Academic Affiliation: Smith College
Anny is a geoscience major at Smith College in Northampton, MA. Her love for geology sparked after spending most of her summers exploring the mountainous landscape of New England and even having the opportunity to adventure to the glaciers of the Northern Cascades. Anny is particularly interested in reconstructing paleoclimates using sedimentology. This summer, Anny used the geophysical self-potential method to analyze the spatial and temporal patterns of groundwater flow in the Upper Gordon Gulch Watershed at the Boulder Creek.
2015- Using the Self-Potential Method to Analyze the Temporal and Spatial Variation of Shallow Groundwater Flow Through Meadows Within the Boulder Creek Critical Zone
Previous studies have examined the potential impacts that a shift in climate can have on the surface water. However, little research has been done on the implications that climate change can have on the water flow in the subsurface. A less explored but highly consequential focus is the measurement of shallow groundwater flow in meadows because of their ability to exist in a fragile environment, making them susceptible to the changes in climate. Meadows provide a clear connection between terrestrial ecosystems and streams in high altitude environment. In the Boulder Creek Critical Zone Observatory outside of Boulder, Colorado, a shift in the climate could lead to a dramatic alteration in precipitation from snow to rain and earlier snowmelt within the watershed. In the past, groundwater was measured by the installation and monitoring of groundwater wells. Although groundwater wells are an effective way to monitor groundwater, they only provide information on the groundwater flow of a single location. Self-potential is a geophysical method that measures the small voltage that occurs when water passes through the sand or soil in the ground. The goal of this project is to measure, through self-potential, the groundwater flow in the upper Gordon Gulch watershed in the Boulder Critical Zone and examine how the groundwater flows in a meadow system. In doing this, we can create effective models to help understand how fragile ecosystems such as meadows are impacted by the change in climate. Data collected during 10 Jun and 24 Jun 2015 show a significant decrease in self-potential values indicating a change in groundwater flow between the two dates. Based on our results we can show that the self-potential method is effective in understanding and mapping the spatial and temporal patterns of groundwater in the subsurface.
2017- The Effect of Earthquakes on Episodic Tremor and Slip Events on the Southern Cascadia Subduction Zone
Episodic tremor and slip (ETS) have been a topic of focus during the last decade and there is much to be learned about these enigmatic events. When oceanic plates subduct into the mantle, friction with the overriding plate causes a stick-slip behavior within the megathrust (where the plates converge), which pulls the upper plate down until it springs back up, resulting in a destructive earthquake that originates from the shallow locked zone (Brudzinski et al., 2007). At great depth, the plate interface is believed to slide freely due to high temperatures. At intermediate depths on the plate interface (~40 km), transient fault slip is observed in the form of ETS events (Gomberg, 2010). These ETS events occur regularly (every 11-24 months), and have a longer duration than normal earthquakes. Researchers have been documenting slow slip events through data obtained by continuously running GPS stations in the Pacific Northwest (Gomberg, 2010). The interaction of earthquakes and ETS can provide constraints on the strength of the fault and the level of stress needed to alter ETS behavior. Earthquakes can trigger slow ETS events, but the connection between these events and earthquake activity is less understood. We previously hypothesized that ETS events are affected by earthquakes and could result in a shift in the recurrence interval of ETS events. ETS events were cataloged using GPS time series and seismic tremor data provided by PANGA in Southern Cascadia for stations YBHB and DDSN to look for evidence of change from three offshore earthquakes, occurring near the Mendocino Triple Junction with magnitudes of 7.2 in 2005, 6.5 in 2010, and 6.8 in 2014. Our results showed that the recurrence rate of ETS in stations YBHB and DDSN was not altered by the three earthquake events. This is likely due to the due to the difference in orientation of the earthquake events from the receiver fault.