USING SEISMIC REFRACTION TOMOGRAPHY TO EXPLORE SUBSURFACE FEATURES OF THE OLD MIDDLE CREEK LAKEBED, SNYDER COUNTY, PA

This study investigates the subsurface characteristics of the Middle Creek (MC) lakebed to improve our understanding of sediment deposition, ancient river channel morphology, and other buried landforms. Located in Selinsgrove, Pennsylvania, MC Lake was initially constructed as a man-made reservoir by damming Middle Creek in 1833. Sediment deposits throughout the lakebed range from 1 to 3 meters in thickness. The reservoir, which extended one mile in length during its operational period, transitioned into a meadow with diverse vegetation after the removal of the dam in 1992. The present study employs a combination of seismic refraction tomography, electrical resistivity, Ground Penetrating Radar surveys, and borehole logging to assess sediment thickness and identify additional geological features within the lakebed. The primary objectives are to delineate the sedimentary structure, reconstruct paleochannel distributions, and provide insights into groundwater flow dynamics. The seismic refraction tomography was applied to analyze sediment layers and reconstruct the paleochannels, offering insights into the historical evolution of Middle Creek. A 230-meter seismic survey, using geophones spaced at 2-meter intervals, identified several paleochannels and a fault line in the central portion of the reservoir. The resulting cross-sectional data reveal sediment distribution and the historical pathways of Middle Creek, thereby enhancing our understanding of the region's geomorphological evolution.