optically stimulated luminescence, pedology, and lichenometry (83). The principal isotopic techniques are radiocarbon, uranium series, helium, potassium-argon, argon-argon, and fission-track dating (84).
The radiocarbon technique is the workhorse for dating sediments younger than about 50,000 years, and its application has begun to supply the time series of large earthquakes for important continental fault systems (85). The advent of accelerator mass spectrometry (AMS) has enabled the carbon dating of samples much smaller than a gram or so by conventional techniques. Radiocarbon ages can be calibrated precisely to about 10,000 years before present using dendrochronology, yielding uncertainties as small as a decade or so. The development of AMS has also been a boon to uranium-thorium disequilibrium dating. Radiocarbon and uranium-thorium analyses of replicate samples have resulted in a calibration curve for radiocarbon dates to about 30,000 years, with uncertainties of a few hundred years (86).