In the Fall of 2015 and 2016, The University of Utah, in collaboration with the National Park Service and the University of Texas at El Paso installed dense seismic arrays centered on Old Faithful Geyser in Yellowstone National Park. The goals of this project are to image the shallow velocity structure beneath and around Old Faithful in order to identify areas of shallow, active hydrothermal activity as well as to learn more about these hydrothermal systems, in particular Old Faithful. The Upper Geyser Basin (Figure 1), where Old Faithful is located, has one of the highest concentrations of hydrothermal features in the world.
Figure 1: The Upper Geyser Basin near Old Faithful (red star) with the main roads in white.
In November of 2015, 133 seismometers were deployed for 2 weeks (Figure 2) collecting continuous passive seismic data. The average station spacing was ~50 meters and the aperture of the entire array was ~1 km.
Figure 2: The 2015 deployment of 133 seismometers (yellow circles) around Old Faithful (red star).
In November of 2016, in order to achieve a higher station density, a different approach was taken in that smaller dense arrays with ~20 meter spacing were deployed for 24-48 hours and then were moved to different locations around Old Faithful for another 24-48 hours until the area of interest was covered (Figure 3). In addition, while each individual array was in, we did active seismic sources using a sledgehammer throughout the array. A subset of instruments was deployed in the same location throughout the experiment in order to tie all the individual sub-arrays together.
Figure 3: The 2016 deployment of 519 individual locations (circles). The stations are color-coded by how long they were deployed. Green circles represent seismometers that were deployed in the same location for the entire time-period of the experiment. Each individual array (labeled 1-7) were deployed for 24-48 hours.
Data are being analyzed to image the shallow subsurface beneath the Upper Geyser Basin near Old Faithful.