ANNALS OF GEOPHYSICS, 56, 6, 2013, S0681; doi:10.4401/ag-6239

Special Issue: Earthquake geology Seismic intensity assignments for the 2008 Andravida (NW Peloponnese, Greece) strike-slip event (June 8, Mw=6.4) based on the application of the Environmental Seismic Intensity scale (ESI 2007) and the European Macroseismic scale (EMS-98). Geological structure, active tectonics, earthquake environmental effects and damage pattern Spyridon D. Mavroulis1,*, Ioannis G. Fountoulis1, Emmanuel N. Skourtsos1, Efthymis L. Lekkas1, Ioannis D. Papanikolaou2

1 National and Kapodistrian University of Athens, Faculty of Geology and Geoenvironment, Department of Dynamic Tectonic Applied Geology, Panepistimiopolis, Athens, Greece 2 Agricultural University of Athens, Department of Geological Sciences and Atmospheric Environment, Laboratory of Mineralogy and Geology, Athens, Greece

Article history Received October 19, 2012; accepted November 14, 2013. Subject classification: Active faults, Earthquake environmental effects, ESI 2007 intensity scale, EMS-98 intensity scale, Strike-slip earthquakes.

ABSTRACT ance design. Correlation of all existing data shows that the geological struc- On June 8, 2008, a strike-slip earthquake (Mw=6.4) was generated NE ture, the active tectonics, and the geotechnical characteristics of the alpine of the Andravida town (NW Peloponnese, western Greece) due to the ac- and post-alpine formations along with the construction type of buildings tivation of the previously unknown western Achaia strike-slip fault zone were of decisive importance in the damage and the EEE distribution. (WAFZ). Extensive structural damage and earthquake environmental ef- fects (EEE) were induced in the NW Peloponnese, offering the opportunity 1. Introduction to test and compare the ESI 2007 and the EMS-98 intensity scales in a Earthquake environmental effects (EEE) have been moderate strike-slip event. No primary EEE were induced, while second- increasingly disregarded in the literature and the prac- ary EEE including seismic fractures, liquefaction phenomena, slope move- tice of macroseismic investigations during the 20th cen- ments and hydrological anomalies were widely observed covering an area tury, while increasing attention has been directed of about 800 km2. The lack of primary effects and the relatively small towards the analysis of the effects on humans and man- surface deformation with respect to the earthquake magnitude is due to made structures. The European Macroseismic scale the thick Gavrovo flysch layer in the affected area that isolated and ab- (EMS-98), which is predominantly used in Europe, con- sorbed the subsurface deformation from the surface. According to the ap- siders three categories of effects: (a) on humans, (b) on plication of the EMS-98 scale, damage to masonry buildings ranged from objects and on nature and (c) damage to buildings grade 3 to 5, while damage in most of R/C buildings ranged from grade [Grünthal 1998]. Its basic advantage over previous 1 to 3. A maximum ESI 2007 intensity VIII-IX is recorded, while the max- macroseismic intensity scales is a definition of vulner- imum EMS-98 intensity is IX. For all the sites where intensity VIII has ability classes for buildings and more precise statistical been recorded the ESI 2007 and the EMS-98 agree, but for others the ESI treatment of collected macroseismic data [Grünthal 2007 intensities values are lower by one or two degrees than the corre- 1998]. This quantification is elaborated in details for the sponding EMS-98 ones, as it is clearly concluded from the comparison of effects on humans, objects and buildings, but not for the produced isoseismals. An exception to this rule is the Valmi village, the effects on nature which are rather briefly summa- where considerable structural damage occurs (IXEMS-98) along with the rized in a table in EMS-98 scale. This allows a large dis- lack of significant EEE (VESI 2007). This variability between the ESI 2007 crepancy between the EEE and the damage pattern. and the EMS-98 intensity values is predominantly attributed to the vul- Recent studies [Dengler and McPherson 1993, nerability of old masonry buildings constructed with no seismic resist- Serva 1994, Dowrick 1996, Esposito et al. 1997, Hancox

S0681 MAVROULIS ET AL. et al. 2002, Michetti et al. 2004, 2007, Castilla and Au- [Guerrieri et al. 2007, Porfido et al. 2007]. Furthermore, demard 2007, Serva et al. 2007, Silva et al. 2008, Re- the EEE are not influenced by human parameters such icherter et al. 2009, Gosar 2012] offered new substantial as effects on people and the manmade environment as evidence that coseismic environmental effects provide the traditional intensity scales (MCS, MM, EMS 1992, valuable information on the earthquake size and its in- etc.) predominantly imply [Michetti et al. 2007]. tensity field, complementing the traditional damage- The integration of the ESI 2007 intensity scale based macroseismic scales. Indeed, with the outstanding with the other scales including EMS-98, provides a bet- growth of paleoseismology and earthquake geology, ter picture of the earthquake scenario, because only nowadays the effects on the environment can be de- EEE allow suitable comparison of the earthquake in- scribed and quantified with a remarkable detail com- tensity both (a) in time: effects on the natural environ- pared with that available at the time of the earlier scales. ment are comparable for a time-window (recent, historic Therefore, today the definition of the intensity degrees and palaeoseismic events) much larger than the period can effectively take advantage of the diagnostic charac- of instrumental record (last century), and (b) in differ- teristics of the effects on natural environment. ent geographic areas: environmental effects do not de- Earthquake environmental effects (EEE) are any pend on peculiar socio-economic conditions or different effect produced by a seismic event on natural environ- building practices. ment [Michetti et al. 2007]. Several decades of research Despite these advantages, there are some limita- on earthquake geology and paleoseismology have tions in the use of the ESI 2007 scale. The ESI 2007 scale pointed out their crucial role in seismic hazard assess- may not accurately describe the damage in the far field ment, due to their relations with the earthquake size [Papanikolaou et al. 2009]. It is important to establish and the location of seismogenic sources [Dengler and that this scale should be used predominantly in the epi- McPherson 1993, Serva 1994, Wells and Coppersmith central area and thus may not accurately describe dam- 1994, Esposito et al. 1997]. The coseismic environ- age in the far field. mental effects considered diagnostic for intensity eval- Also, in deep nonlinear morphogenic events [Ca- uation can be categorized in two main types [Michetti puto 2005], where ruptures cannot reach the surface, et al. 2007]: (a) Primary effects, which are directly the ESI degrees should be correlated with the area, linked to the earthquake energy and in particular to where severe EEE have been recorded. However, in the surface expression of the seismogenic source, in- such cases uncertainties are expected to be higher, im- cluding surface faulting, surface uplift and subsidence plying that the assignment of the ESI 2007 intensities and any other surface evidence of coseismic tectonic should probably be considered less precise for deep deformation; (b) Secondary effects including phenom- events [Papanikolaou et al. 2009]. ena generally induced by the ground shaking. They are Intensive EEE have not been expressed or even conveniently classified into eight main categories that recorded in some earthquakes even though high grades are hydrological anomalies, anomalous waves includ- were assigned using other macroseismic scales, due to ing tsunamis, ground cracks, slope movements, trees the strictly localized area of damage and its limited ge- shaking, liquefactions, dust clouds and jumping stones ographical coverage. However, it is argued that this in- [Michetti et al. 2007]. consistency is probably due to the structural response The use of EEE for seismic intensity assessment of multistorey buildings, the bedrock geology and the has been recently promoted by the ESI 2007 scale, local site effects in accordance with the long distance which evaluates earthquake size and epicenter solely from the epicenter. from EEE. The application of ESI 2007 scale (i) allows This paper focuses on the June 8, 2008, An- the accurate assessment of intensity in sparsely popu- dravida earthquake (Mw=6.4) that affected the NW lated areas, (ii) provides a reliable estimation of earth- Peloponnese (western Greece) causing 2 fatalities and quake size with increasing accuracy towards the highest 214 injuries. The earthquake produced both extensive levels of the scale, where traditional scales saturate and damage and significant EEE in the Ilia and the Achaia ground effects are the only ones that permit a reliable prefectures. estimation of earthquake size, and (iii) allows compar- Five years after the event, we present some con- ison among future, recent and historical earthquakes siderable data about the macroseismic characteristics [Michetti et al. 2004]. In addition, some environmental of the earthquake and about the geology, tectonics and morphogenetic effects (either primary or secondary) seismicity of the epicentral area (NW Peloponnese). can be stored in the palaeoseismological record, allow- This paper offers: (a) a view of the geotectonic and the ing the expansion of the time window for seismic haz- seismotectonic regime of the region affected by the ard assessment up to tens of thousands of years earthquake based on previous works and new field ob-

