for understanding the kinematics of injection-induced frictional sliding. Seismic stress drop is commonly estimated from Brune's corner frequency model and the assumption of a double couple source rather than from direct knowledge of the size of the slipping junction, which is impractical to impossible in...

Heterogeneity of a geomaterial can result from a variety of processes associated with depositional effects, chemical alterations and mechanical actions. In contrast to a non-homogeneous geomaterial where the properties vary gradually from point to point, a heterogeneous geomaterial is one that exhibits abrupt variations in the properties. Recent st...

The paper describes the procedures developed to measure the effective permeability of a large cuboidal region of Indiana Limestone measuring 508 mm. A patch permeability test was performed to measure the permeability characteristics of a local region of the cuboid. The surface measurements are then used to estimate, via a kriging technique, the dis...

The paper presents the mathematical, computational and experimentalapproaches that have been developed recently to estimate the effective permeability of a heterogeneous porous medium. The procedures available for estimating effective permeability are assessed in relation to experimental results derived from steady state fluid flow conducted on a c...

Permeability is a key parameter that has had an important infl uence in the development the disciplines of geosciences and geomechanics. The primary application of the theory of fl ow through a porous medium relates to the mechanics of groundwater fl ow with applications to groundwater hydrology. A theory of fl uid transport through a porous medium...

This thesis describes the experimental configuration and theoretical and computational techniques used to estimate the surface permeability of Indiana Limestone. The experimental procedure involves the application of a uniform flow rate to an open central region of a sealed annular patch. The law governing fluid flow within the porous medium is des...

Permeability is a key parameter important to a variety of applications in geological engineering and in the environmental geosciences. The conventional definition of Darcy flow enables the estimation of permeability at different levels of detail. This lecture will focus on the measurement of surface permeability characteristics of a large cuboidal...

This paper presents a technique for determining the near surface permeability of geomaterials and involves the application of a uniform flow rate to an open central region of a sealed annular patch on an otherwise unsealed flat surface. Darcy's flow is established during attainment of a steady pressure at a constant flow rate. This paper describes...

The measurement of permeability of large specimens of a rock specimen is bound to provide a clearer picture of the distribution of permeability of predominantly sedimentary rocks. Such distributions can be the basis for evaluating the effective permeability of the rock specimen in the presence of permeability inhomogeneity. This paper discusses the...

This paper describes a laboratory experiment designed to measure the bulk permeability of a cuboidal sample of sandstone measuring approximately 450 mm(2) in plan area and 508 mm in height. The relatively large dimensions of the sandstone specimen allow the determination of the permeability of the material by creating a central cavity that can be p...

The conventional procedures for describing fluid flow in porous media largely rely on assumptions of spatial homogeneity and isotropy. In contrast, natu-rally occurring porous geologic media display heterogeneity and anisotropy that is scale-dependent. This paper summarizes results of recent research that uses exper-imental techniques, mathematical...

This paper presents an approach for modelling fluid transients within a heterogeneous fluid-saturated porous medium, through the consideration of the effective parameters that can describe heterogeneity. This enables the application of the classical theory of piezo-conduction to the study of fluid transients in a porous medium where the permeabilit...