Deep deformation of the Longmenshan fault zone related to the 2008 Wenchuan earthquake

Chen, Qi‐Fu; Li, Le

doi:10.1360/n972018-00362

Cited by 14 publications

(13 citation statements)

References 51 publications

(79 reference statements)

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“…The deep rate (6-9.5 mm/a) derived in this study from the inversion of GPS velocities is two to three times higher than the above GPS and geological rates, but similar to the slip rate estimated over a depth range of 4-18 km using repeating earthquakes (3.5-9.6 mm/a; Li et al, 2011). At the same time, Zhao et al (2008) calculated the accumulated Benioff strain using the earthquake catalogue, while Chen et al (2015) conducted a two-dimensional viscoelastic finite-element simulation; both showed that the deep slip rate along the Longmenshan fault plane is higher than the nearsurface slip rate. Chen and Li (2018) analyzed 10 repeating earthquake sequences detected in the central and northern segments of the LFZ (Figure 6), and found that the S06 and S07 sequences at 14-16 km depth near Hongkou-Wenchuan (Figure 6C) and the S10-12 sequences at 4.3-9.5 km depth near Beichuan (Figure 6E) exhibited different degrees of medium-term slip acceleration in around 2006.…”

Section: Discussion Acceleration Process Of Deep Slip Along the Longm...supporting

confidence: 79%

Acceleration of Deep Slip Along the Longmenshan Fault Plane Before the 2008 M8.0 Wenchuan Earthquake

et al. 2022

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The first step toward earthquake forecasting is the identification of variables whose spatio-temporal variation can be connected with pre-seismic crustal deformation. Four periods of campaign Global Positioning System (GPS) observations around the Longmenshan fault zone (LFZ) provide important insights in crustal deformation and deep fault slip before the 2008 M8.0 Wenchuan earthquake. By using TDEFNODE to invert the coupling fraction and dynamic slip deficit rate of the Longmenshan fault plane before the Wenchuan earthquake, we show that under a background of strong coupling, the compressive slip deficit rate perpendicular to fault increased slightly at first and then decreased; a value of ∼1.5–3.6 mm/a along the central–southern segment from 1999 to 2001 increased to ∼1.9–3.9 mm/a from 2001 to 2004, and then decreased to ∼1.1–2.6 mm/a from 2004 to 2007. The dextral slip deficit rate parallel to fault was ∼6 mm/a from 1999 to 2004, before increasing significantly to ∼9.5 mm/a from 2004 to 2007, when the compressive slip deficit rate decreased. At the same time, large-scale GPS velocity profiles show that compressive shortening deformation in the Eastern Tibet Block, perpendicular to fault, increased slightly from 2001 to 2004, and then decreased from 2004 to 2007. Meanwhile, the dextral shear deformation parallel to fault near the LFZ increased significantly from 2004 to 2007. These findings are in good agreement with those calculated using repeating earthquake sequences, indicating that the deep slip rate of the Longmenshan fault plane may have accelerated several years before the Wenchuan earthquake. Our results demonstrate that GPS data can record pre-seismic preparatory processes, and have the potential for use in medium-term large earthquake forecasting.

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Section: Discussion Acceleration Process Of Deep Slip Along the Longm...supporting

confidence: 79%

Acceleration of Deep Slip Along the Longmenshan Fault Plane Before the 2008 M8.0 Wenchuan Earthquake

et al. 2022

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“…Under the continuous action of plate movement, faults will inevitably dislocate (Shi and Ma, 2018). In the Wenchuan earthquake, fault rupture propagation occurred (Chen and Li, 2018;Li et al, 2019). Experiments have suggested that earthquakes may be caused by dislocation due to overcoming fault friction under certain stress conditions (Zheng et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

Mechanical Mechanism of Fault Dislocation Based on in situ Stress State

Shi

Fang

et al. 2020

Front. Earth Sci.

