•A finite element model was developed to explain the causes of the rupture behavior transition of the Wenchuan earthquake.•The auxiliary stress regime transitioned from SH>Sh>Sv in the southwestern ...segment to SH>Sv>Sh in the northeastern segment.•The stress change associated with the significant first subevent reached 1.0 MPa.•Initial stress and stress change jointly controlled the northeastward rupture of the Mw7.9 Wenchuan earthquake.
The rupture process of the Wenchuan earthquake demonstrated a transition from thrust-dominated slip to northeastward strike-slip motion along the Longmen Shan Fault Zone. The initial stress has been reported as playing a critical role in this process; however, the stress changes, especially those caused by the significant first subevent of the Wenchuan earthquake are not well understood. Here, we employ a three-dimensional finite element model of the Sichuan-Yunnan region to analyze the stress change caused by the significant first subevent and explore the possible influence on the following ruptures. The results indicate that the auxiliary maximum principal compressive stress (SH) associated with the significant first subevent was horizontal and that the auxiliary stress regime was SH>Sh>Sv, supporting the ongoing regional thrust motion near the southwestern segment of the rupture plane. However, in the northeastern segment, the auxiliary stress regime transitioned to SH>Sv>Sh, demonstrating that the stress changes promoted the transition of the rupture behavior from predominantly thrust motion in the southwest to right-lateral strike-slip motion in the northeastern segment, which was also supported by the dominant shear stress change and the subtle normal stress change along the fault plane in the northeastern segment. In addition, our modeled results also indicate that the orientation of the maximum principal compressive stress changed from SEE to northeastward NEE along the strike of Longmen Shan Fault Zone. This anticlockwise rotation hastened the rupture behavior transition, suggesting that both the initial stress and the stress changes associated with the first subevent jointly controlled the following northeastward rupture of the Mw7.9 Wenchuan earthquake.
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•The nature of strong earthquake migration is revealed by the killing element group method.•Killing the element group will lead to the stress field adjustment in a large area in ...Chinese mainland.•Killing the element group can simulate some earthquake sequences in Chinese mainland.
In this paper, a three-dimensional finite element model is utilized to investigate the basic features of stress field change of Chinese mainland caused by the loss of fault load-bearing capacity and its influencing factors through the fault destruction with the killing element group method. This method provides a new way to explore the short term change of stress field in a large area and the corresponding migration of strong earthquakes. Our results show that killing the element group will cause the stress field adjustment in a large area. The equivalent stress in more than 55% elements is increased by more than 0.1 MPa. The change in the direction of principal stress is less than 20 degrees in 99.7% areas. The initial stress field greatly influences the stress field adjustment caused by killing the element group. By killing the element group around the 14 November 2001 Kunlunshan Ms 8.1 strong earthquake area, the perturbed stress field is consistent with the actual observed value of in-situ stress. Furthermore, a maximum equivalent stress element appears near the epicenter of the 12 May 2008 Wenchuan Ms 8.1 earthquake. These results suggest that the killing element group method can simulate some earthquake sequences, but further investigations are still required in the killing element group method by considering more non-linear influences on the stress perturbations.
Strong earthquakes that occurred in the Chinese continent are usually characterized by grouped activity, long-distance jumping migration, and different main activity areas formed in different times. ...In the present study, a three-dimensional (3-D) finite element model was set up for the Chinese continent involving surface topography, major active fault zones and initial stress field to study the mechanism of the long-distance jumping migration of main active areas for the strong earthquakes that occurred in the Chinese continent. A number of numerical simulation experiments have been made by introducing the birth and death of element groups under different boundary loading configurations. Our results show that (1) in an environment where always exists an initial stress field in the Earth’s crust, the areas where strong earthquakes have occurred (taken as a killed element in the model) have no longer abilities to concentrate the stress largely enough and can cause the stress adjustment by an order of MPa in a large area, which may be one of the main factors affecting the long-distance jumping migration of the follow-up strong earthquakes, and (2) it is hard to accurately predict where the follow-up strong-earthquakes will occur because it could be affected by many factors such as the loading manner, geological structure, active fault zones, initial stress field, or stress field adjustment induced by strong earthquakes, but in an active period of earthquakes, the major activity area migration of strong earthquakes may be affected largely by the boundary loading configurations. These results suggest that it is helpful to predict a trend of the strong earthquake migration by investigating various kinds of boundary loading manners and the relationship between stress field adjustment induced by strong earthquakes and the regions where the strong earthquakes occurred.
► Migration trend of strong earthquakes in North China was numerically simulated. ► The stiffness reduction technique was used. ► High stress disturbance regions could be locations of future strong ...earthquakes.
Lu et al. (2011) established a finite element model around the entire Chinese continent to simulate the distant migration of strong earthquakes by killing the elements. In this study a new finite element model of North China has been established in the existing Chinese continental model using the GPS observations and the finite element sub-model technique through taking into account geological structure, active faults, surface topography, Moho discontinuity and 3-D velocity structure of the crust and upper mantle in the region. Furthermore, the stress field adjustment was realized by reducing the element stiffness rather than by killing the elements. We calculated the displacement of the Chinese continent model, and took the displacement located at the boundary of North China as the boundary loadings, then computed the initial stress field by considering the gravity effect. The migration of the strong earthquake regions was simulated by performing a number of tests with various kinds of short-term boundary loadings. Locations of strong earthquakes were determined with the highest G (the risk factor of the fault) value and adjustment of the stress field. Our results showed that high stress disturbance regions could be possible regions of future strong earthquakes, and that the initial stress field in North China can be well estimated, if an optimal boundary loading configuration is chosen in the Chinese continental model. These results suggest that the strong earthquake forecast in North China may strongly depend on the stress field and strong earthquake activities in a much wider area, such as the Chinese continent.
