Effect of fault heterogeneity on rupture dynamics: An experimental approach using ultrafast ultrasonic imaging

Abstract

[1] This study is devoted to the experimental investigation of the interaction of a propagating rupture with one or several mechanical heterogeneities. We developed a friction laboratory experiment where a soft elastic solid slides past a rigid flat plate. The system is coupled to an original medical imaging technique, ultrasound speckle interferometry, that allows observing the rupture dynamics as well as the emitted elastic shear wavefield into the solid body. We compare the dynamics of propagating rupture for a homogeneous flat interface and for three cases of heterogeneous sliding surfaces: (1) an interface with a single point-like barrier made of a small rock pebble, (2) an interface with a single linear barrier that joins the edges of the faults in a direction perpendicular to slip, and (3) an interface with multiple barriers disposed on half of its surface area, creating a heterogeneous zone. We obtain experimental observations of dynamic effects that have been predicted by numerical dynamic rupture simulations and provide experimental observations of the following phenomena: a barrier can stop or delay the rupture propagation; a linear single barrier can change the rupture velocity, increasing or decreasing it; we observe transition from subshear to supershear propagation due to the linear barrier; a large heterogeneous area slows down the rupture propagation. We observe a strong variability of the rupture dynamics occurring for identical frictional conditions, which we impute to heterogeneity of the stress field due to both the loading conditions and memory of the stress field due to previous rupture events.

Analogue earthquakes and seismic cycles: experimental modelling across timescales

“…Two loading configurations can be differentiated: shear, including direct shear, ring shear, and Couette shear (e.g. Brune, 1973;Archuleta and Brune, 1975;Schallamach, 1971;Latour et al, 2013b;Fig. 3a-c, e), and (biaxial) compression (e.g.…”

“…The use of softer materials allows us to slow down the rupture process and make it more accessible by means of monitoring. This has been exploited by, e.g., Baumberger et al (2003), Yamaguchi et al (2011), andLatour et al (2013b) using gel sliders (Fig. 3e).…”

“…Fault block models have also been developed to investigate how different configurations of roughness affect the rupture propagation. It has been found that a single linear barrier may both accelerate and decelerate a rupture, while a large heterogeneous barrier slows down the rupture (Latour et al, 2013b). Rousseau and Rosakis (2009) investigated the effect of more complex fault geometries including kinking and branching on rupture propagation in a homalite material.…”

Length scale of interface heterogeneities selects propagation mechanism of frictional slip fronts

“…Brörmann et al (2013) and Romero et al (2014) showed on interfaces with discrete contacts (pillars and spherical caps, respectively) that the transition from sticking to sliding is characterized by slip fronts propagating along the interface, similar to the observations of Rubinstein et al (2004) but at a two-dimensional interface. Latour et al (2013) studied experimentally the effect of interface barriers on frictional slip. They showed, using different configurations of barriers, that heterogeneities can cause rupture arrest/delay as well as increase/decrease of the rupture speed.…”

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“…Two loading configurations can be differentiated: shear, including direct shear, ring shear, and Couette shear (e.g. Brune, 1973;Archuleta and Brune, 1975;Schallamach, 1971;Latour et al, 2013b;Fig. 3a-c, e), and (biaxial) compression (e.g.…”