South African Geophysical Association
(SAGA)

SAGA has a proud history of promoting geophysics in Southern Africa. A list of past short courses follow.

Past Short Courses

Tues 2nd Oct 2003 - CSAMT (Controlled Source Audio-MagnetoTellurics) - 1/2 day

Course Presenters: Dr. Edgar Stettler (CGS), Mrs Janine Cole (CGS), Mr.
Jan van der Walt (Consultant):

1. What is MT and what are its applications.(8-8.35)
2. Basic theory and instrumentation(8:40-9:15)
3. Historical difficulties with MT data (9:20-10:00)
Break 10:00-10:45
4. Modern practice(10:45-11:30)
5. Case Histories (11:35-12:15)
6. StrataGEM-EH4 CSAMT case histories (12:15-13:00)

MT is an alternative to DC electrical surveys. MT can be used for a
variety of targets from shallow (CSAMT) to very deep (1000 km). MT
provides less ambiguity in models in conductive terrains than DC electrics
and vice versa.

MT in general has a higher resolution than DC electrics since 2 soundings at right angles to each other are obtained that also allow the estimation of electrical anisotropy. By the end of the year and into next year one of the biggest MT surveys will be conducted in South and Southern Africa, sponsored by DeBeers, Woodshole Oceanographic Institute (WHOI) and Council for Geoscience (CGS). The purpose of this survey is to augment the recently completed KaapVaal teleseismic survey.

Saturday 13th October 2001 "Wavelet processing" (half day course) - Gordon Cooper (sponsored by Matlab) - SAGA Biennial Conference 2001

Geophysical Applications for the Wavelet Transform

Geophysicists have long been familiar with the many and varied applications of the Fourier transform to their datasets. In the last decade new techniques have become available, termed wavelet transforms (which are not to be confused with the wavelets that are used in seismic reflection data processing), which extend greatly the usefulness of the method. Instead of being limited to sine and cosine functions (which are bad at representing sharp changes in data) like the Fourier transform, wavelet transforms allow a choice of function, which can result in greatly improved efficiency and speed. In addition, wavelet transforms are designed to show how the frequency content of a dataset changes with time (or distance), i.e. they are not limited to datasets with constant frequency content. Hence the variation in the frequency content with time can be analysed and displayed, which is an extremely powerful facility.

The wavelet transform has been used extensively during the last 10 years in diverse fields. Applications include denoising of data, compression of images, feature detection, efficient numerical algorithms, and the solution of partial differential equations. The initial geophysical applications were to seismic data processing, but lately the technique has been used in the processing of potential-field data. Recent work includes applications to the analysis of dipping events in seismic sections, to seismic trace characterisation, and to frequency-time decompositions of seismic data. The potential-field applications include wavelet transform in aeromagnetic processing, in the solution of large-scale inverse problems, and in the profile interpretation of
gravity and magnetic data.

The workshop will focus on concepts and applications rather than proofs of mathematical theorems. Practical sessions will be included to reinforce material covered in the presentations.

2001
The role of airborne EM methods for environmental applications in different geological terrains - David Beamish

Abstract
The talk considers the increasing role of Airborne EM (AEM) methods for environmental purposes in a variety of geological contexts. The environmental business and research sector is already large and it is growing in value, scale and complexity. Ground-based geophysics, particularly non-seismic methods, already has an established presence. In order to tackle environmental work, the geophysicist must be aware of the relevant geological, hydrogeological and environmental issues. Geochemistry, regulatory frameworks, existing databases (GIS) all need to be considered. These topics are reviewed as a background to the subject of modern airborne geophysics applied to the near-surface.

Airborne geophysical systems are typically multi-sensor and even within the active EM techniques, a considerable variety of configurations exist. The airborne systems, their characteristics and applications are reviewed. Tools of the trade, including modelling, inversion and visualisation are also considered. Recent airborne EM case studies are both impressive and revealing; particularly since they are clearly useful and relevant components of highly integrated (meaning across several disciplines) studies. One of the clearest directions lies in the use of AEM for groundwater protection. In many parts of Europe, this forms a key issue in terms of major programmes on sustainability and climate change.

It is possible to highlight the distinction between AEM applied to geological and mineral exploration and its use for land-use characterisation and environmental applications. There are many aspects to this: from most suitable survey parameters, airborne platform and technique through to the validity of the models obtained. One of the most obvious requirements stems from the fact that a wide range of environmental concerns naturally arise in the vicinity of populated areas. Are major conurbations no-go areas for current and future airborne programmes? The talk uses recent detailed case studies largely from Europe, with additional material from North America and Australia. The overall ability of AEM data to differentiate geological, cultural and environmental influences is a persistent theme.