2 ESI 2007 AND EMS-98 FOR A STRIKE-SLIP EVENT servations, (b) the description of the active faults and lacustrine and terrestrial deposits and lie unconformably fault zones that pose seismic hazard for the residential on the alpine basement [Christodoulou 1969, Tsoflias parts of the region, (c) the evaluation of the seismic in- 1977, 1980, 1984, Kamberis et al. 1979, Fleury et al. 1981, tensities based on the guidelines of the ESI 2007 scale Mariolakos et al. 1990, Lekkas et al. 1990, 1992, 2000, [Michetti et al. 2007] and the EMS-98 scale [Grünthal Mariolakos et al. 1995]. 1998], (d) correlation of the seismic intensities with the geological, tectonic and geotechnical regime of the 3. Neotectonics - Active tectonics study area and (e) comparison of both seismic intensity scales and discussion on similarities and differences. 3.1. Introduction NW Peloponnese is one of the most tectonically 2. Geology and seismically active regions of Greece [Mariolakos et The geological formations in the study area can be al. 1995]. The intense tectonic activity from the divided into two major categories: alpine and post- Miocene to the Holocene resulted from its location on alpine (Figure 1). The alpine formations belong to three the external part of the present Hellenic orogenic arc major geotectonic units, the Pindos, Gavrovo and Ion- and the close proximity to the present day NNW-SSE ian units [Philippson 1898, 1959, Renz 1955, Aubouin trending Hellenic subduction zone [Mariolakos et al. and Dercourt 1962, ESSO 1962, Christodoulou 1967, 1995] (Figure 1). Moreover, the diapiric phenomena of 1969, 1971, Tsoflias 1977, 1980, 1984, Dercourt et al. the Triassic evaporites originated between Tertiary and 1978, Fleury 1980, Fleury et al. 1981, Lekkas et al. 1992, Quaternary and caused additional localized deforma- 1995, Mariolakos et al. 1995], which outcrop towards tion [Hageman 1977, Winter 1979, Kowalczyk and Win- the eastern sector of the study area (Figure 1). From ter 1979, Underhill 1985, 1988, Mariolakos et al. 1990]. the structural point of view, these geotectonic units The neotectonic structure of the NW Pelopon- form a succession of three nappes: the Pindos unit (first nese is characterized by the occurrence of large nappe) overthrusts the Gavrovo unit and the Gavrovo grabens or horsts bounded by E-W or NNW-SSE trend- unit (second nappe) overthrusts the Ionian unit (third ing visible or concealed fault zones [Mariolakos et al. nappe) (Figure 1). 1985] (Figure 1). Crucial role in the development of the The Pindos unit crops out in the Panachaiko Mt post-alpine formations was played by the tectonic ac- and the Erymanthos Mts (Figure 1). The unit consists tivity during the sedimentation phase, which created of clastic sediments of Upper Triassic, Lower Creta- smaller horsts and grabens within the major neotec- ceous and Tertiary age, Jurassic radiolarites and Upper tonic macrostructures [Lekkas et al. 2000]. Although Cretaceous pelagic limestones [Philippson 1898, 1959, these smaller structures are dynamically related, as they Renz 1955, Fleury 1980, Tsoflias 1980, 1984, Dercourt et have resulted from an extensional stress field, which al. 1978, Fleury et al. 1981] (Figure 1). prevailed in the NW Peloponnese from the Early The Gavrovo unit consists of the Upper Creta- Pliocene up to present day [Doutsos et al. 1988, Lekkas ceous-Upper Eocene shallow marine carbonates, which et al. 1995, Koukouvelas et al. 1996, Doutsos and crop out on Skolis Mt and the thick Paleocene-Oligocene Kokkalas 2001, Papanikolaou et al. 2007], they followed flysch, which crops out in the surrounding area [Fleury different kinematic evolution [Mariolakos et al. 1995]. 1980, Tsoflias 1980, Fleury et al. 1981] (Figure 1). A great number of faults were active during The Ionian unit has a relatively poor exposure in Pliocene and Pleistocene, whereas others have also re- the study area since it is unconformably overlain by mained active during Holocene time [Lekkas et al. 1992, post-alpine formations. It consists of the Jurassic-Eocene Fountoulis et al. 2013]. The recorded seismicity levels, carbonate sequence [Aubouin and Dercourt 1962, which are among the highest in Greece [Hatzfeld et al. Christodoulou 1967, 1969, 1971] and the Late Eocene- 1990], confirm the neotectonic studies, which show that Early Oligocene overlying flysch exposed near Cape the area is undergoing intense tectonic deformation. Ac- Araxos [Tsoflias 1977]. Moreover, the Triassic evapo- cording to historical and instrumental records, numer- rates are observed in Kyllini peninsula [ESSO 1962, ous destructive earthquakes have taken place in the area Christodoulou 1969, 1971, Tsoflias 1977, Lekkas et al. since 399 BC [Galanopoulos 1955, 1981, Mariolakos et 1990, 1992, Mariolakos et al. 1995] (Figure 1). al. 1995, Papazachos and Papazachou 1997]. The major The post-alpine formations occur in the northern, characteristics of the seismicity of the NW Peloponnese southern and western sector of the study area as parts are that all major earthquakes occurred at shallow of the Patras graben, the Kato Achaia-Fares and the depths (h < 20 km) and had high intensities ranging Pyrgos-Olympia basins (Figure 1). They can be distin- from VI to IX [Galanopoulos 1955, 1981, Mariolakos et guished into Pliocene and Quaternary marine, lagoonal, al. 1995, Papazachos and Papazachou 1997].

3 MAVROULIS ET AL.

Figure 1. Geological map of the wider study area showing the major neotectonic macrostructures (Panachaiko Mt, Erymanthos Mts horst, Kato Achaia - Fares basin, Kyllini horst, Pyrgos - Olympia basin), the smaller neotectonic structures (Gastouni and Simopoulo sub-basins), the active fault zones based on Lekkas et al. [1992, 2000], Vassilakis et al. [2006], Mavroulis et al. [2010], Vassilakis et al. [2011] and Fountoulis et al. [2013] and the focal mechanisms of recent earthquakes in NW Peloponnese (1988 Kyllini, 1993 Patras, 1993 Pyrgos, 2002 Vartholomio, 2008 Andravida earthquakes) from Feng et al. [2010].

4 ESI 2007 AND EMS-98 FOR A STRIKE-SLIP EVENT

3.2. Neotectonic macrostructures of the study area formed palaeorelief developed on the alpine forma- The structural damage and the EEE induced by tions [Lekkas et al. 2000]. the 2008 Andravida earthquake occurred in an area, The neotectonic evolution of the Pyrgos-Olympia where the following neotectonic macrostructures basin was not the same in all its extent [Lekkas et al. occur: 1992, 1994, Mariolakos et al. 1995]. It was influenced by the creation and evolution of smaller tectonic blocks 3.2.1. The Patras graben (2nd order structures). Some of these 2nd order struc- The Gulf of Patras contains a WNW-ESE trend- tures are affected by the presence of evaporites and the ing neotectonic graben structure [Ferentinos et al. related diapiric phenomena (e.g. Kyllini horst) [Lekkas 1985] (Figure 1), which is flanked to the NE by the et al. 1992, Mariolakos et al. 1995]. mountains of Varassova and Klokova reaching an ele- vation of about 1000 m and composed of Cretaceous 3.2.3. The Erymanthos Mts horst limestones and Eocene flysch of the Gavrovo unit The Erymanthos mountain range is a NE-SW [Richter and Mariolakos 1975, Mettos and Karfakis trending horst located E and SE of the Patras graben 1991, Papanikolaou and Lekkas 2008] (Figure 1). To the and NE of the Pyrgos-Olympia basin (Figure 1). It con- NW, it is fringed by Quaternary deltaic deposits of the sists of alpine formations of the Pindos unit and specifi- Acheloos and the Evinos Rivers [Piper and Panagos cally of the clastic sequence of Upper Triassic, Lower 1981]. The southern shore is flanked by Pliocene-Qua- Cretaceous and Tertiary age, the Jurassic radiolarites ternary deposits, which reach a maximum thickness of and the Upper Cretaceous carbonate sequence [Tsoflias 1500 m [Hageman 1979]. Offshore drilling in the south- 1969, 1980, 1984, Dercourt et al. 1978, Fleury et al. ern part of the graben reveals about 1800 m of Neo- 1981] (Figure 1). Fold axes and thrusts of the Pindos for- gene and Pliocene-Quaternary sediments overlying mations in the Erymanthos horst strike N 40-60° E and Triassic anhydrites [Ferentinos et al. 1985]. differ from the rest of the External Hellenides, where Seismic profiling in the Gulf has shown that off- fold axes and thrusts strike N 10-30° W [Mariolakos et shore Plio-Quaternary sediments are affected by wide- al. 1985, Mariolakos and Papanikolaou 1987]. The latter spread active faulting with a WNW-ESE trend reflect the dextral rotation of Erymanthos Mts horst [Ferentinos et al. 1985]. In the NE part of the Gulf, pro- through the activation of E-W trending, sinistral strike filing records show that concealed faulting affects Pleis- slip faults [Mariolakos et al. 1985, Mariolakos and Pa- tocene sequences beneath an undeformed Holocene panikolaou 1987] (Figure 1). surface layer. Onshore neotectonic data from around the Gulf show two groups of normal faults trending 3.3. Active fault zones WNW-ESE and ENE-WSW [Ferentinos et al. 1985, Doutsos et al. 1987, 1988]. To the east of the Gulf, 3.3.1. The Pineios fault zone NNW-SSE and NNE-SSW normal faulting is observed The Pineios fault zone is one of the youngest [Kontopoulos and Doutsos 1985, Doutsos et al. 1987]. structures in NW Peloponnese [Mavroulis 2009, In addition, near-vertical faults have been observed in Mavroulis et al. 2010, Fountoulis et al. 2011a,b, 2013]. It the same area that can be characterized as dip-slip or is an approximately E-W trending active normal fault strike-slip faults (Figure 1). zone located SSW of Skolis Mt and dips southwards (Figure 1). The footwall consists of Upper Pliocene- 3.2.2. The Pyrgos-Olympia basin Pleistocene formations uncomformably overlying the The Pyrgos-Olympia basin is a large graben well-formed palaeorelief developed on the Gavrovo fly- bounded by the Erymanthos Mts horst towards N and sch, while the hanging wall consists of the aforemen- NE, the Gortynia Mts (Tropaea) horst towards E and tioned post-alpine formations and the Holocene the Lapithas Mt horst towards S [Fountoulis and Lekkas alluvial deposits of the Lower Pineios River bed [Kam- 1991, Lekkas et al. 1992, 2000, Mariolakos et al. 1995, beris et al. 1979, Stamatopoulos et al. 1988, Fountoulis Fountoulis et al. 2007a,b] (Figure 1). These horsts con- et al. 2013] (Figure 1). sist of alpine formations and are bounded by fault zones forming impressive morphological discontinu- 3.3.2. The Panopoulo fault zone ities [Lekkas et al. 1992, 2000, Fountoulis et al. 2007a,b] The Panopoulo fault zone bounds the Erymanthos (Figure 1). The basin is filled with Late Miocene- Mts horst in its southern part, trends NW-SE and dips Holocene deposits, with a maximum thickness of ap- to the SW. The footwall of the Panopoulo fault zone proximately 3000 m [Lekkas et al. 2000]. These consists of alpine formations of the Gavrovo and the post-alpine deposits overlay unconformably the well- Pindos units [Dercourt et al. 1978, Fleury et al. 1981,

