- Title: April 2017 Bulletin
- Posted by:
- Date: 10:22 PM
The Million Dollar Question: Which Geophysical Methods Locate Caves Best Over the Edwards Aquifer? A Potpourri of Case Studies from San Antonio and Austin, Texas, USA
Environmental Geophysics Associates
2000 Cullen Avenue, Number 7
Austin, TX, 78757, USA, email@example.com
*First published in the NCKRI Symposium 5, 14th Sinkhole Conference, and reprinted here by the kind permission of the NCKRI, whose permission is required for further use.
This article describes resistivity imaging and natural potential data (NP) collected over six caves between the years of 2000 and 2014, which are air filled and are located in the northern part of Bexar County, San Antonio, and in the south and north of Travis County, Austin, Texas. All caves were encountered through drilling and/or excavation for construction and utility lines or power pole reconstructions. The study area falls into the part of the Recharge Zone of the Edwards Aquifer region and it represents a well-developed karstified and faulted limestone (Stein and Ozuna, 1996).
The resistivity and NP data over these 6 caves suggest that the resistivity data does not specifically determine where karstic features are located in the subsurface. However, it provides significant information on the near-surface geology and geological structure. The NP data, on the other hand, notably defines the location of cave features. Thus the merits of integrating the NP method along with the resistivity imaging over the Edwards Aquifer, in order to reduce the ambiguity in the interpretation, are evident.