This research is to utilize a finite-difference computer program to simulate dynamic rupture fault propogation on non-coplanar fault segments. This 3-D treatment allows the incorporation of fault segment lengts, widths, and depths, stress levels, and velocity structure. For large earthquakes that break through the entire seismogenic zone, the only barrier that remains to terminate the rupture and limit the size of the earthquake must lie along the strike of the fault. A segment can be one of these barriers, but fault segmentation is observed at many different length-scales in the field. The purpose of this project is to quantify the size of this barrier which can control the length of earthquake rupture. This research is a component of the National Earthquake Hazard Reduction Program.