A Probable Earthquake Scenario near Istanbul Determined from Dynamic Simulations

Abstract

To cite this version:Hideo Aochi, Thomas Ulrich. A probable earthquake scenario near Istanbul determined from dynamic simulations. the North Anatolian fault in the Sea of Marmara, which poses a high risk to the nearby city of Istanbul. Several fault geometry models, nucleation points, and initial stress states are tested. The likelihood of each earthquake scenario is evaluated, and a probabilistic assessment of the ground-motion estimation is proposed. The simulation results suggest that the fault geometrical configuration is not favorable for producing an earthquake of magnitude 6-7, as no scenario is found. On the contrary, the probability of occurrence of an earthquake of magnitude greater than 7 is high. Most of these large events are characterized by epicenters located in the central or eastern parts of the Sea of Marmara. However, the possibility of a western-initiated rupture propagating eastward, the worst scenario for the Istanbul region, cannot be ruled out. Many simulations led to supershear ruptures, as observed for the nearby 1999 İzmit earthquake, and this significantly influences ground-motion prediction in the region.

No significant steady state surface creep along the North Anatolian Fault offshore Istanbul: Results of 6 months of seafloor acoustic ranging

“…In the central Marmara Sea, the 70 km long Istanbul-Silivri segment (ISS) of the NAF has had no significant seismic events since at least 1766 and perhaps as far back as 989 [Ambraseys, 2002]. The probability of rupture of NAF segments in the central part of the Marmara Sea is considered to be significant [Murru et al, 2016;Aochi and Ulrich, 2015;Parsons, 2004], and Schmittbuhl et al [2015] recently interpreted the low level of present-day seismicity along the ISS as the signature of a locked behavior. Although Bohnhoff et al [2016] suggest that the maximum expected earthquake in the Istanbul area would probably not exceed a magnitude 7.5, geomechanical models generally predict high strain accumulation along the ISS, sufficient to produce a magnitude 7+ event [Hergert and Heidbach, 2010;Pondard et al, 2007;Armijo et al, 2005;.…”

Subpatch roughness in earthquake rupture investigations

“…For example, kilometer scale step overs or fault bends frequently serve as rupture initiation and termination locations. The probability of multisegment rupture is directly related to amplitude and wavelength of those roughness expressions [e.g., Harris and Day , ; Oglesby , ; Wesnousky , ], affecting the dynamic rupture process and resulting ground‐shaking distribution [ Oglesby and Mai , ; Aochi and Ulrich , ]. Roughness at smaller scales affects the fault's overall resistance to slip, its aseismic versus seismic behavior, the breakdown of shear resistance during sliding, the magnitude of stress concentration and heterogeneity, and the deformation and damage of the fault‐hosting rock [e.g., Candela et al ., ; Shi and Day , ; and references therein].…”

Strong Shaking Predicted in Tokyo From an Expected M7+ Itoigawa‐Shizuoka Earthquake

“…First, the ISTL is likely composed of multiple segments and variable fault geometry, which we do not account for in this study. The effect of fault segmentation and geometrical complexity at various length scales onto the near‐field ground motion are currently an active area of research (Aochi & Madariaga, ; Aochi & Ulrich, ; Lozos, ; Mai et al, ) and are computationally to expensive to produce populations of kinematic sources. While seismic moment may be largely released within a segment, the jumping from one segment to next may excite high‐frequency ground motions (Adda‐Bedia & Madariaga, ).…”