scholarly journals Active tectonic stress field analysis in NW Iran-SE Turkey using earthquake focal mechanism data

2021 ◽  
Vol 30 (2) ◽  
pp. 235-246
Author(s):  
Ahad NOURI MOKHOORI ◽  
Behnam RAHIMI ◽  
Mohsen MOAYYED
Keyword(s):  
Stress Field ◽  
Focal Mechanism ◽  
Tectonic Stress ◽  
Field Analysis ◽  
Tectonic Stress Field ◽  
Nw Iran ◽  
Earthquake Focal Mechanism ◽  
Active Tectonic ◽  
Stress Field Analysis ◽  
Se Turkey

Study on Seismicity and Its Geodynamic Genesis in Ngari Areas

2020 ◽  
Author(s):  
Guangyin Xu ◽  
Qing Wu ◽  
Suyun Wang
Keyword(s):  
Stress Field ◽  
Focal Mechanism ◽  
Seismic Activity ◽  
Tectonic Stress ◽  
Earthquake Catalogue ◽  
Tectonic Stress Field ◽  
Eurasian Plate ◽  
The North ◽  
East Kunlun ◽  
Tectonic Belt

<p>The Ngari area in Tibet is in the forefront of land-continent collisions. The area is accompanied by the polymerization of plates, forming complex structures such as the Tethys Himalayan pleat belt, the Yarlung Zangbo suture belt, and the Gangdese continental margin magma arc from the south to the north. The multi-period dive collision-inland convergence process, the geological structure is complex and the seismicity is very high. Based on the Chinese historical earthquake catalogue, the China Modern Earthquake Catalogue and the seismic data from the International Seismological Center (ISC), we analyzed the seismic activity, focal mechanism and modern tectonic stress field in the Ngari area, and then analyzed the seismicity and its source of geodynamics. The main conclusions are as follows:(1) The seismic activities in the Ngari area are mainly distributed in the Himalayan tectonic belt, the Bangong-Nujiang tectonic belt, the Alkin-East Kunlun tectonic belt, and some near north-south trending tectonic belts; (2) Earthquakes near the Himalayan tectonic belt is dominated by reverse faulting events. The seismic activity near the Bangong-Nujiang tectonic belt and the Alkin-East Kunlun tectonic belt is dominated by strike-slip earthquakes. Near the north-south extensional tectonic belt, the earthquakes show as the normal faulting events. (3) The main direction of the modern tectonic stress field in the study area is near north-south direction; (4) Seismic activity, focal mechanism and modern tectonic stress field show that the geodynamic source in the Ngari region is from Collision and squeezing the between the Eurasian plate and the Indian Ocean plate.</p>

scholarly journals RECONSTRUCTION OF THE TECTONIC STRESS FIELD IN THE DEEP PARTS OF THE SOUTHERN KURIL-KAMCHATKA AND NORTHERN JAPAN SUBDUCTION ZONES

2020 ◽  
Vol 11 (4) ◽  
pp. 743-755
Author(s):  
D. A. Safonov
Keyword(s):  
Stress Field ◽  
Uniaxial Compression ◽  
Subduction Zones ◽  
Tectonic Stress ◽  
Lithospheric Plate ◽  
Tectonic Stress Field ◽  
The Pacific ◽  
Earthquake Focal Mechanism ◽  
Hinge Zone ◽  
Northern Japan

Earthquake focal mechanisms in the Southern Kuril-Kamchatka and Northern Japan subduction zones were analysed to investigate the features of the tectonic stress field inside the Pacific lithospheric plate subducting into the upper mantle. Earthquake focal mechanism (hypocenter depths of more than 200 km) were taken from the 1966– 2018 NIED, IMGiG FEB RAS and GlobalCMT catalogues. The tectonic stress field was reconstructed by the cataclastic analysis method, using a coordinate system related to the subducting plate. In most parts of the studied seismic focal zone, the axis of the principal compression stress approximately coincides with the direction of the Pacific lithospheric plate subduction beneath the Sea of Okhotsk. It slightly deviates towards the hinge zone separating the studied regions. The principal tension stress axis is most often perpendicular to the plate movement, but less stable in direction. This leads to compression relative to the slab in some parts of the studied regions, and causes shearing in others. The hinge zone is marked by the unstable position of the tension axis and high values of the Lode–Nadai coefficient, corresponding to the conditions of uniaxial compression, while the compression direction remains the same, towards the slab movement. Two more areas of uniaxial compression are located below the Sea of Japan at depths of 400–500 km.

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