22nd EEGS Symposium on the Application of Geophysics to Engineering and Environmental Problems

Inversion of 1D technique (VES and TDEM) by using Global Search Procedures (GSPs) as proved to be
effective in evidencing local minima and equivalence problems, evaluating non-uniqueness in
the solution, and estimating the values and uncertainties of the model parameters.

The inversion of Rayleigh wave dispersion curves can yield the shear wave velocity profile which
gives the image of subsurface. In most of the existing techniques of computing Rayleigh wave dispersion
curves, it is assumed that the subsurface consists of horizontally flat layers.

Although it is generally known that the active MASW method tends to average out the near-field
effect of surface waves through the slant-stack process implicitly incorporated in dispersion imaging and
therefore one optimum source offset (X1) is usually employed for a given survey, a long source offset to
ensure recording of long wavelengths can sometimes result in a lack of short-wavelength energy due to
excessive attenuation and, on the other hand, the use of a short source offset can result in the opposite
consequence.

Regularization is necessary for inversion of ill-posed geophysical problems. Appraisal of inverse
models is essential to a meaningful interpretation of these models. Because uncertainties are associated
with regularization parameters, extra conditions are usually required to determine proper parameters for
assessing inverse models.

Code was designed at The Ohio State University Department of Electrical and Computer Engineering in conjunction with the School of Earth Sciences with the goal of forward modeling subsurface geological systems. To attain this goal the finite difference time domain (FDTD) method was implemented through single- and multi-processor systems leading to the name parallel finite difference time domain (PFDTD).

Fractures are caused by changes in stress patterns. Fracture delineation using geophysical
techniques allows for a better understanding of stress processes and fluid flow. The main objective of
this study is to delineate and map fractures in a granitic body with the help of attribute algorithms. The
data is a 3D GPR survey consisting of 24 parallel lines on the Tishomingo Anticline in southern
Oklahoma. Changes in the dielectric constant between the granite and the fracture fill (air or water) will
produce a distinctive amplitude response related to geological features characteristic of the fractures.
Amplitude attribute algorithms allow the identification of fracture patterns. The resulting fracture
interpretation is corroborated by the surface fracture data.

Identifying the location of the island of Ithaca, legendary home of Odysseus, has been a problem
for historians for centuries. The modern island of Ithaki, in the Ionian Sea, does not match the
description in Homer’s epic poem. In 2003 Robert Bittlestone initiated a study of the Paliki peninsula in
western Cephalonia in an attempt to determine whether this was the island that Homer called Ithaca,
then separated from the rest of Cephalonia by a sea channel later described by the Greek geographer
Strabo.

In the sea harbor of IJmuiden, the Netherlands, a sandy island was removed. In the light of high
archeological expectance a geoarcheological inventory was compulsory prior to the digging and
dredging. Prospective geoarcheological research in aeolian environments concerns a standard procedure
involving the determination of paleosols by borings. The paleosols were found at the site obliging
digging of an inventory trench. Before the trenching a 100 MHz ground-penetrating radar (GPR) survey
was conducted yielding a penetration depth of about 6 to 7 m. Rationale was to deduce the suitability of
GPR for prospecting geoarcheological research in coastal dunes. Radar facies units were compared with
observations in the trench. Furthermore, 14C and OSL dating of molluscs and sediments was done.

On-going studies of the flood-control levees in the Sacramento valley, California have included airborne EM and magnetic surveys, DC resistivity surveys, cone penetrometer testing and reverse-circulation borings. This paper reports on how airborne EM is being used to provide a regional overview of the levee foundations, tie-together and extend the CPT and boring information, as well as providing mapping of the horizontal extent of sand channels.

The failure of earthen embankments is associated with erosion, overtopping, seepage, piping,
slope failures, and slides. Precursory evidence for certain failures can be identified by visual inspection;
however, others are not so easily detected. Seismic imaging and monitoring may provide unique and
valuable precursory information about the onset of piping, seepage, and anomalous pore pressures to
assist in the evaluation of the integrity of an earthen embankment.

We use multi-channel analysis of surface waves (MASW) on seismic data to assess the practical impact of the assumed compressional-velocity and density parameters on the inverted shear-wave velocity results. The practical secondary-parameter impact evaluation was performed on data acquired in the arctic. The ice-sheet compressional-, shear-wave velocity and density variations with depth were available from laboratory and field measurement and served as reference for analyzing the MASW inversion.

