Reservoir-Triggered Earthquakes Around the Atatürk Dam (Southeastern Turkey)

Abstract

Reservoir-triggered seismicity has been observed near dams during construction, impoundment, and cyclic filling in many parts of the earth. In Turkey, the number of dams has increased substantially over the last decade, with Atatürk Dam being the largest dam in Turkey with a total water capacity of 48.7 billion m3. After the construction of the dam, the monitoring network has improved. Considering earthquakes above the long-term completeness magnitude of MC = 3.5, the local seismicity rate has substantially increased after the filling of the reservoir. Recently, two damaging earthquakes of Mw 5.5 and Mw 5.1 occurred in the town of Samsat near the Atatürk Reservoir in 2017 and 2018, respectively. In this study, we analyze the spatio-temporal evolution of seismicity and its source properties in relation to the temporal water-level variations and the stresses resulting from surface loading and pore-pressure diffusion. We find that water-level and seismicity rate are anti-correlated, which is explained by the stabilization effect of the gravitational induced stress imposed by water loading on the local faults. On the other hand, we find that the overall effective stress in the seismogenic zone increased over decades due to pore-pressure diffusion, explaining the enhanced background seismicity during recent years. Additionally, we observe a progressive decrease of the Gutenberg-Richter b-value. Our results indicate that the stressing rate finally focused on the region where the two damaging earthquakes occurred in 2017 and 2018.

Fast 1-D Velocity Optimization Inversion to 3D Velocity Imaging: A Case Study of Sichuan Maerkang Earthquake Swarm in 2022

“…It plays a unique role in the correction of velocity models in regions with complex tectonic settings. To obtain reliable results, VELEST needs a wide range of calculations, randomly perturbs the initial speed model, and finally selects the optimal model by relying on the average root mean square of travel time(RMS) [18][19][20][21]. This process is a time-consuming process.…”

Seismicity modulation due to hydrological loading in a stable continental region: a case study from the Jektvik swarm sequence in Northern Norway

“…Hydrological loads can be significant enough to cause elastic ground deformation, alter tectonic stress and modulate seismicity, as shown for northeastern Japan by Heki (2003). To test the significance of the static load change from snow accumulation in the area, we follow (Deng et al, 2010;Büyükakpınar et al, 2021) and model 3-D Coulomb failure stress changes (∆CF F ). We computed the 3-D stress tensor due to surface loading on a half-space elastic media using Boussinesq-Cerruti solutions (see Deng et al, 2010).…”

“…8) in Jektvik by 1.5 to 1.8 kPa at depth of up to 8 km. We consider that these changes in hydrological loading are sufficient to trigger seismicity through stress and pore pressure changes (Deng et al, 2010;Büyükakpınar et al, 2021), even though they are quite small. Previous studies show that small ∆CF F variations (a few kPa) are able to modulate the seismicity (Christiansen et al, 2007;Pollitz et al, 2013;Craig et al, 2017).…”

The 2019–2020 Khalili (Iran) Earthquake Sequence—Anthropogenic Seismicity in the Zagros Simply Folded Belt?

“…The synthetic beams are constructed assuming source‐ and receiver‐specific crustal models (after Karasözen et al., 2019, and CRUST2.0 model, Bassin et al., 2000) and a global AK135 model (KennettEngdahl, Buland, & Buland, 1995) for the propagation of the seismic waves in between. This method is extensively used to estimate the focal depth of earthquakes in several other regions (e.g., Braun et al., 2018; Büyükakpınar et al., 2021; Cesca et al., 2021; Gaebler et al., 2019; Negi et al., 2017). Results from all of the analyzed arrays are consistent with a focal depth of ∼4–5 km for both the M w 5.7 earthquake (Figure 4) and the M w 5.4 earthquake (Figure S10 in Supporting Information S1).…”