The recent fault kinematics in the westernmost part of the Getic nappe system (Eastern Serbia): Evidence from fault slip and focal mechanism data

Abstract In this study we performed a calculation of the tectonic stress tensor based on fault slip data and all available focal mechanisms in order to determine the principal stress axes and the recent tectonic regime of the westernmost unit of the Getic nappe system (Gornjak-Ravanica Zone, Eastern Serbia). The study is based on a combined dataset involving paleostress analyses, the inversion of focal mechanisms and remote sensing. The results show dominant strike-slip kinematics with the maximal compression axis oriented NNE-SSW. This is compatible with a combined northward motion and counterclockwise rotation of the Adria plate as the controlling factor. However, the local stress field is also shown to be of great importance and is superimposed on the far-field stress. We managed to distinguish three areas with distinct seismic activity. The northern part of the research area is characterized by transtensional tectonics, possibly under the influence of the extension in the areas situated more to the northeast. The central and seismically most active part is dominated by strike-slip tectonics whereas the southern area is slightly transpressional, possibly under the influence of the rigid Moesian Platform situated to the east of the research area. The dominant active fault systems are oriented N-S (to NE-SW) and NW-SE and they occur as structures of either regional or local significance. Regional structures are active in the northern and central part of the study area, while the active fault systems in the southern part are marked as locally important. This study suggests that seismicity of this area is controlled by the release of accumulated stress at local accommodation zones which are favourably oriented in respect to the active regional stress field.

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The characteristics of tectonic stress field about strike slip earthquake-generating structure in the Chinese mainland

Acta Seismologica Sinica ◽

10.1007/bf02650742 ◽

1994 ◽

Vol 7 (4) ◽

pp. 567-575 ◽

Cited By ~ 2

Author(s):

Wen-Lin Huan ◽

Su-Yun Wang ◽

Zhao-Yi Song

Keyword(s):

Stress Field ◽

Tectonic Stress ◽

Chinese Mainland ◽

Strike Slip ◽

Tectonic Stress Field ◽

The Chinese Mainland

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The 1991 Sierra Madre earthquake sequence in southern California: Seismological and tectonic analysis

Bulletin of the Seismological Society of America ◽

10.1785/bssa0840041058 ◽

1994 ◽

Vol 84 (4) ◽

pp. 1058-1074 ◽

Cited By ~ 2

Author(s):

Egill Hauksson

Keyword(s):

Los Angeles ◽

Fault Plane ◽

B Value ◽

Tectonic Stress ◽

Aftershock Sequence ◽

Strike Slip ◽

Focal Mechanisms ◽

Stress Axis ◽

The North ◽

Sierra Madre

Abstract The (ML 5.8) Sierra Madre earthquake of 28 June 1991 occurred at a depth of 12 km under the San Gabriel Mountains of the central Transverse Ranges. Since at least 1932 this region had been quiescent for M ≧ 3. The mainshock focal mechanism derived from first-motion polarities exhibited almost pure thrust faulting, with a rake of 82° on a plane striking N62°E and dipping 50° to the north. The event appears to have occurred on the Clamshell-Sawpit fault, a splay of the Sierra Madre fault zone. The aftershock sequence following the mainshock occurred at a depth of 9 to 14 km and was deficient in small earthquakes, having a b value of 0.6. Twenty nine single-event focal mechanisms were determined for aftershocks of M > 1.5. The 4-km-long segment of the Clamshell-Sawpit fault that may have ruptured in the mainshock is outlined by several thrust focal mechanisms with an east-northeast-striking fault plane dipping to the north. To the west, several thrust aftershocks with east-striking nodal planes suggest some complexity in the aftershock faulting, such as a curved rupture surface. In addition, several strike-slip and normal faulting events occurred along the edges of the mainshock fault plane, indicating secondary tear faulting. The tectonic stress field driving the coexisting left-lateral strike-slip and thrust faults in the northern Los Angeles basin is north-south horizontal compression with vertical intermediate or minimum principal stress axis.

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Spatial variation in the present-day stress field and tectonic regime of Northeast Tibet from moment tensor solutions of local earthquake data

Geophysical Journal International ◽

10.1093/gji/ggaa013 ◽

2020 ◽

Vol 221 (1) ◽

pp. 478-491 ◽

Cited By ~ 1

Author(s):

Zhengyang Pan ◽

Jiankun He ◽

Zhigang Shao

Keyword(s):

