Browsing by Author "Toker, M."

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Azimuthal Rotation-Dependent Spatial Distributional Patterns of Small Repeaters Estimated From Microseismic Data-Set of Gokova Gulf (sw-Turkey)
(EAGE Publishing BV, 2019) Toker, M.
Small repeating earthquakes reveal properties such as the temporal and spatial clustering of events, which serve as a key tool to constrain the rate/state stress transfer and seismogenetic properties of active seismic areas. In our case, azimuthal rotation-dependent spatial patterns of the small repeaters were estimated from the four yearsmicroseismic data set (~10.000 events) of Gokova Gulf (GG) (SW-Turkey). The process of microseismicity taking place in Gokova Gulf in 2010-2014 was relocated in an attempt to quantify the prominent seismogeneity in the GG and to unveil properties of the associated current stress state of the GG and its projected surroundings at crustal depths. In the present study, we evaluated the 26th November 2012 Bozburun mainshock (Mw 4.4, 4.8) with its accompanying small repeating events and its accompanying multiple aftershock series; the 16th May 2013 Ula aftershock (Mw 4.6), the 25th March 2014 Bozburun aftershock (Mw 4.0), the 1th May 2014 Bodrum aftershock (Mw 4.0) with their accompanying small repeating events, symptomatically occurring in the Bozburun, Ula, and Bodrum areas of the GG by using the microseismic data set. Then, we produced azimuth-dependent, rotational and cross sectional distributional patterns of all microearthquake clusters at depth, up to ~ 160 km. Copyright © Congress of Balkan Geophysical Society, BGS 2019. All rights reserved.
Co- and Pre-Seismic Crustal Deformations Related To Large Earthquakes Between Years of 2009 and 2023 Using Continuous Cors-Tr Gnss Observations in the Anatolian Diagonal (Turkey)
(Geophysical Center Ras, 2023) Dokukin, P.; Guvenaltin, M. A.; Kaftan, V.; Toker, M.
Synoptic animations of internal displacements and deformations of the earth's crust were obtained based on the results of continuous GNSS observations in Eastern Anatolia from 2009 to 2023. The spatiotemporal patterns of the seismic deformation process in connection with the tectonics of the region have been identified. It is shown that dilatation and total shear strains evolve in concert with the migration of the strongest earthquakes Elazig, Elazig-Malatya and devastate Karamanmara & scedil; series. Two years before the occurrence of the devastating earthquakes of 2023, a deficit of internal displacements of GNSS stations developed in the area of their epicenters. The conducted research suggests that the strongest events of 2009-2023 are connected by a unitary seismic deformation process. The most important action in this case is the SW movement of the Anatolian block as monolithic element. In the development of movements and deformations, a flow of increasing stresses is observed in the direction from Karliova Triple Junction to the SW to the area of the strongest seismic events on February 2023. It originates east of the Karliova Triple Junction where the Arabian Plate encounters an obstacle. The role of mantle flows in the seismic process is assessed.
Fk-Array Response To Four Greenland Glacial Earthquakes From Geopsy Transfer Functions
(Finish Environment Institute, 2019) Toker, M.
Using the German Regional Seismic Network (GRSN), we analyzed the Rayleigh waves of four Greenland, Mw~5, glacial earthquakes. We obtained their > 30 s period fk-array simulation parameters using the array transfer-functions procedures incorporated in Gpfksimulator GEOPSY software. This analysis has allowed us to estimate their slowness, azimuth and back-azimuth parameters. Further, it also revealed several unique long period phases. These results have enabled us to put the four events in the context of numerous other Greenland glacial events whose source mechanisms do not match those typical of tectonic earthquakes. Instead, they add to the evolving understanding of a new class of source models associated with rapid moving outlet glaciers. Our discussion also includes a summary of the technical details of our analysis and a list of the simulation parameters for the GRSN. © 2019, Finish Environment Institute. All rights reserved.
