Retrospective Prediction of Macroseismic Intensities Using Strong Ground Motion Simulation: The Case of the 1978 Thessaloniki (Greece) Earthquake (M6.5)

Abstract

Abstract. The densely populated city of Thessaloniki (Northern Greece) is situated in the vicinity of active seismic faults, capable of producing moderate to strong earthquakes. The city has been severely affected by such events several times during the last 15 centuries. The most recent event occurred on 20 June 1978 (M6.5) in the Mygdonian graben, with an epicentral distance of about 30 km, causing extended damage in the city, with macroseismic intensities between MSK V+ and VIII+. The majority of buildings affected by the earthquake were of reinforced-concrete typology, typical to many southern European metropolitan areas. The source properties of the normal-faulting causative event and the source-to-city propagation path are well known from previous studies. The soil structure under the metropolitan area of Thessaloniki is assigned NEHRP categories B, C, D on the basis of geotechnical and geologic information and single-station ambient-noise measurements. A finite source model and various rupture scenarios of the June 1978 earthquake are used to perform forward stochastic modeling of strong ground motion in terms of peak ground and spectral acceleration. Rock motion is assessed under the city and it is transferred to the surface in accordance with the respective soil category. A GIS tool is employed to compare the estimated strong-motion parameters with the observed detailed damage pattern induced by the 1978 earthquake. For selected natural periods, a satisfactory correlation is established between macroseismic intensity and peak ground and spectral acceleration, thus encouraging the application of stochastic modeling for generating realistic ground-shaking scenarios in metropolitan areas.

Simulation of strong ground motion on near-fault rock outcrop for engineering purposes: the case of the city of Xanthi (northern Greece)

“…It has also been adopted in several studies of earthquakes in the broader Aegean area (e.g. Benetatos and Kiratzi 2004;Karastathis et al 2010;Margaris and Boore 1998;Mountrakis et al 2012;Roumelioti et al 2004;Theodulidis et al 2006) and is considered as an effective tool, especially in cases where the sparsity of seismological data does not facilitate the application of more refined and physically sound methods.…”

Testing the Applicability of Correlations between Topographic Slope and VS30 for Europe

“…Therefore, methods based on information available from remote-sensing data (in this case topographic slope) are attractive in their apparent ability to provide first-order information on site classes very rapidly. As an example, we have chosen the city of Thessaloniki (Greece) as a test case for comparison between the results of a recent microzonation, which was based on geophysical measurements, local geology, H/V measurements and damage patterns of the 1978 damaging earthquake, (Theodulidis et al, 2006) and the site classes predicted by the Vs,30-slope correlations of Wald and Allen (2007). The results of this comparison are shown in Figure 8 using both grdgradient of GMT and the Slope tool of ArcGIS.…”

“…The results of this comparison are shown in Figure 8 using both grdgradient of GMT and the Slope tool of ArcGIS. Other microzonations exist for Thessaloniki, for example that by Anastasiadis et al (2001) used by Pitilakis et al (2006) for risk scenarios, which shows significant differences to the map of Theodulidis et al (2006).…”

Engineering geological parameters affecting the response of Τhessaloniki's urban fill to a major seismic event

“…The earthquake is one of the 5 or 6 major seismic events that have struck the city of Thessaloniki in its 2300 year history. The characteristics of the earthquake reported in Theodulidis et al (2006) The earthquake caused 49 deaths, one collapse of an 8-storey R/C building and damages to buildings with a repair cost equal to 1.6% the cost of replacing the existing building stock (Penelis et al, 1989). Following this event there was a general inspection and recording of the damages sustained by the buildings of the whole urban area at the time of the event.…”