D. Enescu and D. Jianu
Abstract
In the first part of the study, the authors expose a critical review of the
results previously obtained [3], [5] in the determination of the magnitudes
of the Vrancea earthquakes.
For the determination of magnitude, the following formula was utilized:
Under the hypothesis that in the case of the Vrancea deep earthquakes (h
150
km) the epicentral distance corresponding to a certain station is constant,
for log following values were determined: Bucharest – 2.74; Bacau – 2.50;
Focsani – 2.05 and Iassy – 2.47.
In order to avoid at least a part of the numerous errors crated when estimating
the magnitude, it was recommended that the magnitude M of an earthquake should
be considered the arithmetic mean of the magnitudes obtained for all Romanian
stations which have recorded the earthquake.
In Table 2, the calculated magnitudes of 377 deep earthquakes in Vrancea, during
the period 1937 to 1962 are given.
The frequency graph of earthquakes (Fig. 1) was constructed, and by means of
the method of least squares the following relationship was obtained:
log N = 3.45 – 0.70 M.
The period considered for the determination of this relationship is of 26
years (1937– 1962).