A revised and extended earthquake catalogue for Greece since 1900

Abstract

An earthquake catalogue for Greece is presented covering the period 1900-1985. It is based on a similar effort attempted a few years ago. The present version contains more than double the number of events, i.e. 4310 events compared with 1806 events, than in the previous papers. It also includes another 1711 events which took place in the region in an Appendix. The accuracy and completeness of the parameters of these shocks were insufficient for inclusion in the main catalogue without affecting the catalogue's homogeneity. For the new entries magnitudes are redetermined using Uppsala's reading as before, whereas the other parameters have been rechecked against local macroseismic information. The completeness of this catalogue varies according to the period of observation, but the lower threshold of completely reported magnitudes has been substantially decreased allowing for more detailed seismicity studies to be performed.

Focal mechanism and depth of the 1956 Amorgos twin earthquakes from waveform matching of analogue seismograms

“…Color scale is truncated at a waveform misfit of 6. Comninakis and Papazachos (1986), (middle) Makropoulos et al (1989) and (right) Okal et al (2009). area A R of about 900 km 2 and an average displacement D of about 1.0 m. Our estimate of moment magnitude is smaller than the magnitude values given by other authors (Table 1). One possible reason could be a directivity effect caused by the very small azimuthal coverage provided by the few usable historic traces.…”

“…On 9 July 1956 (03:11 GMT), one of the strongest earthquakes in the southern Aegean in the 20th century occurred between the islands of Amorgos and Santorini with a magnitude of M S = 7.4 (Makropoulos et al, 1989). A second strong earthquake (03:24 GMT) with a magnitude of M S = 7.2 occurred just 13 min later in the same region.…”

“…Since surface waves are much more affected by such lithospheric complexity than body waves, we restricted ourselves to matching P and S wave phases only. Finally, since three slightly differing locations of the earthquake have been proposed in the literature (Comninakis and Papazachos, 1986;Makropoulos et al, 1989;Okal et al, 2009), we performed the grid search for all of them. The smallest waveform misfit achievable for each trial source depth (Fig.…”

“…1). The first earthquake was located at the northern flank of the graben southwest of Amorgos (Comninakis and Papazachos, 1986;Makropoulos et al, 1989;Okal et al, 2009). Epicenter locations of the second earthquake vary from the northern graben shoulder southwest of Amorgos (Comninakis and Papazachos, 1986) and the northeastern Santorini-Coloumbo volcanic complex (Makropoulos et al, 1989) to the southern graben shoulder near Anafi (Okal et al, 2009).…”

“…While the two earthquakes have been unanimously located in the Santorini-Amorgos graben, focal parameters and focal depth are controversial (Table 1) or affected by large uncertainties (Galanopoulos, 1982;Comninakis and Papazachos, 1986;Makropoulos et al, 1989). For the first event, Shirokova (1972) proposed a fault plane solution of a ENE-WSW striking normal fault with a slight dip to the SSE, calculated from first-motion polarities of P phases (Fig.…”