碩士 / 國立臺灣大學 / 海洋研究所 / 104 / The continental collision between Arabia and Eurasia created the strike-slip fault conjugates in Anatolia as well as the folds and thrust belts in the Caucasus Mountains. The Black Sea, on the contrary, is tectonically stable and absent of notable earthquakes. In previous studies, focal mechanisms in the Caucasus regions are determined primarily for large earthquakes using global waveform data. Small earthquakes are primarily studied with polarity data, thus the reliability of focal mechanisms highly depends on station coverage.
In this study we use regional waveforms of a new seismic array to constrain the focal mechanisms and depths of the earthquakes with M>3.5 in the Greater Caucasus, Trans-Lesser Caucasus (mainly in Javakheti Highland) and the eastern Black Sea. There is a total of 20 new events for the studied area (Latitude 40–44⁰N and Longitude 40–47⁰E) in time period 2012.01.01–2014.05.30. We also update 4 focal mechanisms from previous study.
On December 12 of 2012, an M 5.8 earthquake sequence occurred in the eastern Black Sea region beneath an extended continental margin called Shatsky Ridge. The fault plane solutions of the main shock and 5 aftershocks are all in strike-slip faulting. Depth of rupture is as deep as ~30 km. Location of five focal mechanisms is aligned at WNW-ESE direction, which coincides with one of the fault plane, indicating left-lateral slip. A group of small aftershocks scattered toward northeast direction at shallower depth. Based on the seismic reflection profiles nearby, we conclude that the main rupture fall along the existing normal fault created associated with back-arc spreading of Eastern Black Sea basin in the past, but now reactivated as strike-slip due to compressive stress. A second rupture is triggered along a conjugate fault perpendicular to the main fault, which can be correlated with a transform fault developed during the ocean spreading.
Javakheti is a volcanic highland where swarms of small earthquakes are continuously occurring in its eastern ridge. Collectively, the total of 20 earthquakes here is dominated by strike-slip faulting. Only three small thrust events are found in north of the swarm area. Earthquakes in eastern foothill of Javakheti ridge show small amount of normal-faulting component, which indicates east-west extension, consistent with the fault outcrops nearby and the east-west relative motion form GPS data.
| Identifer | oai:union.ndltd.org:TW/104NTU05279031 |
| Date | January 2016 |
| Creators | Che-Hao Hsu, 許哲豪 |
| Contributors | Tai Lin Tseng, Chin Wu Chen, 曾泰琳, 陳勁吾 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 109 |
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