Standard Rupture Format

Duo edited this page Sep 27, 2018 · 9 revisions

SeisSol supports the Standard Rupture Format (SRF) for kinematic rupture models. Details about the file format can be found at the SCEC Wiki. With help of the SRF format, one may specify several subfaults (point sources), where one may give individual source time function for each subfault. The location, however, is given in latitude, longitude, and depth such that it becomes necessary to convert those into the coordinate system used by the mesh, which we call the Mesh Coordinate System (MCS). In a software package, one usually has the option to directly convert coordinate systems during runtime or to use an intermediate format which does not require coordinate conversion. Here, we opted for the second approach, because

  • we do not complicate the build and use of SeisSol and
  • we are able to use a binary format which greatly reduces the loading time.

Hint: Use krfviewer to inspect Standard Rupture Format files and to test projections.

Note: There is a slit difference in SRF version 1.0 and 2.0.
Point line 1 in 1.0: longitude latitude depth strike dip area tinit dt.
Point line 1 in 2.0: longitude latitude depth strike dip area tinit dt vs den.

NetCDF Rupture Format (NRF)

The NRF is an intermediate format for describing kinematic rupture models. It is not meant to be used directly but it should be generated from a SRF file. To do so, you require the tool rconv. Note that some python scripts required for compiling rconv are given as a symbolic link in rconv, the link being a relative path. This mean that you need the whole SeisSol repository to compile it.

Specifying the MCS

The main input parameter of rconv is the specification of the MCS. It is very important to specify it right, otherwise you will get wrong moment tensors and wrong subfault locations. The MCS can be specified by a string describing its projection in the same way as you would use the cartographic software proj.4. For example,

+proj=utm +zone=10 +datum=WGS84 +units=m +axis=ned +no_defs

would lead to UTM projection of latitude and longitude and

+proj=geocent +datum=WGS84 +units=m +axis=seu +no_defs

would lead to a geocentric coordinate system. You can test the correctness of your projection string by invoking cs2cs from the proj.4 application suite. For example,

echo 11.669 48.263 0.476 | cs2cs +proj=lonlat +datum=WGS84 +units=km +to +proj=utm +zone=33 +datum=WGS84 +units=m +axis=ned

Besides correct projections, it is also important to specify the axis orientation with the +axis option. Examples:

  • +axis=ned: x=north, y=east, z=down
  • +axis=enu: x=east, y=north, z=up
  • +axis=seu: x=south, y=east, z=up

If the axis description does not fit your mesh, your moment tensor will not be rotated correctly (according to strike, dip, and rake angles).

How to use Rconv

To use e.g. Mercator projection, you can run

rconv -i input.srf -o output.nrf -m “+proj=merc +lon_0=central_longtitude +y_0=translation_along_y +x_0=translation_along_x +units=m +axis=enu” -x visualization.xdmf

More projection options can be found in proj.4 website.

Checking the NRF file

You may manually inspect a NRF file in order to verify its correctness. If you have NetCDF installed, you may enter

ncdump -v subfaults sources.nrf | less

and obtain something like

  compound Subfault {
    double tinit ;
    double timestep ;
    double mu ;
    double area ;
    Vector3 tan1 ;
    Vector3 tan2 ;
    Vector3 normal ;
  }; // Subfault
...
	Subfault subfaults(source) ;
		Subfault_units subfaults:units = {"s", "s", "pascal", "m^2", "m", "m", "m"} ;
...
 centres = {23166.2135886125, -13374.980382819, 1250}, 
    {22733.1990108113, -13124.9814335668, 1250}, 
...
 subfaults = 
    {10.617000000043, 0.001, 0, 250000, {-0.866025403784439, 0.5, -0}, {3.06161699786838e-17, 5.30287619362453e-17, -1}, {-0.5, -0.866025403784439, -6.12323399573677e-17}}, 
    {10.446600000043, 0.001, 0, 250000, {-0.866025403784439, 0.5, -0}, {3.06161699786838e-17, 5.30287619362453e-17, -1}, {-0.5, -0.866025403784439, -6.12323399573677e-17}}, 

which tells you the following:

  • The first point source is located at x=23166.2135886125, y=-13374.980382819, z=1250.
  • The STF of the source starts acting after 10.617000000043 seconds.
  • The distance between samples in the STF is 0.001 seconds.
  • The shear modulus is 0 Pa, which means that SeisSol will take the shear modulus from the element in which the point source resides.
  • The subfault has an area of 250000 square meters. (Be careful, in the SRF you have to give it in square centimetres.)
  • u_1 = {-0.866025403784439, 0.5, -0}, u_2 = {3.06161699786838e-17, 5.30287619362453e-17, -1}, u_3 = {-0.5, -0.866025403784439, -6.12323399573677e-17}, where u_1 is the strike direction, u_2 is orthogonal to the strike direction but lies in the fault plane, and u_3 is the normal direction.

Using an NRF file in SeisSol

Add the following section to your parameter file:

&SourceType
Type = 42
FileName = 'sources.nrf'
/
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