ANNALS OF GEOPHYSICS, 56, 6, 2013, S0675; doi:10.4401/ag-6237 Special Issue: Earthquake geology Application of the Environmental Seismic Intensity scale (ESI 2007) and the European Macroseismic Scale (EMS-98) to the Kalamata (SW Peloponnese, Greece) earthquake (Ms=6.2, September 13, 1986) and correlation with neotectonic structures and active faults Ioannis G. Fountoulis, Spyridon D. Mavroulis* National and Kapodistrian University of Athens, Faculty of Geology and Geoenvironment, Department of Dynamic Tectonic Applied Geology, Panepistimiopolis, Athens, Greece Article history Received October 16, 2012; accepted June 11, 2013. Subject classification: Neotectonics, Earthquake environmental effects, ESI 2007 intensity scale, EMS-98 intensity scale, Kalamata earthquake. ABSTRACT based on evaluation of the earthquake effects on hu- On September 13, 1986, a shallow earthquake (Ms=6.2) struck the city mans, manmade structures and the natural environ- of Kalamata and the surrounding areas (SW Peloponnese, Greece) re- ment. However, in the early versions of these scales, the sulting in 20 fatalities, over 300 injuries, extensive structural damage and earthquake effects on the natural environment were many earthquake environmental effects (EEE). The main shock was fol- scarcely included. Their presence in the scale was mostly lowed by several aftershocks, the strongest of which occurred two days due to many references to ground cracks, landslides and later (Ms=5.4). The EEE induced by the 1986 Kalamata earthquake se- landscape modifications contained in the historical re- quence include ground subsidence, seismic faults, seismic fractures, rock- ports [Guerrieri and Vittori 2007]. Later, in the second falls and hydrological anomalies. The maximum ESI 2007 intensity for half of the 20th century, these effects have been in- the main shock has been evaluated as IXESI 2007, strongly related to the creasingly disregarded in the literature and the practice active fault zones and the reactivated faults observed in the area as well of macroseismic investigations, while increasing atten- as to the intense morphology of the activated Dimiova-Perivolakia tion has been directed towards the analysis of the effects graben, which is a 2nd order neotectonic structure located in the SE mar- on humans and manmade structures [Gosar 2012]. gin of the Kalamata-Kyparissia mega-graben and bounded by active fault The EMS-98 scale, which is nowadays predomi- zones. The major structural damage of the main shock was selective and nantly used in Europe, considers three categories of ef- limited to villages founded on the activated Dimiova-Perivolakia graben fects: (a) on humans, (b) on objects and on nature and (IXEMS-98 ) and to the Kalamata city (IXEMS-98 ) and its eastern suburbs (c) damage to buildings [Grünthal 1998]. Its basic ad- (IXEMS-98 ) located at the crossing of the prolongation of two major active vantage in comparison to previous scales is a definition fault zones of the affected area. On the contrary, damage of this size was of vulnerability classes for buildings and more precise not observed in the surrounding neotectonic structures, which were not ac- statistical treatment of collected macroseismic data tivated during this earthquake sequence. It is concluded that both inten- [Grünthal 1998]. This quantification is elaborated in de- sity scales fit in with the neotectonic regime of the area. The ESI 2007 tails for the first three effects, but not for the effects on scale complemented the EMS-98 seismic intensities and provided a com- nature which are rather briefly summarized in a table in pleted picture of the strength and the effects of the September 13, 1986, EMS-98 scale. Effects on nature, summed up in the Kalamata earthquake on the natural and the manmade environment. EMS-98 scale by the term “seismogeological” effects, Moreover, it contributed to a better picture of the earthquake scenario and are divided into four groups: (a) hydrological effects, in- represents a useful and reliable tool for seismic hazard assessment. cluding changes in the well water level, waves on stand- ing water from local shaking, lake water turbidity, 1. Introduction changes in the flow of springs and overflow of lakes, The twelve degrees macroseismic intensity scales, (b) slope failure effects, including landslides and rock- developed since the beginning of the 20th century, were falls, (c) processes on flat ground, including cracks and S0675 FOUNTOULIS AND MAVROULIS fissures as well as (d) convergent processes (complex The use of EEE for intensity assessment has been cases) such as landslides (hydrological) and liquefaction recently promoted by the Environmental Seismic In- phenomena [Grünthal 1998]. This latter group covers tensity scale (ESI 2007) since it