Karl J Ellefsen

The finite-difference time-domain method was used to simulate radar waves that were generated by a transmitting antenna inside a borehole. The simulations were of four different models that included features such as a water-filled borehole and an antenna with resistive loading. For each model, radiation patterns for the far-field region were calculated. The radiation patterns show that the amplitu

To understand the electromagnetic waves generated by a prototype dielectric logging tool, a numerical study was conducted using both the finite-difference, time-domain method and a frequency-wavenumber method. When the propagation velocity in the borehole was greater than that in the formation (e.g., an air-filled borehole in the unsaturated zone), only a guided wave propagated along the borehole.

In this report are four different models that represent an antenna used by personnel at the U.S. Geological Survey for crosswell investigations. The four models vary in complexity and concomitantly the accuracy with which they represent the actual antenna. These models are used in numerical simulations of the antenna to determine how it radiates radar waves.

No abstract available.

Program FD_BH is used to simulate the electromagnetic waves generated by an antenna in a borehole. The model representing the antenna may include metallic parts, a coaxial cable as a feed to the driving point, and resistive loading. The program is written in the C programming language, and the program has been tested on both the Windows and the UNIX operating systems. This Open-File Report describ

Program pick_sw is used to interactively pick travel times from S-wave data. It is assumed that the data are collected using 2 shots of opposite polarity at each shot location. The traces must be in either the SEG-2 format or the SU format. The program is written in the IDL and C programming languages, and the program is executed under the Windows operating system. (The program may also execute un

Near Mirror Lake, New Hampshire (USA), hydraulically conductive, fractured bedrock was investigated with the crosswell seismic method to determine whether this method could provide any information about hydraulic conductivity between wells. To this end, crosswell seismic data, acoustic logs from boreholes, image logs from boreholes, and single borehole hydraulic tests were analyzed. The analysis s

To understand better how a borehole antenna radiates radar waves into a formation, this phenomenon is simulated numerically using the finite-difference, time-domain method. The simulations are of two different antenna models that include features like a driving point fed by a coaxial cable, resistive loading of the antenna, and a water-filled borehole. For each model, traces are calculated in the

To obtain subsurface geologic information about the alluvium in the Big Thompson River valley, S-wave refraction data were collected along three roads that cross the valley. The refraction data were used to estimate velocities and thickness for a layered-earth model; from these models, three cross sections of the river valley were constructed. These cross sections show the thickness and the gross

No abstract available.

No abstract available.

No abstract available.