A new theoretical model has been developed for transient controlled-source electromagnetic (CSEM) exploration of multi-layer aquifers. The method is applicable to fractured rock and other types of lithology which exhibit length-scale dependent heterogenity. A roughness parameter β is used, in the present paper, as a proxy for fracture density.

The electroseismic phenomenon is a conversion from electromagnetic energy to elastic wave
energy that occurs at electric double layers, such as clay-water interfaces, where charge has
accumulated. The electroseismic coupling and measured response are functions of a number of physical
properties that control ionic strength and current flow; coupling increases with increased pore water
conductivity, temperature, and permeability and with decreased pore tortuosity, viscosity, and volumeto-
surface ratios in the pores.

This study is concerned with investigating the subsurface geology of the Holocene- Late
Pleistocene lithostratigraphic sequence in the central part of Dakahlyia Governorate, east Nile Delta
using the shallow penetration geophysical techniques.

Geophysical inverse problems are ill-posed: the objective function has its minimum in a flat
elongated valley or surrounded by many local minima. Local optimization methods give unpredictable
results if no prior information is available. Traditionally this has generated mistrust on the use of
geophysical inverse methods (equivalence problem in VES).

Springs can be supported by large regional flow systems or relatively small more local systems.
The spring will respond differently to local stresses or climatic changes depending on its flow system. It
is often difficult to determine the source of a spring due to the remote nature of many springs, and sparse
subsurface information.

The Kovaya Limestone Mine is situated on the Saurashtra coast of India. Though the Mine is dependent on the Desalination plant installed in the Plant for its domestic and industrial water requirements, there is significant withdrawal of groundwater by the large number of bore wells and open wells, which are present in the agricultural fields lying in the leased area of the mine. The heavy withdrawal of groundwater has led to intrusion of seawater.

Enhanced bioremediation is increasingly used to accelerate cleanup of recalcitrant compounds and has been identified as the preferred remedial treatment at a substantial number of contaminated DoD (Department of Defense) sites.

The biodegradation of solid waste in bioreactor landfills is dependant on a number of factors
including moisture content. Identification of relatively wet and dry areas throughout the landfill would
help operators determine where moisture should be added or not. This study attempts to utilize seismic
borehole techniques to identify changes in seismic wave velocity through the waste due to the addition
of moisture.

The use of dissolution wells for mining salt has been common practice for over a century, leaving behind brine-filled “salt jugs” or voids in the subsurface which, over time, can migrate through overlying rock formations, potentially leading to sinkhole formation and public safety hazards. In an effort to determine the relative range of stress on the roof rock above these jugs at various stages of failure, evaluate the extent of void migration, and aid in remediation planning, shear-wave reflection surveys were conducted at a well field near Hutchinson, Kansas, where drill-confirmed dissolution features exist in the 125-m deep Hutchinson Salt Member.

A 3-D seismic survey was performed to evaluate the practicality of this method to map very shallow objectives (less than 100 m). The survey was conducted in an area near San Francisco Bay where the geology consisted mainly of fluvial/deltaic geology. The site was located between the Hayward and San Andreas faults.

In this paper a procedure for two-dimensional unsteady thermo-mechanical analysis of layered
structures is presented, allowing the determination of the temperature and stress field at each step the
construction period. The finite element method is employed in the methodology. Numerical
simulation are focused on concrete structures, particularly roller compacted concrete (RCC) dams. A
time varying elasticity modulus is introduced in the model. One case study is presented and analysis
under different design approaches.

In this paper we present two techniques for Transverse Gradiometer (TG) data processing and
their practical application. Using our method, the transverse gradient is measured using dual sensors.
The longitudinal gradient is obtained using profile data history and the vertical gradient component is
computed synthetically based on 2-D potential field theory using the Total Field along the profile.

The purpose of the present paper is to investigate the Hopfield neural network as a flexible detection method of Ferro-magnetic sources from magnetic anomaly data. The observed magnetic anomaly is approximated over a steel drum by an equivalent dipole source. The Hopfield network was used to obtain the magnetic moment at a set of regular locations. For each location, the Hopfield network reaches its stable state and the location of minimum Hopfield energy signifies the target location. To escape from the local minimum of the network energy function, the scaled input technique is proposed.