Stress Field ◽

Compressive Stress ◽

Moment Tensor ◽

Strike Slip ◽

Focal Mechanisms ◽

Qilian Mountains ◽

Compression Axis ◽

The South ◽

Maximum Compression ◽

Stress Orientation

SUMMARY Focal mechanism solutions and their predicted stress pattern can be used to investigate tectonic deformation in seismically active zones and contribute to understanding and constraining the kinematic patterns of the outward growth and uplift of the Tibetan Plateau. Herein, we determined the focal mechanisms of 398 earthquakes in Northeast Tibet recorded by the China National Seismic Network (CNSN) by using the cut-and-paste method. The results show that the earthquakes predominately exhibited thrust and strike-slip faulting mechanisms with very few normal events. We then combined the derived focal mechanisms with global centroid moment tensor (GCMT) catalogue solutions and previously published solutions to predict the regional distribution of the stress field through a damped linear inversion. The inversion results show that most of region is dominated by a thrust faulting regime. From the southern East Kunlun fault in the west to the northern Qilian Mountains along the Altyn Tagh fault (ATF), the maximum compression axis rotates slightly clockwise; farther to the south of the Haiyuan fault in the east, there is an evident clockwise rotation of the maximum compression axis, especially at the eastern end of the Haiyuan fault. In the Qilian Mountains, the axis of the compressive stress orientation approximately trends NE–SW, which does not markedly differ from the direction of India–Eurasia convergence, emphasizing the importance of the compressive stress in reflecting the remote effects of this continental collision. The overall spatial pattern of the principal stress axes is closely consistent with the GPS-derived horizontal surface velocity. A comparison of the stress and strain rate fields demonstrated that the orientations of the crustal stress axes and the surface strain axes were almost identical, which indicates that a diffuse model is more suitable for describing the tectonic characteristics of Northeast Tibet. Additionally, the compressive stress orientation rotated to ENE–WSW in the northern Qilian Mountains along the ATF and to ENE–WSW or E–W along the eastern part of the Haiyuan fault and its adjacent area to the south, highlighting the occurrence of strain partitioning along large left-lateral strike-slip faults or the lateral variation of crustal strength across these faults. Combining geodetic, geological and seismological results, we suggest that a hybrid model incorporating both the diffuse model associated with shortening and thickening of the upper crust and the asthenospheric flow model accounting for the low-velocity zone in the middle-lower crust may reflect the primary mode of crustal deformation in Northeast Tibet.

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Inversion of Initial Geo-Stress in High and Steep Slope

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.170-173.1325 ◽

2012 ◽

Vol 170-173 ◽

pp. 1325-1329

Author(s):

Zhong Fan Yuan ◽

Pei Hua Xu ◽

Zhao Rong Ye

Keyword(s):

Stress Field ◽

Field Distribution ◽

Decisive Role ◽

Local Stress ◽

Field Measurements ◽

Tectonic Stress ◽

In Situ Stress ◽

Initial Stress Field ◽

Principal Compressive Stress ◽

Geological Conditions

At present, due to various reasons, cannot do a large number of field measurements, and the measured results often can only reflect the local stress field distribution. What’s more, the measured results has discreteness, it’s difficult to describe the law of the initial stress field distribution in the entire region. This paper combines topographic and geological conditions and the measured in-situ stress value of Jinping I hydropower station dam area, using FLAC3D4.0, select geological section profile of II1 exploration line for reference, to simulate the incised process of the valley. We get the stress field distribution when rock gravity acting alone, and exert horizontal tectonic stress based on the calculate result of gravity field in the VI terrace model. We inversion the distribution of current Valley stress field, and validate the rationality of the design after compare with the measured data. We obtain the features of stress field of current valley. And we also proved that the regional principal compressive stress plays a decisive role in the formation of the current valley stress field.

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The relation of the seismicity in the eastern part of the Ukrainian Carpathians and the distribution of electrical conductivity in the Earth’s crust

Geologica Carpathica ◽

10.2478/geoca-2019-0028 ◽

2019 ◽

Vol 70 (6) ◽

pp. 483-493

Author(s):

Svetlana Kováčiková ◽

Igor Logvinov ◽

Viktor Tarasov

Keyword(s):

Electrical Conductivity ◽

Seismic Data ◽

Active Fault ◽

Tectonic Stress ◽

Fault System ◽

3D Inversion ◽

Fault Systems ◽

Earthquake Sources ◽

Eastern Carpathians ◽

Outer Carpathians

Abstract We present results of a study of the peculiarities of the seismicity and electrical conductivity distribution beneath the Ukrainian Eastern Carpathians. Based on the analysis of seismic data for the years 1999–2016, specific zones of concentration of earthquake sources related to the principal fault systems and their intersections have been distinguished. This paper covers two zones, one linked to the contact of the Outer Carpathians and the Carpathian Foredeep and another one linked to the fault system transverse to the Carpathians strike. Both belts of earthquake sources concentration correlate well with the geoelectric models of the studied area obtained as a result of 2D and quasi-3D inversion. Most of the seismic events occur at the intersection of the mentioned seismic zones, at shallower depths, than the main conductive structures appear, concentrated at their marginal parts. The interrelation of both phenomena suggests their common explanation by processes occurring in active fault systems: fracturing, shear deformation, migration of highly mineralized fluids, high porous pressure, accumulation and release of tectonic stress.

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