Source mechanisms and faulting analysis of the aftershocks in the Lake Ercek area (Eastern Anatolia, Turkey) during the 2011 Van event (Mw 7.1): Implications for the regional stress field and ongoing deformation processes

Abstract

In this study, we analysed the source mechanisms and faulting pattern of the aftershocks in the Lake Ercek area, Eastern Anatolia, during the 2011 Van event (Mw 7.1). The fault plane solutions of the aftershocks were used to derive a stress tensor acting around Lake Ercek. The estimated seismological parameters (focal mechanism solutions, stress tensor, and fault focal analyses) were integrated with field surveys and high resolution seismic reflection data so as to better understand the main faulting patterns and deformational features which are the causatives of the observed geomorphological features within and around Lake Ercek. The focal parameters of the 56 aftershocks with magnitude range 3.5 = 45-60 degrees) in and along its margins where the various folds, basement highs with eroded surfaces and several low-angle normal faults are evident; (c) the majority of the aftershocks have reverse-thrust mechanism with some strike-slip components in the Lake Ercek area (N- and S-margins). Strike-slip and normal faulting events are also evident (E- and W-margins, respectively); (d) the normal and reverse mechanisms with some strike-slip component are mostly confined in the upper crust (0-15 kin), compatible with NS-striking normal and WE-striking reverse faults in the marginal sections of the lake; (e) the WE-striking reverse faulting in the N- and S-margins seems to have the seismic potential to generate destructive earthquakes in the lake area; (f) the tectonic implications of the regional stress field and ongoing deformation processes in the lake are defined and supported by field observations and seismic reflection data. The result of these analyses reveals N -S compression/W-E extension in the lake and also the collisional/compressional regime taking place in a region of Lakes Van and Ercek.