Global Test of Seismic Event Locations Using Three Dimensional Earth Models
By Qi-fu Chen and Raymond J. Willemann
In order to update ISC global location procedure with three-dimensional Earth models it is necessary to adequately investigate the effect of different models. In this paper, we conduct a global test for location accuracy using two different 3-D models and three 1-D models with different distance range of P-phase data. The 3-D models include one spherical harmonic model (SP12) and one irregular grid model (KH07) which are represented in terms of different 3-D model parameterizations. The worldwide distributed events from pIDC ground-truth database, EHB98 catalogue, and well study explosions and earthquakes were selected to perform our global test.
Our study demonstrates clear significant improvement in event locations over any of the 1-D models (J-B, PREM, ak135). The irregular grid 3-D model KH07 offers the possibility to compute accurate earthquake hypocenters with regional and local phase data, which is very important constraint to location accuracy. It provides the possibility to approach same epicenter accuracy for earthquakes and explosions. Based on the global test, the mislocation distributions of different F-E geographical and seismic regions were summarized, and we found that the error for the high active seismic belts is obviously smaller than other areas. The application comparison for an actual one-month Bulletin clearly displays that 3-D model KH07 improved residuals and location uncertainty compared to those in the ISC Bulletin.
Test Events used by Global Test of Seismic Event Locations Using Three Dimensional Earth Models are available for ftp from the ISC.
Test Data Selection
This page provides a capability to select from the results of the one month trial, January 1998, of event locations using the KH07 three dimensional Earth model.
Author ISC_JB is the ISC location using JB 1 dimensional model which was published for January 1998.
Author ISC_KH07 is the ISC location using KH07 3 dimensional model.
The inital starting point used for the relocation using KH07 3 dimensional model was the prime origin from the published Bulletin for January 1998. Where this was and ISC epicentre the author will be ISC_JB, where the inital author was not ISC they are indicated with _INIT appended to the agency name.
The standard guidlines for the normal ISC web search apply.