Could the Coseismic Fractures of a Lake Ice Reflect the Earthquake Mechanism?: (Afyon Earthquakes of 2 March 2002, Central Anatolia, Turkey)

Abstract

Eyewitness reports that the two moderate earthquakes (3 February 2002) in Afyon, Central Anatolia, Turkey, produced fractures at the icy surface of a partially frozen lake near the reactivated fault scarp. In places along the shoreline, the ice thrusted towards, the land. Far from the shoreline, several fractures developed on the approximately 15 cm-thick ice of the lake. Among them, geometric features of two fracture junctions suggest that fractures accommodated lateral movements. Almost no coupling should exist between the ice and the shaking ground because of the water beneath the ice, these fractures cannot be directly associated to ground ruptures. Alternatively, we propose that the great inertia of the ice mass caused the collision of the ice layer with the shore land when the ground beneath this layer. moved towards the lake. As a result, the ice-ground interface deformed and the icy "hinterland" fractured. The orientations of the stress axes deduced from fracturation fit with those suggested by focal mechanism solutions and ground rupturing. Consequently, the ice of the lake surface seems to indirectly record the mechanism of the Afyon earthquakes. (C) 2003 Editions scientifiques et medicales Elsevier SAS. All rights reserved.