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.

testevents.txt Description of test data files
testevents.doc Description of test data files

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.

Selection Guidelines

The standard guidlines for the normal ISC web search apply.

A brief description of the format of the online Bulletin and of the links to additional data about the event is also available. Please note that Include links: must be checked to shown the links.

Start: Year: 1998 End: Year: 1998
Start: Month: 01 End: Month:
Start: Day: End: Day:
Start: Hour: End: Hour:
Depth inc. unknown
No. Phases inc. unknown
Magnitude About Magnitude Restrictions
Values inc. unknown
No. Amplitudes inc. unknown
Rectangular Region Circular Region
Maximum Latitude
Center Latitude
Center Longitude
Minimum Longitude
Maximum Longitude
Maximum Distance
Minimum Latitude
Degrees Kilometers
Include phases: Include secondary origins: Include magnitudes: Include comments: Include pP depths: Include headers: Include links: