Earthquake Induced Soft Sediment Deformation Structures (Seismites): Van Gölü Basin, Eastern Anatolia

Abstract

The Van Gölü Basin is one of the basins located on the Eastern Anatolia Plateau and it includes Van Gölü, which is the largest sodic lake in the world, within its boundaries. The basin was formed in the Late Pliocene and attained its final shape with Quaternary volcanic activity. Deformation structures are found in Quaternary aged sandy and silty lacustrine sediments in the Van Gölü Basin. These soft sediment deformation structures formed by liquefaction or fluidization of the unconsolidated sediments are classified in three groups, being those of contorted structures (simple and complex convolute bedding and ball-pillow structures), water escape structures (dish and pillar structures), and load structures (flame structures). Deformation structures may occur by overpressure, waves that originated in storms, sudden changes in groundwater movements and seismic shaking. Based on the field observations, regional tectonic and sedimentological data and previous studies, it is concluded that these deformation structures have been developed and may be called seismites. The existence of seismites in different levels of lacustrine sediments in the Van Gölü Basin is an indicator of a Quaternary tectonic activity in the region as well as an indicator of frequent occurrences of earthquakes with magnitudes of 5 or greater.