Locating earthquake epicenter without a seismic velocity model

TL;DR

This paper introduces a novel seismic epicenter location method that does not require a seismic velocity model, using a linear relationship between log distance and log travel time, effective even with poorly known Earth structures.

Contribution

The method derives from dimensional analysis and applies a linear log-log relationship to locate earthquake epicenters without an Earth velocity model, demonstrated on real seismic data.

Findings

97.2% of epicenters located within 0.1° error

Effective in areas with poorly known seismic velocity structures

Suitable as a starting point for other location methods

Abstract

We present a method for locating the seismic event epicenters without assuming an Earth model of the seismic velocity structure, based on the linear relationship between $\log R$ and $\log t$ (where $R$ is the radius of spherical P wave propagated outwards from the hypocenter, $t$ is the travle-time of the P wave). This relationship is derived from the dimensional analysis and a lot of theoretical or real seismic data, in which the earthquake can be considered to be a point source. Application to 1209 events occurred from 2014 to 2017 in the IASPEI Ground Truth (GT) reference events list shows that our method can locate the correct seismic event epicenters in a simple way. $\sim 97.2$ % of seismic epicenters are located with both longitude and latitude errors $\in[-0.1^\circ, +0.1^\circ]$. This ratio can increase if with a finer search grid. As a direct and global-search location, this method may be useful in obtaining the earthquake epicenters occurred in the areas where the seismic velocity structure is poorly known, the starting points or the constraints for other location methods.