Unique near‐surface seismic‐reflection characteristics within an abandoned salt‐mine well field, Hutchinson, Kansas

Abstract

High-resolution seismic reflections have been used effectively to investigate sinkholes resulting from the dissolution of a bedded salt unit found throughout most of central Kansas. A seismic reflection survey was conducted to investigate the shallow subsurface between a sinkhole that formed catastrophically within a few tens of meters of a main east/west rail line. Data quality was significantly below expectations and not equivalent to other seismic data from this area where acquisition parameters, equipment, and target intervals were similar. Near-surface tomographic and MASW analyses revealed a highly irregular bedrock surface characterized by what appear to be a high concentration of short wavelength dissolution features. These bedrock features are below about 20 m of unconsolidated sediments with physical dimensions several meters deep and several meters wide. Data quality is quite good on other seismic reflection surveys from this general area where these bedrock features are not present. Pronounced static shifts and degradation in spectral characteristics of reflections where these bedrock features are present seems to be isolated to an area suspected to be the crest of a relatively broad anticlinal structure where surface fractures could have provided a conduit for fresh water to access shallow, thin evaporite layers within the thick shale sequence in the upper 200 m. Broadband high-resolution compressional-wave energy suffered significantly from this highly irregular bedrock topography.

Near‐surface utility of vibroseis

“…Resolution and signal-to-noise ratio of near-surface seismic reflection data are appreciably improved through optimized source coupling (Walters et al, 2006), use of low-noise baseplate and mass sensors and non-telemetry pilot (Rademacker et al, 2005), site-specific pre-correlation processing approaches (Miller et al, 2005), and site-and equipment-specific approaches to the correlation step (correlation with synthetic or deconvolution with ground force). Unlike an explosive or projectile source where saturated, fine grain sediments provide the best transmission of high frequency signal (Miller et al, 1986), the highest frequency response was observed when the baseplate was coupled to a compacted, minimally deforming surface.…”

Shear‐Wave Velocity as an Indicator of Increased Stress and Failure Potential Associated with Dissolution‐Mining Voids

“…Previous studies have demonstrated the ability of seismic-reflection methods to image the subsurface expression of sinkholes and bedding geometries within the disturbed zone using compressional waves (Miller et al, 1993;Miller et al, 2005); however, no work has been done to evaluate void-induced changes in the localized stress field or the effect on seismic properties that may be indicative of near-term roof failure potential.…”