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.