Earthquake histories and Holocene acceleration of fault displacement rates

Displacement rates for normal and reverse faults (n = 57) are generally higher when averaged for the Holocene (~10 ka) than for the late Quaternary (~300 ka) and longer time scales. Holocene acceleration of displacement rates could be attributed to geological processes that produce increases of tectonic tempo. We propose an alternative model in which the observed rate changes arise from variability in earthquake slip and/or recurrence coupled with a sampling bias toward those faults that are best represented at the Earth's surface and that accrued displacement fastest during the Holocene. This model is consistent with displacement rates measured over time intervals of as long as -300 ka for 129 faults from the Taupo Rift, New Zealand. Departures of earthquake parameters and associated displacement rates from their long-term (>300 ka) averages are attributed to fault interactions and occur on time intervals inversely related to these long-term displacement rates and to regional strain rates.