Abstract
On September 13, 1986, a shallow earthquake (Ms=6.2) struck the city of Kalamata and the surrounding areas (SW Peloponnese, Greece) resulting in 20 fatalities, over 300 injuries, extensive structural damage and many earthquake environmental effects (EEE). The main shock was followed by several aftershocks, the strongest of which occurred two days later (Ms=5.4). The EEE induced by the 1986 Kalamata earthquake sequence include ground subsidence, seismic faults, seismic fractures, rockfalls and hydrological anomalies. The maximum ESI 2007 intensity for the main shock has been evaluated as IX<sub>ESI 2007</sub>, strongly related to the active fault zones and the reactivated faults observed in the area as well as to the intense morphology of the activated Dimiova-Perivolakia graben, which is a 2nd order neotectonic structure located in the SE margin of the Kalamata-Kyparissia mega-graben and bounded by active fault zones. The major structural damage of the main shock was selective and limited to villages founded on the activated Dimiova-Perivolakia graben (IX<sub>EMS-98</sub>) and to the Kalamata city (IX<sub>EMS-98</sub>) and its eastern suburbs (IX<sub>EMS-98</sub>) located at the crossing of the prolongation of two major active fault zones of the affected area. On the contrary, damage of this size was not observed in the surrounding neotectonic structures, which were not activated during this earthquake sequence. It is concluded that both intensity scales fit in with the neotectonic regime of the area. The ESI 2007 scale complemented the EMS-98 seismic intensities and provided a completed picture of the strength and the effects of the September 13, 1986, Kalamata earthquake on the natural and the manmade environment. Moreover, it contributed to a better picture of the earthquake scenario and represents a useful and reliable tool for seismic hazard assessment.
Highlights
The twelve degrees macroseismic intensity scales, developed since the beginning of the 20th century, were based on evaluation of the earthquake effects on humans, manmade structures and the natural environment
This paper focuses on the September 13, 1986, Kalamata earthquake that affected the Kalamata area located in Messinia (SW Peloponnese, Greece)
Neotectonic macrostructures of Messinia The Messinia area comprises four neotectonic mega-structures (1st order structures), which are the following from E to W: (i) the N-S striking Taygetos Mt mega-horst, (ii) the Kalamata-Kyparissia mega-graben striking N-S in its southern part and E-W further to the north, (iii) the very complex morphotectonic megastructure of Kyparissia Mts-Lykodimo Mt striking N-S and considered as horst in comparison with the eastern Kalamata-Kyparissia mega-graben and as graben in comparison with the following Gargallianoi-Pylos megahorst and (iv) the Gargallianoi-Pylos mega-horst occurred along the western coast of Messinia [Mariolakos et al 1986, Mariolakos 1990] (Figures 1b, 2a)
Summary
The twelve degrees macroseismic intensity scales, developed since the beginning of the 20th century, were based on evaluation of the earthquake effects on humans, manmade structures and the natural environment. The effects of earthquakes on the ground have often been included in intensity scales but are in practice quite hard to benefit from [Grünthal 1998] This is because these effects are complex, and are often influenced by various factors such as inherent slope stability, level of water table, etc., which may not be readily apparent to the observer. The continental Middle-Late Pleistocene deposits consist mainly of red-colored, polymictic but always siliceous sands and conglomerates, the pebbles of which come exclusively from metamorphic rocks and/or radiolarites They overlie unconformably the older formations and are deposited on a well formed palaeorelief, which is different from the recent one in its details [Mariolakos et al 1986]. Alluvial fans, unconsolidated or partly consolidated material, river deposits, fluvial terraces, talus cones and scree represent the Holocene [Mariolakos et al 1986]
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