Application of Ultra Wide-band MT Data for Deep Investigations: Based on Synthetic Data Example of Canadian Shield
Abstract
10,000 Hz - 50,000 seconds Ultra Wide-Band Magnetotellurics (UMT) has become widely used since 2015 with the development of new extended frequency range induction sensors and continuous high sampling rate recording units. This new technology allows the full frequency range of MT data including AMT, MT and LP bands to be acquired with the same equipment in one recording at the same sounding station. Although the technology allows wideband data to be acquired, the usage of this data for recent widely spaced (low density) MT grids is still not common.
In this study we focus on the effect of high frequencies for deep lithospheric investigation surveys which are often done using fluxgate magnetic sensors whose adequate sensitivity to the natural fields starts at 0.05 Hz (several kilometers). We created a synthetic ultra wide-band data set using the conceptual geological model of Canadian Shield, and then evaluated the 3D inversion results of UMT, MT+LP versus LP data only. We used those synthetic data models to estimate minimum grid size for reliable 3D inversion for each MT frequency range. Also we showed that wideband UMT data used for large scale grid provides critical near surface information, improves calculated depths through inversions and to shift effects. As a matter of historical interest, we note that Canada's LITHOPROBE project in 1980s-1990s adopted a workflow requiring successive AMT+MT+LP soundings at the same location.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMGP13B0596F
- Keywords:
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- 0925 Magnetic and electrical methods;
- EXPLORATION GEOPHYSICS;
- 1515 Geomagnetic induction;
- GEOMAGNETISM AND PALEOMAGNETISM;
- 3006 Marine electromagnetics;
- MARINE GEOLOGY AND GEOPHYSICS;
- 3914 Electrical properties;
- MINERAL PHYSICS