## 7 Secondary Environmental Effects Induced by the 1953 Ionian Sea Earthquakes
### Secondary Effects Induced by the 12 August 1953 Ionian Sea Earthquake in Cephalonia Island
#### 7.3.1 Slope Failures  
The earthquake on 12 August 1953 triggered slope failures in several sites. Related information was extracted not only from the official report of the IGUR [20], but also from several newspapers of local and national circulation including TA NEA, TAXYDROMOS, ELEFTHERIA, EMPROS, I MERA, NEOLOGS PATRON and PELOPONNISOS. The triggered slope failures can be classified into the detachment of boulders from abrupt slopes and subsequent rockfalls and landslides. In the majority of the affected sites, the triggered slope failures were rockfalls; boulders detached from steep slopes and rolled downward, crushing buildings and causing structural and non-structural damage to roads, resulting in traffic and communication disruption between affected villages, and to vegetation, including mainly olive groves and vineyards. In several villages, they aggravated damage induced by the earthquake ground motion resulted in greater fatalities and injuries. In particular, villages founded on alpine formations in the mountainous areas of Cephalonia were mostly destroyed by these slope failures. These sites are distributed along slopes in (Figures 9-11):  
* the northern part of Erissos peninsula (Markoulata village)
* the southern part of Erissos peninsula (Karousata, Lekatsatsa, Logarata villages)
* Myrtos beach
* the eastern margin of Thinia valley (Agonas village and Ayia Kyriaki area)
* the western part of Aenos fault block comprising slopes of Ayia Dynati Mt (Kourouklata village, Drapano area)
* the western part of the Avgo Mt in eastern part of Cephalonia (Sami, Zervata and Katapodata villages)
* the eastern part of Roudi Mt (Pyrgi village)
* the southern part of the Atros Mt (Tzanata and Monastiraki villages)
* the southern front of Aenos Mt (Atoupades, Kolaitis, Arginia, Chionata and Plateies villages)
* the southeastern end of Cephalonia (Skala area, Anninata village)
* the northeastern end of Argostoli peninsula (Argostoli area)
* the eastern part of Paliki peninsula (Ntouri area and the southeastern end Paliki). Moreover, failures were observed along slopes in the road network leading from Sami to Argostoli and from Argostoli to Livadi. In Markoulata village, located in the northern part of the fault block of Erissos peninsula, rockfalls took place along an adjacent hill [20] (Figure 11). Along the southern slopes of Kalon Mt (Figure 9a,b and Figure 11), which is located in the southern part of the fault block of Erissos peninsula and composed of highly fragmented limestone rockmass, extended rockfalls were triggered [20]. Rockfalls were generated along a gorge between Karousata and Lekatsata, resulting in damage to olive trees. Rockfalls were also induced at a large scale in the areas of Logarata and Karousata. Part of the damage observed in the building stock of these villages is attributed to rockfalls. These effects are attributed to the occurrence of the Ayia Efimia fault, juxtaposing the Erissos fault block in the north against the Aenos Mt fault block in the south [11; 12; 37] (Figure 9a). Figure 9: **(a)** View of the Pylaros valley from the north. It is a NW–SE-trending valley formed along the transition zone from Erissos peninsula and located northwards to the Aenos fault block, located southwards. Failures, mainly rockfalls, were triggered by the 12 August 1953 Ionian Sea earthquake along the slopes of Ayia Dynati Mt **(a)** belonging to the fault block of Aenos Mt) and Kalon Mt **(b)** belonging to the fault block of Erissos peninsula). **(c)** The coastal areas of Myrtos occurred at the northwestern part of the transition zone between the fault block of Erissos peninsula located northwards and the Aenos Mt fault block located southwards. It constitutes a zone with very high landslide susceptibility, affected not only by earthquakes, such as the early 2014 earthquakes [11] but also by intense hydrometeorological effects, such as the Ianos medicane in September 2020 [45]. **(d)** In 2014, a limestone boulder detached from the slope, rolled down and reached Myrtos beach.