The Vrancea, Romania, earthquake of March 4, 1977 — a quite successful prediction

Abstract

The available data on the destructive intermediate earthquakes ( M ⩾ 6 3 4 ) in the Vrancea, Romania, region have been examined with the aim of revealing some time-magnitude regularities. The basic idea is that the total sequence (≅ 1100–1973 yr.), which appears as random, could be decomposed in some regular source-components which, by extrapolation, are superimposed to predict the future total sequence. The common nature of faulting (reverse dip-slip) and inferred regularities in the time-magnitude pattern of destructive Romanian earthquakes — (a) three active (seismic) time-bands alternating with quiet periods, the existence of (b) “quasicycles” and of (c) “supercycles” — led to the following predictions: (1) the occurrence of a shock with M ≈ 6 3 4 − 7 in 1980 ± 13 years; and (2) later earthquakes are predicted in 2005, in 2030–2040 ( M ≈ 6 3 4 − 7 ), and one with nearly maximum magnitude ( M = 7 1 2 −7 3 4 ) in 2070–2090. In every century, about 40 years represent a time interval of high seismic danger for Romania and, according to the proposed long-term time-magnitude model, three destructive earthquakes arc to occur in (and/or near) the evidenced seismic periods P 1, P 2 and P 3. It is shown that, taking into account the actual difficulties involved in the earthquake prediction, the Vrancea destructive earthquake of March 4, 1977 ( M = 7.1) was quite successfully predicted.