Muting the noise cone in near‐surface reflection data: An example from southeastern Kansas

Abstract

A 300-m near-surface seismic reflection profile was collected in southeastern Kansas to locate a fault(s) associated with a recognized stratigraphic offset on either side of a region of unexposed bedrock. A substantial increase in the S/N ratio of the final stacked section was achieved by muting all data arriving in time after the airwave. Methods of applying traditional seismic data processing techniques to near-surface data (200 ms of data or less) often differ notably from hydrocarbon exploration-scale processing (3-4 s of data or more). The example of noise cone muting used is contrary to normal exploration-scale seismic data processing philosophy, which is to include all data containing signal. The noise cone mute applied to the data removed more than one-third of the total data volume, some of which contains signal. In this case, however, the severe muting resulted in a higher S/N ratio in the final stacked section, even though some signal could be identified within the muted data. This example supports the suggestion that nontraditional techniques sometimes need to be considered when processing near-surface seismic data.

Depth characterization of shallow aquifers with seismic reflection, Part I—The failure of NMO velocity analysis and quantitative error prediction

“…Velocity filtering is ineffective at separating this energy at near offset. Baker et al (1998) discuss a region defined as the noise cone, within which primary reflected energy is masked by slow, highamplitude coherent noise ( Figure 2). The noise cone is contained within the t-x boundary defined by moveout at the noise cone velocity (v nc ).…”

Depth characterization of shallow aquifers with seismic reflection, Part II—Prestack depth migration and field examples

“…Prior to PSDM, the data should follow the same noise suppression scheme as followed for NMO processing. This includes muting the first break and refractions [although under certain conditions acceptable results may be obtained if this step is bypassed (Pasasa et al, 1998)] and attenuating the noise cone with any of the commonly used approaches, including f -k filtering and inside muting (Baker et al, 1998).…”

“…This leads to significant depth prediction errors if the Dix equation is assumed valid. The problem is exaggerated in the shallow environment because extremely low S/N ratios in the near-offset regime often require recording reflections at large offset-todepth ratios (Hunter et al, 1984;Baker et al, 1998;Bradford, 2002). Stacking velocity increases with increasing offset range, leading to greater divergence from the NMO assumption.…”

Source-Dependent Frequency Content of Ultrashallow Seismic Reflection Data

“…Ideally, a deconvolution routine can be used during data processing to compress a long-duration source pulse so that it simulates a shorter pulse. However, several of the basic assumptions underlying deconvolution (Yilmaz, 1987) are often violated with respect to near-surface reflection data (Baker et al, 1998). First, the reflectivity series of the subsurface is assumed to be spatially random, but SSR data often image only one or two reflectors.…”

“…Obtaining seismic images from depths shallower than 10 m, however, has not been successful until recently. There are numerous examples of using seismic reflection techniques to examine the upper 100 m of the earth's subsurface (e.g., Hunter et al, 1984;Goforth and Hayward, 1992;Miller et al, 1995;Baker et al, 1998). However, shallow (less than 10 m) reflection seismology has only become possible recently due to improvements in equipment, survey design, and processing procedures (Steeples and Knapp, 1982).…”