Paleoseismology and earthquake potential of Manisa fault

This study aims to reveal the current tectonic characteristics and seismicity of the region as a result of the structural geological and paleoseismological studies carried out on the eastern segment of the Manisa Fault where Manisa city center is located. According to earthquake catalogs, many destructive earthquakes have occurred in and around Manisa province in the historical period. However, studies on the seismic sources of these earthquakes are very limited. Although old earthquakes on the western segment of the Manisa Fault, which is thought to be the source of a significant number of these earthquakes, have been revealed, information about the earthquakes caused by the eastern segment has not yet been obtained. In this study, the fault traces of the eastern segment of the Manisa Fault (between Kayapınar east and Yukarıçobanisa) were mapped at 1:25000 and 1:5000 scales and trench-based paleoseismology studies were carried out for the first time by identifying suitable areas. According to the mapping studies, Manisa Fault, which borders the southern part of Manisa Basin, is an active structure with prominent north-trending fault steepnesses in the current morphology. In the east, it has a convex geometry in the NW-SE direction between Yukarıçobanisa and Manisa city center. Towards the west, the Manisa Fault has a length of 45 km and presents approximately NW-SE strike between Manisa city center and Kayapınar and again NW-SSE strike between Kayapınar and Akgedik. As a result of the field observations, 5 trench excavations for paleoseismology were identified in the study area. As a result of the investigations carried out in the trenches, 26 samples were taken from colluvial wedges and paleotopsoil levels for the application of optically stimulated luminescence (OSL) and radiocarbon (14C) methods. When the obtained analysis results were evaluated, it was determined that it was the source of 6 destructive earthquakes in the Late Pleistocene-Holocene interval. These earthquakes correspond to 30.6 ± 8.8 thousand years (E1), 15.0 ± 5.0 thousand years (E2), 6.6 ± 1.3 thousand years (E3), 2.9 ± 1.3 thousand years (E4), 0.8 ± 0.4 thousand years (E5), and 0.1 ± 0.1 thousand years (E6), respectively. The recurrence interval of the related earthquakes was found to be between 950 and 3800 years for the Holocene period, and considering that the last earthquake occurred in 1862 AD for the central and eastern part of the Manisa Fault, it is seen that the fault has not produced a destructive earthquake for 161 years.