Geology Version

Geological oceanography course has the current directions.  Those below might be out of date.

The geology version of MICRODEM has a limited menu and toolbar:

Viewing and visualizing terrain

Measuring fault scarps

Earthquake focal mechanisms


DEM opened, and earthquake focal mechanisms selected with plotting by colored symbols.

Plot single focal mechanism on the map by clicking

One of the two nodal planes will be the fault plane.

The southwestern earthquakes lies in a valley, far away from any bedrock exposures.  The strike appears to be approximately east-west, and the ridge to the southeast might represent the fault scarp.

This shows the result of using the three point problem (on the structural geology computation window).  After selecting three points on the SW side of the ridge, the computer calculated the plane which passes though them (N63W 21SW), and shows where its outcrop would project.

The plane passes close to the epicenter, but the focus is 35 km deep, which would affect the results depending on which of the two focal planes represented the fault rupture surface.

This dip is significantly different than the two focal planes ( N76W 45N, and N82E 47S), and the strike is different from the focal plane with a south dip).

The ridge is probably not a fault line scarp from the fault associated with this earthquake.

Calculate menu has a Bearing tool is being used to measure the trend of the long linear valleys in the NW part of the map, as they could be related to a fault.

The 115 degrees measured is N75W, fairly close to the second focal plane.  The segment closer to the dialog box actually has an even closer fit.

The large number of valleys and lineaments oriented NW-SE suggest that the second focal plane may well be the orientation of the fault.

Record of the southeastern of the two earthquakes, obtaining by using  Identify data base records button on the map toolbar or the database table display and then double clicking on the epicenter. Explanation of the fields.

The two possible fault planes have nearly identical strikes (284 and 82) and dips (45 and 47), but have very different dip directions.  The dip direction is not in the data base, but can be computed as 90 degrees clockwise from the strike.  In this case, Plane 1 dips to the N (284+90=374=14, and Plane 2 dips to the S (82+90=172).  Standard geological shorthand for the two planes would be N76W 45N, and N82E 47S.http://

Record of the northwestern of the two earthquakes, obtaining by using the Identify data base records button on the map toolbar and then double clicking on the epicenter. 

The two planes are N36E, 74SE and N58W, 75NE

OpenGL 3D view of faults and their scarps.  This was selected on the Landsat TM of the area, so the view combines the satellite imagery with SRTM topography.  You can rotate and zoom the view.
Variable opacity merge combines  TM satellite imagery with a reflectance view of SRTM DEM.  This emphasizes the fault scarps, although the direction of lighting in the reflectance view determines which faults will be highlighted.  In this option you can interactively adjust the opacity, and which of the two scenes dominates the display.

Last revision 10/8/2014