Stress tensor inversion from focal mechanism solutions and earthquake probability analysis of Western Anatolia, Turkey

Download
index.pdf
2015
Shah, Syed Tanvir
Show full item record
208
views
159
downloads
Western Anatolia is one of the most important tectonic elements of Turkey, and constitutes the eastern margin of Aegean Extensional Province. The area is one of the most seismically active continental margins around the globe experiencing NS extension. Earthquake data in this study is used to analyze the active stress patterns and to estimate the earthquake probabilities for different sub-regions in western Anatolia. Various processing techniques to attain homogeneity are applied to the earthquake catalogue for the area, which is then used for investigation of spatial and temporal variations in frequency magnitude distribution. More frequently occurring smaller magnitude earthquakes represented by high b-values are associated with relatively low stress conditions. The prominent high b-value regions identified in the study area are along Bakırçay Graben and between İzmir and Manisa. Spatial distribution of high b-values correlates well with the distribution of hot springs and high heat flow anomalies. The temporal variations in b- values are associated with major earthquakes in the region. Before the earthquake, b-vales show a small scale decrease followed by an abrupt increase after the event and this variation disappears after some time. Focal mechanism solution data is used for determining the orientations and ratios of principal stress components in the area. Minimum principal stress (σ3) is sub horizontal in the region trending in almost NS (N15 E) direction and the region is characterized mainly by normal fault regime. The area is sub-divided into 10 sub-regions based on the variations in focal mechanism solutions and tectonic setting. The results for sub-regions showed that apart from the predominant extensional regime; Bakırçay and Gulf of Sığacık sub-regions are dominated by strike-slip, while Manisa and Soma sub-regions are dominated by extensional strike-slip regimes. These sub-regions roughly coincide with the İzmir Balıkesir Transfer Zone (IBTZ), which is characterized by mixture of normal and strike-slip faults. Computed principle stress directions shows that the area is mostly characterized by NS extension except Gökova region marked by NWSE extension and Dinar and Fethiye regions displaying more variable stress tensor solutions with more dominant NE-SW extension. The earthquake probabilities computed using Gutenberg-Richter relation and Gumbel extreme value method shows that the whole region has a return period of 3 and 7 years for a magnitude 6 earthquake. According to our results, Simav and Gulf of Gökova sub-regions have highest and Manisa has lowest earthquake probabilities. The fractal dimension (Dc) analysis illustrates that Gulf of Gökova and Fethiye sub-regions have highest and Dinar-Burdur, Büyük Menderes and Gulf of Sığacık have lowest levels of seismicity clustering. The comparison of results computed for sub-regions also showed that a-, b- values and stress variance are negatively correlated with Dc and stress ratio (R) while Dc correlates positively with R.
Seismology., Earthquake prediction., Geophysical prediction., Earthquake engineering.
http://etd.lib.metu.edu.tr/upload/12618444/index.pdf
https://hdl.handle.net/11511/24426
Graduate School of Natural and Applied Sciences, Thesis

Suggestions

Spatial variations of active stress patterns and frequencymagnitude distribution of earthquakes in Western Anatolia, Turkey
Shah, S Tanvir; Özacar, Atilla Arda (null; 2018-04-23)
Western Anatolia is one of the most important tectonic elements of Turkey, and constitutes the eastern margin of Aegean Extensional Province. The area is one of the most seismically active continental margins around the globe experiencing N-S extension. Earthquake data in this study is used to analyze the active stress patterns and to estimate the earthquake return periods for different sub-regions in western Anatolia. Focal mechanism solution data is used for determining the orientations and ratios of prin...
Earthquake focal mechanism and stress tensor analysis along the central segment of the North Anatolian fault
Karasözen, Ezgi; Özacar, Atilla Arda; Kaymakcı, Nuretdin; Department of Geological Engineering (2010)
The North Anatolian Fault (NAF) is one of the world’s largest active continental strikeslip faults, and forms the northern margin of the Anatolian plate. Although its geologic and geomorphologic features are well defined, crustal deformation and associated seismicity around central segment of the NAF is relatively less-known. In this study, we analyzed locations and focal mechanisms of 172 events with magnitude ≥ 3, which are recorded by 39 broadband seismic stations deployed by the North Anatolian Passive ...
Earthquake Detection Near the Central Anatolian Fault Zone Using Continuous Data from the CD-CAT Experiment
Russell, Joshua B.; Beck, Susan L.; Turkelli, Niyazi; Kalafat, Doğan; Özacar, Atilla Arda; Sandvol, Eric (2014-12-15)
In central Turkey, the Anatolian plate is actively being pushed by Arabian plate convergence in the east and pulled by Hellenic arc retreat to the west; however, there is also ample evidence of internal plate deformation. This region provides an opportunity to gain a deeper understanding of the transition from collisional (eastern Anatolia) to escape tectonics (western Anatolia). The Continental Dynamics: Central Anatolian Tectonics (CD-CAT) experiment, consists of a dense array of 71 broadband seismometers...
Evaluation of alluvial deposits in Gemlik basin in terms of earthquake codes.
Avşar, Ulaş; Doyuran, Vedat; Department of Geological Engineering (2006)
Gemlik County is located in the Marmara Region (NW Turkey), which has been affected by destructive earthquakes sourced from North Anatolian Fault System throughout its history. The bulk of the settlement rests on alluvial deposits of the Gemlik pull-apart basin. So, it is vital to investigate the foundation soils in this basin and the response of them to earthquakes. Many earthquake codes were established by the authorities in different countries of the world to estimate the possible ground shaking and seis...
Modeling of a historical earthquake in Erzincan, Turkey (Ms similar to 7.8, in 1939) using regional seismological information obtained from a recent event
Karim Zadeh Naghshineh, Shaghayegh; Askan Gündoğan, Ayşegül (2018-06-01)
Located within a basin structure, at the conjunction of North East Anatolian, North Anatolian and Ovacik Faults, Erzincan city center (Turkey) is one of the most hazardous regions in the world. Combination of the seismotectonic and geological settings of the region has resulted in series of significant seismic activities including the 1939 (Ms similar to 7.8) as well as the 1992 (Mw = 6.6) earthquakes. The devastative 1939 earthquake occurred in the pre-instrumental era in the region with no available local...
Citation Formats
S. T. Shah, “Stress tensor inversion from focal mechanism solutions and earthquake probability analysis of Western Anatolia, Turkey,” M.S. - Master of Science, Middle East Technical University, 2015.
METU IIS - Integrated Information Service open@metu.edu.tr