A probabilistic seismic hazard assessment for Greece and the surrounding region including site-specific considerations

T. M. Tsapanos, P. Mäntyniemi, A. Kijko

Abstract


A probabilistic approach was applied to map the seismic hazard in Greece and the surrounding region. The procedure
does not require any specification of seismic sources or/and seismic zones and allows for the use of the
whole seismological record, comprising both historical and instrumental data, available for the region of interest.
The new seismic hazard map prepared for Greece and its vicinity specifies a 10% probability of exceedance
of the given Peak Ground Acceleration (PGA) values for shallow seismicity and intermediate soil conditions for
an exposure time of 50 years. When preparing the map, the new PGA attenuation relation given by Margaris et
al. (2001) was employed. The new map shows a spatial distribution of the seismic hazard that corresponds well
with the features of shallow seismicity within the examined region. It depicts the level of seismic hazard in which
the exceedance of the PGA value of 0.25 g may be expected to occur within limited areas. The highest estimated
levels of seismic hazard inside the territory of Greece are found in the Northern Sporades Islands, where PGA
values in excess of 0.50 g are reached at individual sites, and in the Zante Island in Western Greece, where PGA
values in the range of 0.35 g to 0.40 g are obtained at more numerous localities. High values are also observed
in the sea between the Karpathos and Rhodes islands, near the Island of Amorgos (Cyclades Archipelago) and
in the Southwestern Peloponnesus. The levels of seismic hazard at the sites of seven Greek cities (Athens, Jannena,
Kalamata, Kozani, Larisa, Rhodes and Thessaloniki) were also estimated in terms of probabilities that a
given PGA value will be exceeded at least once during a time interval of 1, 50 and 100 years at those sites. These
probabilities were based on the maximum horizontal PGA values obtained by applying the design earthquake
procedure, and the respective median values obtained were 0.24 g for Athens, 0.28 g for Jannena, 0.30 g for
Kalamata, 0.21 g for Kozani, 0.24 g for Larisa, 0.43 g for Rhodes and 0.35 g for Thessaloniki. The probabilities
of exceedance of the estimated maximum possible PGA value were also calculated for the cities to illustrate the
uncertainty of maximum PGA assessment.

Keywords


seismicity of Greece;probabilistic seismic;hazard;peak ground acceleration;design earthquake procedure

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References


DOI: https://doi.org/10.4401/ag-3367
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Published by INGV, Istituto Nazionale di Geofisica e Vulcanologia - ISSN: 2037-416X