Potrillo Volcanic Field - Fault Scarps

Fault Scarps

The approximate age of the East Potrillo’s faulting is estimated to be around 57,000 to 377,000 years. The age of the faulting was determined by the utilization of three different processes that show similar results on the dates of the faulting on the east Potrillo mountains that is caused by the Rio Grande rift. The first method to determine age was the scarp heightslope- angle relationship created by Buckman and Anderson in 1979. The maximum scarp angle increases approximately linearly with the logarithm of the scarp height. In other terms, plotting the maximum height of a slope versus the maximum slope angle allows the age of the fault to be estimated; since the shallower the angle is the older the fault scarp becomes.

The second method used was the linear-plus-cubic diffusion, which is a model of fault scarping. This method uses the diffusive process on hill slopes, such as rain-splash and wind erosion, that move sediment down hill. t = t’(SO)*2/k (0). The last method used to date the faulting was the morphologic dating without numerical model. Such a technique requires that down slope debris instability is a timedependent function of slope angle, in units of volume per time per length of contour (Nash, 2005). The scarp ages can be determined based on the relationship Ta/Tb = H*-2 b / H-2 b From the first method we can conclude that there were at least five seismic events that did not occur at the same time. From method two we can say than the faulting ages between 57ka to 377ka with surface offset of 11.2m that had a magnitude of 6-7 earthquakes. Finally the third method of dating concludes that the relative ages of the east Potrillo fault scarps ranges form 153,000 to 239,000.