D. ENESCU si V. SMALBERGHER
Centrul de Fizica Pamantului si Seismologie, Bucuresti – Magurele
SEISMIC ENERGY RELEASED BY THE TECTONIC EARTHQUAKE FOCI.
ADAPTATIONS AND APLICATIONS TO THE VRANCEA EARTHQUAKES
(Abstract)
Taking into account the equations of the displacement field determined by
Kostov (1964, a; 1964, b; 1970) for the seismic source represented by the double
couple propagating with velocity v < VS on a faulting surface of eliptic
shape, in the first part of the paper relations (13) – (16) are deduced
expressing the energy released by this source in the form of longitudinal and
transverse waves.
The second part particularizes relations (13) – (16) for the case of
Vrancea intermediate earthquakes. This is made by taking into consideration
the parameters expressed by (17) and solving the integrals (5) and (9) – (12).
Thus, formulae (25) – (28) are obtained. The ratio of the energies in
S and P waves (relation (29)) and the average ratio of the amplitudes in P
and S waves (relation (30)) are calculated. One ascertains that theoretical
values expressed by (29) and (30) are confirmed by observations data of Vrancea
intermediate earthquakes.
The object of the third part is the comparison of the results obtained in this
paper with those deduced by Enescu (1961, 1963) taking into consideration Vvedenskaya's
model (1956, 1959). Though the two models (Kostrov and Vvedenskaya) are different
and Vvedenskaya's model has some deficiencies, the results concerning the seismic
energy Es = EP + ES released by the two sources are practically identical.
The explanation is given in the paper.
The fourth part contains the results of formula (28) applied to the estimation
of seismic energy released by seven Vrancea intermediate earthquakes. Obtained
results are in good agreement with those deduced by formula (39) (Table).
The main conclusions of the paper are synthetized in its final part.