Aseismic creep on faults and flank instability at Mount Etna volcano, Sicily

Abstract

Abstract This paper presents new data on the nature and significance of shallow fault creep in the Etna region. Sixteen sites where creep behaviour is obvious, have been identified, both from analysis of historical records, and from field surveys. Creep rates at each site vary considerably, from 0.5 to 2.3 cm a −1 , and two extreme types of aseismic slip are recognized; (a) near-continuous, long-period movement along the aseismic segments of faults, and (b) spasmodic, short-lived, pre- and post-seismic movement related to seismically active fault segments. At most creep sites active displacements range from purely extensional to dip-slip. In some cases oblique-slip movements prevail, whereas purely strike-slip movements have been detected at only a single site. The overall creep kinematics indicate that surface creep on faults is a mode of discontinuous strain restricted to the faults displacing a sector of the eastern flank of the volcanic edifice bordered by the Pernicana fault, the NE Rift, the SE Rift and the Trecastagni-Mascalucia fault zone. We suggest that this mobile sector of the sea-facing flank of the volcano, including its uppermost clay-rich basement, is slowly sliding southeast under the control of a main deep-seated detachment surface.