Crustal and upper mantle velocity structure in the vicinity of the eastern Tennessee seismic zone based upon radial P wave transfer functions

Abstract

Teleseismic transfer function analysis is used to investigate crust and upper mantle velocity structure in the vicinity of the active eastern Tennessee seismic zone (ETSZ). The ETSZ is associated with the New York-Alabama (NY-AL) magnetic lineament, a prominent aeromagnetic anomaly indicative of Grenville-age, basement structure. Radial component, P wave transfer functions for 10 short-period stations operated by the Center for Earthquake Research and Information are inverted for velocity structure. Velocity profiles are also determined for three broadband stations by converting the instrument response to that of an S-13 short-period seismometer. Distinct differences in the velocity profiles are found for stations located on either side of the NY-AL magnetic lineament; velocities west of the lineament are lower than velocities to the east of the lineament in the upper 10 km and in the depth range 30 to 50 km. A gradational Moho boundary is found beneath several stations located in the Valley and Ridge province. A Moho boundary is absent at four Valley and Ridge stations located east of the magnetic lineament and south of 35.5°N.

Imaging crustal structure beneath the southern Appalachians with wavefield migration

“…Over this length scale, Moho depth varies by less than 3–4 km in the plane‐normal direction, with a maximum plane‐normal dip of <3° for the D line [ Parker et al, ]. In addition, the presence of the Moho waning in both W and D line inversions and the apparent absence of a Moho velocity increase in nearby single station analyses [ Graw et al, ] add confidence. Small‐scale reductions in apparent Moho amplitude on the W line correlate with lower station density (e.g., ~255 km and ~305 km, Figure ), and the continuity of the Moho in the PPs individual mode inversion (Figure S5b) indicates that these are probably not real structures.…”

“…A reduction of Moho amplitude appears not only in this study beneath the Blue Ridge province but also as a more complete loss of Moho amplitude below nearby stations [ Graw et al, ] and in a zone straddling the Blue Ridge Escarpment that lies ~200 km to the northeast [ Wagner et al, ]. A weak Moho velocity contrast in the general area of this study is also reported in a continent‐scale joint inversion of Ps receiver function and surface wave data, although the Moho anomalies are not correlated in detail [ Shen and Ritzwoller , ].…”

“…Today, the Appalachians are a tectonically quiescent, decaying orogen, yet geomorphology and thermochronology studies [Gallen et al, 2013;McKeon et al, 2014;Miller et al, 2013;Prince et al, 2010;Prince and Spotila, 2013;Willett et al, 2014] indicate relatively recent (≥3 Ma) topographic rejuvenation of these mountains over a range of time and length scales. Proposed forcing mechanisms include dynamic topography [Forte et al, 2007;Liu, 2014;Rowley et al, 2013] and lower crustal delamination [Wagner et al, 2012;Gallen et al, 2013;Graw et al, 2015], indicating that deep crustal and mantle structures may control the ongoing evolution of these Paleozoic mountains.…”

Group velocity tomography of the upper crust in the eastern Tennessee seismic zone from ambient noise data

“…S2), which is < 2 km in this area [Brandmayr and Vlahovic, 2016]. This area of complex geologic features likely hosts terrains accreted during the Iapetus subduction and rich in metasedimentary rocks [Graw et al, 2015].…”

The upper crust of the Eastern Tennessee Seismic Zone: Insights from potential fields inversion

“…We tend to rule out this possibility since this effect should be systematic, but no or little overestimation occurred in the Cumberland Plateau, Blue Ridge, Piedmont, and Coastal Plain. Mooney and Kaban [2010] report a sedimentary cover thickness of about 6 km beneath the Valley and Ridge, and Graw et al [2015] estimated, using receiver functions, V P < km/s down to 8-10 km of the depth along the NY-AL lineament. These values are within the range of our estimate, although Graw et al [2015] interpret their findings as low velocity basement crust, which is consistent with previous studies that estimated a shallower sedimentary cover in the area [Sodbinow and Bollinger, 1978;Owens et al, 1984].…”