Open AccessImaging upper‐mantle discontinuity topography usingunderside‐reflection data
Author(s) -
Neele Filip,
Regt Han de
Publication year - 1999
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1046/j.1365-246x.1999.00768.x
Subject(s) - classification of discontinuities , geology , discontinuity (linguistics) , wavelength , fresnel zone , amplitude , inversion (geology) , slab , geometry , seismology , geodesy , optics , geophysics , mathematics , tectonics , mathematical analysis , physics , diffraction
This paper presents a method to invert underside‐reflection ( P d P or S d S arrivals) data for lateral depth variations of upper‐mantle discontinuities, combining traveltime and amplitude data. The method greatly improves the resolution of small‐scale undulations obtained by existing imaging methods and does not suffer from the long‐wavelength biases that are likely to be present in currently available models. Existing inversion methods account for the large size of the Fresnel zone of underside reflections, but not for its complexity, arising from the mini‐max traveltime nature of PP‐ and SS ‐related waves. This neglect results in long‐wavelength artefacts from small‐scale undulations of the discontinuities, obscuring true long‐wavelength depth variations. The inversion method presented in this paper uses a complex‐valued sensitivity kernel, derived from the representation of underside reflections through a Kirchhoff integral formulation. The sensitivity kernel accounts for the varying sensitivity of the waveforms to discontinuity structure over the Fresnel zone. The method is applied to a large, synthetic data set. The data set consists of P d P amplitudes and traveltimes. The results show that the new inversion method resolves depth variations on a lateral scale that is smaller than the size of the Fresnel zone of individual underside reflections (but larger than the dominant wavelength), retaining the resolution of large‐scale variations. The results presented here suggest that the discontinuity depth variations induced by slab penetration of the 670 discontinuity could be resolved by current broad‐band P 6 7 0 P data sets.