10.1. Comprehensive Workflows: TMI Magnetics

Author: Devin C. Cowan

Published: February, 2022

Requires GIFtools v3.0 or later

Here, we present a general workflow for loading, interpreting, processing and inverting total magnetic intensity (TMI) magnetic data. We begin with TMI data in a basic XYZ format. Our goal is to process and invert the TMI data to recover a 3D magnetic susceptibility model for a local survey area. For this tutorial, we have both local and regional datasets; the later of which can be used to constrain the local-scale inversion if available. You may work with the tutorial datasets provided or use your own data:

• Download the tutorial data

We would like to thank our program sponsors for providing the local survey data used to create this comprehensive workflow. The regional-scale data were queried from the Natural Resources Canada Geoscience Data Repository for Geophysical Data .

Regional and local TMI anomaly data (above). Local susceptibility models recovered with inversion using various norms (bottom).

Tutorial Sections

• 10.1.1. - Understanding TMI anomalies
• 10.1.2. - Loading data and cursory interpretation
• 10.1.3. - Equivalent source inversion
• 10.1.4. - Upward continuation and reduction to pole
• 10.1.5. - Polynomial detrending
• 10.1.6. - Data interpretation (including remanence)
• 10.1.7. - Uncertainties for TMI anomaly data
• 10.1.8. - Mesh design
• 10.1.9. - Least-squares inversion
• 10.1.10. - Examining inversion outputs
• 10.1.11. - Local inversion using regional removal
• 10.1.12. - Sparse norm inversion