4. Declustered earthquake catalog without duplicates for the western U.S.

In processing step 3, declustering is applied to flag aftershocks and foreshocks in catalog wmm.c2. Each earthquake is considered a potential mainshock, and an algorithm searches for events within a specified distance from its epicenter and time after its origin (Gardner and Knopoff, 1974). A smaller earthquake found within a window is an aftershock. If a larger earthquake is found, the first earthquake is a foreshock of the larger one. WUS catalog wmm.c3 is produced by deleting aftershocks and foreshocks from wmm.c2; it consists of statistically independent earthquakes with moment magnitudes greater than or equal to 2.5.