5 MAVROULIS ET AL.

Lekkas et al. 1992]. The hanging wall consists of Upper felt throughout Peloponnese, western Greece and At- Pliocene-Pleistocene lacustrine or marine clays and tica, but predominantly in the Patras city and its sub- Pleistocene terrigenous conglomerates of the Pyrgos- urbs. More than 15 villages and cities suffered significant Olympia basin [Lekkas et al. 1992] (Figure 1). damage. Three villages were evacuated in order to The Panopoulo fault zone was formed between avoid rockfall risk during the aftershock activity. Over- Mid-Upper Miocene and Upper Pliocene and it was ac- all, thousands of buildings suffered small to severe dam- tive even during the Upper Pliocene-Pleistocene age, whereas hundreds collapsed. [Lekkas et al. 1992]. This fault zone is now entirely cov- The epicenter was located in the Andravida area, ered by recent formations and specifically by a soil hori- 35 km SW from the city of Patras (Figure 1). The main zon with thickness of several meters (5 m thick in the shock is consistently located at depths 19-24 km if dif- Panopoulo village area) [Lekkas et al. 1992]. ferent absolute locations are considered and at 18 km depth after wave cross correlation (WCC) relocation 3.3.3. The Peiros fault zone method [Konstantinou et al. 2009]. All provided focal South of the Patras Gulf, the Skolis Mt and the mechanisms demonstrate a NE-SW trending strike-slip Araxos Cape consist of Mesozoic limestones (Figure 1). seismic fault zone that dips towards NW at a steep These outcrops suggest an intense tectonic uplift and angle (Figure 1). The spatial distribution of aftershock erosion of the overlying thick Tertiary flysch. This up- seismicity with most hypocentral depths in the range lift contrasts with the sea floor subsidence of the Patras between 15 and 25 km [Konstantinou et al. 2009] was Gulf and reveals the existence of a N-dipping normal clearly aligned along a NE-SW axis for a total length of fault in the southern part of the Gulf, parallel to the about 60 km (Figure 1). This is consistent with the Kato Achaia coast [Dufaure 1975]. The western part of strike of one of the two nodal planes indicated by the this fault occurs in the northern part of the study area focal mechanism of the main shock. and henceforth referred to as the Peiros fault zone (Fig- The Andravida earthquake is the largest but not ure 1). The Peiros fault zone trends NW-SE and dips to- the first strike-slip event in the recent history of the wards NE. This fault zone propagates westwards to the NW Peloponnese. Strike-slip earthquakes are common Patras Gulf and it is reported as active due to: (a) the in western Greece and are due to a compressional com- recorded deformation of the sea bed [Ferentinos et al. ponent of the differential motion between the Africa 1985], (b) the study of microseismicity [Melis et al. and Eurasian plates [Benetatos et al. 2004]. Over 30 ad- 1989] and (c) the high rates of Holocene subsidence ditional dominantly strike-slip crustal earthquakes with [Chronis et al. 1991]. Mw>4.0 have been recorded between 1965 and 2009 in the NW Peloponnese and the surrounding regions 3.3.4. The western Achaia fault zone from published reports and earthquake catalogues. The epicenter of the 2008 Andravida earthquake Apart from the microseismic experiments carried out is located on a previously unknown almost vertical seis- by Hatzfeld et al. [1989, 1990], recent studies of seis- mogenic zone, which is covered by Quaternary deposits micity in Peloponnese recorded earthquakes with and the thick Gavrovo flysch (Figure 1). Furthermore, focal mechanisms, that indicate dextral strike-slip mo- there is no direct morphotectonic or geological evi- tion in the NW Peloponnese [Hatzfeld et al. 2000, dence at surface [Mavroulis et al. 2010]. The fault plane Sachpazi et al. 2000, Benetatos et al. 2004]. Recent solution of the earthquake is consistent with dextral strike-slip events in this area include the offshore strike-slip on a steep NE-SW trending fault (Figure 1). Kyllini earthquake in October 16, 1988 (Mw=5.8), and The distribution of the aftershock sequence also shows the offshore Vartholomio earthquake in December 2, an alignment along a NE-SW trend for more than 60 2002 (Mw=5.6) [Lekkas et al. 1990, 1995, Mariolakos et km, revealing a structure sub-parallel to the dextral al. 1991, 1995, Roumelioti et al. 2004] (Figure 1). These strike-slip Cephalonia transform fault zone [Konstanti- events were generated about 30-40 km WSW of the nou et al. 2009, Vassilakis et al. 2011]. We will refer to 2008 Andravida event. this NE-SW trending zone of deformation as the west- A broad and multidisciplinary effort was con- ern Achaia fault zone (WAFZ). ducted by several research groups in campaigns of in- strumental measures and surveys [Ganas et al. 2009, 4. The June 8, 2008, Andravida strike-slip earthquake Konstantinou et al. 2009, Feng et al. 2010, Papadopou- (Mw=6.4) los et al. 2010]. Special attention was also devoted to the On June 8, 2008, at 15:25 local time, an earthquake description and mapping of the effects induced by the of Mw=6.4 struck the NW Peloponnese. It was the Andravida earthquake on the natural and the manmade largest instrumentally recorded event in this area. It was environment. Numerous groups of scientists have con-

6 ESI 2007 AND EMS-98 FOR A STRIKE-SLIP EVENT tributed to the collection of these data [Lekkas et al. (sands, pebbles) with poor coherence. Their thickness is 2008a,b, Margaris et al. 2010, Pavlides et al. 2008, Ganas small ranging from 1 m to several meters and the width et al. 2009, Konstantinou et al. 2009, Koukouvelas et al. of the outcrops varies. Their geomechanical behavior 2010, Mavroulis et al. 2010, Feng et al. 2010, Papadopou- and properties vary widely depending on their particle los et al. 2010], which are presented below in detail. size distribution and their mineralogical composition, while small scale subsidence and swelling phenomena 5. Andravida earthquake environmental effects (EEE) are frequently observed. The alluvial deposits are loose, Several EEE have been recorded and presented in include clays, silts, sands and pebbles and are easily Table 1 and Figures 2 and 3. erodible and leached by surface water. Their frequent and rapid changes in their lithological composition and 5.1. Primary EEE grain size distribution vertically and horizontally con- No effects, which are directly linked to the earth- trol their physical and mechanical properties, while quake energy and in particular to the surface expres- their thickness, their lithological anisotropy and the sion of the seismogenic source, were induced by the morphological slope affect their behavior especially in 2008 Andravida strike-slip earthquake. There was no the case of dynamic loading. primary surface faulting observed and the surface de- The NE-SW trending surface fractures observed in formation was smaller compared to the Andravida Kato Achaia show a dominant strike-slip component. earthquake magnitude. The burial depth and downdip These fractures exceed 300 m in length and 5 cm in extent of the seismogenic fault within a homogeneous width with a horizontal displacement estimated to be elastic earth cannot explain the observed small surface around 20 cm. Some NW-SE trending extensional frac- deformation. Therefore, Feng et al. [2010] argue that tures were also observed in the area. Despite the fact the compositionally weak, 3 km thick flysch layer acted that the fractures in the Kato Achaia area have the same as a near-surface decoupling agent, which isolates sub- NE-SW trend with the seismogenic strike-slip WAFZ surface deformation from the surface. Particularly, the that caused the Andravida earthquake, they could not strain energy released by the thick pile of flysch proba- be considered as primary effects and as the surface ex- bly could not sustain the coseismic rupture propagation pression of the WAFZ due to their limited length and below the pre-orogenic carbonates to the surface; alter- width. An intensity VIIIESI-2007 was assigned for the natively the weak flysch may allow for an essentially de- Kato Achaia surface fractures (Table 1, Figure 4). coupled cap with lower overall stress, and hence lateral NW-SE trending transverse surface fractures were slip in the carbonates will not necessarily propagate observed in the Nissi area, in Holocene loose torrential through the flysch layer [Feng et al. 2010]. The remain- deposits consisting of clayey-sandy materials with grav- ing strain in the flysch during coseismic rupture might els and cobbles (Table 1, Figures 2, 3a,b). They present be released by interseismic ductile deformation or fail similar characteristics and behavior to those of the al- in subsequent, smaller earthquakes [Feng et al. 2010]. luvial deposits mentioned above. They were 300 m long, 20 cm wide, at least 1.5 m deep and their vertical 5.2. Secondary EEE throw was estimated to be around 40 cm, with uplift on the western side. The horizontal displacement of 5.2.1. Surface fractures approximately 20 cm shows significant strike-slip com- Surface fractures were among the most character- ponent. An intensity VIIIESI-2007 was assigned for the istic secondary effects triggered by the 2008 Andravida Nissi surface fractures (Table 1, Figure 4). earthquake implying a VIIIESI-2007 intensity (Table 1, Transverse extensional surface fractures trending Figures 2, 3). They were observed (a) in the Kato Achaia NW-SE were also observed in the Dafni area on a Pleis- area, (b) in the Nissi area and (c) in the Dafni area (Table tocene marine formation with medium to coarse- 1, Figures 2, 3). The Kato Achaia town and the Dafni grained sands and well-bedded grits with intercalations village are located at the northern and the southern of medium-grained sandstones (Table 1, Figures 2, 3c). ends of the aftershocks distribution respectively, while It is characterized by medium to high coherence and the Nissi village is located west of the surface projec- low resistance in weathering. An intensive fracturing is tion of the seismogenic dextral strike-slip fault zone usually present, while the manifestation of shallow ro- (Figure 2). tational and/or translational slides is frequently ob- Surface fractures in the Kato Achaia area occurred served. Its mechanical characteristics and behavior are in Holocene loose formations and especially in coastal strongly influenced by the degree of saturation, so that and alluvial deposits (Table 1, Figure 2). The coastal de- in case of full saturation a considerable reduction of posits consist of fine and coarse grained materials shear strength is observed. These surface fractures

