Temporal clustering of paleoseismic events on the Oued Fodda Fault, Algeria

Paleoseismic investigations of the Oued Fodda Fault, which underwent surface-fault rupture during the Algeria earthquake of October 10, 1980 (M (sub s) 7.3), indicate that the average recurrence interval based on the long-term geologic slip rate (past 100 ka) is at least an order of magnitude longer than the intervals between recent surface-faulting events, which are determined by radiocarbon dating of faulted colluvial deposits exposed in trenches across the fault. Evidence from trenches excavated across the 1980 surface rupture indicates that there have been at least three and possibly four surface-faulting events on the Oued Fodda Fault during the past 1.5 ka (including the 1980 earthquake). The cumulative slip on the Oued Fodda Fault was produced by relatively short episodes characterized by frequent displacements (surface-faulting events every hundred years) separated by long periods of quiescence lasting several thousands to tens of thousands of years.--Modified journal abstract.