This paper is to suggest two algorithmic methods for providing fast scans to localize Hypocenter depths, given, first, a spheroidal Epicenter position and then incorporating the geometry of a spheroidal Earth model. The system formed to fulfill this aim consists of: knowledge of the sensor net in active receipt of the Earthquake energy (P-wave onset-timings, station coordinates); the generation of the set of spheroidal geodesics from Epicenter to individual stations; the scanning algorithm deployed and the capture of the data output from this. In this paper three algorithm methods are proposed for the scan: an “Orthogonal” mode and an “Oblique” mode and an “Orthogonal Spherical” mode. Further, this latter fast algorithm is described as employing only a reduced Earth model in the form of a Sphere. However, this latter exposition is not the main objective. The main object is to improve the accuracy of the Hypocenter localization by incorporating spheroidal geodesics at speed.

Key Words: Earthquake, Epicenter, Hypocenter, Spheroid, Geodesic, Orthogonal Transform.