Recent gravitative mass movements in a highly tectonically active arc system: The Hellenic Arc

Abstract

The Hellenic Arc system is located within one of the world's most seismically active areas and has experienced extreme tectonism throughout Tertiary and Quaternary times. This paper discusses the various types of gravitative mass movements that have been detected and examines their causative factors in environments of high tectonic and seismic activity. The areas surveyed are the Sporadhes and Corinth grabens in the back-arc basin, the Zante-Cephalonia shelf on the inner slope of the Hellenic trench, and the Kythera ridge in the outer island arc. The various types of gravitative mass movements that have been documented include: (i) sliding of large masses with no or only slight internal deformation, (ii) sliding of masses with disintegration of the sediment fabric to debris flows and (iii) slow downslope creep. The mass movements are associated with fault escarpments, delta fronts and well-stratified slopes with slope gradients ranging from 2 to 40°. Earthquakes seem to be the main mechanism initiating mass movement, but other mechanisms such as increasing topographic gradient, gas in the sediment pores and heavy rain, can also independently trigger and/or contribute to the initiation of mass movements.