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ARS Home » Southeast Area » Oxford, Mississippi » National Sedimentation Laboratory » Watershed Physical Processes Research » Research » Publications at this Location » Publication #248341
Title: Investigation of the near subsurface using acoustic to seismic coupling

Author
item HOWARD, WHEELER - Miltec Corporation
item HICKEY, CRAIG - University Of Mississippi

Submitted to: Ecohydrology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/24/2009
Publication Date: 8/18/2009
Citation: Howard, W., Hickey, C.J. 2009. Investigation of the near subsurface using acoustic to seismic coupling. Ecohydrology. 2:263-269

Interpretive Summary: This research investigates using sound waves in the air to excite vibrations in the ground in order to map the top of the fragipan horizon, a natural soil layer often observed within the top meter of the soil. Field data was collected at two sites with different depths to the fragipan. The acoustic and seismic data indicates higher amplitude, lower frequency peaks at the site with the deeper fragipan horizon. At the site with the shallower fragipan horizon the majority of the structure in the field data is located at higher frequencies. A simple resonant frequency (1/4 wavelength) model used to interpret the acoustic and seismic data and a field calibration technique to permit more accurate mapping of the top of the fragipan horizon over field scales is discussed.

Technical Abstract: Agricultural, hydrological and civil engineering applications have realized a need for information of the near subsurface over large areas. In order to obtain this spatially distributed data over such scales, the measurement technique must be highly mobile with a short acquisition time. Therefore, some type of remote sensing or geophysical technique must be utilized. Geophysical measurements are sensitive to the distribution of physical properties, such as the electrical conductivity, dielectric constant, mass density, mechanical properties, etc., of the ground. In most instances, the geophysical properties must be reconciled with physical properties used by the soil scientist. This paper presents a preliminary investigation of the use of acoustic to seismic (A/S) coupling measurements for measuring the depth to the top of the fragipan horizon. Fragipans influence the hydrology and ecohydrology of the soil on a field scale. A suite of traditional geophysical measurements was taken to characterize the soils at two sites with different depths to the fragipan horizon. Data at these two field sites indicate that this A/S technique is sensitive to the spatial variability of the depth to the fragipan horizon. At present, inversion of the A/S data for the fragipan depth requires use of data from a separate geophysical measurement or soil cores to provide a field calibration.