will unquestionably pro- instances where more than one type of process is in- vide an added value to traditional intensity evaluations volved in producing the effect. For each type of effects (i) allowing the accurate assessment of intensity in three intensity ranges are presented in tabular form: (a) sparsely populated areas, (ii) providing a reliable esti- the possible range of observations, (b) the range of in- mation of earthquake size with increasing accuracy to- tensities that is typical for this effect, and (c) the range wards the highest levels of the scale, where traditional of intensities for which this effect is most usefully em- scales saturate and ground effects are the only ones that ployed as diagnostic [Grünthal 1998]. permit a reliable estimation of earthquake size, and (iii) The effects of earthquakes on the ground have allowing comparison among future, recent and histor- often been included in intensity scales but are in prac- ical earthquakes [Michetti et al. 2004]. In addition, some tice quite hard to benefit from [Grünthal 1998]. This is environmental morphogenetic effects (either primary because these effects are complex, and are often influ- or secondary) can be stored in the palaeoseismological enced by various factors such as inherent slope stability, record, allowing the expansion of the time window for level of water table, etc., which may not be readily ap- seismic hazard assessment up to tens of thousands of parent to the observer. The result is that most of these years [Guerrieri et al. 2007, Porfido et al. 2007]. Fur- effects can be seen at a wide range of intensity degrees thermore, the EEE are not influenced by human pa- which prevents its practical use in intensities assessment rameters such as effects on people and the manmade [Grünthal 1998]. environment as the traditional intensity scales (MCS, Nevertheless, recent studies [Dengler and McPher- MM, EMS 1992, etc.) predominantly have built in. son 1993, Serva 1994, Dowrick 1996, Esposito et al. This paper focuses on the September 13, 1986, 1997, Hancox et al. 2002, Michetti et al. 2004, 2007, Kalamata earthquake that affected the Kalamata area Castilla and Audemard 2007, Serva et al. 2007, Silva et located in Messinia (SW Peloponnese, Greece). It aims al. 2008, Reicherter et al. 2009] have offered new sub- to: (a) the presentation of the geotectonic and seismo- stantial evidence that coseismic environmental effects tectonic regime of the earthquake affected region provide precious information on the earthquake size based on field data, (b) the presentation of the earth- and its intensity field, complementing the traditional quake induced environmental effects and structural damage-based macroseismic scales. As a matter of fact, damage, (c) the seismic intensity assignments for the with the outstanding growth of paleoseismology as a September 13, 1986, Kalamata earthquake based on the new independent discipline, nowadays the effects on guidelines of the Environmental Seismic Intensity scale the environment can be described and quantified with (ESI 2007) [Michetti et al. 2007] and the European a remarkable detail compared with that available at the Macroseimic Scale (EMS-98) [Grünthal 1998], (d) the time of the earlier scales. Therefore, today the defini- determination of their geographical distribution, (e) tion of the intensity degrees can effectively take advan- the interpretation of the intensity values data and their tage of the diagnostic characteristics of the effects on distribution to the neotectonic structures and the active the natural environment. fault zones of the area as well as at (f) the conduction Earthquake environmental effects (EEE) are any of a comparative evaluation review on the application effect produced by a seismic event on the natural envi- of both ESI 2007 and EMS 98 scales. ronment [Michetti et al. 2007]. The coseismic environ- mental effects considered more diagnostic for intensity 2. Geological setting evaluation can be categorized in two main types: (a) The geological formations in the wider Kalamata Primary effects, which are the surface expressions of area can be divided into two major categories: alpine the seismogenic tectonic source, including surface fault- and post-alpine (Figure 1). ing, surface uplift and subsidence and any other surface evidence of coseismic tectonic deformation; (b) Sec- 2.1. Alpine formations ondary effects, which include phenomena generally in- The following four alpine geotectonic units occur duced by the ground shaking [Michetti et al. 2007] and from bottom to top [Mariolakos et al. 1986, Psonis are conveniently classified into eight main categories 1986] (Figure 2a,b): (a) the Mani unit consisting mainly that are hydrological anomalies, anomalous waves in- of Upper Senonian-Upper