Envronmental seismology is the study of seismic signals that originate from Earth surface processes. My work in environmental seismology includes the study of repeating earthquakes in within glaciers and landslides, the seismic wave field associated with water flowing through the Greenland Ice Sheet, and of hydraulic fracturing in geothermal systems, glaciers, volcanoes.
What process is responsible for generating this seismic wave field?
A commonly occuring problem in environmental seismology is that of determining what action caused an observed wave form. Compared to the study of seismograms associated with large tectonic earthquakes, the seismograms associated with many environmental processes may initially appear more vexing. My research develops new ways to understand these signals. This type of conundrum is epitomized by the trace shown above as it lacks many of the features that facilitate the interpretation of large impulsive events (like earthquakes), i.e., a clear onset, readily identifiable wave phases, etc.
Mysterious seismic signals are often speculatatively hypothesized to be related to subsurface fluids. I've developed quantitative methods to test such hypotheses. These methods are based in the frequency content of seismograms. In particular, my work on repeating earthquakes and hydraulic resonance found that these processes have distinct spectral signatures:
The spacing of spectral peaks therefore allows for the interpretation of a broad class of seismograms.