Reply on the comments of G. A. Papadopoulos on the paper ‘Preseismic quiescence before large earthquakes in the Aegean and surrounding area’

Abstract

A considerable body of observations has been accumulated during the last decade relevant to the problem of long-term earthquake prediction in the Aegean and surrounding area by identifying precursory seismicity patterns. Much of this work concerns the effort to detect preseismic quiescence, that is, drop of the low magnitude seismicity rate in the seismogenic area of strong expected events by plotting the cumulative number of these small earthquakes as a function of time (Wyss & Baer 1981a,b; Papazachos 1980; Papazachos & Comninakis 1980; Papadimitriou 1984; Papadimitriou & Papazachos 1985a,b, Papaioannou, Tsapanos & Papazachos 1987). In a recent paper from our laboratory which appeared in Annales Geophysicae (Karakaisis et al. 1987), we made an effort to generalize the application of this method in the whole Aegean and surrounding area (34N-43N, 18E30E), that is, in an area which includes the Aegean Sea, Greece, Albania, Southern Yugoslavia, Southern Bulgaria and Western Turkey. The paper consists of two main parts. In the first part, it has been shown that most of the earthquakes with MsS7.0 which occurred in this area during the period 1947-1983 were preceded by a drop of the seismicity rate in rather broad areas around the epicentres of these earthquakes. In the second part of our paper, we made plots of the cumulative number of shocks for all seismic zones of this area. These plots show that 11 of the shallow seismicity zones or parts of these zones and two zones of intermediate depth seismicity are at quiescence now. On the basis of these observations and of other people's work on seismicity patterns in these zones we made the hypothesis that these zones may experience strong earthquakes. It is pointed out in our paper that this work is of a rather qualitative character and further and more detailed studies are needed for quantitative results. This can be facilitated by the establishment of a dense telemetric seismograph network in Greece. Papadopoulos (this issue) claims that our results are of questionable validity because, according to his opinion, we applied an inappropriate method and we should have applied other quantitative methods that he suggests, and because our data sample for each case is small. Furthermore, he writes that we have overestimated the seismic potential of this area, that is, the number of the expected strong earthquakes in our paper is much larger than the number he calculates. Finally, he accuses