# Robert C. ViescaTufts University | Tufts · Department of Civil and Environmental Engineering

Robert C. Viesca

PhD

## About

39

Publications

8,034

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677

Citations

Introduction

Additional affiliations

September 2018 - present

September 2012 - August 2018

September 2011 - August 2012

Education

September 2005 - November 2011

September 2001 - May 2005

## Publications

Publications (39)

Earthquake swarms attributed to subsurface fluid injection are usually assumed to occur on faults destabilized by increased pore-fluid pressures. However, fluid injection could also activate aseismic slip, which might outpace pore-fluid migration and transmit earthquake-triggering stress changes beyond the fluid-pressurized region. We tested this t...

The frictional properties of large faults are expected to vary in space. However, fault models often assume properties are homogeneous, or nearly so. We investigate the conditions under which the details of variations may be neglected and properties homogenized. We do so by examining the behavior of nonlinear solutions for unstably accelerating fau...

We assess if a characteristic length for an interfacial slip instability follows from theoretical descriptions of sliding friction. We examine friction laws and their coupling with the elasticity of bodies in contact and show that such a length does not always exist. We consider a range of descriptions for frictional strength and show that the area...

There is scientific and industrial interest in understanding how geologic faults respond to transient sources of fluid. Natural and artificial sources can elevate pore fluid pressure on the fault frictional interface, which may induce slip. We consider a simple boundary value problem to provide an elementary model of the physical process and to pro...

We investigate the quasi-static growth of a fluid-driven frictional shear crack that propagates in mixed mode (II+III) on a planar fault interface that separates two identical half-spaces of a three-dimensional solid. The fault interface is characterized by a shear strength equal to the product of a constant friction coefficient and the local effec...

We investigate the quasi-static growth of a fluid-driven frictional shear crack that propagates in mixed mode (II+III) on a planar fault interface that separates two identical half-spaces of a three-dimensional solid. The fault interface is characterized by a shear strength equal to the product of a constant friction coefficient and the local effec...

There is scientific and industrial interest in understanding how geologic faults respond to transient sources of fluid. Natural and artificial sources of fluid can elevate pore fluid pressure on the fault frictional interface, which may induce slip. We consider a simple boundary value problem to
provide an elementary model of the physical process a...

The frictional properties of large faults are expected to vary in space. However, fault models often assume that properties are homogeneous, or nearly so. We investigate the conditions under which the details of variations may be neglected and properties homogenized. We do so by examining the behaviour of nonlinear solutions for unstably accelerati...

We examine a simple mechanism for the spatio-temporal evolution of transient, slow slip. We consider the problem of slip on a fault that lies within an elastic continuum and whose strength is proportional to sliding rate. This rate dependence may correspond to a viscously deforming shear zone or the linearization of a non-linear, rate-dependent fau...

We examine a simple mechanism for the spatio-temporal evolution of transient, slow slip. We consider the problem of slip on a fault that lies within an elastic continuum and whose strength is proportional to sliding rate. This rate dependence may correspond to a viscously deforming shear zone or the linearization of a non-linear, rate-dependent fau...

Fluid-driven fracture presents an interesting case of crack elasticity and fracture propagation non-
linearly coupled to fluid flow. With the exceptions of a few numerical studies, previous hydraulic fracture modeling efforts have been based on the premise of Linear Elastic Fracture Mechanics (LEFM): specifically, that the damage (aka cohesive) zon...

We consider numerical solutions in which the linear elastic response to an opening- or sliding- mode fracture couples with one or more processes. Classic examples of such problems include traction-free cracks leading to stress singularities or cracks with cohesive-zone strength requirements leading to non-singular stress distributions. These classi...

We examine the development of an instability of fault slip rate. We consider a slip rate and state dependence of fault frictional strength, in which frictional properties and normal stress are functions of position. We pose the problem for a slip rate distribution that diverges quasi-statically within finite time in a self-similar fashion. Scenario...

We present a model for dynamic weakening of faults based on local flash heating at microscopic asperity contacts coupled to bulk heating at macroscopic scale. We estimate the fracture energy G associated with that rheology, and find that for constant slip rate histories G scales with slip δ as G ~ δ^2 at small slip, while G ~ δ^1/2 at large slip. T...

We examine the development of a frictional instability, with diverging sliding rate, at the interface of elastic bodies in contact. Evolution of friction is determined by a slip rate and state dependence. Following Viesca [2016], we show through an appropriate change of variable, the existence of blowup solutions that are fixed points of a dynamica...

Examining a nonlinear instability of sliding rate on a frictional interface of elastic bodies, we investigate whether lab-constrained frictional relations suggest universal scaling under even the simplest of configurations. We find blow-up solutions by solving an equivalent, classical problem in fracture mechanics. The solutions are fixed points of...

Laboratory simulations of earthquakes show that at high slip rates, faults can weaken significantly, aiding rupture [1–3] . Various mechanisms, such as thermal pressurization and flash heating, have been proposed to cause this weakening during laboratory experiments [1,4–6], yet the processes that aid fault slip in nature remain unknown. Measuremen...

