Travel-time corrections for stations in the Guangdong seismic network and their impact on earthquake location accuracy

Abstract

The travel-time corrections for the primary seismic phases of 72 stations in the Guangdong seismic network, relative to the 1D South China travel-time model, were determined using joint hypocentral determination (JHD) and statistical analysis methods. The travel-time corrections for the Pg phase of 72 stations range between −0.25 ​s and 0.14 ​s, while the corrections for the Sg phase range between 0.27 ​s and 0.35 ​s, and those for the Pn phase are between −0.86 ​s and 0.07 ​s. The spatial distribution of travel-time corrections for Pg, Sg, and Pn phases of 72 stations correlates well with the geological structure in this region. This indicates that the travel-time corrections for Pg and Sg phases are mainly caused by the discrepancy between the actual crustal velocity structure beneath the stations and the 1D South China travel-time model. These corrections empirically compensate for systematic travel-time errors arising from such discrepancies. The primary factor contributing to the travel-time corrections for the Pn phase is the Moho undulations or tilt. These corrections are intended to compensate for systematic errors in travel time caused by variations in the actual Moho. By integrating the obtained travel-time corrections into the HYPO-SAT location algorithm, test results showed an obvious improvement in location accuracy and origin time precision for explosion events. The variation of horizontal distance between repeating earthquake pairs has also improved, with 86% of the repeating earthquake pair spacing being more accurately estimated after correction. This suggests the crucial significance of travel-time correction in earthquake location, and the consideration of travel-time correction exerts a notable impact on enhancing earthquake location accuracy.