Unknown
In:
Geophys. Res. Lett., Luxembourg, Conseil de l'Europe, vol. 31, no. 9, pp. 1-4,
pp. L09602, (ISSN: 1340-4202)
Publication Date:
2004
Description:
We show that relative earthquake location using double-difference methods
requires an accurate knowledge of the velocity structure throughout the study region to
prevent artifacts in the relative position of hypocenters. The velocity structure
determines the ray paths between hypocenters and receivers. These ray paths, and the
corresponding ray take-off angles at the hypocenters, determine the partial derivatives
of travel time with respect to the hypocentral coordinates which form the inversion
kernel that maps double-differences into hypocentral perturbations. Thus the large-scale
velocity structure enters into the core of the double-difference technique. By employing
a 1D layered model with sharp interfaces to perform double-difference inversion of
synthetic data generated using a simple, 1D gradient model; we show that inappropriate
choice of the velocity model, combined with unbalanced source-receiver distributions,
can lead to significant distortion and bias in the relative hypocenter positions of
closely spaced events.
Keywords:
Seismology
;
Location
;
Velocity depth profile
;
Error analysis
;
7215
;
Seismology:
;
Earthquake
;
parameters
;
7230
;
Seismicity
;
and
;
seismotectonics
;
7260
;
Theory
;
and
;
modeling
;
8180
;
Tectonophysics:
;
Tomography
;
GRL
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