Computer re-evaluation of earthquake mechanism solutions

Abstract
A program has been written which determines the best positions of the P-nodal planes and B axis for any set of observations and defines the variations possible in these potiitions. In the best and in the extreme positions a number of parameters are calculated: (1) with Model I assumed, and each plane taken in turn as the fault, the strike and dip components are computed; (2) with Model II assumed, the orientation of the pressure and tension axes is calculated. This program has been applied to the data 011 618 earthquakes; these include all earthquakes for which solutions have previously been published anywhere in the world and for which the data are available, together with a large number of European earthquakes for which data have been collected through the European Seismological Commission's Working Group on Earthquake Mechanism (Dr. A. R. Ritsema, chairman) . Where more than one author has considered an earthquake, the data of each are treated separately and are then combined to produce a final solution. The entire print-out is included in the paper. Of the 618 earthquakes, 70 provide unique solutions in which none of the parameters vary by more than 10 degrees. For these the paper provides a listing of the observations on which the solution is based, together with the constants of the observing stations, the theorctical amplitude and polarity for each of these stations reduced to the focal sphere, and a plot of the data and solution on a Byerly projection.

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