USING THE H TO V SPECTRAL RATIO METHOD TO BETTER MAP THE BEDROCK TOPOGRAPHY AND DRIFT THICKNESS OF THE PREGLACIAL TEAYS RIVER WITHIN THE ANNA SEISMIC ZONE, OHIO

In 1937, a M 5.4 earthquake, the largest recorded earthquake in Ohio’s history, occurred near the Village of Anna in western Ohio. This area of the state is home to one of Ohio’s most active seismic zones, commonly referred to as the Anna Seismic Zone. The Anna Seismic Zone has experienced more than 75 earthquakes since recordkeeping began in the early 19th century. In order to learn more about subsurface of this region, the Ohio Department of Natural Resources, Division of Geological Survey has been collecting Horizontal to Vertical Spectral Ratio (HVSR) data in this area since 2017. These data are being used to create high-resolution maps of the near subsurface. The main feature being imaged through the collection of these data is the preglacial Teays River Valley, which is characterized by significantly thicker glacial drift and a higher average shear wave velocity than the surrounding upland regions.

HVSR data will improve our understanding of the Teays Valley geomorphology and provides insight into how drift thickness and the shear wave velocity of the glacial sediments deposited in the region can affect seismic amplification. By interpreting data collected via HSVR, we can create more accurate seismic hazard maps across the region and across the state.