112-10 Characterization of Ambient Seismic Data to Define Topography of an Incised Bedrock Valley

Session: Geophysics in Investigating and Exploring for Mineral, Energy and Groundwater Resources (Posters)

Poster Booth No.: 244

Presenting Author:

Caleb Ortman

Authors:

Ortman, Caleb¹, Drager, Lillian², Fanning, Aiden³, Kiene, Lani⁴, Young, Steven⁵, Balikian, Riley⁶, Thomason, Jason F.⁷, Mwakanyamale-Gilkie, Kisa⁸, Malone, David H.⁹

(1) Department of Geography, Geology, and the Environment, Illinois State University, Department of Geography & Geology, Normal, IL, USA, (2) Illinois State University, Department of Geography & Geology, Normal, IL, USA, (3) Department of Geography, Geology, and the Environment, Illinois State University, Department of Geography & Geology, Normal, IL, USA, (4) Illinois State University, Department of Geography & Geology, Normal, IL, USA, (5) Illinois State Geological Survery, University of Illinois, Champaign, IL, USA, (6) Illinois State Geological Survey, University of Illinois, Champaign, IL, USA, (7) Illinois State Geological Survey, University of Illinois, Champaign, IL, USA, (8) Illinois State Geological Survery, University of Illinois, Champaign, IL, USA, (9) Illinois State University, Department of Geography and Geology, Normal, IL, USA,

Abstract:

Ambient seismic data, using horizontal-to-vertical spectral ratio (HVSR) methods, have been collected to characterize bedrock depths and geometries in northern Illinois since 2021. Within the last year, we have collected over 300 points of HVSR data on a variety of instruments along a deeply incised bedrock valley and its tributaries. These HVSR soundings have been utilized to redefine interpretations of this valley with important implications for local and regional groundwater resources. In addition to HVSR data, other ground-based and geophysical measurements have been used to refine bedrock depth interpretations. As a part of this campaign, several HVSR soundings were acquired near locations where bedrock depth is known (e.g. boreholes) and were used to develop a highly localized equation to transform frequency data to bedrock depth. The density of soundings and the relationship developed from these localized calibration points has produced more accurate bedrock characterizations than those generated from regional calibration equations. This enables more accurate and higher quality interpretations of bedrock topography that account for local geology and lithology. Continued refinement of bedrock topography in this region using HVSR and other geophysical techniques can contribute to enhanced groundwater resource management in northern Illinois.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9923

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