7 MAVROULIS ET AL. ESI 2007 Intensity - V - Strong / Marginal V - Strong / Marginal Effects in the environment Effects VII - Damaging / Appreciable VI - Slightly damagingVI - Slightly / Modest VIII - Heavily damaging / Extensive VIII - Heavily damaging / Extensive VIII - Heavily VIII - Heavily damaging / Extensive VIII - Heavily Depth: 1.5 m Width: 20 cm Width: Length: 300 m from 4 to 12 cm (c) lateral spreading Description of EEE Vertical throw: 40 cm throw: Vertical strike-slip component Ejection of sands grey and width up to 22 cm , accompanied by two ground two cracks, accompanied by cracks on the pavement 2 Length: 300 m Width: 5 cm Length: 300 m Width: Landslide (volume < 10 m3) Landslide (volume Landslide (volume < 10 m3) Landslide (volume Horizontal displacement: 20 cm Horizontal displacement: 20 cm sea and vertical subsidence ofsea and vertical 2 cm (b) ejection of sandy material from small (a) sand volcanoes with diameter ranging(a) sand volcanoes NW-SE trending (transverse) surface fractures (transverse) trending NW-SE with horizontal displacement of the 4 cm toward tures with length rangingtures from 50 cm to 4 meters (a) Ejected grey sandy material forming vent frac- sandy material forming(a) Ejected grey vent (b) Sand volcanoes with diameter up to 8 cm in an (b) Sand volcanoes area ofarea 1 km NE-SW trending surface fracturesNE-SW trending with a dominant Liquefaction Liquefaction Liquefaction Type ofType EEE Surface fractures Surface fractures Secondary effect, Secondary effect, Secondary effect, Secondary effect, Secondary effect, Secondary effect, Secondary effect, Slope movements Slope movements Latitude 38.084280626 38.075855135 38.080655047 38.083577846 38.083207950 38.085919865 38.085654912 38.075948882 38.005173843 Coordinates Longitude 21.313602890 21.325247331 21.334612499 21.340100602 21.334215760 21.364415315 21.353815502 21.235887630 21.333680114 (Alikes) Nissi village (sea shore of(sea shore the Kato Achaia area Kato Achaia area Kato Achaia area Kato Achaia area Kato Achaia area Sites (in Figure 2) Kato Achaia town) List of earthquake (Mw=6.4). 8, 2008, Andravida the June by sites with the EEE triggered Table 1. Table 8 ESI 2007 AND EMS-98 FOR A STRIKE-SLIP EVENT ESI 2007 Intensity - V - Strong / Marginal Effects in the environment Effects VI - Slightly damagingVI - Slightly / Modest damagingVI - Slightly / Modest VI - Slightly damagingVI - Slightly / Modest damagingVI - Slightly / Modest VI - Slightly damagingVI - Slightly / Modest VIII - Heavily damaging / Extensive VIII - Heavily VIII - Heavily damaging / Extensive VIII - Heavily ) 3 Depth: 1.5 m Width: 10 cm Width: towards the river towards Small sand volcano Description of EEE from ground fissures and width up to 15 cm from small ground cracks Landslide (volume <10 m Landslide (volume Length: hundreds ofLength: hundreds meters extensional surface fracturesextensional NW-SE trending (transverse) trending NW-SE of Yrmini in Kounoupeli area Ejection of fine-grained material Small sand boils involving clear sand Small sand boils involving (b) Horizontal displacement of 1-2 cm (a) Ejection of coarse-grained material (a) Renewed flow of flow springs (a) Renewed the curative (c) Sand volcanoes with diameter up to 17 cm (c) Sand volcanoes 3 smaller ones with diameter up to 70 cm each (b) Smaller surficial flows along the same coast (b) Smaller surficial flows (d) Lateral spreading at the Pineios River banks (d) Lateral at the Pineios River spreading (c) Turbidity of and springs wells (c) Turbidity in several water (b) Vent fractures with length more than 5 meters fractures with length more (b) Vent (a) 2 sand-mud boils with diameter up to 85 cm and (a) 2 sand-mud Liquefaction Liquefaction Liquefaction Liquefaction Liquefaction Type ofType EEE Surface fractures Secondary effect, Secondary effect, Secondary effect, Secondary effect, Secondary effect, Secondary effect, Secondary effect, Secondary effect, Slope movements Hydrological anomalies Hydrological Latitude 38.001358310 37.562108882 37.525539307 37.534371297 38.031359923 38.055762768 37.562397350 37.563521140 37.500249714 38.084855302 Coordinates Longitude 21.313918848 21.232432301 21.310759358 21.284705860 21.283409919 21.382714877 21.283355847 21.302713420 21.193831519 21.205468581 Nissi Dafni area Oinoi area Kounoupeli Tsoukaleika Manolada beach Sites (in Figure 2) (Pineios River banks) (Pineios River (continued from previous page). List of from previous earthquake(continued (Mw=6.4). 8, 2008, Andravida the June by sites with the EEE triggered Close to the Kalivakia village Close to the Roupakia village (shore of(shore the Pineios artificial lake) (shore of(shore the Pineios artificial lake) Table 1 Table 9 MAVROULIS ET AL. ESI 2007 Intensity - V - Strong / Marginal V - Strong / Marginal V - Strong / Marginal V - Strong / Marginal V - Strong / Marginal V - Strong / Marginal V - Strong / Marginal V - Strong / Marginal V - Strong / Marginal V - Strong / Marginal Effects in the environment Effects ) ) 3 3 ) ) 3 3 ) 3 ) ) ) 3 3 3 ) ) 3 3 (volume <10 m (volume (volume <10 m (volume Description of EEE Landslide (volume <10 m Landslide (volume Landslide (volume <10 m Landslide (volume <10 m Landslide (volume Rock toppling failures of toppling failures Rock limestones Lefkochori fault zone (volume <10 m Lefkochori fault zone (volume Rock toppling failures of toppling failures Rock limestones at the dipping towards the road (volume <10 m the road (volume dipping towards dipping towards the road (volume <10 m the road (volume dipping towards Landslides along the active Pineios fault zone Landslides along the active of sands with consolidated or silts, clays, marly Sliding of formations consisting of alternations Sliding of marls along bedding planes and joints Sliding of marls along bedding planes and joints western slopes of <10 m the Skolis Mt (volume non-consolidated conglomerates (volume <10 m non-consolidated conglomerates (volume Rock toppling failures of toppling failures Rock limestones along the active Type ofType EEE Secondary effect, Secondary effect, Secondary effect, Secondary effect, Secondary effect, Secondary effect, Secondary effect, Secondary effect, Secondary effect, Secondary effect, Slope movements Slope movements Slope movements Slope movements Slope movements Slope movements Slope movements Slope movements Slope movements Slope movements Latitude 38.092803508 37.540554416 38.111568534 37.422065603 37.560517620 37.590362705 37.542134671 37.434676681 38.352500073 37.404163374 Coordinates Longitude 21.395829218 21.343057309 21.343339906 21.324217909 20.325317214 22.115590708 21.233510597 22.005041384 21.332694557 21.394094201 Latzoi Portes Neraida Diakofto Santomeri Lefkochori Vrachneika Porto KatsikiPorto Sites (in Figure 2) Pigadi and Simiza area (continued from previous two pages). List of two earthquake from previous (Mw=6.4). 8, 2008, Andravida (continued the June by sites with the EEE triggered Road from Portes to Valmi from Portes Road (western steep slopes of the Skolis Mt) (western steep slopes of the Skolis Mt) Table 1 Table 10 ESI 2007 AND EMS-98 FOR A STRIKE-SLIP EVENT

Figure 2. The spatial distribution of the 2008 Andravida EEE in (a) the NW Peloponnese wide area and (b) in the epicentral area of the 2008 Andravida earthquake according to the Table 1. The percentage distribution of the Andravida EEE by type is also presented. The epicenter distribution for the Andravida aftershock sequence is from the aftershocks catalogue presented by the Department of Seismotectonics, Earth- quake Planning and Protection Organization (from June 8 to June 20, 2008) [Lalechos et al. 2008].

