Isostatic Residual

The Isostatic Residual extension uses a modified version of the USGS algorithm to calculate the Airy isostatic regional and residual gravity from a topographic grid.

The extension calculates the depth to the Moho (the "root") based on the topographic grid, terrain density, Moho density contrast, and the depth of sea level compensation. It then calculates the 3D gravity response of that root at sea level, extending out to a radius of 166.7 km. To generate a complete Airy regional model, this output must be combined with a solution that extends beyond the 166.7 km limit.

Working in Oasis montaj requires a project file (*.gpf). A project encompasses all items in your workspace, including:

  • Data files such as databases, grids, maps, voxels, geosurfaces, and 3D views

  • Visualization tools like histograms and scatter plots

  • Project settings, including the menus currently displayed

This structure ensures that your entire working environment is saved and easily restored.

To begin working with the Isostatic Residual extension, we recommend opening a new project and then loading the menus related to the extension.

Open a New Project

  1. On the Project menu select New. The New Project dialog will open.

    You can also select Create new project from the startup dialog that appears when you launch Oasis montaj.

  2. In the New Project dialog, specify the name and location for your new project file (*.gpf), then click Save.

  3. The new project will open, enabling the main menus, toolbar icons, and the Project Explorer. These visual indicators confirm that the system is ready for use.

Load the Menus

  1. On the Project menu, select Manage Menus, or click the Manage Menus icon on the Project Explorer toolbar. The Manage Menus dialog will appear.

  2. Expand the Extensions node, select Isostatic Residual, and click OK. The menus related to the extension will now appear on the main menu bar.

The menu system is designed to provide quick access to a variety of tools and to guide you through the primary processing and filtering workflows in the extension.

To automatically load these menus in future projects, specify them in the Default menus field of the General Settings dialog.

Accessing Help

Once the Isostatic Residual menus are loaded, click the Help button in any dialog opened from these menu items:

  • The reference topic for the current dialog will be displayed.

  • Use the Help Topics tab to navigate to others topics of interest.

  • Use the Search tab to find specific topics by entering keywords.