Reducing Systematic Errors for Seismic Event Locations in Anisotropic Regional Structures
Abstract
In CTBT applications many events of interest are only detected at regional distances. Providing more accurate prediction of P-wave propagation at regional distances is therefore of particular importance in seismic event location. At such distances (2-14) the phase Pn is the seismic phase that is most frequently reported and which thus controls the location accuracy. We are working on reducing systematic errors in Pn travel-times and thus seismic event location at regional distances. In recent work the P.I. has mapped lateral and anisotropic variations in Pn velocities beneath continents across the globe (Smith and Ekstrom, 1999). This work provides the most comprehensive and possibly most accurate mapping of anisotropic Pn velocities available to date. While the lateral variations in Pn velocities that were mapped were strong, and are likely to contribute to improved location capabilities, strong (up to 10%) anisotropic signatures were also observed. The horizontally travelling Pn phase should therefore accumulate large travel time residuals due to both heterogeneity and anisotropy, which would result in large systematic location errors. The question remains whether this new mapping can provide, in a practical sense, significant reductions in systematic event mislocation at the regional scale. Preliminary results indicate that, even in areas of good station coverage, a distinct difference in location is obtained using anisotropic models.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 2000
- Accession Number
- ADA529941
Entities
People
- Douglas A. Wiens
- Gideon P. Smith
Organizations
- University of Washington