Karl J Ellefsen

An S-wave refraction survey was conducted in the Yampa River valley near Steamboat Springs, Colo., to determine how well this method could map alluvium, a major source of construction aggregate. At the field site, about 1 m of soil overlaid 8 m of alluvium that, in turn, overlaid sedimentary bedrock. The traveltimes of the direct and refracted S-waves were used to construct velocity...

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...

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...

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.

OVERVIEW Program seg2_edit is used to edit and manipulate files that contain seismic (or radar) data stored in the SEG-2 format. The program is written in the standard C++ programming language, including its standard library. The program has been compiled with Microsoft Visual C++ .NET and tested on the Microsoft Windows 98, 2000, and XP operating systems. Nonetheless, because of the...

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...