Condensed from a paper published by the Geophysical Institute of the University of Zagreb (Ser. III, No. 8, 1957).
C. Zeissig has given a graphical method for determining an epicenter by using direction lines which have been derived from the P times on pairs of stations.
By a modified procedure it is possible—assuming an approximate value for the epicenter and the origin time—to draw the direction lines as straight lines on a large-scale map, whereby a preliminary condition for an accurate location of an earthquake is obtained.
As the most probable epicenter there can be taken the center of gravity of selected intersection points of reliable direction lines. The selection itself is based on criteria which follow from a detailed study of the reliability of the lines and points.
As an illustration of the method, a solution is given for one earthquake.