Channel flow and fault segmentation with implications for the generation of earthquakes in the Longmenshan fault zone, eastern Tibetan Plateau

SUMMARY Estimation of lithospheric viscosity remains challenging, especially for variations with spatial scales less than 100 km. Some recent studies have developed a method to determine viscosity structure from electrical conductivity models determined from magnetotelluric (MT) data. This method was initially applied to the extensional transition zone from the Great Basin to Colorado Plateau. Here, we use this approach to infer the effective lithospheric viscosity in a convergent setting by using an MT profile that crosses the eastern margin of the Tibetan Plateau. The profile extends from the Songpan-Ganzi block, crosses the 2008 Wenchuan earthquake epicentre region and ends in the Sichuan basin. The preferred viscosity structure is characterized by the middle-lower crustal viscosities in the range 2.42 × 1018 to 2.69 × 1021 Pa s below the Songpan-Ganzi block. In the Longmenshan fault zone and 2008 Wenchuan Ms8.0 earthquake area, the crustal viscosity is higher and in the range 4.32 × 1018 to 5.10 × 1021 Pa s with significant small-scale (<100 km) lateral variations. The MT-derived viscosities are consistent with previous regional-scale estimates but reveal the viscosity structure in more detail. The preferred geodynamic model can explain both the crustal deformation velocity and the small-scale lateral variations of surface topography. It implies that the crustal deformation is driven by mantle flow that results in a weak coupling of the upper and middle-lower crust beneath the eastern Tibetan Plateau. The inferred viscosity structure may help further understand the earthquake mechanisms in the Longmenshan fault zone.

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Seismic Structure of Local Crustal Earthquakes beneath the Zipingpu Reservoir of Longmenshan Fault Zone

International Journal of Geophysics ◽

10.1155/2011/407673 ◽

2011 ◽

Vol 2011 ◽

pp. 1-6 ◽

Cited By ~ 1

Author(s):

Haiou Li ◽

Xiwei Xu ◽

Wentao Ma ◽

Ronghua Xie ◽

Jingli Yuan ◽

...

Keyword(s):

Fault Zone ◽

Three Dimensional ◽

P Wave ◽

The Tibetan Plateau ◽

Seismic Structure ◽

Infiltration Depth ◽

Low Velocity ◽

Longmenshan Fault Zone ◽

Velocity Models ◽

Longmenshan Fault

Three-dimensional P wave velocity models under the Zipingpu reservoir in Longmenshan fault zone are obtained with a resolution of 2 km in the horizontal direction and 1 km in depth. We used a total of 8589 P wave arrival times from 1014 local earthquakes recorded by both the Zipingpu reservoir network and temporary stations deployed in the area. The 3-D velocity images at shallow depth show the low-velocity regions have strong correlation with the surface trace of the Zipingpu reservoir. According to the extension of those low-velocity regions, the infiltration depth directly from the Zipingpu reservoir itself is limited to 3.5 km depth, while the infiltration depth downwards along the Beichuan-Yingxiu fault in the study area is about 5.5 km depth. Results show the low-velocity region in the east part of the study area is related to the Proterozoic sedimentary rocks. The Guanxian-Anxian fault is well delineated by obvious velocity contrast and may mark the border between the Tibetan Plateau in the west and the Sichuan basin in the east.

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Evaluation of crustal inhomogeneity parameters in the southern Longmenshan fault zone and adjacent regions

Journal of Seismology ◽

10.1007/s10950-020-09949-w ◽

2020 ◽

Vol 24 (6) ◽

pp. 1175-1188

Author(s):

Xiao-Ping Fan ◽

Yi-Cheng He ◽

Cong-Jie Yang ◽

Jun-Fei Wang

Keyword(s):

Fault Zone ◽

Lower Crust ◽

Tectonic Deformation ◽

Upper Crust ◽

Crust And Upper Mantle ◽

Study Region ◽

Waveform Data ◽

Longmenshan Fault Zone ◽

Deformation Features ◽

Longmenshan Fault

AbstractBroadband teleseismic waveform data from 13 earthquakes recorded by 70 digital seismic stations were selected to evaluate the inhomogeneity parameters of the crustal medium in the southern Longmenshan fault zone and its adjacent regions using the teleseismic fluctuation wavefield method. Results show that a strong inhomogeneity exists beneath the study region, which can be divided into three blocks according to its structure and tectonic deformation features. These are known as the Sichuan-Qinghai Block, the Sichuan-Yunnan Block, and the Mid-Sichuan Block. The velocity fluctuation ratios of the three blocks are approximately 5.1%, 3.6%, and 5.1% in the upper crust and 5.1%, 3.8%, and 4.9% in the lower crust. The inhomogeneity correlation lengths of the three blocks are about 10.1 km, 14.0 km, and 10.7 km in the upper crust and 11.8 km, 17.0 km, and 11.8 km in the lower crust. The differences in the crustal medium inhomogeneity beneath the Sichuan-Yunnan Block, the Sichuan-Qinghai Block, and the Mid-Sichuan Block may be related to intensive tectonic movement and material flow in the crust and upper mantle.

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Distinct tectonic activities in Guangxi, China due to large earthquakes on the Longmenshan fault zone

Physics of The Earth and Planetary Interiors ◽

10.1016/j.pepi.2020.106557 ◽

2020 ◽

Vol 307 ◽

pp. 106557

Author(s):

Huaizhong Yu ◽

Jing Zhao ◽

Xiaoxia Liu ◽

Chen Yu ◽

Chong Yue ◽

...

Keyword(s):

Fault Zone ◽

Longmenshan Fault Zone ◽

Longmenshan Fault ◽

Large Earthquakes ◽

Tectonic Activities

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Seismic Potential Around the Northeastern Edge of the Longmenshan Fault Zone as Inferred from Seismological Observations

Pure and Applied Geophysics ◽

10.1007/s00024-019-02098-3 ◽

2019 ◽

Vol 177 (1) ◽

pp. 37-53 ◽

Cited By ~ 1

Author(s):

Reiken Matsushita ◽

Kazutoshi Imanishi ◽

Makiko Ohtani ◽

Yasuto Kuwahara ◽

Jiuhui Chen ◽

...

Keyword(s):

Fault Zone ◽

Longmenshan Fault Zone ◽

Seismic Potential ◽

Longmenshan Fault

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Research on Transverse Faults in the Longmenshan Fault Zone, China

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1010-1012.1380 ◽

2014 ◽

Vol 1010-1012 ◽

pp. 1380-1386

Author(s):

Wei Feng Wang ◽

Chuan Hua Zhu ◽

Yan Bin Qing ◽

Xin Jian Shan

Keyword(s):

Remote Sensing ◽

Fault Zone ◽

Field Studies ◽

Geophysical Data ◽

Remote Sensing Images ◽

Longmenshan Fault Zone ◽

Geomorphic Features ◽

Longmenshan Fault ◽

Regional Tectonic

The Longmenshan fault zone has been a research hotspot, but fewer scholars have paid attention to its transverse faults. According to the analysis of regional tectonic, seismic activities, geomorphic features, remote sensing images, and deep geophysical data, combined with field studies, the existence, distribution and type of the transverse faults in the Longmenshan fault zone were demonstrated. Research shows that there are 9 transverse faults that lie parallel to each other approximately at ~50km intervals in the Longmenshan fault zone. And transverse faults can be divided into regional transverse faults and localized transverse faults with NW strike, nearly EW strike and nearly SN strike.

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