The Environmental Seismic Intensity Scale (ESI 2007) in Greece, addition of new events and its relationship with magnitude in Greece and the Mediterranean; preliminary attenuation relationships

Abstract

The Environmental Seismic Intensity (ESI) scale has been officially released in 2007 and is based on the quantification of Earthquake Environmental Effects. Due to its quantitative nature, the scale improves the process of assessing macroseismic intensities, particularly in the epicentral area of those cases in which sole traditional intensity scales prove to be ineffective. Following a large number of publications that applied this relatively newly established scale, there is some need for parametrization. This is because this intensity scale can offer new insights to seismic hazard assessment and has the potential to reduce the uncertainties that stem from traditional macroseismic scales. This study has three main goals. Firstly, to enrich and compile an ESI 2007 database from earthquakes in Greece by adding 4 new events. Secondly, to extract a relationship between Magnitude and the ESI 2007 for Greece and the Mediterranean. Thirdly, to offer a preliminary estimate of how the intensity attenuates with distance, after developing a code in Python language to assist this process. The ESI 2007 scale was applied in the 1995 Ms = 6.6 Kozani-Grevena earthquake, the 1978 Mw = 6.5 Thessaloniki earthquake, the historic 1894 Atalanti earthquake sequence (M = 6.4 and M = 6.8) and the 365AD event in Crete (M = 8.4). These events were selected because they have well documented and extensive co-seismic effects, including primary and secondary surface ruptures, rockfalls, landslides and liquefaction phenomena. For the Kozani earthquake, extracted results were correlated with SAR interferograms, in order to provide a complete and high spatial resolution of the ground deformation. Both the Kozani-Grevena and the Thessaloniki events produced a maximum intensity IX on the ESI 2007 scale, the Atalanti earthquake produced a maximum intensity X and the 365AD Crete earthquake a maximum intensity XII. Overall, the ESI 2007 scale compares fairly well with the traditional macroseismic scales except for some villages in the Kozani-Grevena epicentral area where due to the poor quality of buildings, existing scales overestimated the intensity by one degree compared to the ESI 2007. It is interesting to note that both for Greece and the Mediterranean area a strong correlation exists between Mw and the ESI 2007 scale. In particular, the following relationships between the Mw and the ESI scale have been extracted: i) for Greece Io(ESI 2007) = 3.1427 exp (0.1643Mw) and ii) for the Mediterranean Io(ESI 2007) = 3.3543exp (0.1557Mw).However, more events and more data regarding the intensity distributions are required to establish the intensity attenuation with distance.