Geophysical observations suggest that mature faults weaken significantly at seismic slip rates. Thermal pressurization and thermal decomposition are two mechanisms commonly used to explain this dynamic weakening. Both rely on pore fluid pressurization with thermal pressurization achieving this through thermal expansion of native solids and pore flu...

Earthquakes are generated because faults lose strength with increasing slip and slip rate. Among the simplest representations of slip-dependent strength is the linear slip-weakening model, characterised by a linear drop to a residual friction. However, healed fault rocks often exhibit some slip strengthening before the onset of weakening. Here we i...

We model landslide initiation as slip surface growth driven by locally
elevated pore pressure, with particular reference to submarine slides.
Assuming an elastic medium and friction that weakens with slip,
solutions exist in which the slip surface may dynamically grow, without
further pore pressure increases, at a rate of the order of the sediment...

We address the nucleation of dynamic landslide rupture in response to
gradual pore pressure increases. Nucleation marks the onset of
acceleration of the overlying slope mass due to the suddenly rapid
enlargement of a sub-surface zone of shear failure, previously deforming
quasi-statically. We model that zone as a planar surface undergoing
initially...

Geological materials near the Earth's surface and within the Earth's
crust contain pore spaces, largely saturated with water. In this work I
study how changes in the pressure of this saturating pore fluid affect
deformation, focusing on the deformation of shear ruptures occurring
during an earthquake or a landslide. I represent ruptures in both
con...

Elastic reciprocity and geometric symmetry are used to constrain the expressions for stresses due to introduction of line dislocations near a half-space surface. Specifically, a relationship is shown to exist between the changes induced by dislocations of orthogonal Burgers vectors (normal and parallel to the free surface). These results are used t...

Given the low angles of continental slopes, sedimentation alone may not be sufficient to initiate failure, in which case a source of locally elevated pore pressure p is a likely candidate. Heterogeneities in p may arise from spatially variable sources of gas (e.g., Fleischer et al., Geo-Mar. Lett. 2001), variations in permeability, and channelized...

When a region of intense shear in a slope is much thinner than other relevant geometric lengths, this shear failure may be
approximated as localized slip, as in faulting, with strength determined by frictional properties of the sediment and effective
stress normal to the failure surface. Peak and residual frictional strengths of submarine sediments...

Increases in pore pressure are often cited as potential mechanisms for landslide initiation, both subaerial and submarine. Such mechanisms are particularly appealing to account for failures in the submarine environment, where shallow slope angles seem to preclude downslope movement. Considering the submarine environment, the rapid deposition of sed...

Here we consider shear rupture along a slip surface in a fluid-saturated elastic-plastic porous medium, like in landslide and earthquake modeling, and assume that there are different poro-elasto-plastic response properties on the two sides of the slip surface. This different response may be because the fault bordering materials are dissimilar, or j...

1] We present an analysis of inelastic off-fault response in fluid-saturated material during earthquake shear rupture. The analysis is conducted for 2-D plane strain deformation using an explicit dynamic finite element formulation. Along the fault, linear slip-weakening behavior is specified, and the off-fault material is described using an elastic...

When considering dynamic fault rupture in fluid-saturated elastic-plastic materials, it is sensible to assume locally undrained behavior everywhere except in small diffusive boundary layers along the rupture surface. To evaluate undrained pore pressure changes, we consider here not just the linear poroelastic effect expressed in terms of the Skempt...

We examine factors that determine the extent and distribution of off-fault Coulomb plasticity during earthquake rupture propagations in regions where pore fluids are present at full saturation. The dynamic finite element method, in the form of ABAQUS Explicit, is used with linear slip-weakening behavior along the fault. Material surrounding the fau...

We extend a dynamic model of inelastic off-fault response during earthquake rupture propagation (Templeton and Rice, this meeting) to include the effects of changes in pore pressure in a fully saturated medium. The model is analyzed by dynamic finite element procedures with ABAQUS Explicit. It incorporates a failure condition along the fault in the...

Experie nce in the design of steel and concrete floor systems to control vibrations suggests that a floor system's vibration characteristics are often fundamental to its acceptable performance. In such cases, serviceability drives the design instead of strength. This is particularly true for laboratory floors that support sensitive equipment and fl...

We present an analysis of inelastic off-fault response in fluid-saturated material during earthquake shear rupture. The analysis is conducted for 2-D plane strain deformation using an explicit dynamic finite element formulation. Along the fault, linear slip-weakening behavior is specified, and the off-fault material is described using an elastic-pl...

## Projects

Projects (3)

We are interested in uncovering physics of fast and slow fault slip induced by anthropogenic activity, e.g. hydraulic fracturing, fluid waste sequestration in the subsurface, hydrocarbon recovery, etc. The similarities/connections between the induced and natural earthquakes and fault creep, e.g. in how it is coupled with dynamics of fault fluids, are also explored.