Regional arrivals, similarly to short-period teleseismic P waves, have a spectral structure that the Fourier transforms of individual sensors at arrays for events located in limited source regions can be decomposed into source and site spectral factors. This structure has been demonstrated to be valid for Pn and Lg arrivals at NORESS. This property of regional arrivals can be exploited for: (a) Grouping events with respect to relative location; (b) Identifying events with differing source mechanisms; and (c) Finding differences in the source time functions between closely spaced events.
Potentially useful techniques for accomplishing such analyses consist of computing site-averaged interevent coherences, interevent and intersite equalization methods combined with correlation techniques. The advantage of such approaches is that we need not know much about the propagation characteristics (Green's functions) along the paths to an array.