Analyzing Topographic Profiles of the Surprise Valley Fault to Determine Age

The Surprise Valley fault is a normal fault located in the northwestern portion of the Basin and Range province. In the last ~20 ka the Surprise Valley fault has experienced 5 major surface-rupturing earthquakes, and numerous fault scarps are present along its length. Analysis of topographic profiles across fault scarps can provide evidence for (1) the number of earthquakes whose surface ruptures are visible, and (2) the age of the fault scarps. Thus, analysis of many topographic profiles from multiple locations along the Surprise Valley fault can determine whether the current surface deformation is the result of one large earthquake or separate earthquakes over smaller segments of the fault. Analyzing topographic profiles involves measuring the slope of the scarp, comparing these slopes between all profiles, and grouping them accordingly. Age of fault scarps can be determined through the use of diffusion equations, and tied to known earthquake age data. If all the slopes are similar and a single event is indicated, offset can be determined and mapped. If multiple groups and, therefore, events are indicated, each group of fault scarps can be tied to a known earthquake in the past. These data can then constrain the magnitude of past earthquakes. This work will facilitate comparison of the motion and seismic hazards of the Surprise Valley fault with other known faults of the Basin and Range in its northwestern reaches