Le crisi sismiche recent

Nel 1995-1998 si è verificata una notevole attività sismica culminata il 27 agosto 1997 con un terremoto di magnitudo 5.3 (Papadopoulos et al., 1998). Durante questo periodo di intensa attività si sono riattivate lineamenti tettonici anche importanti generalmente in direzione ONO-ESE.

Recentemente, nel 2002-2003, un altro evento di questo tipo ha condotto alla formazione di un’ampia frattura nella pianura di Lakki (Volentik et al., 2005). Questa frattura superficiale si era inizialmente aperta il 29 novembre del 2001, dando luogo alla formazione di una zona depressa lunga complessivamente 257 m, e articolata in tre bracci distinti, con una ampiezza di circa 4-5 m. La massima profondità raggiunta era di 15 m. Dalla fine di dicembre 2002, questa frattura si è poi ulteriormente estesa verso sudovest, di altri 270 m, raggiungendo un’ampiezza di 10 m circa e per profondità massime di circa 11 m. Tuttavia nessuna anomalia termica, né evidenze di degassamento sono state registrata nell’area della frattura; nello stesso modo non sono stati osservati movimenti verticali rilevanti delle zone opposte ai lati della frattura, né anomalie particolari nella composizione, temperatura e attività delle fumarole. La teoria più probabile per spiegare la formazione di questa frattura identifica la causa in una

subsidenza dei sedimenti superficiali che formano la base della caldera in cavità e fratture preesistenti al di sotto della copertura sedimentaria stessa (Vougioukalakis, 2005).

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