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Comparing geologic structural mapping techniques in tectonically active region of Lake Van using gravity and seismological data

Doğan Mustafa Berkay, Sayın Tuba Sönmez

Acta Geophysica

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2024

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Vol. 72, no. 3

1587--1600

EN

The Van Lake region is situated within the boundary of the collision zone between the Arabian and Eurasian plates, which has resulted in the formation of a variety of geological structures, including faults, volcanoes, and uplifted mountain ranges. A comprehensive understanding of these structures can yield significant information pertaining to the region’s tectonic history, as well as potential tectonic hazards. In the present study, several structural mapping techniques, including lineament detection techniques [Horizontal Gradient Magnitude (HGM), Analytic Signal (AS), and Tilt Angle] and curvature analysis attributes (Differential, Gaussian, Mean, and Shape Index), were analyzed and compared the results obtained using both Earth Gravity Model 2008 (EGM2008) Bouguer gravity and seismological data, with the goal of determining the most effective (suitable) edge detection method in order to gain a better understanding of high-stress regions and areas of potential seismic hazard in the vicinity of Van Lake. It is of great importance to investigate the behavior of faults and the curvatures of structural features within the crust, as they play a significant role in determining the distribution of stress, and subsequently, its impact on surface structures. The results show that HGM and AS are effective in defining fault strikes and trends, while Gaussian curvature attributes can detect lineaments and structural edges. Differential curvature attributes were found to be best suited for complex tectonic regions. The study also reveals a coherent relationship between fold orientation and fault strikes with the regional principal stress direction. The current study has focused on a region characterized by a significant negative anomaly, which appears to be a valley-like fold structure with a highly inclined interlimb angle. This area, referred to as the “silent” zone, is seismically quiet with regard to earthquakes and faults. However, focal mechanism results support the orientation of the interlimb angle fold in the vicinity of this region. The existence of a strong negative anomaly in the eastern part of the study area highlights the requirement for additional geological field observations and seismic surveys to evaluate the potential earthquake hazards. In the course of comparing various structural mapping techniques, it was concluded that the application of second-order vertical derivative of gravity potential is a suggested approach for identifying the edges of causative structures.

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U-Th ages and facies properties of Edremit travertines and tufas, Van, Eastern Anatolia : implications for the neotectonics of the region

Yeşilova Çetin, Güngör Yeşilova Pelin, Açlan Mustafa, Yu Tsai-Luen, Shen Chuan-Chou

Geological Quarterly

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2021

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Vol. 65, No. 2

art. no. 28

EN

Travertine formation is one of the most important archives of active tectonics in a region and provides information about climate, water temperature and quantity, and biological activity. The Edremit travertines and tufas extend over nearly 160 km2 within the boundaries of the Edremit area to the east of Lake Van (eastern Turkey), and yield important evidence towards understanding the neotectonics of the region. The Edremit travertines and tufas were studied throughout their full stratigraphic extent, the factors controlling the formation of these deposits were examined, and the succession was sampled for U/Th analysis. Travertine formation was found to occur from 542-29.7 ka, with two different tufa formation periods: from 29.7-5.8 ka and 5.8-2.08 ka. Pauses in travertine formation (palaeosols) were identified from 510-470 ka, 289-269 ka and 91-34 ka. Our study showed that climate parameters affected the formation of tufa, while the Edremit travertines developed under the control of tectonism. The Van Fault is directly associated with travertine development and its age was identified as 542 ka or older. Since the Gürpιnar Fault, one of the most important faults in the region, is effective in shaping the southern slope of the travertines and limiting the movement of the Van Fault, its age should be younger than 542.4 ka. The Elmalιk Fault played an active role in the formation of the Edremit tufas and is proposed to be 29.7 ka in age, from stratigraphic relationships in the region.

3

Seismogenic structures in Quaternary lacustrine deposits of Lake Van (eastern Turkey)

Üner S.

Geologos

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2014

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Vol. 20, No. 2

79--87

EN

Soft-sediment deformation structures formed by liquefaction and/or fluidisation of unconsolidated sediments due to seismic shocks are frequent in the Quaternary sandy, silty and clayey deposits of Lake Van. They are present in both marginal and deep lacustrine facies. Their morphology and interpreted genesis imply that they should be considered as fluid-escape structures (dish and pillar structures, flame structures and sand volcanoes), contorted structures (simple and complex convolutions and ball-and-pillow structures) and other structures (disturbed layers and slump structures). The most recently formed structures are related to the October 23rd, 2011 Van-Tabanlı (Mw 7.2) earthquake. The exist-ence of seismites at various stratigraphic levels in the lacustrine deposits is indicative of tectonic activity that frequently triggered earthquakes with magnitudes of 5 or more, affecting the Lake Van Basin.