Earthquake Focal Mechanisms

Option on Stats button  on table display window.

Requires a Harvard CMT project database file.  This  should only be selected for a limited subset of the data because the full database might take too much time, and if you want to see spatial patterns you need a small area with consistent patterns.

  • Focal mechanisms: draw all the focal mechanisms on a single image.
  • Graph by latitude
  • Graph by longitude
  • Graph by latitude (km units).
  • Graph by longitude (km units).  By default the graph will have no vertical exaggeration.

  • Focal planes on stereonet.  Too much data will probably make this very hard to interpret.  With a reasonable number of mechanisms, you can see trends.
    • There appears to be a single set of strike-slip faults, nearly vertical, with a strike either about N20E or N 70W.
    • There is a single set of normal faults, with a strike betweeen N50E and N90, with dips either to the N or S at about 45 degrees.
  • Poles to focal planes on stereonet (the pole is the line normal to the plane, which projects to a point on the stereonet.).  Too much data will probably make this very hard to interpret.
  • Dip directions for focal planes on stereonet.  Too much data will probably make this very hard to interpret.
    • The normal faults are in green, and there are two groupings: moderate dips down to the NW, and moderate dips down to the SE
Rose diagrams, strikes.  Example analysis.
Rose diagrams, dip directions.   Example analysis.
Insert dip directions and dip and strike.  Inserts four new fields, which allows you to get  output with the dip and strike or the dip direction.  You can then create tables with the information, or statistics on the dip directions.


  • Map query to restrict the data base to the region you want to investigate.
  • Graph earthquakes by depth against either latitude or longitude, color coded by focal mechanism, with the choice "Earthquake depth-focal mechanism" option from the Stats button of the Table display window.  
  • On the graph, ID a record by double clicking.  It will be highlighted (as in the one in the lower right of the graph), and display the earthquakes characteristics.

Display earthquake record, using 

  • ID button on the map toolbar,
  • ID button on the database toolbar.

Then double click on the map.

Tabs show the beach ball, and orientations of  focal planes.


Plotting options.

KML Beachball export

Last revision 3/26/2019