  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.