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Fault dislocation occurs under certain stress conditions. Based on the mechanical relationship between the direction of crustal stress and fault occurrence, three criteriafault dislocation trend, fault strike dislocation trend, and dip dislocation trend-are put forward. According to these three criteria, the fault slip and the type of slip can be inferred. The parameters that have great influence on the characteristics of fault slip are fault dip angle, angle between horizontal principal stress and fault strike, depth, lateral pressure coefficient, internal friction angle, and cohesion of fault plane. Fault slip is more likely to occur in the environment of high deviation stress, low friction angle, and dip angle of about 40 •. Fault rupture is a point-to-surface and deep-to-shallow process. When the criterion value of the local position of the fault is greater than 0, it will lead to the slip of the nearby fault. When the slip range of the fault extends to the surface, it will cause large earthquakes with large-scale surface rupture. The theoretical calculation is basically consistent with the numerical simulation results. According to the theory in this paper, the slip instability state of Longmen Mountain Fault Zone under different stress conditions is calculated, and the results show that when the lateral pressure coefficient is greater than 2.5, dislocation occurs in the deep part of the fault.

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“…to the west boundary of our models from top to bottom [19,36]. Because of the uncertainty in the quantitative determination of long-term slip rate [37], the recurrence intervals like Wenchuan earthquake in YBF changes greatly. Data from paleoseismic activity indicate that the average recurrence period is around 3000 years [38]; while the results of the viscoelastic finite element model [39] show that the recurrence period of strong earthquakes similar to the Wenchuan earthquake is between 4200 and 6500 years.…”

Section: Boundary Conditionmentioning

confidence: 98%

Numerical Simulation Study on the Influence of Branching Structure of Longmen Shan Thrust Belt on the Nucleation of Mw7.9 Wenchuan Earthquake

Yue

Shan

et al. 2020

Remote Sensing

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On the Longmen Shan thrust belt (LMS) on the eastern margin of Tibet Plateau, the Mw7.9 Wenchuan earthquake occurred in 2008. As for the dynamic cause of the Wenchuan earthquake, many scholars have studied the rheological difference and terrain elevation difference on both sides of the fault. However, previous studies have simplified the LMS as a single listric-reverse fault. In fact, the LMS is composed of four faults with different dip angles in the shallow part, and the faults are Wenchuan-Maoxian fault (WMF), Yingxiu-Beichuan fault (YBF), Guanxian-Jiangyou fault (GJF) and Range Front Thrust (RFT) from west to east. However, the control of the branching structure of these faults on the distribution and accumulation of stress and strain during the seismogenic of the Wenchuan earthquake has not been discussed. In this paper, four viscoelastic finite element models with different fault numbers and combination structures are built to analyze the effect of fault branching structures on the stress distribution and accumulation during the seismogenic of Wenchuan earthquake, and we use geodetic data such as GPS and precise leveling data to constrain our models. At the same time, we also study the influence of the existence of the detachment layer, which is formed by the low-resistivity and low-velocity layer, between the upper and lower crust of the Bayan Har block and the change of its frontal edge position on the stress accumulation and distribution. The results show that the combinations of YBF and GJF is most conducive to the concentration of equivalent stress below the intersection of the two faults, and the accumulated stress on GJF is shallower than that on YBF, which means that more stress is transferred to the surface along GJF; and the existence of a detachment layer can effectively promote the accumulation of stress at the bottom of YBF and GJF, and the closer the frontal edge position of the detachment layer is to the LMS fault, the more favorable the stress accumulation is. Based on the magnitude of stress accumulation at the bottom of the intersection of YBF and GJF, we speculate that the frontal edge position of the detachment layer may cross YBF and expand eastward.

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Deep deformation of the Longmenshan fault zone related to the 2008 Wenchuan earthquake

Abstract: The crustal structures of the central Longmenshan along and its margins as related to the seismotectonics of the 2008 Wenchuan Earthquake

Cited by 14 publications

References 51 publications

Acceleration of Deep Slip Along the Longmenshan Fault Plane Before the 2008 M8.0 Wenchuan Earthquake

Acceleration of Deep Slip Along the Longmenshan Fault Plane Before the 2008 M8.0 Wenchuan Earthquake

Mechanical Mechanism of Fault Dislocation Based on in situ Stress State

Numerical Simulation Study on the Influence of Branching Structure of Longmen Shan Thrust Belt on the Nucleation of Mw7.9 Wenchuan Earthquake

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