fcastro25 / invg

A MATLAB GUI for forward modelling and compact inversion of gravity anomaly data

invG

A comprehensive program for gravity interpretation, written in MATLAB with Graphical User Interface (GUI). Final Year Project

Main functions

1. Extraction field data stored in '.gxf' formmat
2. Forward modelling
3. Inversion
4. Generate analytical signal for testing the inversion algorithm.

It is written and tested in Matlab 2013b

Reference

Inversion algorithm:
Last, B. J., & Kubik, K. (1983). Compact gravity inversion. Geophysics, 48(6), 713-721

Design of GUI:
Stocco, S., Godio, A., & Sambuelli, L. (2009). Modelling and compact inversion of magnetic data: A Matlab code. Computers & Geosciences, 35(10), 2111-2118.

Analytical formula of simple shaped anomalous mass:
Telford, W. M., & Sheriff, R. E. (1990). Applied geophysics (2nd Edition). Cambridge university press.

Before Start

Download all the following files. Functions of each file is stated in 'README.txt'

Start the programme

Type invG and press 'Enter'. A window with 4 options will popup:

• Extract data
• Forward modelling
• Inversion
• Synthetic data

Extract data

1. Click 'File' -> 'Open' -> choose a '.gxf' file
2. Click the 'Choose profile' button,
3. Select 2 points on the contour map
4. Give a name to the '.txt' file if you want to save it
5. Click 'Exit' -> 'Inversion' to direct to the inversion menu

Inversion

Given a observed gravitational signal, find the possible 2D cross-sectional density anomoly distribution using damped weighted least-square algorithm developed by Last & Kubik (1983)

Forward modelling

Compute the gravitational signal for anomalous density distribution with simple geometry and known analytical formula

Synthetic data

Generate synthemtic data for testing the compact inversion algorithm. Synthetic signals are calculated by analytical formula (see Theoretical_Background.pdf)

1. Click 'Example'
2. Choose the shape of anomalous mass (2D trapizoidal prism / sphere / semi-infinite slab)
3. Modify the geometry, depth and density
4. Click 'Compute'
5. Save the profile as '.txt' by 'File'-> 'Save'
6. Click 'Inversion' to import the current profile to the inversion menu