Strike-slip plate boundaries
The occurrence of large damaging earthquakes near densely populated regions can result in dramatic numbers of human casualties, damage to key infrastructure (e.g. hospitals, roads) and the loss of accommodation for hundreds of thousands citizens. The largest earthquake magnitudes on Earth reach magnitudes M~9 and exclusively occur along subduction zones. In contrast, strike-slip transform faults tend to rupture in earthquakes with magnitudes not exceeding M~8 [e.g. Wesnousky, 1988; Martínez-Garzón et al., 2015; Bohnhoff et al., 2016]. However, the latter generally pose a larger hazard and risk since they can rupture along the Earths’ surface and due to their eventual proximity to densely-populated mega-cities. Well-known examples are the San Francisco Bay Area and the Los Angeles basin along the San Andreas Fault in California or the Istanbul-Marmara region near the North Anatolian Fault Zone in Turkey. High-resolution monitoring and near-real time analysis of ongoing seismic and aseismic deformation in these areas is an essential pre-requisite to better determine the local seismic potential and to optimize risk-reduction infrastructure.
A large focus of SAIDAN is the study of tectonic deformation at the North Anatolian Fault. The North Anatolian Fault Zone (NAFZ) in Turkey represents a ~1100 km long right-lateral strike-slip plate boundary [Barka et al., 2002; Sengör, 2005] slipping at an average rate of 20-30 mm/yr [McClusky et al., 2000; Ergintav et al., 2014]. The Sea of Marmara region in northwestern Turkey currently represents a ‘seismic gap’ with a high probability for an M>7 earthquake in direct proximity to the Istanbul Metropolitan region with its >13 million inhabitants. At its eastern portion close to Istanbul (Princes Islands fault), a locked fault portion representing a potential nucleation point for the pending Marmara earthquake was identified from absence of microseismicity and from GPS data [Bohnhoff et al., 2013; Ergintav et al., 2014]. Towards the western part of the Marmara section there are first indications for fault creep [Schmittbuhl et al., 2016; Bohnhoff et al., in press]. However, to date, no information on potential low-frequency signals embedded in the crustal deformation of the whole region exists. The area immediately to the south of the locked Princes Islands fault recently hosted a MW 4.2 earthquake that showed pre-shock activity indicating an emergent failure process [Malin et al., in review].