First let me tell you a little bit about how fission track works..
Fission tracks develop in a crystal over time as uranium spontaneously decays. The fission track age is therefore a function of the number of tracks that have formed.
FTs anneal (or shrink) rapidly as the temperature rises above about 100ÉC and if they completely dissappear, then a heated crystal can appear much younger. Becauese of annealing, a fission track age records the time since a crystal was last exposed to these high temperatures.
Our project compares crystals close to a fault with crystals far from the fault. Any difference in the ages of these samples is attributed to the effects of shear heating.