EPICENTRE ACCURACY BASED ON SEISMIC NETWORK CRITERIA

Abstract

We establish reliable and conservative estimates for epicentre location accuracy using data that are readily available in published seismic bulletins. A large variety of seismic studies rely on catalogues of event locations, making proper assessment of location uncertainty critical. Event location and uncertainty parameters in most global, regional and national earthquake catalogues are obtained from traditional linearized inversion methods using a 1-D Earth model to predict traveltimes. Reported catalogue uncertainties are based on the assumption that error processes are Gaussian, zero mean and uncorrelated. Unfortunately, these assumptions are commonly violated, leading to the underestimation of true location uncertainty, especially at high confidence levels. We find that catalogue location accuracy is most reliably estimated by station geometry. We make use of two explosions with exactly known epicentres to develop local network location (0-2.5 deg) accuracy criteria. Using Monte Carlo simulations