Date of Award

Spring 2017

Degree Name

Master of Science

Department

Geological and Environmental Sciences

First Advisor

Dr. William A. Sauck

Second Advisor

Dr. Alan E. Kehew

Third Advisor

Dr. Robb Gillespie

Keywords

HVSR, Geology, Geophysics, Gravity, Glacial geology

Access Setting

Masters Thesis-Open Access

Abstract

The Horizontal to Vertical Spectral Ratio (HVSR) passive, single sensor seismic technique has been used together with gravimetry to study the topography hidden below the glacial drift of two 7.5’ quadrangles in Barry Co., MI. 265 stations were observed with both instruments along roads at nominal spacings of about 0.4 to 0.8 km. Occasional water wells and oil wells with documented penetrations of the base of glacial were used to calibrate the local power law regression calibration. This was also compared with the statewide calibration curve previously established. Results are presented as maps of Simple Bouguer Anomaly, Residual Bouguer Anomaly, glacial drift thickness, and elevation at the base of the glacial drift (from HVSR). Additionally, a modified Residual Gravity map was made by using the drift thickness from HVSR for removing the gravity effect of the glacial drift. Residual gravity was quite helpful in isolating anomaly sources originating from the igneous/metamorphic basement rocks, as this area is in a zone of steep gravity gradient along a flank of the MI branch of the mid-continent geophysical anomaly. The HVSR results are much more useful than gravity changes in this region for estimating thickness of the glacial drift. The HVSR-determined thicknesses were valuable to improve on the reported locations of incised tunnel valleys in this area. Observations of conditions (weather and terrain) conducive to good HVSR spectra are discussed.

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