Correction of earthquake location estimation in a small-seismic-array system

Abstract

An array of regularly spaced seismic stations can estimate the location of a distant earthquake using arrival times at the stations of seismic waves generated by the earthquakes. However, the accuracy decreases as the distance to the epicentre of the earthquake from the array increases. This paper is concerned with the modification of the estimated location by removing its bias which is locally systematic but globally complex, reflecting the structure of the Earth's interior. Spline surfaces are used to model such biases. Then a Bayesian procedure is carried out not only to tune the smoothness constraints but also to select the best combination among various sums of squares of differently weighted residuals and various roughness penalties for the smoothing. Using the estimated splines of the posterior mode, the newly determined epicentre locations are transformed to confirm its practical utility. Residual distributions show that our procedure improves the modification by the conventional procedure. A spatial pattern of the residuals reveals some geophysical characteristics.