by IOSIF TRAIAN and IOSIF SIEGLINDE
An energy classification of the Vrancea earthquakes is performed. For the interval of magnitude, 2.5 < M < 5.5 the relation:
lg E = 10.5 + 2.0 M
is obtained. On the basis of the graph K = f(M), extrapolated
in the range of small magnitudes, and of the nomogram drawn up by Fedotov,
the magnitudes
for 200 microearthquakes having occurred in the region and recorded at the
seismic station Vrancioaia (– 0.3 < M < 2.5) were determined.
The graph lg (A/T) = f(M) presents a jump for S – P = 9s
which corresponds to a discontinuity limit situated in the upper mantle at
a depth of about 80
km. It is assumed that this is the upper limit of the low velocity layer.