Since the disastrous 1939 Erzincan earthquake, there have been seven earthquakes measuring over 7.0 on the Richter scale, each has happened at a point progressively further west. Seismologists studying this pattern, believe that earthquakes happen in "storms" over a number of decades and that one earthquake triggers the next. By analysing the stresses caused along the fault by each earthquake, they were able to forecast a disturbance that hit the town of İzmit with such devastating effect in August 1999. It is thought that the chain is not complete, and that an earthquake will soon strike further west along the fault - perhaps in the heavily populated city of Istanbul.