Purpose

This panel is used to calculate the moment tensor and draw the focal mechanism of a list of geophysical sources.

An example involving this panel can be found in the tutorial.

Technical Note

This panel can be used to calculate the moment tensor of any source (Elastic Dislocation, Point Pressure), or source combination, and generate the related "beach ball" diagram, exportable as PDF file. This panel is automatically displayed after running a Non-Linear Inversion or a Linear Inversion. The beach ball diagram can be created in three ways:

•by adding sources to the source list interface, then clicking on "Start" (the "Direct draw" option must be unchecked);

•by directly writing the Strike, Dip and Rake angles, then clicking on "Start" (the "Direct draw" option must be checked);

•by directly writing the tensor elements Txx, Tyy, Tzz, Txy, Txz and Tyz, then clicking the "Focal Mech." button; X, Y and Z axes correspond to the East, North and Up directions, respectively;

Since the source list can contain sources of any type, the moment tensor is calculated accounting for all the shear and tensile components, as the opening of an Elastic Dislocation or the volume change of a Point Pressure source). To exclude from this calculation the tensile components, the "Use only shear components" option must be checked.

The "Seismic Moment" and the "Magnitude" are calculated only with the shear components, regardless whether the "Use only shear components" option is checked or not. When only tensile sources are present, the "Seismic Moment" and "Magnitude" values are set as not available. The same occurs when the moment tensor and the beach ball are calculated with the "Direct draw" option through the Strike, Dip and Rake angles.

The INPUT Sources folder allows to create, recover and setup the sources for which the tensor and the focal mechanism is calculated. Two sources are available: Elastic dislocation source, used to model the surface displacement induced by a dislocation over a source in an elastic and homogeneous half-space [Okada, 1985]; Point pressure source, used to model the surface displacement induced by an expanding or compressing point-source [Mogi, 1958]. The "Edit..." button must be used to properly set the source(s).

INPUT Sources

ADD SOURCES

New

Elastic Dislocation (Okada): open the panel to set the parameters of an elastic dislocation/opening

Point Pressure (Mogi): open the panel to set the parameters of a point volume source

Import

From Shapefile: add a source from an InSAR or GPS shapefile

From XML Project File…: retrieve a source from an existing XML Project File

From Global-CMT catalog…: open a panel to initialize the source parameters from the ID of an event from the Global CMT catalog (https://www.globalcmt.org/CMTsearch.html)

From USGS waveform inversion finite fault…: open a panel to create a source from the slip distribution provided by USGS and based on the waveform inversion (a link or a *.param file can be supplied)

EDIT SOURCES

Edit parameters…: set the source properties through a source dependent panel

Remove: remove the selected source(s) from the list

Options

Use only shear components

Exclude the volume change components from the moment tensor calculation (see the Technical Note)

Direct draw

Allow to enter the Strike, Dip and Rake angles to calculate the moment tensor and draw the beach ball

Tensor

Enter in the cells the tensor components Txx, Tyy, Tzz, Txy, Txz and Tyz components.

Reset

Cancel the Moment Tensor components.

Focal Mechanism

Draw the beach ball diagram from the Tensor components.

Save to PDF...

Save the beach ball diagram to a PDF file.

General Functions

Start

Start of the processing.

Cancel

The window will be closed.

Help

Specific help document section.

Specific Function(s)

None.

References

None.

Interferometry - Displacement Modeling - Tools - Calculate and Draw Focal Mechanism

Interferometry - Displacement Modeling - Tools - Calculate and Draw Focal Mechanism

Purpose