Heightened Odds of Large Earthquakes Near Istanbul: An Interaction-Based Probability Calculation

Abstract

We calculate the probability of strong shaking in Istanbul, an urban center of 10 million people, from the description of earthquakes on the North Anatolian fault system in the Marmara Sea during the past 500 years and test the resulting catalog against the frequency of damage in Istanbul during the preceding millennium. Departing from current practice, we include the time-dependent effect of stress transferred by the 1999 moment magnitude M = 7.4 Izmit earthquake to faults nearer to Istanbul. We find a 62 +/- 15% probability (one standard deviation) of strong shaking during the next 30 years and 32 +/- 12% during the next decade.

Earthquake hazard in Marmara Region, Turkey

“…Recent studies conducted after the 1999 Kocaeli (Mw=7.4) and Düzce (Mw=7.2) earthquakes indicate (assuming that the stress regime in the Marmara Sea remains unchanged) about 65% probability for the occurrence of an Mw>=7.0 magnitude earthquake effecting Istanbul Parsons [15]. The association of earthquakes between 1500 to present with the segmentation proposed for the North Anatolian Fault in the Marmara Region is given in Table 1.…”

Re-evaluation of the surface ruptures of the November 1951 earthquake series in eastern Taiwan, and its neotectonic implications

“…This mechanism has been invoked, for example, to explain the progressive failure of the North Anatolian fault between 1939 and 1999 (e.g., Stein et al, 1997), and to calculate future seismic hazards along the fault (e.g., Hubert-Ferrari et al, 2000;Parsons et al, 2000). In general, after a major earthquake, areas where stress has increased are favored areas for aftershocks and/or subsequent mainshocks occur (Harris, 1998).…”

Investigation of Coulomb stress changes in south Tibet (central Himalayas) due to the 25th April 2015 M W 7.8 Nepal earthquake using a Coulomb stress transfer model

“…This lobe is 40 km to the west of the mainshock, where the M W 6.5 Big Bear earthquake struck 2.5 h afterwards (Stein 1999). In Turkey, the 1999 M W 7.4 Izmit earthquake was followed by the M W 7.1 Düzce earthquake that is a triggered event by the former about three months later (Parsons et al 2000). In the 2008 Wenchuan event, some faults to the south of the Longmenshan fault exhibited increased transferred Coulomb stress (Parsons et al 2008), especially the Ya'an thrust and Xianshuihe fault, which were shown to have distinctly greater changes in Coulomb stress than other faults.…”

“…A big earthquake can cause stresses on faults to decrease or increase, and it also alters stresses elsewhere (Parsons et al 2000). Earthquakes are more prone to being observed in regions of increased stress, while they are less seen where off-fault stresses decrease (Stein 1999).…”

“…Rearrangement of stresses in the crust commonly leads to subsequent damaging earthquakes (Stein et al 1997;Stein 1999;Parsons et al 2000;McCloskey et al 2005). A big earthquake can cause stresses on faults to decrease or increase, and it also alters stresses elsewhere (Parsons et al 2000).…”