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Shelton, CT, United States

Park C.B.,Park Seismic LLC
Proceedings of the Symposium on the Application of Geophyics to Engineering and Environmental Problems, SAGEEP | Year: 2010

In a roadside passive surface-wave survey under a typical urban setting with relatively heavy traffic and a complicated network of roads, a field record usually contains surface wave events generated from multiple source points scattered around the survey location. It is, however, those dominating energy events coming from one common surface point on the road that are used as signal in most advanced dispersion analysis methods based on the 2-D wavefield transformation. Events from other locations interfere adversely with signal events during the analysis if they take comparable energy or are largely ignored in the case of insignificant energy. A long record (e.g., 120 sec) is divided into many subsets of much shorter time of a proper length (e.g., 1 sec) and are treated as independent records of only one (or none) of a dominating event. By utilizing an advanced technique to detect fairly accurately the source location of the event, subsets are processed for their own dispersion images by using the scheme commonly used in the active MASW survey. Multiple data sets of the dispersion image are then stacked to result in an image of the highest signal-to-noise ratio (S/N) ever possible. This is demonstrated by using a field record acquired with a linear receiver array deployed along a busy street that contains events from complex source points and therefore could not be processed for any interpretable dispersion image using other methods currently available.

Nasseri-Moghaddam A.,Inspec Sol Inc. | Park C.B.,Park Seismic LLC
Proceedings of the Symposium on the Application of Geophyics to Engineering and Environmental Problems, SAGEEP | Year: 2010

The effect of source offset distance and the geophone array length on the dispersion curves are discussed in this paper. The source offset distance was changed systematically at sites with various subsurface conditions to investigate its effect on quality of data and the corresponding dispersion curves. Further, tests were carried out at same locations with various geophone intervals to evaluate the effect of the array length on the quality of the data and dispersion curves. Active and passive data were collected and the dispersion images were combined for possible improvement in dispersion image with enhanced multimodal delineation over a broadened bandwidth. It is observed that source offsets in the range of 25% to 45% of the array length provide dispersion curves with reasonable quality. Further, collecting data with different geophone intervals (same array mid station) improves the resolution of the obtained dispersion image. Multi geometry technique is suggested to obtain better quality field data. In this approach two (or more) different geophone intervals are used with same mid station. Passive and active data at two or more offset distances are collected for each of the array geometries. Stacking the obtained dispersion images can also result in a better quality dispersion curve.

Carnevale M.,Hager GeoScience Inc. | Park C.B.,Park Seismic LLC
Proceedings of the Symposium on the Application of Geophyics to Engineering and Environmental Problems, SAGEEP | Year: 2010

Since its inception as a subsurface imaging technique, the multichannel analysis of surface waves (MASW) seismic method has been used in a variety of environmental and geotechnical applications. One of the more interesting applications is performing subsurface imaging in a beach environment. Although the loose and dry ground surface appears to present a formidable obstruction to the application of MASW for deep imaging, there could be an anonymous unexploited source of energy to make it happen. We look at the possibility that low frequency energy from ocean wave fronts can be introduced into seismic recordings made during MASW surveys along a beach or shoreline. Seismic data from MASW beach and shoreline surveys in Massachusetts will be examined for possible evidence of constructive or destructive interference from energy produced by ocean waves. The possible relationships of MASW survey geometry and the geography of the project settings are also examined. This study aims at evaluating the possible exploitation of ocean energy for deep MASW surveys in beach and shoreline environments.

Park C.B.,Park Seismic LLC | Taylor C.,GeoView Inc.
Proceedings of the Symposium on the Application of Geophyics to Engineering and Environmental Problems, SAGEEP | Year: 2010

By running three parallel and one crossing lines of conventional 2D MASW surveys followed by normal 1-D MASW inversions, a 3D characterization was attempted as a pilot study over an area of a known sinkhole 10-40 ft deep with lateral dimension smaller than 50 ft. Shear-velocity (Vs) data sets from each line were then used as constraints to calculate a cubic grid data in x (east-west), y (southnorth), and z (depth) directions by using a 3D inverse-distance-weighted (IDW) interpolation scheme. When displayed in depth-stripping mode at 5-ft depth intervals, velocity anomalies of substantially lower values than those in the ambient are recognized in the surface and depth locations that correlate fairly well with those identified in a geologic cross section previously compiled from other methods of well drilling, CPT, and GPR surveys. Properly selecting offset range during data acquisition and subsequent dispersion analysis seems critically important for the successful detection of a sinkhole.

Yaede J.R.,Brigham Young University | McBride J.H.,Brigham Young University | Nelson S.T.,Brigham Young University | Park C.B.,Park Seismic LLC | And 6 more authors.
Geosphere | Year: 2015

Estimates of the thickness variation in lateritic weathering profiles (LWPs) are important in tropical areas underlain by young basalt lavas like those found in Hawaii. Seismic shear-wave velocity data were obtained by a new application of multichannel analysis of surface waves (MASW) to map variations in the LWP and to derive the downward rate of advance of the weathering front in basaltic lavas. The MASW technique proved highly capable of imaging the internal structure and base of the critical zone, as confirmed by borehole data and direct field measurements. Profile thickness thus obtained, rapidly and without drilling, has applications to engineering and geochemical studies. The rate of advance of the weathering front derived from MASW in Oahu ranged from 0.010 m/ka to 0.026 m/ka in mesic zones (~1500 mm/a rainfall), whereas an area with ~800 mm/a revealed rates from 0.005 m/ka to 0.011 m/ka. These rates are comparable to those derived from recent solute-based mass balance studies of ground and surface water. Conventional P-wave seismic reflection did not perform as well for detecting boundaries due to a gradational seismic velocity structure within the weathering profile. Shear-wave velocity models showed internal variations that may be caused by textural differences in parental lava flows. Limitations in imaging depth were overcome by innovative experiment designs. Increasing source-receiver offsets and merging surface-wave dispersion curves allowed for a more objective derivation of velocity-frequency relations. Further improvements were made from a recently developed form of the combined active and passive source technique. These advances allowed for more detailed and deeper imaging of the subsurface with greater confidence. Velocity models derived from MASW can thus describe the LWP in terms of depth and variability in stiffness. © 2015 Geological Society of America.

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