On 12 May 2008, the devastating Wenchuan earthquake struck the Longmenshan fault zone, which comprised the eastern margin of the Tibetan Plateau, and this fault zone was predominantly a convergent ...boundary with a right-lateral strike-slip component. After such a large-magnitude earthquake, it was crucial to analyze the influences of the earthquake on the surrounding faults and the potential seismic activity. In this paper, a complex viscoelastic model of western Sichuan and eastern Tibet regions was constructed including the topography. Based on the findings of co-seismic static slip distribution, we calculated the stress change caused by the Wenchuan earthquake with the post-seismic relaxation into consideration. Our preliminary results indicated that: (1) The tectonic stressing rate was relatively high in Kunlun mountain pass-Jiangcuo, Ganzi-Yushu, Xianshuihe and Zemuhe faults; while in the east Kunlun and Longriba was medium; also the value was less in the Minjiang, Longmenshan, Anninghe and Huya faults. As to the Longmenshan fault, the value was 0.28×10
−3
MPa/a to 0.35×10
−3
MPa/a, which is coincident with the previous long recurrence interval of Wenchuan earthquake; (2) The Wenchuan earthquake not only caused the Coulomb stress decrease in the source region, but also the stress increase in the two terminals, especially the northeastern segment, which is comparatively consistent with the aftershock distribution. Meanwhile, the high concentration areas of the static slip distribution were corresponding to the Coulomb stress reductions; (3) The Coulomb stress change caused by Wenchuan earthquake showed significant increase on five major faults, which were northwestern segment of Xianshuihe fault, eastern Kunlun fault, Longriba fault, Minjiang fault and Huya fault respectively; also the Coulomb stress on the fault plane of the Yushu earthquake was faintly increased; (4) We defined the recurrence interval as the time needed to accumulate the magnitude of the stress drop, and the recurrence interval of Wenchuan earthquake was estimated about 1 714 a to 2 143 a correspondingly.
Global plate motion and earthquake activity Li, Yanxing; Luan, Xiwu; Lu, Yuanzhong ...
Geodesy and Geodynamics,
2010, 2010-00-00, 2010-01-01, Letnik:
1, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The global plate motion rates Ω are not uniform in time and space. The rotation rates were larger than 0.545°/Ma for Cocos, Philippine Sea, Pacific, Nazca, Australia, India and Arabia plates, but ...smaller than 0.315°/Ma. for other plates. Compared to 1997.0, the Ω values of the three oceanic plates in 2000.0 increased by, respectively, 2.4%, 2.1% and 41.7%, and the northward movement rates of the the India plate and western part of the Australia plate increased by 3.38 mm/a on the average. The spatial distribution of earthquakes was dependent on earthquake magnitude. Earthquakes of 5.0 ≤ Mw < 7.0 were located mainly in plate-margin zones and intra-plate crustal deformation zones joining the southern margin of Eurasia plate. Earthquakes of Mw ≥ 7.0 concentrated basically in the circum-Pacific and South Asia zones, but hardly in mid-ocean-ridge seismic zones. Earthquakes of Mw ≥ 8.0 were located only in the margin zones of the India, Australia, Pacific and Nazca plates orthogonal to the direction of plate motion. Compared with previous eighteen years, global earthquake activity enhanced obviously after 1994, especially after 2001. The Ω value of a plate was closely related to the activity of strong earthquakes. The largest earthquakes were located in the front-margin zones of plates having the largest Ω values. Energy released by strong earthquakes comes mainly from kinetic energy of the plates. Global seismicity enhancement was caused mainly by the acceleration of the three oceanic plates. Larger enhancement of global earthquake activity lagged behind the movement acceleration of the three oceanic plates by four years.
Using three dimensional (3D) viscoelastic finite element method (FEM) we study the dynamic evolution pattern of the coseismic change of Coulomb failure stress and postseismic change, on time scale of ...hundreds years, of rheological effect induced by theM ^sub S^=7.2 Xingtai earthquake on March 22, 1966. Then, we simulate the coseismic disturbance in stress field in North China and dynamic change rate on one-year scale caused by the Xingtai earthquake and Tangshan earthquake during 15 years from 1966 to 1980. Finally, we discuss the triggering of a strong earthquake to another future strong earthquake.PUBLICATION ABSTRACT
Based on data of fault movement surveying, we simulate the evolution process of three dimensional stress field in North China by three dimensional finite element method. Evolutional patterns in ...one-year time scale from 1986 to 1997 have been illustrated and the evolution characteristics of stress field have been analyzed. In comparison with the seismic activity among that time interval in North China, we have primarily discussed the relationship between the evolution of stress field and seismic activity.PUBLICATION ABSTRACT
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