T. Hara et al., INVERSION FOR LATERALLY HETEROGENEOUS UPPER-MANTLE S-WAVE VELOCITY STRUCTURE USING ITERATIVE WAVE-FORM INVERSION, Geophysical journal international, 115(3), 1993, pp. 667-698
In contrast to previous work, which treats the Earth's lateral heterog
eneity as an infinitesimal perturbation to a spherically symmetrical s
tarting model, we conduct iterative linearized waveform inversion for
the Earth's laterally heterogeneous structure. We use the Direct Solut
ion Method (DSM) (Geller et al. 1990a) to calculate synthetic seismogr
ams and their partial derivatives for a laterally heterogeneous earth
model. We invert surface-wave data from the IDA and GEOSCOPE networks.
We expand the lateral heterogeneity of rigidity in spherical harmonic
s up to angular order number 8 and use three parameters to specify the
depth dependence of each harmonic, giving us a total of 240 unknowns.
The short-wavelength lateral heterogeneity (s = 4, 6 and 8) in the de
eper part of the upper mantle obtained by this study differs significa
ntly from M84A. The relative improvement in the variance reduction as
compared with model M84A is about 20 per cent for the IDA data and mor
e than 100 per cent for the GEOSCOPE data.