RECEIVER FUNCTION ANALYSIS OF THE EASTERN TENNESSEE SEISMIC ZONE

We present results from a receiver function analysis involving short period instruments located in the active eastern Tennessee seismic zone (ETSZ). Studies involving basement rocks in eastern Tennessee are sparse despite the fact that these rocks host the ETSZ and are associated with a prominent aeromagnetic lineament called the New York–Alabama (NY-AL) magnetic lineament. The NY-AL magnetic lineament is thought to represent a major, northeast trending Grenvillian fault, but its relationship to basement structure is enigmatic. The lineament is pronounced in eastern Tennessee and is defined, progressing from NW to SE, by an abrupt change from positive to negative anomalies. A band of negative gravity anomalies coincides with the positive magnetic anomalies, adding further complexity to any interpretation of basement features. The vertical projection of the NY-AL magnetic lineament separates very seismogenic crust to the SE from much less seismogenic crust to the NW, suggesting that the lineament represents an ancient basement fault that is reactivating in the present day stress field. Better characterization of the basement feature will help assess its seismic hazard potential. We use the east Tennessee seismic network operated by the Center for Earthquake Research and Information (23 short-period and 3 broadband seismometers) as well as IRIS station TZTN to compute receiver functions in an attempt to better define the basement feature associated with the magnetic lineament. Teleseismic earthquakes within a 30°-90° epicentral distance, at depths greater than 30 km, and greater than M_w 6.0 are used for processing. A spectral waterlevel deconvolution is used in the receiver function calculations. The receiver functions are then source-side stacked to utilize all of the crustal reverberations to accurately calculate depth. Results indicate different crustal structure across the NY-AL lineament; crustal structure west of the lineament is more complicated than structure to the east. Our results will be used to test a new interpretation of basement faulting associated with the magnetic lineament that involves roughly 200 km of right-lateral strike-slip motion.