Date of Award


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Degree Name

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First Advisor

Anthony R. Lowry


To accurately determine the earthquake hazard posed by a fault, we need to understand both strain accumulation and release along the fault. Strain accumulates during aseismic periods but it is released during fault slip events that can be either seismic or aseismic. Aseismic slow slip events are motions similar to earthquakes but they occur over much longer timescales. Slow slip is not felt at the Earth’s surface but it can be recorded in GPS time series. A deformation modeling tool that was applied in Guerrero, Mexico by Lowry et. al. (2001) fits a hyperbolic tangent function to GPS time series and can be used to distinguish slow slip events from noise in the data and from non-tectonic deformation. Time series from the Plate Boundary Observatory, Wasatch Front GPS Network, and Basin and Range Geodetic Network were analyzed for transient deformation during the period encompassing 2004 to 2008. Data suggests several transient motions including a possible slow slip event beginning in mid-2008 and continuing into 2009. Both seismic and aseismic slip influence the earthquake cycle, and slow fault slip events offer a window into frictional properties on fault surfaces that will rupture in future earthquakes. Consequently, as we increase our understanding of aseismic slip and why it occurs, we eventually may expect to develop predictive models of fault slip through time by combining measurements of aseismic and seismic slip in models that reflect the physics of frictional slip on faults.