Description
The most recent large Laguna Salada fault rupture occurred at 23:20 Pacific Standard Time on February 23, 1892 and exhibited oblique normal-dextral slip. The moment magnitude was estimated to be Mw7.2, with maximum intensity (MMI) of X in the western Imperial Valley and VII (Severe) in San Diego. This fault exhibited about 55 km of surface faulting, with horizontal displacement as large as 4 m and dip slip as high as 5 m. To further examine the extent of this earthquake, a pair of fault scarps in the Yuha Desert that were suspected as possibly having ruptured in 1892 were chosen to examine. These scarps were chosen because on aerial imagery, they could be seen crossing late Quaternary alluvium, and thus were suspected to be young. They were analyzed by first profiling the scarps, followed by calculations of the scarp ages using diffusion modeling. Finally, scarp profiles were compared to data from known examples of surface ruptures of the 1892 earthquake. It was ascertained that both scarps were possibly a result of the 1892 earthquake or one of its aftershocks.