Insar Analysis of Ayvacik 2017 (Mw 5.3) Earthquake Swarm (Canakkale, Nw-Turkey)
(International Society for Photogrammetry and Remote Sensing, 2019) Abdikan, S.; Imamoglu, M.; Alasag, T.; Toker, M.; Kutoglu, S.H.; Sahin, S.
In this study, the deformation of Ayvacik Canakkale earthquake and aftershocks of 5.3 (Mw), which were observed on 6 February 2017 in Gulpinar Ayvacik and felt from the surrounding cities, were analyzed by InSAR and strain reduction technique. The earthquake is occurred at the Biga peninsula which is located at the south segment of North Anatolian Fault zone. The first shock (Ml Combining double low line 4.8) started on 14 January 2017 in the region, and after the second shock (Ml Combining double low line 5.4) on February 6, 2017, seismic storm continued with the large and small earthquakes. It was seen that 31 of these earthquakes have a size of 4 and above and occurred on the Tuzla fault. Since classical geodetic methods are not performed regularly and frequently, and are spatially provide point-based displacements, they are often insufficient to monitor sudden earthquakes. For this purpose, the deformation values were obtained along the line of sight (LOS) direction of Synesthetic Aperture Radar (SAR) sensor using Differential Interferometric SAR (DInSAR) method. For the geophysical analysis coulomb technique was applied and the continuity of the changes in the sea is determined. © Authors 2019.
Source Mechanisms and Faulting Analysis of the Aftershocks in the Lake Ercek Area (Eastern Anatolia, Turkey) During the 2011 Van Event (Mw 7.1): Implications for the Regional Stress Field and Ongoing Deformation Processes
(Pergamon-elsevier Science Ltd, 2017) Toker, M.; Pinar, A.; Tur, H.
In this study, we analysed the source mechanisms and faulting pattern of the aftershocks in the Lake Ercek area, Eastern Anatolia, during the 2011 Van event (Mw 7.1). The fault plane solutions of the aftershocks were used to derive a stress tensor acting around Lake Ercek. The estimated seismological parameters (focal mechanism solutions, stress tensor, and fault focal analyses) were integrated with field surveys and high resolution seismic reflection data so as to better understand the main faulting patterns and deformational features which are the causatives of the observed geomorphological features within and around Lake Ercek. The focal parameters of the 56 aftershocks with magnitude range 3.5 <= Mw <= 5.5 were obtained using the regional broadband seismic data from the network of Kandilli Observatory and Earthquake Research Institute (KOERI) through the Centroid Moment Tensor (CMT) inversion of locally observed broadband-waves. The implications for the lateral variation of the stress field in the lake area were based on information derived from integration of seismicity and stress tensor inversion results. The major outcomes of our analyses were as follows: (a) The maximum principal stress axis is close to horizontal and aligned in NNW-SSE direction, the minimum compressional stress axis is close to vertical and aligned in an ENE-WSW direction, the intermediate stress axis is close to horizontal and is parallel to the strike of the ruptured fault plane, while the stress ratio is (R = 0.6); (b) the lake basin is mostly deformed by dip-slip faults (dips >= 45-60 degrees) in and along its margins where the various folds, basement highs with eroded surfaces and several low-angle normal faults are evident; (c) the majority of the aftershocks have reverse-thrust mechanism with some strike-slip components in the Lake Ercek area (N- and S-margins). Strike-slip and normal faulting events are also evident (E- and W-margins, respectively); (d) the normal and reverse mechanisms with some strike-slip component are mostly confined in the upper crust (0-15 kin), compatible with NS-striking normal and WE-striking reverse faults in the marginal sections of the lake; (e) the WE-striking reverse faulting in the N- and S-margins seems to have the seismic potential to generate destructive earthquakes in the lake area; (f) the tectonic implications of the regional stress field and ongoing deformation processes in the lake are defined and supported by field observations and seismic reflection data. The result of these analyses reveals N -S compression/W-E extension in the lake and also the collisional/compressional regime taking place in a region of Lakes Van and Ercek.