Key points are not available for this paper at this time.
Author Posting. © Blackwell, 2004. This article is posted here by permission of Blackwell for personal use, not for redistribution. The definitive version was published in Geophysical Journal International 157 (2004): 988–1006, doi:10.1111/j.1365-246X.2004.02203.x.
Chave et al. (2004) studied this question.