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Range of Earth structure nonuniqueness implied by body wave observations
Author(s) -
Wiggins Ralph A.,
McMechan George A.,
Toksöz M. Nafi
Publication year - 1973
Publication title -
reviews of geophysics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 8.087
H-Index - 156
eISSN - 1944-9208
pISSN - 8755-1209
DOI - 10.1029/rg011i001p00087
Subject(s) - inversion (geology) , mantle (geology) , perturbation (astronomy) , earth model , inner core , physics , core–mantle boundary , geology , earth structure , geophysics , travel time , geodesy , computational physics , seismology , quantum mechanics , transport engineering , engineering , tectonics
The Herglotz‐Wiechert integral for the direct inversion of ray parameter versus distance curves can be manipulated to find the envelope of all possible models consistent with geometrical body wave observations (travel time and ray parameter versus distance). Such an extremal inversion approach has been used to find the uncertainty bounds for the velocity structure in the mantle and core. We find, for example, that there is an uncertainty of ±40 km in the radius of the inner core boundary, ±18 km at the core‐mantle boundary, and ±35 km at the 435‐km transition zone. The velocity uncertainty is about ±0.08 km/sec for P and S waves in the lower mantle and about ±0.20 km/sec in the core. Experiments with various combinations of ray types in the core indicate that rather crude observations of SKKS‐SKS travel times confine the range of possible models far more dramatically than do the most precise estimates of PmKP travel times. Comparisons of results from extremal inversion and linearized perturbation inversions indicate that body wave behavior is too strongly nonlinear for linearized schemes to be effective for predicting uncertainty.