An Assessment of the Seismicity of the Bursa Region from a Temporary Seismic Network

Abstract

A temporary earthquake station network of 11 seismological recorders was operated in the Bursa region, south of the Marmara Sea in the northwest of Turkey, which is located at the southern strand of the North Anatolian Fault Zone (NAFZ). We located 384 earthquakes out of a total of 582 recorded events that span the study area between 28.50-30.00°E longitudes and 39.75-40.75°N latitudes. The depth of most events was found to be less than 29 km, and the magnitude interval ranges were between 0.3 B M L B 5.4, with RMS less than or equal to 0.2. Seismic activities were concentrated southeast of Uludag Mountain (UM), in the Kestel-Igdir area and along the Gemlik Fault (GF). In the study, we computed 10 focal mechanisms from temporary and permanents networks. The predominant feature of the computed focal mechanisms is the relatively widespread near horizontal northwest-southeast (NW-SE) T-axis orientation. These fault planes have been used to obtain the orientation and shape factor (R, magnitude stress ratio) of the principal stress tensors (r 1 , r 2 , r 3 ). The resulting stress tensors reveal r 1 closer to the vertical (oriented NE-SW) and r 2 , r 3 horizontal with R = 0.5. These results confirm that Bursa and its vicinity could be defined by an extensional regime showing a primarily normal to oblique-slip motion character. It differs from what might be expected from the stress tensor inversion for the NAFZ. Different fault patterns related to structural heterogeneity from the north to the south in the study area caused a change in the stress regime from strike-slip to normal faulting.

Pore water geochemistry at two seismogenic areas in the Sea of Marmara

“…Earthquake historical catalogs suggest that the last major earthquakes occurred along the middle NAF branch in 1419, 1855, and 1863 [Ambraseys, 2000[Ambraseys, , 2001Ambraseys, 2006;Ambraseys, 2006;Gasperini et al, 2011;Gok and Polat, 2012;Gorur and Cagatay, 2010;Karabulut et al, 2011;Pondrelli et al, 2011;Tanircan and Savas, 2011;Yalciner et al, 2002]. Seismological data suggest that a moderate earthquake (M w 5 5.2) occurred along this fault segment in 24 October 2006 [Irmak et al, 2007;Pondrelli et al, 2011].…”

Investigating Subsidence in the Bursa Plain, Turkey, Using Ascending and Descending Sentinel-1 Satellite Data

“…The alluvium has high transmissivity in comparison with the Neogene deposits surrounding the Nilufer Valley [52] The city of Bursa is located within the area with the highest probability of strong earthquakes in Turkey (i.e., first-degree seismic hazard zone). The seismicity of the region is controlled mainly by active faults, such as the Gemlik Fault, Geyve-Iznik Fault Yenisehir Fault, Bursa Fault, and the Inonu-Eskisehir Fault Zone [53]. Bursa also hosts thermal springs that follow major fracture zones [54].…”