2010 - 19th Annual NC State Undergraduate Research Spring Symposium

Session Time : 4/22/10 10:30 AM - 4/22/10 11:45 AM

Content Area : Physics

Student Presenters :
Kate Lynn Foco Physics

Mentors and/or Co-Authors :
Karen Daniels Physics

Abstract Title : Effects of Packing Density on Granular Stick-Slip Events

Abstract :
Earthquakes are caused by rocks along a fault slipping past each other and then returning to a stationary state. The physics underlying this important natural phenomenon is not well understood. The goal of this research is to investigate similar phenomena in a laboratory setting: a quasi-two-dimensional apparatus consisting of photoelastic particles that are subjected to linear shear. We vary the particle packing density (phi) from 0.775 to 0.815 to determine its effect on the behavior of these types of “stick-slip” events. The runs at the lower limit of phi fail to enter a state of jamming and simply flow as a liquid. The upper limit is very near the point where particles are unable to rearrange and, as a result, act as a solid. Boundary data on event size and the interval of events as a function of phi were collected and smoothed for noise. We observe that the data at all phi exhibit a power law distribution which closely matches that of real earthquakes. Additionally, both small and large events show a characteristic, Gaussian shape.