An Example of Determining Fault Properties from Morphological Analysis of Pockmarks is Sapanca Lake, Located on the North Anatolian Fault, Turkiye

Abstract

Lake Sapanca is located in the Eastern Marmara region of Turkiye and formed as a tectonic lake by the right-lateral strike slip North Anatolian Fault (NAF). Located 33 m above sea level, this tectonic lake has a length of 16 km in the east-west direction and 5 km in the north-south direction. The area in which the lake is located is on the Izmit-Sapanca Corridor, which is bordered by the segments of the northern branch of the NAF, between the Samanlı Mountains to the south and the Kocaeli Peneplain to the north. Multibeam bathymetry and high-resolution seismic data were acquired in the lake as a part of a TUBITAK project (Project No: 117Y130) in August 2018 to determine the structural and stratigraphic elements of the lake. Many pockmark structures, as well as lineaments related to the NAF, were observed on multibeam maps giving cm-scale resolution on the lake bottom. Thus, the effects of NAF in the lake can be better determined depending on the geometrical properties of the pockmarks, more than 300 in number, which are formed due to gas or fluid outflows from the lake-bottom, and their distribution in certain parts of the lake. In order to determine these features of pockmarks, semi-automatic approaches of QGIS and ARCGIS software programs were used and it was observed that the pockmark distribution increased along the lineament direction of the NAF and in the northeast of the lake. Moreover, we conclude that, the consistent orientation of the individual pockmarks may indicate that all pockmarks were formed in a relatively short period of time or that the bottom current regime in the lake has been effective for a long time.