Reassessment of Several Historical Hellenic Arc Earthquakes Within the Context of Regional Tsunami Risk
Abstract
The eastern Mediterranean region is exposed to substantial tsunami risk from both earthquakes and submarine slumps. However, neither large magnitude nor tsunamigenic earthquakes occur frequently here, hampering comprehensive study of these events and consequential hazard. The analysis of analogue seismograms from events taking place prior to the advent of widespread digital recording can be used to augment our understanding and assessment of regional tsunami hazard. We reassess a number of large (M~7) historical earthquakes occurring in various regions of the Hellenic Arc on 26 June 1926, 6 October 1947, 9 February 1948, and 24/25 April 1957 for which epicentral locations and depths, magnitudes, and focal mechanisms are poorly constrained. Near-field tsunamis are associated with both the 1947 and 1948 earthquakes. Events are relocated using the method of Wysession et al. (1991); measurements of the spectral amplitudes of long-period Love and Rayleigh waves are inverted for moment tensors using the PDFM algorithm of Reymond and Okal (2000). Preliminary results include seismic moments (in dyn-cm) of 1.3×1027 (1947), 9.7×1026 (1948), 5.8×1026 (1957a), and 1.8×1027 (1957b). Initial focal mechanisms and locations for these events are consistent with the regional stress field resulting from the ongoing collision between the African and Eurasian plates. Relocated depths for the 1947 and 1948 events (57±15 and 60±15 km, respectively) suggest that the sources of near-field tsunamis associated with these events likely involved submarine slumping or landslides induced by these earthquakes, as in the 1956 Amorgos earthquake recently studied by Synolakis et al. (2008).
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFMOS53B1302E
- Keywords:
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- 4564 Tsunamis and storm surges;
- 7230 Seismicity and tectonics (1207;
- 1217;
- 1240;
- 1242);
- 9335 Europe