This thesis addresses the use of Geographic Information Systems to create accurate geological maps for a portion of the San Andreas fault zone near Parkfield, California. Such maps are needed in field studies currently underway at the San Andreas Fault Observatory at Depth (SAFOD). Geologic data recently collected for the area must be put into digital format for further scientific studies related to earthquakes.

Two software tools, Environmental Systems Research Institute's (ESRI) ArcGIS and Adobe Illustrator, are used to draw the fault linework. Then, the two sets of digital map data are displayed in ArcGIS as separate layers for analysis. Using the measurement tool in ArcGIS, the distances between fault lines drawn in each of the two software packages and fault lines drawn on the aerial photo in the field are determined. Testing and analysis concludes in acceptable software accuracy results. Detailed steps, findings, and comparison of the two methods ensues.