Illuminating Fault Structure of the Eastern Tennessee Seismic Zone using 15 Years of Seismicity with a Matched Filter Technique

The Eastern Tennessee Seismic Zone (ETSZ) is the second most active seismic zone in the eastern United States, after the New Madrid Seismic zone in the Mississippi Valley area. The current seismicity forms a 300 km long diffuse zone from northeastern Alabama to southwestern Virginia, without clear lineation of fault structures. The largest present-day earthquakes are about M~4.6, however causes of seismicity in the ETSZ remain unclear. A few faults have been identified in the region, but many remain unknown or poorly constrained at depth. Our objective is to gain new insight into the structures of seismogenic faults in the ETSZ using a matched filter technique to detect earthquakes not previously catalogued in the ETSZ. We create templates from over 967 catalogued templates spanning over 15 years (January 2005 to May 2020). These templates are then used to detect missing events within the 15-year time period. We also calculate the magnitudes of new events using principle-component fitting between templates and newly detected events. Cross-correlation based arrival time refinements are calculated to relocate the events. We use two relocation algorithms, XCORLOC and HYPODD, to comparatively relocate detected events in the ETSZ. Relocated hypocenters are examined to resolve fault structures and orientations. We plan to compare orientation of seismogenic faults to previous seismological studies. Our ultimate goal is to use spatio-temporal changes of seismicity during the last 15 years reveal subsurface fault structures and the driving forces of seismicity along the ETSZ.