What Rubber and Jello Can Teach Us About Earthquakes and Fractures

Many systems in geophysics, including faults, ice sheets, and hill slopes, are predominantly stable, but become unstable catastrophically, with severe societal consequences when they do. However, the behaviors of these systems are difficult to predict because they involve extreme spatial and temporal scales, accumulating stresses over decades or centuries, but nucleating failure processes in fractions of a second, which start at the micron-scale but lead to kilometers of deformation. In this talk, I will discuss how I utilize techniques from applied physics to build scaled-down experiments that explore these complex problems in systems where a wide range of unique properties can be tuned to make otherwise impossible observations. I will present two examples: First, using a scaled, transparent laboratory fault where slip at the interface can be directly imaged, I will show that fully confined, slow slip events in our system follow earthquake-like and frictional scaling, but display seismological stress drops that are invariant to not only normal stress, but also normal stress heterogeneity and to a large extent frictional properties. However, this invariance disappears as more ruptures are allowed to reach the edge of the system. Second, I will discuss how material heterogeneity leads to brittle fracture roughness, and show that the resultant morphology of a crack is, surprisingly, not dependent upon the details of the medium, but is instead controlled entirely by a single parameter: the probability to perturb the fracture front above a critical size to produce a step-like instability

About this Series

Only students may enroll in this class but all members of the MIT community are welcome to attend the talks. This seminar series is an overview of classical papers and recent research in geophysics. Fields to be covered include geodesy and earthquake physics (e.g. tectonic earthquakes, induced seismicity, glacial earthquakes). Contact jkastorf@mit.edu for more information and Zoom password.