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a Distribution of the 2019 Silivri earthquakes. The numbers with source mechanism solutions are from Additional file 1: Table S1. Green-colored lines show dextral oblique thrust faults, yellow-and red-colored lines show dextral strike-slip, and orange-colored lines stand for normal faults. b Correlation of kinematic analysis of the source mechanism solution (in dark blue color) and fault planes (in red color)
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The North Anatolian Fault Zone is a dextral system operating between the Eurasian and Anatolian plates in northern Turkey. Across the Marmara Sea south of İstanbul, it deforms at ~18 mm/year slip rate, where the statistics of historical earthquakes suggest that a few M7+ earthquakes are generated every ~250 years. Currently, M7+ earthquakes are ove...
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... contents up to 50 Hz. Under these circumstances, harmonics below 35 Hz are recorded sufficiently. According to the lambda-over-four rule (Geller and Mueller 1980), this allows hypocentral precision up to 43 m. Combining these improvements, we obtained 76 m average spatial accuracy for 214 relative hypocenter locations (Additional file 1: Fig. S5). The size of the earthquake cluster we analyzed is 15 by 8 km and the average error of our initial absolute hypocenters are 1.4 and 1.7 km in the horizontal and vertical axis, respectively. In addition, the double difference earthquake relocation algorithm has an Şahin et al. Earth, Planets and Space (2022) 74:167 additional ...
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... relocated Silivri earthquake distribution displays a diffuse view in the north of the NAFZ. This diffuse view in the seismicity is well correlated with the mapped faults, and the spatial allocation of the M4+ earthquakes coincides with the secondary fault surfaces in the north of NAFZ (Fig. 5 and Additional file 1: Fig. S6). Therefore, the spatiotemporal distribution of the relocated earthquake hypocenters indicates that three individual faults have been activated during the 2019 Silivri earthquakes. The M4.7 foreshock activated the dextral Silivri Ridge Fault on September 24, 2019, and was followed 51 h later by the M5.8 ...
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... the spatiotemporal distribution of the relocated earthquake hypocenters indicates that three individual faults have been activated during the 2019 Silivri earthquakes. The M4.7 foreshock activated the dextral Silivri Ridge Fault on September 24, 2019, and was followed 51 h later by the M5.8 mainshock activating the Silivri Fault to the north (Fig. 5a, Additional file 1: Fig. S6; Table S1). On the same day, the Silivri Ridge Southern Border Fault in the south and the Silivri Fault in the north have been activated, generating two M4.1 earthquakes (Fig. 5a and Additional file 1: Fig. S6). After that, the seismicity progressively migrated towards the main fault segment beneath the ...
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... Silivri Ridge Fault on September 24, 2019, and was followed 51 h later by the M5.8 mainshock activating the Silivri Fault to the north (Fig. 5a, Additional file 1: Fig. S6; Table S1). On the same day, the Silivri Ridge Southern Border Fault in the south and the Silivri Fault in the north have been activated, generating two M4.1 earthquakes (Fig. 5a and Additional file 1: Fig. S6). After that, the seismicity progressively migrated towards the main fault segment beneath the Silivri Ridge. The aftershock activity decayed after an M4.7 earthquake developed in the west of Silivri Ridge Southern Border Fault on January 11, 2020, and the area became completely silent after the M4.2 and ...
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... After that, the seismicity progressively migrated towards the main fault segment beneath the Silivri Ridge. The aftershock activity decayed after an M4.7 earthquake developed in the west of Silivri Ridge Southern Border Fault on January 11, 2020, and the area became completely silent after the M4.2 and the M3.6 earthquakes on September 24, 2020 (Fig. 5a, Additional file 1: Fig. S6; Table S1). These two 2020 earthquakes, of which fault plane solutions are dominantly dextral strike-slip, have occurred between NAFZ-D and Silivri Ridge Southern Border Fault (Additional file 1: Fig. ...
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... planes on the source mechanism solutions around the Silivri Fault revolve in the same direction as the surface trace of the Silivri Fault (Fig. 5a). Since the faults are modeled as a non-planar surface in this study, a slight deviation (up to 15-degree) in the surface trace of the fault and focal mechanism solution is expected (Additional file 1: Fig. S6). The Silivri Ridge Fault (SRF) and Silivri Ridge Southern Border Fault (SRSBF) seems in agreement with focal mechanism ...
