Abstract
We devise and apply a method to account for the effect of the aspherical
structure of the Earth in locating earthquakes. This technique relies
upon the ability to detect the average structural signal present
in the residuals between source and receiver and correct for this
signal during location, using a phenomenological description that
we call Empirical Heterogeneity Corrections (EHC). EHC are employed
in the relocation of a large set of well-constrained teleseismic
earthquakes selected among the events reported by the Bulletins of
the International Seismological Centre 1964-1995. The rms length
of EHC relocation vectors for these events is about 10ukm. The method
is also tested against a selected set of ground-truth events, both
earthquakes and explosions, whose locations are independently known
by nonseismic means. The rms length of the mislocation vectors for
the test events, compared to their original mislocation in the reference
1-D model SP6, is reduced in the EHC relocation by 17\% for explosions
and 12\% for earthquakes. Our technique provides a successful alternative
to the use of 3-D structural models, approximately reaching the same
value of effectiveness in improving event location.
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