11 MAVROULIS ET AL.

Figure 3. View of the most characteristic 2008 Andravida EEE. (a, b, c) NW-SE trending transverse surface fractures were observed in the Nissi area. (d, e) Rock toppling failures of limestones took place at the western foothills of Skolis Mt, in the Santomeri (d) and the Portes (e) villages. (e) Cretaceous carbonates overthrust shaly flysch at the western steep slopes of Skolis Mt. The flysch strata close to the thrust sur- face are steeply dipping and overturned. (f) Landslides and failures of artificial slopes took place along the national roads of the study area (Vrachneika). (g) Landslide along the road from the Portes to the Valmi village. (h) Surface fractures and flows of liquefied material ob- served in the Kato Achaia area. (i) Sand boils in the Nissi area.

12 ESI 2007 AND EMS-98 FOR A STRIKE-SLIP EVENT were 10 cm wide and at least 1.5 m deep. An intensity (Table 1, Figure 4). VIIIESI-2007 was assigned for the Dafni surface fractures Close to a stream estuary located 2 km west of the (Table 1, Figure 4). Kato Achaia town (Alikes area), liquefaction phenom- ena were also observed including: (a) sand volcanoes 5.2.2. Liquefaction phenomena with diameter ranging from 4 to 12 cm, (b) ejection of Impressive liquefaction phenomena were concen- sandy material from small cracks on the pavement and trated in sites formed by loose alluvial deposits, both at (c) lateral spreading (Table 1). An intensity VIIESI-2007 the areas located north (Kato Achaia, Alikes and Nissi) was assigned for the Alikes site (Table 1, Figure 4). and south (Roupakia, Kalivakia, Oinoi) of the epicenter A small sand volcano was also observed in loose [Papathanassiou et al. 2008] (Table 1, Figures 2, 3). It is alluvial deposits in the Nissi village (Figure 2b). Minor important to note that no liquefaction phenomena liquefaction phenomena also occurred at the Manolada were observed in the Lower Pineios River delta area, beach (Figure 2b) and they were manifested as small where liquefaction and other forms of ground failure sand boils involving clear sand. An intensity VIESI-2007 were observed during the previous offshore earth- was assigned for both sites (Table 1, Figure 4). quakes of October 16, 1988, in Kyllini peninsula pre- sented and described by Mariolakos et al. [1989, 1995] 5.2.3. Slope movements and Lekkas et al. [1990] and of December 2, 2002, in The 2008 Andravida earthquake triggered a num- Vartholomio presented and described by Apostolidis et ber of small (volume < 10 m3) and isolated slope move- al. [2002]. ments in several localities over a wide area including the Typical examples of liquefaction phenomena were NW Peloponnese, Aitoloakarnania and Ionian Islands reported at the Pineios River Lake (Figure 2). This area (Table 1, Figures 2, 3). These slope movements include: consists of loose mainly fine-grained alluvial deposits (a) sliding of marls along bedding planes and joints dip- of the Pineios River (Figure 2b), which present poor co- ping towards the national road from Patras to Pyrgos herence, small scale subsidence and swelling phenom- near Vrachneika (VESI 2007) and towards the national ena. At the shore of the Pineios artificial lake, close to road from Patras to Corinth near Diakofto (VESI 2007), the Roupakia village (Figure 2b), the following lique- (b) rock toppling failures of limestones in the eastern faction phenomena were reported: (a) two sand-mud margin of the Pyrgos-Olympia basin, along the Lefko- boils with diameter up to 85 cm and three smaller ones chori fault zone, which is active [Fountoulis et al. with diameter up to 70 cm each, (b) vent fractures with 2007a,b] (VESI 2007), (c) landslides along the active Pineios length more than 5 meters and width up to 15 cm, (c) fault zone in the wider area of Pigadi and Simiza villages sand volcanoes with diameter up to 17 cm and (d) a lat- (VESI 2007), (d) rock toppling failures of limestones in the eral spreading at the Pineios River banks [Papathanas- wider area of Santomeri and Portes villages at the west- siou et al. 2008] (Table 1). Therefore, the assigned ern slopes of the Skolis Mt (VESI 2007), (e) sliding of for- intensity for this area is VIIIESI-2007 (Table 1, Figure 4). mations consisting of alternations of clays, silts, sands Fine-grained material was ejected from ground fis- with consolidated or non-consolidated conglomerates sures at the Pineios River shore close to the Kalivakia along the road from Portes to Valmi village (VESI 2007) village (Figure 2b), while coarse-grained material was and along the road near Tsoukaleika village in the ejected from small ground cracks at the Pineios River Achaia prefecture and near Latzoi and Neraida in the banks, few kilometers to the south [Papathanassiou et Ilia prefecture. Other slope movements and particularly al. 2008] (Table 1). At the same place, a horizontal dis- rockfalls were also observed northwestwards as far as the placement of 1-2 cm towards the river was observed. Porto Katsiki beach in the island of Lefkada (VESI 2007) The assigned intensity for both areas is VIESI 2007 (Table (Table 1, Figures 2, 3). 1, Figure 4). In the evaluation of the total area of the distribu- Impressive liquefaction phenomena were also ob- tion of the EEE and the ESI 2007 intensities, it is rec- served in the loose coastal and alluvial deposits of the ommended not to include isolated effects which Kato Achaia area (Figure 2) including: (a) ejected grey occurred in the far field. Therefore, the slope move- sandy material forming vent fractures with length rang- ments observed in the SW part of the Lefkada Isl. (Porto ing from 50 cm to 4 m and width up to 22 cm and (b) Katsiki), in the eastern part of the Achaia prefecture (Di- sand volcanoes with diameter up to 8 cm in an area of akofto village), in the central-western Peloponnese 1 km2, accompanied by two ground cracks with hori- (Lefkochori village) and in the Pyrgos municipality (Lat- zontal displacement of 4 cm toward the sea and verti- zoi and Neraida villages) (Figure 2a) were not taken into cal subsidence of 2 cm [Papathanassiou et al. 2008] account for the final assignment of the environmental (Table 1). Hence, intensity VIIIESI-2007 was assigned seismic intensities of the study area.

13 MAVROULIS ET AL.

Landslides in the Kato Achaia, Vrachneika and ceous limestones of the Paxoi unit [Lekkas et al. 2001] Tsoukaleika areas occurred in friable Pliocene sand- observed along the Porto Katsiki beach. stones, sandy clays and clayey marls with sparse in- tercalations of conglomerates (Figures 2b, 3f). The 5.2.4. Hydrological anomalies lithological facies of this formation are variable. The Hydrological phenomena were observed in hot non-uniform and anisotropic behavior of the formation springs and wells including renewed flow of springs and as a whole and the rapid change of its mechanical char- changes in water discharges as well as water turbidity. acteristics vertically and horizontally resulting from its The renewed flow of the curative springs of Yrmini in heterogeneity cause the generation of shallow failures Kounoupeli area was reported by Pavlides et al. [2008] and slides along natural and artificial slopes, as hap- (Table 1, Figure 2). These coastal springs located north- pened in the areas above. west of Nea Manolada and the hot water spring from Landslides in the area of the Pigadi and the Simiza NW-SE trending cracks occurred in limestones of the villages occurred in a Pleistocene marine formation Ionian unit as well as from an IGME drilling. It is re- with medium to coarse-grained sands and well-bedded markable that the flow had been stopped since the off- grits with intercalations of medium-grained sand- shore 1988 Kyllini earthquake and reestablished after stones. This formation is faulted by the active Pineios the 2008 Andravida earthquake with larger discharge fault zone [Fountoulis et al. 2013] (Figures 1, 3b). The rates. Artesian phenomena and out-flows causing dam- tectonic deformation along this active fault zone re- age of the borehole sealing have also been identified. sulted in a dense net of discontinuities and the rela- Considering the aforementioned data, an intensity tively loose formations facilitated these slope VIESI-2007 was assigned for the site of Kounoupeli. movements. Smaller surficial flows were detected along the same Landslides along the road from the Portes to the coast in a NW-SE direction. Moreover, water turbidity Valmi village were observed in an Upper Pliocene-Lower was reported in several wells and springs in the flat area Pleistocene formation consisting of clays, silts, sands between Nea Manolada and Vartholomio villages. with conglomerates, with varying coherence, strong heterogeneity and high anisotropy in its behavior. 5.3. Conclusions on the EEE and the corresponding ESI Skolis Mt is the most impressive topographic fea- 2007 intensities ture of the study area, a N-S trending steep mountain, In total, secondary effects in 29 sites have been reaching an altitude of 1000 m, rising above the lower recorded, described, mapped and classified in the fol- flysch relief. Cretaceous carbonates overthrust shaly fly- lowing four categories: seismic fractures (24%), lique- sch at its western flank [Fleury 1980, Tsoflias 1980, faction phenomena (28%), slope movements (45%) Fleury et al. 1981]. The flysch strata close to the thrust [including landslides (35%) and rockfalls (10%)], and hy- surface are steeply dipping and overturned (Figure 3e) drological anomalies (3%) (Table 1, Figures 2, 3). The clearly revealing the intense tectonic deformation of total areal distribution of secondary EEE is about 800 the area. The Gavrovo Cretaceous carbonates are also km2. Based on this total area, the ESI 2007 epicentral highly fractured by E-W trending inactive faults [Lekkas intensity degree is VIII-IX and closer to IX (Figure 4). et al. 1992]. This intense and multiple fracturing along The Andravida EEE are classified as marginal to with the erosion and weathering processes contribute extensive. A maximum VIIIESI 2007 intensity has been as- to the decreased cohesion along the steep slopes of the signed to several sites (Kato Achaia, Nissi and Pineios mountain and resulted in the generation of rockfalls Lake areas) (Table 1, Figures 2, 4), where surface frac- during the 2008 Andravida event (Figures 2b, 3d,e). tures up to 20 cm wide and up to hundreds meters long Rockfalls also occurred in the eastern margin of as well as impressive liquefaction phenomena were ob- the Pyrgos-Olympia basin (Figure 2a) and are linked served in post-alpine formations. Intensity VIIESI 2007 to the highly fractured carbonates of Tripolis unit was assigned to the Dafni area, where surface fractures along the Lefkochori fault zone, which is active [Foun- were observed. A minimum intensity equal to V was toulis et al. 2007a,b]. This is an area where suitable observed within the alpine basement (western slopes conditions for the generation of rockfalls already ex- of Skolis Mt) as well as in the post-alpine formations isted before the earthquake, which simply triggered (Pigadi, Simiza, Valmi and Vrachneika villages) respec- these phenomena. tively, where small volume (<10 m3) rockfalls and land- Rockfalls in the NW part of the Lefkada Isl. (Fig- slides were triggered. An ESI 2007 intensity map was ure 2a) are directly linked to the active faults defining constructed depicting the spatial distribution of the ef- the neotectonic unit of Lefkata peninsula [Lekkas et al. fects and the isoseismals based on the ESI 2007 intensi- 2001] and forming the impressive fault scarps in Creta- ties (Figure 4).

