Model Creation¶
This workflow describes how to create a new model in IGMAS+ using a "traditional" workflow using vertical sections (planes) or working sections. Historically, the idea behind this approach was to construct the model along seismic lines, which acted as constraints on the modelling.
This approach was used in IGMAS+ since the beginning and represents an alternative to building a model using horizons (or "flying carpets"), such as Moho interface, intra-crustal layers, etc.
The "flying carpet" approach is described in the Import horizons chapter and in the Molasse Basin example.
Start a new project¶
In the Menu Bar select File → New Project:
Note
This function is available only if there is no model loaded.
This is the wizard to create a new project:
There are two possible ways of creating a project/model:
- New Model: build a new model using working sections - explained in this chapter and in the EVA example.
- Horizon Import: build a model by importing layer surfaces (horizons) - explained in Import horizons chapter and in the Molasse Basin example.
Setup a new model¶
To build a new model, choose New Model. The New Project Settings window will open:
Set the origin (X, Y), the horizontal size (width in X and Y denoted as Distance in both cases) and the vertical size (Depth).
Don't forget to choose the units (meters m or kilometers km).
Default values are 0 for X and Y, 10 for Distance, and 5 for Depth with m as units.
Click on Next.
Setup the distribution of working sections¶
Here you can set the distribution of working sections:
- Set the Azimuth - the orientation of the model sections in relation to the true north
- Set the Spacing - the distance between the sections or change Count - number of sections
Click Preview to see the distribution of the working sections after the changes.
You can also user Reset to return to the default values.
More information on how to set the distribution of working sections can be found in the EVA example example.
Click Finish to continue.
The result is a new project with a new model consisting of working sections:
Save the created project¶
After creating a project, both Save Project and Save as will allow you to save the created project within a folder. In both cases IGMAS+ will ask for a directory name and a new directory (global folder) and subdirectory (timeline folder) will be created. This directory structure keeps the valuable information about project changes over time. In this way you can always recover old and current models.
Triangulate the model¶
The triangulation is the process of creating a mesh of triangles that link the working sections of the model together.
It is a necessary step because the further modelling process is based on the triangulated model.
Click on Edit → Model - Triangulation in the Menu Bar or use the Triangulate Sections icon 
to triangulate the model between the sections:
If you don't have the stations in the model, the checkbox "new calculation of gravity and anomalies" is not relevant.
If you already have the stations in the model, keep the checkmark in this checkbox if you want to perform the calculation of gravity and anomalies after triangulation, and click Finish.
If you want to calculate the gravity and anomalies later, uncheck the box.
You can do this later by selecting the Tools → Re-Calculate Anomaly option in the Menu Bar or using the icon 
.
The result of the triangulation will appear in the 3D View:
Setup body parameters¶
Calculation of anomalies requires the definition of the physical parameters of the model bodies - densities for gravity modelling and susceptibilities for magnetic modelling.
Go to the Body Manager Tab.
The list of bodies contains the default name for bodies (new_body) and the name for the surrounding reference body (reference).
To add density, choose Add Parameter, select Units (e.g. t/m), select Type - "Density".
Set the two density values for the two bodies, e.g. keep 0.0 t/m for the "reference body" and set 1.0 t/m for the "new body". To do this, double click Left Button on the value and enter the new one:
In a similar way, you can assign other parameters to the bodies, e.g. susceptibility.
Note
If the parameter already exists, IGMAS+ will inform you about it. It is not possible to overwrite the existing parameters by accident. Instead, you can change the existing parameters manually or by assigning the same value to all of them. For that click Right Button on the parameter name in te table header in the Body Manager Tab and select Set/Add Values to... in the context menu:
Setup stations¶
Create station grid¶
There is a possibility to create a grid of stations in the model.
This is useful in case you want to create a model with a regular grid of stations, e.g. for testing purposes.
Choose Tools → Create Station - Grid.
The Station Grid window will open:
Enter the area of the stations: The origin of the grid (X, Y), the size of the station grid (Distance in and ) and the grid step (X-Step, Y-Step).
The total number of stations is calculated automatically and is shown in this window as well.
The stations are displayed as red dots, the station area (surface triangulated in between station points) is reddish:
Import stations¶
If you have measured data at the stations, you can import it into the model.
For instance, we can use a CSV file with X, Y, Z coordinates and height.
For that in the Menu Bar select File → Import → Stations:
and pick the corresponding file with the data.
More information on how to import the station data can be found in the Import stations chapter.
Calculate anomalies¶
Once the model is triangulated, stations are created and imported, and the body parameters are set, you can calculate the anomalies.
To do this, select the Menu Bar and choose Tools → Calculate Anomaly or use the icon 
.
Select the type of anomaly you want to calculate (e.g. calc Gz).
Click Finish to accept the changes and start the calculation.
The result will be shown in the 3D View:
To see the calculated anomalies in the 2D View, select Add View in the Tool Bar and then select 2D View:
