Inverting magnetotelluric data with distortion correction—stability, uniqueness and trade-off with model structure
| Autor: | A. T. Basokur, Anna Avdeeva, Erhan Erdogan, Max Moorkamp |
|---|---|
| Rok vydání: | 2020 |
| Předmět: |
Electromagnetic theory
010504 meteorology & atmospheric sciences Distortion correction Inverse theory Inversion (meteorology) 010502 geochemistry & geophysics 01 natural sciences Geophysics Geochemistry and Petrology Magnetotellurics Uniqueness Algorithm Geology 0105 earth and related environmental sciences |
| Zdroj: | Geophysical Journal International. 222:1620-1638 |
| ISSN: | 1365-246X 0956-540X |
| Popis: | SUMMARY Galvanic distortion of magnetotelluric (MT) data is a common effect that can impede the reliable imaging of subsurface structures. Recently, we presented an inversion approach that includes a mathematical description of the effect of galvanic distortion as inversion parameters and demonstrated its efficiency with real data. We now systematically investigate the stability of this inversion approach with respect to different inversion strategies, starting models and model parametrizations. We utilize a data set of 310 MT sites that were acquired for geothermal exploration. In addition to impedance tensor estimates over a broad frequency range, the data set also comprises transient electromagnetic measurements to determine near surface conductivity and estimates of distortion at each site. We therefore can compare our inversion approach to these distortion estimates and the resulting inversion models. Our experiments show that inversion with distortion correction produces stable results for various inversion strategies and for different starting models. Compared to inversions without distortion correction, we can reproduce the observed data better and reduce subsurface artefacts. In contrast, shifting the impedance curves at high frequencies to match the transient electromagnetic measurements reduces the misfit of the starting model, but does not have a strong impact on the final results. Thus our results suggest that including a description of distortion in the inversion is more efficient and should become a standard approach for MT inversion. |
| Databáze: | OpenAIRE |
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