14 ESI 2007 AND EMS-98 FOR A STRIKE-SLIP EVENT

Figure 4. The 2008 Andravida earthquake isoseismal map based on the ESI 2007 intensities.

6. Structural damage in the affected area and EMS-98 including partial collapse of walls (Figure 5b) and (c) de- intensities struction (grade 5) comprising total or near total col- lapse of the building (Figure 5c). Damage in most of the 6.1. Type of structures and structural damage R/C buildings was concentrated in non-load carrying The majority of structures in the study area can be components, infill and partition walls, comprising (a) broadly categorized in two main types, which are: (a) moderate damage (grade 2) such as diagonal cracking one or two storey stone masonry buildings with insuf- in brick partition walls as an influence of prevailing ficient or non-existent seismic resistance design and (b) shear forces in brick partition walls and panels (Figure reinforced concrete (R/C) buildings. Most of the R/C 5d), (b) substantial to heavy damage (grade 3) including buildings were built according to the Greek Seismic detachments of the walls from the surrounding R/C Code that was implemented in 1959 with subsequent frame (Figure 5e) and (c) destruction of the R/C build- revisions and upgrades. ing (grade 5) comprising collapse of ground floor due to After detailed engineering surveys and evaluations damage to R/C elements (Figure 5f). of the earthquake affected buildings in western Greece Extensive damage was observed to the highly vul- (conducted by the Earthquake Recover Service of the nerable monumental buildings and especially to Greek Ministry of Infrastructure, Transport and Net- churches and their bell towers including (a) cracks ob- works), 1874 buildings were considered unsafe to occupy served at the exterior walls as well at the junctions of (580, 1266 and 28 red carded buildings in Ilia, Achaia and the exterior walls, at several interior masonry arches Aitoloakarnania prefectures respectively), while 5630 and around openings or at the top of the exterior walls buildings were considered suitable only for restricted use on which wood roofs rest (Figure 5g), (b) partial col- or access until repairs are completed (2330, 2902 and 398 lapse of the exterior walls (Figure 5h) and (c) total col- yellow carded buildings in Ilia, Achaia and Aitoloakar- lapse of the building (Figure 5i). nania prefectures respectively) (http://www.yas.gr). Damage to bridges included cracks in the road as- Structural damage to masonry buildings induced phalt surface, transverse to the longitudinal axis of the by the 2008 Andravida earthquake includes (a) substan- bridge (Figure 5j,k,l). tial to heavy damage (grade 3) comprising large and ex- Bending of railway lines with 20 cm displacement tensive cracks in most walls and fall of very large pieces due to seismic fractures has been observed in the Kato of plaster (Figure 5a), (b) very heavy damage (grade 4) Achaia railway station (Figure 5m).

15 MAVROULIS ET AL.

Figure 5. Structural damage induced by the 2008 Andravida earthquake: (a) damage of grade 3 to masonry building in the Nissi village in- cluding large and extensive cracks in most walls and fall of very large pieces of plaster, (b) damage of grade 4 to masonry building in the Valmi village including partial collapse of walls, (c) damage of grade 5 to masonry building in the Valmi village including total or near total collapse, (d) damage of grade 2 to R/C building in the Stafidokampos village including diagonal cracking in brick partition wall, (e) damage of grade 3 to R/C building in the Valmi village including detachments of the walls from the surrounding R/C frame and (f) damage of grade 5 to R/C building in the Didacheika village including collapse of ground floor due to damage to R/C elements, (g, h, i) damage to monumental build- ings including (g) cracks observed at the exterior walls as well at the junctions of the exterior walls, at several interior masonry arches and around openings or at the top of the exterior walls on which wood roofs rest (Nissi village), (h) partial collapse of the exterior walls (Psari area), (i) total collapse of the church (Valmi village). (j, k, l) Damage to bridges included cracks in the road asphalt surface, transverse to the longitudinal axis of the bridge (Kato Achaia area). (m) Railway line in the Kato Achaia train station deformed by the earthquake.

6.2. EMS-98 intensities Mavroulis 2009, Mavroulis et al. 2010, Papadopoulos et Based on field surveys immediately after the main al. 2010], EMS-98 intensities were assigned to the local- shock aiming at the description, mapping and classifi- ities that suffered damage by the earthquake. An iso- cation of the damage induced by the earthquake on in- seismal map was also constructed and depicts the frastructure and constructions in the NW Peloponnese spatial distribution of the structural damage and the [Lekkas et al. 2008a,b,c, Margaris et al. 2008, 2010, isoseismals based on the EMS-98 intensities (Figure 6).

16 ESI 2007 AND EMS-98 FOR A STRIKE-SLIP EVENT

Figure 6. The 2008 Andravida earthquake isoseismal map based on the EMS-98 intensities.

Damage due to shocks between building of different Town/Village EMS-98 ESI 2007 height and stiffness or observations from special struc- tures, such as lighthouses, radio towers, bridges etc. Valmi IX V were not taken into account for the EMS-98 seismic in- Kato Achaia VIII VIII tensity assignments for the 2008 Andravida event al- Didacheika VIII ways bearing in mind the limitations and the special cases of the EMS-98 scale. The damage to monumen- Fostaina VIII tal buildings, such as churches and their bell towers are Eleochori VIII only presented below and have been not taken into ac- Nissi VIII VIII count for the EMS-98 seismic intensity assignments. The maximum EMS-98 intensity was assigned to Varda VIII the Valmi village (IXEMS-98) (Table 2, Figure 6) located Nea Manolada VIII close to the eastern tip of the active Pineios fault zone and founded on an Upper Pliocene-Pleistocene forma- Lapas VIII tion consisting of sandy or silty clays with local inter- Santomeri VII V calations of coarse-grained sands with varying coherence, Portes VII V strong heterogeneity and high anisotropy in its behav- ior. It is estimated that 85% of the masonry buildings in Vartholomio VII the Valmi village were considered unsafe to occupy suf- Gastouni VII fering damage ranging from grade 3 (large and exten- Andravida VII sive cracks in most walls and fall of very large pieces of plaster) to grade 5 (total or near total collapse) (Figure Vrachneika VII V 5b,c). Many (40-50%) R/C buildings suffered moderate Tsoukaleika VI V damage of grade 2, as cracking of load-carrying com- ponents were observed especially in columns and joists Pigadi VI V (Figure 5e) and a few (5%) of grade 3, as brick infill Simiza VI V walls were detached from the surrounding R/C frame. Kato Achaia is the area that was shaken most vio- Table 2. EMS-98 and ESI 2007 intensities obtained in the region.

