What Are Aftershocks, Foreshocks and Earthquake Clusters?
The calculations in this system are based on known behaviors of aftershocks. Scientists have shown that the rules governing aftershock behavior also apply to “aftershocks” that are larger than their main shock – i.e., the possibility that the first event was a foreshock. These rules include: Aftershock Facts: In a cluster, the earthquake with the largest magnitude is called the main shock; anything before it is a foreshock and anything after it is an aftershock. A main shock will be redefined as a foreshock if a subsequent event has a larger magnitude. The rate of main shocks after foreshocks follows the same patterns as aftershocks after main shocks. Aftershock sequences follow predictable patterns as a group, although the individual earthquakes are random and unpredictable. This pattern tells us that aftershocks decay with increasing time, increasing distance, and increasing magnitude. It is this average pattern that this system uses to make real-time predictions about the probabilit
