Long-term slip rates and characteristic slip:: keys to active fault behaviour and earthquake hazard

Over periods of thousands of years, active faults tend to slip at constant rates. Pioneer studies of large Asian faults show that cosmogenic radionuclides (Be-10, Al-26) provide an unparalleled tool to date surface features, whose offsets yield the longest records of recent cumulative movement. The technique is thus uniquely suited to determine long-term (10-100 ka) slip rates. Such rates, combined with coseismic slip-amounts, can give access to recurrence times of earthquakes of similar sizes. Landform dating morphochronology - is therefore essential to understand fault-behaviour, evaluate seismic hazard, and build physical earthquake models. It is irreplaceable because long-term slip-rates on interacting faults need not coincide with GPS-derived, interseismic rates, and can be difficult to obtain from paleo-seismological trenching. (C) 2001 Academie des sciences Editions scientifiques et medicales Elsevier SAS.