Premium
Accounting for lateral variations of the upper mantle gradient in P n tomography studies
Author(s) -
Phillips W. S.,
Begnaud M. L.,
Rowe C. A.,
Steck L. K.,
Myers S. C.,
Pasyanos M. E.,
Ballard S.
Publication year - 2007
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2007gl029338
Subject(s) - geology , tomography , velocity gradient , mantle (geology) , geodesy , temperature gradient , seismic tomography , geometry , geophysics , physics , mathematics , optics , meteorology , mechanics
The effect of an upper mantle velocity gradient on regional arrival times has been approximated by a cubic distance term, which can be extended to two dimensions for use in tomographic studies. To demonstrate this, we add a laterally varying upper mantle gradient to the standard P n time‐term tomography technique, and apply to a data set from Asia compiled using ground truth, event location criteria. We observe strong lateral variations in the gradient, ranging from −0.001 to 0.003 s −1 , with high gradients associated with the Tethys convergence zone. The gradient patterns may reflect lateral variations in the thermal gradient of the mantle lid. Variance reduction is 63% with respect to P n tomography without gradients. Adding gradients allows the use of longer path lengths, improving velocity image definition in high‐gradient regions with sparse station distribution, such as Tibet.