17 MAVROULIS ET AL. lently and sustained much damage to its buildings in the degree of looseness, the orientation of discontinu- the northern part of the affected area. It is located close ities, the dip of slopes and the action of water. The be- to the northern tip of the activated blind strike slip fault havior of the old Quaternary deposits is controlled by zone and founded on the Peiros River alluvial deposits, the thickness, their lithological anisotropy and the slope which are characterized by frequent and rapid changes angle, especially in the case of dynamic loading. Fur- in their lithological composition and grain size distri- thermore, the dominant cause for the damage in many bution vertically and horizontally. Many (40 %) ma- structures as well as for the inconsistency between the sonry buildings suffered damage of grade 4, as they higher EMS-98 compared to the ESI 2007 values in sev- sustained serious failure of walls and partial structural eral villages was the poor building quality. Buildings are failure of roofs and floors and a few of them had to be highly vulnerable since they are predominantly old ma- demolished. A few (10 %) masonry buildings under- sonry buildings with no earthquake-resistant design. went damage of grade 5, as they totally or almost to- The Nissi village is located northwest of the earth- tally collapsed. A few (5 %) R/C buildings suffered quake epicenter and founded on loose Pleistocene tor- damage of grade 2, as cracks were observed in the brick rential deposits consisting of sands in the lower beds infill walls. The estimated EMS-98 intensity in these vil- and rubbles in the upper beds as well as on a Pleistocene lages was as high as VIII (Table 2, Figure 6). formation of medium to coarse-grained sands and well- Many churches both in the Valmi village (Figure bedded grits with medium coherence, low resistance in 5i) and the Kato Achaia town collapsed or underwent weathering and intensive fracturing. The most widely serious structural damage. Extensive cracking was ob- observed damages in masonry buildings of the Nissi vil- served at the exterior walls as well as in almost every lage were the cracking of the load-carrying walls and interior arch and dome that constitute its structural sys- the detachment of large pieces of plasters applied on tem. Damage to several masonry bell towers were also walls (grade 3), serious failure of load-carrying walls observed in many cases due to the different height and (grade 4) and the total or almost total collapse of the stiffness between the main church building and the ma- construction (grade 5). A VIIIEMS-98 intensity was as- sonry bell towers. signed (Table 2, Figure 6). The Didacheika, the Fostaina and the Eleochori The villages of Varda, Nea Manolada and Lapas villages are located within the Kato Achaia-Fares are located north of the Nissi area. They are founded basin. The first is founded on old Quaternary deposits on Pleistocene formations and alluvial deposits con- consisting of polygenic, loose conglomeratic breccia sisting mainly of clayey-sandy material and gravels. The with terra rossa and local intercalations of red clayey structural damage and the EMS-98 intensity (VIII) are sand, while the other two villages are founded on the similar to those of the Nissi village. Gavrovo flysch sediments consisting mainly of pelites Structural damage also occurred in the western and conglomerates. These three villages suffered simi- slopes of the Skolis Mt especially in the Santomeri and lar damage to those of Kato Achaia. Thus, the esti- Portes villages (Figures 1, 3). Rockfalls from the steep mated EMS-98 intensity in these villages was as high as slopes of Skolis Mt consisting of Gavrovo limestone VIII (Figure 6). Many (30-40%) one-storey and two- over-thrusting flysch caused damage of grade 5 to one of storey masonry buildings underwent damage of grade the masonry buildings in the Santomeri village. Many 5, as they were totally or partially collapsed and another (50%) masonry buildings suffered damage of grade 3, as 10% suffered severe structural damage in the Fostaina large and extensive cracking and failure of partition and village. A few (5%) of the R/C buildings of the Di- brick infill walls were observed and a few (10%) of them dacheika village experienced cracking of the brick fill sustained damage of grade 4, as they underwent serious walls and detachments of the walls from the sur- failure of walls. Similar damage and percentage of the rounding R/C frame, while one collapsed possibly due damaged buildings were reported in the neighboring to constructional defect. Portes village. Thus, a VIIEMS-98 intensity was assigned In the above mentioned areas of Didacheika, Fos- in the Santomeri and Portes villages (Table 2, Figure 6). taina and Elaiochori, it seems that the foundation factor Another area that suffered structural damage is the (subsurface composed mainly of old Quaternary de- Pyrgos-Olympia basin with Gastouni and Simopoulo posits and flysch sediments) was the predominant cause sub-basins (Figure 1), which are filled with loose of damage. The surficial flysch beds usually show a Holocene deposits, Upper Pleistocene coherent cal- medium to strong weathering and a dense net of dis- careous sandstones, Pleistocene conglomerates in a continuities causing secondary looseness. This forma- loose siliceous matrix and Pliocene-Pleistocene clays, tion gives a weathering mantle of varying thickness. Its silts, sands and sandstones [Kamberis 1987, Lekkas et geotechnical behavior is anisotropic and controlled by al. 1992] (Figure 1). The thickness, the strong hetero-

18 ESI 2007 AND EMS-98 FOR A STRIKE-SLIP EVENT geneity, the lithological anisotropy of these formations served E of this fault zone. For all the sites where in- results in the non-uniform and the high anisotropic be- tensity VIII has been recorded the ESI 2007 and the havior of the formations and the rapid change of the EMS-98 agree, but for others the ESI 2007 intensities mechanical characteristics in the different horizons values are lower by one or two degrees than the corre- both vertically and laterally. Damage of grade 1 was ob- sponding EMS-98 ones, as it is clearly concluded from served in a few (5%) of the R/C buildings including the comparison of the produced isoseismals (Table 2, cracking of brick infill walls and hairline cracks of Figure 7). An exception to this rule is the Valmi village, columns as an extension of cracks in non-load carrying where considerable structural damage occurs along components. The usual damage of grade 3 in many with the lack of significant EEE, so that the VESI 2007 in- (30%) masonry buildings and damage of grade 4 in a tensity is four degrees lower than the IXEMS-98 intensity few (10%) of them were also observed. A VIIEMS-98 in- (Table 2, Figure 7). tensity was assigned in this area (Table 2, Figure 6). Firstly, we have to consider that the ESI 2007 in- In Vrachneika and Tsoukaleika founded on coastal tensity scale is calibrated on the basis of only seismi- and alluvial deposits, few masonry buildings (20 %) suf- cally induced ground effects and does not take into fered negligible to slight damage. A few (5 %) of the consideration the earthquake effects on structures and R/C buildings suffered slight damage such as fine the perceptibility of the strong ground motion. There- cracks in plaster and fall of small pieces of plaster. A fore, where no or limited ground damage is observed, VIEMS-98 intensity was assigned in the Vrachneika and for instance in the almost total destroyed Valmi village, Tsoukaleika villages (Table 2, Figure 6). where no coseismic primary and insignificant second- ary environmental effects were observed, the ESI 2007 7. Discussion scale provide seismic intensity lower than the tradi- The identification of the previously unknown dex- tional macroseismic intensity scales, underestimating tral strike-slip fault zone that generated the 2008 An- the overall effects of an earthquake to the manmade dravida earthquake provides useful information environment. regarding the internal deformation of the area. It is ev- Moreover, the generation of several earthquakes ident that a lot of settlements located in the NW Pelo- that struck the NW Peloponnese in recent years in- ponnese are exposed to significant seismic hazard due cluding Kyllini (October 16, 1988, Mw=5.8), Pyrgos to the proximity to several active fault zones and faults (March 3, 1993, Mw=5.4), Patras (July 14, 1993, Mw=5.4) (e.g. Pineios, Panopoulo, Peiros, WA fault zones) capa- and Vartholomio (December 2, 2002, Mw=5.6) earth- ble of storing enough potential energy to rupture and quakes (Figure 1), had certainly weakened the stone ma- generating major devastating earthquakes. sonry buildings, many of them constructed using fluvial The analysis of the field observations allowed us stones and poor quality mortar, which had been badly to map the spatial distribution of EEE and structural or inadequately restored afterwards. Thus, in the rural damage and assign seismic intensities based on the ESI area of the NW Peloponnese, which is mostly con- 2007 and EMS-98 scales. The assigned seismic intensi- structed according to the first Greek Seismic Code or ties allowed us to construct the respective isoseismal with insufficient or nonexistent seismic resistance design, maps for the Andravida earthquake. This information is the evaluation of the intensity based only on the EMS-98 essential for the identification and characterization of scale may overestimate the “strength” of the earthquake the most vulnerable sites exposed to the occurrence of and the ground shaking. The opposite is likely in urban earthquake environmental effects (seismically induced areas constructed according to modern code provisions, liquefaction phenomena, slope movements, ground where the evaluation of the seismic intensity based only settlements, etc.), the better assessment of the future on EMS-98 scale may underestimate the “strength” of impact of a similar event on towns and villages like the earthquake and the ground shaking. these in the NW Peloponnese that are characterized by Guerrieri et al. [2009] have drawn similar conclu- strong urban and infrastructural growth. sions after the application of the ESI 2007 scale and the The evaluated ESI 2007 intensities were compared MCS scale for the 1997 Umbria-Marche (Central Italy) with the assessed intensities based on the EMS-98 scale seismic sequence and the comparison of the corre- (Table 2, Figure 7). The maximum ESI 2007 intensity sponding intensities. The ESI 2007 intensity values have based on the parameters and the total area of the dis- frequently resulted one degree or even more lower than tribution of the secondary EEE is VIII-IX, while the the MCS ones, with some exceptions. This variability maximum EMS-98 intensity is IX. The VIIIESI 2007 is between the ESI 2007 and the MCS intensity values is mostly observed NW of the surface projection of the predominantly attributed to the poor maintenance of seismogenic strike-slip WAFZ, while the IXEMS-98 is ob- buildings due to the inconstant habitation. So, the MCS

19 MAVROULIS ET AL.

Figure 7. Comparison, similarities and differences between ESI 2007 and EMS-98 intensities and isoseismals for the 2008 Andravida earthquake. intensity field has resulted slightly overestimated with its quantitative nature, also promises to offer higher ob- respect to what expected for an event of Mw=5.6 in the jectivity in the process of assessing macroseismic intensi- Apennines. ties particularly in the epicentral area than do traditional Therefore, it is concluded that the integration of intensity scales that are influenced by human parameters. the ESI 2007 scale with the EMS-98 scale and other tra- The ESI 2007 scale follows the same criteria (EEE) for all ditional intensity scales provides a better picture of the events and can compare not only events from different earthquake effect on the built and the natural environ- tectonic settings, but also contemporary and future earth- ment. The combined evaluation of the constructed quakes with historical events. It offers higher spatial res- isoseismal maps based on the ESI 2007 and EMS-98 seis- olution and coverage and incorporates also site effects. mic intensities have once more confirmed the crucial As a result, a re-appraisal of historical and recent earth- role of the EEE and the structural damage in the quakes so as to constrain the ESI 2007 scale may prove process of seismic intensity assignments and the seis- beneficial for the seismic hazard assessment by reducing mic hazard assessment in the NW Peloponnese. They the uncertainty implied in the attenuation laws and even- can be also evaluated and used in mitigation strategies, tually in the seismic hazard maps [Papanikolaou 2011]. community preparedness and response planning as well As more data from earthquakes from different tectonic as in disaster management in the case of a future event settings as well as recent and past historical events are of similar or larger magnitude. gathered enlarging the dataset and requiring no need Furthermore, the application of the recently in- for intensity scale conversions, the compilation of an troduced ESI 2007 scale for the 2008 Andravida strike- ESI 2007 intensity attenuation relationship should be slip event enlarges the dataset from earthquakes from one of the future goals for seismic hazard assessment different tectonic settings and especially from moder- [Papanikolaou 2011]. The ESI 2007 will definitely make ate strike-slip events. The fact, that this moderate strike- an impact in seismic hazard assessment in the near fu- slip event did not trigger primary but only secondary ture if, as expected, could reduce this uncertainty. environmental effects, can also be used to infer the threshold magnitude for surface faulting in the NW 8. Conclusions Peloponnese and to calibrate palaeoearthquake size No primary EEE were induced by the 2008 An- from both primary and secondary effects. dravida earthquake. However, secondary EEE were The recent introduction of the ESI 2007 scale, due to widely observed including seismic fractures, liquefac-