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... are modeled as a non-planar surface in this study, a slight deviation (up to 15-degree) in the surface trace of the fault and focal mechanism solution is expected (Additional file 1: Fig. S6). The Silivri Ridge Fault (SRF) and Silivri Ridge Southern Border Fault (SRSBF) seems in agreement with focal mechanism solutions in their vicinity as well ( Fig. 5a and Additional file 1: Fig. S6). The kinematic analysis of the fault planes mapped from seismic reflection profiles and the kinematic analysis of the planes obtained from the source mechanism solutions of M4 + earthquakes are compatible with each other in the main stress direction, as shown in Fig. ...
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... solutions in their vicinity as well ( Fig. 5a and Additional file 1: Fig. S6). The kinematic analysis of the fault planes mapped from seismic reflection profiles and the kinematic analysis of the planes obtained from the source mechanism solutions of M4 + earthquakes are compatible with each other in the main stress direction, as shown in Fig. ...
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... 6, Additional file 1: Figs. S8, and S9). This corresponds to 10% of the preloaded stress increase on the NAFZ-D (Fig. 6f and Additional file 1: Fig. S10). The stress increase on Silivri Ridge Fault and Silivri Ridge Southern Border Fault is above 10% of the inter-seismic storage. This probably triggered the M4.7 earthquake on January 11, 2020 (Fig. 5, Additional file 1: Fig. S6; Table ...
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... the maximum on the surfaces of the secondary fault system. The rate of overall stress change on the main segments (NAFZ-C and NAFZ-D) is reaching its maximum, where the pre-Coulomb stress is relatively low along the fault surface. The microseismic activity is observable, where the overall stress change is reaching its maximum on the NAFZ-D (Figs. 5, 6f, Additional file 1: Figs. S10a-c, S11). In addition, the stress-increased fault patches display concordance with aftershock activity (Figs. 5, 6, Additional file 1: Figs. S9, S10). The westward migration of M7+ earthquakes along the NAFZ has terminated right in the eastern edge of the Marmara seismic gap during the 1999 Izmit ...
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... its maximum, where the pre-Coulomb stress is relatively low along the fault surface. The microseismic activity is observable, where the overall stress change is reaching its maximum on the NAFZ-D (Figs. 5, 6f, Additional file 1: Figs. S10a-c, S11). In addition, the stress-increased fault patches display concordance with aftershock activity (Figs. 5, 6, Additional file 1: Figs. S9, S10). The westward migration of M7+ earthquakes along the NAFZ has terminated right in the eastern edge of the Marmara seismic gap during the 1999 Izmit earthquake. According to our calculations, the 2019 Silivri earthquakes have substantially increased the Coulomb stress on the main segment of the NAFZ in ...
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... seismic reflection profile was adopted from Demirbağ (2004). Figure S5. The uncertainty distribution of hypocenters. ...
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Citations
Kuwait National Seismic Network (KNSN) data shows the clustering of earthquakes in northern and southern clusters. Spatial correlation between these clusters and oil fields led previous studies to declare that oil production/injection triggered earthquakes, but some suggested the possibility of tectonic causes.
This study addresses the genuine objective of uncovering the origin of Kuwait earthquakes by analyzing relationships between earthquake spatial and temporal patterns, oil production/injection, structural and tectonic setting, and subsurface fluid pressures.
A kinematic model of the Jal Az-Zor dextral-slip fault was presented as a decipherer to the earthquake's origin. The northern and southern clusters represent leading quadrants, where increased mean stress causes earthquakes. Dibdibah Trough and Kuwait Bay represent trailing quadrants with decreased mean stress and a lack of earthquakes. The small percentage of earthquakes falling outside clusters are caused by the concentration of regional compressive stresses related to Arabian Plate motion on pre-existing faults. Triggering earthquakes by oil field operations requires 10% pressure increase above the original pressures, which never occurs in Kuwait oil fields.
The results of this study emphasize the significance of understanding fault kinematics to assess earthquake hazards and the need to focus on engineering requirements for developments in the leading quadrants areas.
