THIS WEEK
FRIDAY JUNE 2 @ 1P PDT
Looking inside granular materials
Karen Daniels, North Carolina State University
Granular materials such as those found near the Earth’s surface are inherently heterogeneous, and continuum models of properties such as the shear modulus and sound speed often fail. One promising alternative is to build an understanding of bulk behaviors from measurements at the particle scale. Our lab’s experiments make use of idealized, optically birefringent materials to quantify the interparticle forces - and thereby directly measure the stress tensor at the particle scale - within compressed or sheared granular materials. I will describe both these methods, and the heterogeneous network of forces that they reveal. Through our experiments, I will talk about several frameworks capable of connecting the internal structure of disordered materials to their rigidity and/or failure under loading, and describe how we apply these ideas. [more info] [register]
NEXT WEEK
FRIDAY JUNE 9 @ 1P PDT
Mechanical behavior of lubricated faults during earthquake nucleation and propagation
Marie Violay, EPFL
Natural and human Induced Fluid Earthquakes (FIEs) have been observed and recorded for decades. These events can be responsible for significant human, economical and infrastructure damage. FIEs result from the interaction between fluid pressure perturbations, in-situ stresses, frictional and rupture processes at micro to macro scales, and the geometric complexity of the fault zone. Methods for risk assessment and forecasting (in terms of time, location and magnitude) of FIEs require a sound physical basis. However, much of the primary parameters controlling FIE dynamics cannot be measured by geophysical methods. Thus, to establish new general constitutive physical FIE laws, the temporal- and spatial-scale dependence of FIEs should first be properly investigated in the laboratory. here we studied the influence of viscous lubricant in the nucleation and propagation of spontaneous frictional ruptures. We adopted a multi-scale experimental approach. [more info][register]
Have a great summer!