20 ESI 2007 AND EMS-98 FOR A STRIKE-SLIP EVENT tion phenomena, slope movements (rockfalls and land- The EEE induced by the 2008 Andravida earth- slides) and hydrological phenomena in hot springs and quake were generally not aligned in specific orienta- wells. The majority of sites in the NW Peloponnese are tions, but concentrated in the northern and southern characterized by ESI 2007 intensities lower by one or tip of the WAFZ as well as close to and northwest of two degrees than the corresponding EMS-98 ones. the epicenter of the main shock. This distribution of The spatial distribution of the Andravida earth- EEE includes the surface projection of the causative quake aftershocks indicates a linear NE-SW trending dextral strike-slip WAFZ, but the area, where maxi- seismogenic structure. This is consistent with the strike mum seismic intensities (VIIIESI 2007) occur, is observed of one of the two nodal planes indicated by the focal north and northwest of the causative WAFZ and is not mechanism of the main shock revealing a NE-SW dex- identical with the surface projection of the zone. tral strike-slip fault zone. No significant surface frac- Generally, surface faulting associated to strike-slip tures of this orientation were observed during our field events of Mw=6.4 is about 13 km in length and 30 cm reconnaissance of the NW Peloponnese. The only in max displacement according to the equations pre- closely spaced set of fractures that are in agreement sented by Wells and Coppersmith [1994]. Thus, the lack with this direction is the one observed in the Kato of surface faulting and the observed small surface de- Achaia area. However, they cannot be considered as pri- formation induced by the 2008 Andravida earthquake is mary effects that are directly linked to the earthquake smaller compared to its magnitude and not character- energy and in particular to the surface expression of the istic for a Mw=6.4 strike-slip event with this focal depth. seismogenic structure due to their limited length and The burial depth and downdip extent of the fault width. The other observed directions of surface frac- within a homogeneous elastic earth cannot explain the tures are characterized as secondary effects induced by observed small surface deformation. Therefore, Feng the ground shaking and were caused by the differential et al. [2010] argue that the compositionally weak, 3 km seismic response of several loose lithologies, the lateral thick flysch layer acted as a near-surface decoupling instability of surficial formations (e.g. fractures in the agent, which isolates subsurface deformation from the Nissi area) and the liquefaction of the underlying for- surface. Particularly, the strain energy released by the mations (e.g. fractures in the Kato Achaia area). The thick pile of flysch probably could not sustain the co- various trends are due to the geometry of slopes (e.g. seismic rupture propagation below the pre-orogenic fractures in the Dafni area), the orientation of bedding carbonates to the surface. Alternatively, the weak fly- planes of fine- and coarse-grained phases, the presence sch may allow for an essentially decoupled cap with of morphological discontinuities and the instability lower overall stress, and hence lateral slip in the car- conditions in the vicinity of drainage channels (e.g. bonates will not necessarily propagate through the fly- fractures in the Nissi and Dafni areas), canals and coast- sch layer [Feng et al. 2010]. The remaining strain in the lines (e.g. fractures in the Kato Achaia area). flysch during coseismic rupture might be released by Slope movements were associated with the strong interseismic ductile deformation or fail in subsequent, ground shaking. They were due to: (a) the presence of smaller earthquakes [Feng et al. 2010]. geological formations with mechanical characteristics According to the EMS-98 classification of buildings that make formations susceptible to failure, (b) the damage [Grünthal 1998], damage to masonry buildings strong heterogeneity and the rapid change of the me- ranged from grade 3 to grade 5, while damage in most chanical characteristics in the different horizons both of R/C buildings ranged from grade 1 to grade 3. Mon- vertically and horizontally resulting in non-uniform and umental buildings and special structures also suffered anisotropic mechanical behavior of formations, (c) the extensive damage. It is concluded that the severity and intense and multiple fracturing, erosion and weather- the distribution of the structural damage is controlled ing contributing to the decreased cohesion along the by the following factors: western steep slopes of the Skolis Mt as well as (d) the (a) The local geological and soil conditions. The intense tectonic deformation along active fault zones western flat area as well as the central and the south- resulting in a dense net of discontinuities and sectors ern hilly area, where the most extensive damage oc- of decreased cohesion and formations loosening. curred, consist mainly of Neogene and Quaternary Liquefaction phenomena were observed close to deposits. It is important to note that the earthquake river banks and coastlines (e.g. the Pineios and Peiros damage was comparatively smaller in villages founded Rivers banks, stream bank in the Nissi area, the Kato on the alpine basement (e.g. intensity VIIEMS-98 was as- Achaia and Manolada coastal areas). They occurred due signed to Portes and Santomeri villages on the western to the local soil conditions, the shallow water table and slopes of Skolis Mt). the earthquake loading. The Neogene deposits are mainly fine-grained and

21 MAVROULIS ET AL. the Quaternary deposits are (i) loose and mainly coarse- Caputo, R. (2005). Ground effects of large morpho- grained or mixed coarse- and fine-grained phases and genic earthquakes, Journal of Geodynamics, 40 (2- (ii) coherent and mainly coarse-grained or mixed coarse- 3), 113-118. and fine-grained phases. They are particularly sensitive Castilla, R.A., and F. Audemard (2007). Sand blows as a to dynamic loading and they are easily erodible and potential tool for magnitude estimation of pre-in- leached by surface water. They are characterized by in- strumental earthquakes. Journal of Seismology, 11, tense heterogeneity of their mechanical characteristics 473-487. in different horizons both vertically and horizontally re- Christodoulou, G. (1967). About the age of Kastro sulting in anisotropic mechanical behavior. The mani- limestones, NW Peloponnese, Greece, Greek Geo- festation of rotational and/or translational slides is logical Society Publication, 7, 121-136 (in Greek). frequent. Differential settlements usually take place in Christodoulou, G. (1969). Geological Map of Greece: areas with a predominance of clays and clayey marls. Vartholomio sheet, scale 1:50,000, IGME 1969, Moreover, the central area consists of flysch that Athens. usually show a medium to strong weathering and a Christodoulou, G. (1971). Über die Neogene Ablage- dense net of discontinuities, causing intense secondary runen im Gebiet von Kyllini (NW Peloponnes), looseness. Landslide phenomena occurred with an in- IGME, Special Publication, 11, 1-60. creased frequency, usually affecting weathering mantle Chronis, G., D.J.W Piper and C. Anagnostou (1991). and upper fragmentation zone. The geotechnical be- Late Quaternary evolution of the Gulf of Patras, havior presents a clear anisotropy and rapid changes Greece: Tectonism, deltaic sedimentation and sea- controlled by the orientation of discontinuities, the dip level change, Marine Geology, 97, 191-209. of slope, the action of surface water and the degree of Dengler, L., and R. McPherson (1993). The 17 August looseness. 1991 Honeydaw earthquake north coast California: (b) The construction type of buildings. The An- a case for revising the Modified Mercalli Scale in dravida earthquake caused moderate to very heavy sparsely populated areas, Bulletin of the Seismo- structural damage (grade 3-5) to masonry buildings in- logical Society of America, 83, 1081-1094. cluding houses with one or two stores and insufficient Dercourt, J., F. Meilliez, J.M. Flament and P. De Wever or nonexistent seismic resistance design. Most of the (1978). Geological Map of Greece: Kertezi sheet, R/C buildings constructed according to the revised and scale 1: 50,000, IGME 1978, Athens. upgraded Greek Seismic Code sustained damage rang- Doutsos, T., N. Kontopoulos and D. Frydas (1987). Neo- ing from nil to moderate (grades 1-3) having an ade- tectonic evolution of northwestern-continental quate response during this earthquake. Greece, Geologische Rundschau, 76, 433-452. Doutsos, T., N. Kontopoulos and G. Poulimenos (1988). Acknowledgements. Professor Ioannis Fountoulis sadly The Corinth-Patras rift as the initial stage of conti- passed away (16/2/2013) before the publication of this article. He nental fragmentation behind an active island arc was a dear friend and colleague who left too soon. He will be an in- spiration to us, never forgotten and immeasurably missed. Dr. (Greece), Basin Research, 1, 177-190. Christoph Grützner and an anonymous reviewer are acknowledged Doutsos, T., and S. Kokkalas (2001). 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*Corresponding author: Spyridon D. Mavroulis, National and Kapodistrian University of Athens, Faculty of Geology and Geoenvironment, Department of Dynamic Tectonic Applied Geology, Panepistimiopolis, Athens, Greece; email: [email protected].

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