HR: 0800h
AN: H21A-0187    [Abstracts]
TI: Analysis of the Two-Dimensional Effect in the H/V Spectral Ratio Method for Bedrock Depth Estimation
AU: * Liu, L
EM: Lanbo.Liu@UConn.edu
AF: Dept. of Civil & Environ. Engineering, UNiversity of Connecticut, 261 Glenbrook Road, U- 2037, Storrs, CT 06269-2037, United States
AU: Zhu, L
EM: Lieyuan.Zhu@UConn.edu
AF: Dept. of Civil & Environ. Engineering, UNiversity of Connecticut, 261 Glenbrook Road, U- 2037, Storrs, CT 06269-2037, United States
AU: Lane, J W
EM: jwlane@USGS.gov
AF: Branch of Geophysics, Groundwater Office, U.S. Geological Survey, Sherman Place, Depot Campus, Storrs, CT 06269, United States
AB: The horizontal-to-vertical spectral ratio (H/V) method for analysis of microtremor surveys is widely used as a practical and economical way to obtain bedrock depth information for hydrogeological studies and to assess potential site effects for earthquake damage. This method is effective because it relies on the resonance frequency of vibration of the sedimentary layers, even when there are certain uncertainties in the vibration's amplitude. Because of its ease of use, many scientists use the H/V method as an exploration tool since, in the one-dimensional case, the resonance frequency is linked to the shear-wave velocity and the sediment thickness. The accuracy of the H/V method suffers, however, when the sediment-bedrock interface has small-wavelength undulations because the method assumes a horizontally layered earth. To investigate the effect of unevenness of the bedrock interface on the peak H/V value and to quantify the applicability of this method for estimation of depth to bedrock at a watershed scale, we conducted a series of tests using a finite-difference time-domain numerical model. The general conclusion is that when the wavelength of the bedrock undulation is less than three times the depth to bedrock, there can be a significant effect on the estimate of the fundamental frequency as determined by the H/V method.
DE: 1810 Debris flow and landslides
DE: 1829 Groundwater hydrology
DE: 1835 Hydrogeophysics
DE: 1879 Watershed
SC: Hydrology [H]
MN: 2007 Fall Meeting