scholarly journals Interpretation of long-offset transient electromagnetic data from Mount Merapi, Indonesia, using a three-dimensional optimization approach

2005 ◽  
Vol 110 (B3) ◽  
Author(s):  
Michael Commer
Keyword(s):  
Three Dimensional ◽  
Optimization Approach ◽  
Electromagnetic Data ◽  
Transient Electromagnetic ◽  
Long Offset ◽  
Dimensional Optimization

Interpretation of 3-D effects in long‐offset transient electromagnetic (LOTEM) soundings in the Münsterland area/Germany

Geophysics ◽  
1992 ◽  
Vol 57 (9) ◽  
pp. 1127-1137 ◽  
Author(s):  
Andreas Hördt ◽  
Vladimir L. Druskin ◽  
Leonid A. Knizhnerman ◽  
Kurt‐Martin Strack
Keyword(s):  
Integral Equation ◽  
Thin Sheet ◽  
Three Dimensional ◽  
Equation Modeling ◽  
Data Sets ◽  
Sign Reversal ◽  
Near Surface ◽  
Transient Electromagnetic ◽  
Long Offset ◽  
Geological Situation

The interpretation of long‐offset transient electromagnetic (LOTEM) data is usually based on layered earth models. Effects of lateral conductivity variations are commonly explained qualitatively, because three‐dimensional (3-D) numerical modeling is not readily available for complex geology. One of the first quantitative 3-D interpretations of LOTEM data is carried out using measurements from the Münsterland basin in northern Germany. In this survey area, four data sets show effects of lateral variations including a sign reversal in the measured voltage curve at one site. This sign reversal is a clear indicator of two‐dimensional (2-D) or 3-D conductivity structure, and can be caused by current channeling in a near‐surface conductive body. Our interpretation strategy involves three different 3-D forward modeling programs. A thin‐sheet integral equation modeling routine used with inversion gives a first guess about the location and strike of the anomaly. A volume integral equation program allows models that may be considered possible geological explanations for the conductivity anomaly. A new finite‐difference algorithm permits modeling of much more complex conductivity structures for simulating a realistic geological situation. The final model has the zone of anomalous conductivity aligned below a creek system at the surface. Since the creeks flow along weak zones in this area, the interpretation seems geologically reasonable. The interpreted model also yields a good fit to the data.

THE STRUCTURE OF THE UIMON DEPRESSION OF GORNY ALTAI ACCORDING TO THE DATA OF NON - STATIONARY ELECTROMAGNETIC SOUNDING

2020 ◽  
pp. 66-76
Author(s):  
A. M. Sanchaa ◽  
◽  
N. N. Nevedrova ◽  
S. M. Babushkin ◽  
◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Deep Structure ◽  
Three Dimensional ◽  
Electromagnetic Sounding ◽  
Layered Model ◽  
Electromagnetic Data ◽  
Deep Well ◽  
Transient Electromagnetic ◽  
Gorny Altai ◽  
Good Agreement

The article presents the deep structure of the poorly studied Uimon depression in Gorny Altai according to the data of transient electromagnetic sounding. The studies are relevant due to the high seismic hazard of the area, and are also in demand for prospecting and exploration of minerals predicted there. In order to construct geoelectrical models, data from several years of measurements were used, during which more than sixty soundings were performed. According to the electromagnetic data, the first deep well was drilled to a depth of 400 m in the central part of the depression, which uncovered a Neogene – Quaternary section. The well column is in good agreement with the geoelectrical models. At that stage, the interpretation was performed using computer systems within the framework of a horizontally layered model. The interpretation results are presented in the form of sections and three – dimensional visualizations that clearly reflect the structure of the depression.

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