Scientists say the plates move relative to one another at speeds ranging from 0.5 to 8 inches a year. Large tremors usually occur at the boundaries of tectonic plates. These stresses build until the fault suddenly snaps, setting off an earthquake. The San Andreas fault that cuts down through California is also a strike-slip fault. In an earthquake, stresses are relieved along the section where the fault slips, but increase in nearby areas that are still stuck.
Geologists see the North Anatolian fault almost like a buttoned shirt being pulled apart.
When one button pops off, that transfers the stress to the next button, making it the one likely to pop off next. Jim Dewey of the U.S. Geological Survey in Boulder, Colo., suggests a run in a stocking as another analogy. Once it gets going, it keeps going. Those observations confirmed that stress was building up along the northern branch of the fault, the one that runs near Izmit. A continuous monitoring system was planned for the region, which may have provided some warning.