A geometrical error in some computer programs based on the Aki-Christofferson-Husebye (ACH) method of teleseismic tomography

Citation
Br. Julian et al., A geometrical error in some computer programs based on the Aki-Christofferson-Husebye (ACH) method of teleseismic tomography, B SEIS S AM, 90(6), 2000, pp. 1554-1558
Citations number
9
Categorie Soggetti
Earth Sciences
Journal title
BULLETIN OF THE SEISMOLOGICAL SOCIETY OF AMERICA
ISSN journal
00371106 → ACNP
Volume
90
Issue
6
Year of publication
2000
Pages
1554 - 1558
Database
ISI
SICI code
0037-1106(200012)90:6<1554:AGEISC>2.0.ZU;2-T
Abstract
Some computer programs based on the Aki-Christofferson-Husebye (ACH) method of teleseismic tomography contain an error caused by identifying local gri d directions with azimuths on the spherical Earth. This error, which is mos t severe in high latitudes, introduces systematic errors into computed ray paths and distorts inferred Earth models. It is best dealt with by explicit ly correcting for the difference between true and grid directions. Methods for computing these directions are presented in this article and are likely to be useful in many other kinds of regional geophysical studies that use Cartesian coordinates and flat-earth approximations.