WIDE-ANGLE SEISMIC REFLECTION STUDIES OF THE ELBERTON GRANITE AND SURROUNDING INNER PIEDMONT, NORTHEAST GEORGIA

A wide-angle seismic reflection experiment was conducted using 20 PRS-4 seismometers with 3-component 4.5 Hz geophones across the Inner Piedmont province, southern Appalachians, northeast Georgia. The study addresses the question of crustal, Moho and uppermost mantle structure. This study also investigates the tectonic relationship between the Elberton granite batholith and Appalachian thrusting. In this work, a new approach to image the Elberton granite is presented. A total of twenty timed dimension-stone and crushed-stone quarry blasts were recorded in Summer 2000. The experiment was designed to take advantage of the increase in reflection coefficients near the critical angle to image relatively subtle contrasts in the acoustic impedance. The receiver spacings were chosen tight enough, 50 - 150m, to avoid losing any major arrivals. Recorded lines range in length from 1 - 3 km, with shot-receiver distances from 9 - 16 km in the Elberton granite and 25 - 120 km in the Inner Piedmont. Shot gathers show strong first arrivals, Moho reflections and other reflections from within the crust. Shear wave arrivals are also strong, especially from Moho. For the Elberton surveys, the seismic recordings will be used to place constraints on the timing of emplacement of the granite. If reflections underneath the granite are present without distortion, then it is likely that the Elberton granite is not a rooted body, but rather a tabular intrusion or an allocthon that was transported from the southeast. Otherwise, if the laminated reflections associated with the thrusting are disturbed, then it is likely that the intrusion occurred after faulting. Further recordings will be added to fill the gaps.