PNNL

Abstract

We re-examine the utility of teleseismic seismic complexity discriminants in a multivariate setting using United Kingdom array data. We measure a complexity discriminant taken on array beams by simply taking the logarithm of the ratio of the P wave coda signal to that of the first arriving direct P wave (?CF). The single station complexity discriminant shows marginal performance with shallow earthquakes having more complex signatures than those from explosions or deep earthquakes. However, when combined with the mb – Ms discriminant significant improvements are observed. In particular, signal complexity can be used to improve discrimination performance over mb – Ms alone as well improve differentiation between shallow and deep earthquakes. When complexity discriminants are combined with mb – Ms there is a tendency for explosions, shallow earthquakes and deep earthquakes to form three distinct populations. Importantly, multistation complexity discriminants have false alarm rates similar to those observed for network mb - Ms in support of predictions based on simulations of Bowers (1996).