Initial Publication Date: July 19, 2016

Analog modeling of fault asperity kinematics using a modified squeezebox design and wax media

Matty Mookerjee, Sonoma State University
Kyle Kucker, Redwood Hill Farm
Daniel Martin, Sonoma State University
Paige Paquette, Sonoma State University

Using a modified squeezebox deformation modeling rig, we have been able to recreate the kinematics of a deforming body of rock as it encounters a deep fault asperity within a fault zone. While the classic squeezebox utilizes sand to demonstrate brittle, Mohr-Coulomb style deformations, our modified squeezebox utilizes a viscoplastic wax analog, consisting of spherical strain markers "cemented" into a wax matrix.
Our squeezebox rig is composed of a reservoir, made from 0.25-inch aluminum plating with a molded polyurethane push-plate at one end. A trailer jack, equipped with a stepper motor to ensure constant displacement rates, drives the push-plate forward. Deformation is facilitated by the addition of heating elements lining the underside and exterior walls of the aluminum reservoir. An asperity, fashioned out of aluminum, is secured to the floor of the squeezebox reservoir. The additional overburden of rock is simulated using water filled bladders and lead shot resting on the upper surface of the fused wax block.
As expected, changing the strain rate and temperature conditions has significant impact on the material properties. Further experimentations are anticipated to document the amount of material flow perpendicular to the compression direction in the vicinity of the asperity, and how exactly that local non-plane strain deformation is ultimately balanced within the larger scale flowing body in a system with nonmoving lateral boundaries. We hypothesize that the major factor contributing to whether slip continues on an existing fault versus the initiation of a new fault is associated with the local strains associated with fault surface irregularities.


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