Interpretation of Landsat Thematic Mapper Satellite Imagery at Los Azufres Geothermal Field, Michoacan, Mexico

Document Type

Article

Journal/Book Title/Conference

Geothermal Resources Council Transactions

Volume

14

Issue

2

Publisher

Geothermal Resources Council

Publication Date

8-1-1990

First Page

1553

Last Page

1559

Abstract

This report documents part of a cooperative study by CFE and UURI of a Landsat 5 image of the Los Azufres geothermal area and its surroundings. The objective was to determine if processing and interpretation of satellite imagery are useful in volcanic environments for mapping structures, hydrothermal alteration, rock types and for soil geochemical anomalies manifest in vegetation. Several processing steps were carried out using the ERDAS image-processing system installed on an AT-equivalent PC at UURI in an attempt to detect characteristic signatures from hydrothermally altered areas and to enhance linear and other structurally related geologic features. A great deal of structural information is recorded in the Landsat image. Most of the interpreted linear features are believed to be due to faulting and fracturing. and there are more interpreted linears than there are mapped faults. The additional information contributed from the image interpretation may prove useful in planning for further development of the Los Azufres area. Signatures reasonably characteristic of hydrothermally altered areas were developed after considerable experimentation with various false-color images of the direct digital data and of derived band ratios. This is a significant result because it implies that the method may be useful in helping to assess other areas of known geothermal occurrence which are less thoroughly mapped than is Los Azufres. We believe that satellite imagery interpretation may contribute cost effectively to an exploration program by ( I ) outlining areas of strong and/or young faulting. (2) outlining areas where faulting and fracturing are more intense, (3) detecting hydrothermal alteration with a reasonable degree of reliability after calibration over known alteration, (4) outlining areas of young volcanic deposits, and (5) helping to guide geologic field work and prioritize areas.

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