Databases of surface wave dispersion

S. Carannante, L. Boschi

Abstract


Observations of seismic surface waves provide the most important constraint on the elastic properties of the Earths
lithosphere and upper mantle. Two databases of fundamental mode surface wave dispersion were recently compiled
and published by groups at Harvard (Ekström et al., 1997) and Utrecht/Oxford (Trampert and Woodhouse, 1995,
2001), and later employed in 3-d global tomographic studies. Although based on similar sets of seismic records,
the two databases show some significant discrepancies. We derive phase velocity maps from both, and compare
them to quantify the discrepancies and assess the relative quality of the data; in this endeavour, we take careful account
of the effects of regularization and parametrization. At short periods, where Love waves are mostly sensitive
to crustal structure and thickness, we refer our comparison to a map of the Earths crust derived from independent
data. On the assumption that second-order effects like seismic anisotropy and scattering can be neglected, we find
the measurements of Ekström et al. (1997) of better quality; those of Trampert and Woodhouse (2001) result in
phase velocity maps of much higher spatial frequency and, accordingly, more difficult to explain and justify geophysically.
The discrepancy is partly explained by the more conservative a priori selection of data implemented by
Ekström et al. (1997). Nevertheless, it becomes more significant with decreasing period, which indicates that it
could also be traced to the different measurement techniques employed by the authors.

Keywords


seismic tomography;upper mantle;lateral resolution;azimuthal anisotropy

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References


DOI: https://doi.org/10.4401/ag-3245
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Published by INGV, Istituto Nazionale di Geofisica e Vulcanologia - ISSN: 2037-416X