Three-Dimensional V P and V P /V S Structure in the Longtan Reservoir Area by Local Earthquake Tomography

Zhou, Lianqing; Zhao, Chen; Chen, Zhangli; Zheng, Sheng

doi:10.1007/s00024-011-0300-8

Cited by 10 publications

(7 citation statements)

References 21 publications

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“…Many scholars have continued to study the tectonic activities and seismicity beneath this reservoir in relation to the earthquake. Reviews of the more recent studies were proposed by Ma and Zhou et al (Ma et al, 2012;Zhou et al, 2012).…”

Section: Discussionmentioning

confidence: 95%

Influence of the impoundment of the Three Gorges Reservoir on the micro-seismicity and the 2013 M5.1 Badong earthquake (Yangtze, China)

Zhang

Cheng

Pang

et al. 2016

Physics of the Earth and Planetary Interiors

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On December 16, 2013, right after the Three Gorges Reservoir (TGR) reached its highest annual water level, a powerful M5.1 earthquake occurred in Badong County, China's Hubei Province. The epicenter is 5.5km away from the upstream boundary and 100km from the dam. Was this earthquake triggered by the impoundment of the TGR, and what are itssubsequences? To answer these questions, we constructed a coupled three-dimensional poroelastic finite element model to examine the ground surface deformation, the Coulomb Failure Stress change (∆CFS) due to the variation of elastic stress and pore pressure, and the elastic strain energy potential accumulation in the TGR region upon the occurrence of this event.Our calculated maximum surface deformation values beneath the TGR compare well with GPS observations, which validates our numerical model. At the hypocenter of the earthquake, ∆CFS is around 8.0~11.0kPa, revealing that it may be eventually triggered by the impoundment. We also discovered that the total elastic strain energy potential accumulation due to the impounded water load is around 1.7×10¹²J, merely equivalent to 0.01% of the total energy released by this event, indicating that the this earthquake is predominately controlled by the typical regional 2 tectonic settings as well as the weak fault zones, and the reservoir impoundment might only facilitate its procedure or occurrence. Furthermore, the stress level in this region remains high after this earthquake and the subsequent reservoir-triggered micro-seismicity or even bigger event are highly possible.

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Section: Discussionmentioning

confidence: 95%

Influence of the impoundment of the Three Gorges Reservoir on the micro-seismicity and the 2013 M5.1 Badong earthquake (Yangtze, China)

Zhang

Cheng

Pang

et al. 2016

Physics of the Earth and Planetary Interiors

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“…Most of these earthquake clusters are in the low‐ Q P , low‐ Q S and low‐ Q S / Q P regions and the regions less than 7 km in depth (Figs 13–17), suggesting that water infiltration may be an important factor in inducing the earthquakes. The 3‐D V P and V P / V S tomographic images in Longtan reservoir area had been obtained by Zhou et al (2011), the result show that both low V P and high V P / V S features are discovered in shallow layers less than 7 km deep beneath the main rivers. Besides, low V P and high V P / V S anomalies are discovered in the regions, such as the dam area and the area around the Youla river, where low Q P and Q S anomalies are detected.…”

Section: Discussionmentioning

confidence: 99%

“…We used the 3-D velocity structure model in the Longtan reservoir area previously obtained by Zhou et al (2011) as the initial input velocity model and applied a uniform Q P value as the initial model for the Q P inversion. By calculating the traveltime residuals of different input Q P models at the interval of 50 in the range from 100 to 700, we selected the value of 350 corresponding to the minimum traveltime residual as the input Q P model.…”

Section: Model and Parametersmentioning

confidence: 99%

“…Its storage and hydropower capacity rank second only to the world‐famous Three Gorges hydropower project in China (Chen 1989). So far, there are few studies on the 3‐D medium structure in the Longtan reservoir area except a study on the 3‐D V P and V P / V S structure (Zhou et al 2011). The 3‐D V P and V P / V S images show that low‐ V P and high‐ V P / V S anomalies exist around the main rivers of the Longtan reservoir area, which indicate that there may exist water infiltration above the depth of about 7 km in the reservoir area.…”

Section: Introductionmentioning

confidence: 99%

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Inferring water infiltration in the Longtan reservoir area by three-dimensional attenuation tomography

Zhou¹,

Zhao²,

Zheng³

et al. 2011

Geophysical Journal International

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S U M M A R YHigh-resolution 3-D Q P and Q S models at depths of 0∼14 km in the Longtan reservoir area, which were used to further infer the water infiltration around the reservoir, were constructed by the local earthquake tomography technique. The inversion used t * values measured from velocity spectral amplitudes of 16 134 P-wave and 17 027 S-wave observations of 2828 events recorded by 23 digital seismic stations in the Longtan reservoir area. 3-D Q P and Q S tomographic images suggest a close relation between the attenuation models and water infiltration. Low Q P and Q S exist down to 4∼7 km depths beneath the main rivers in the reservoir area, whereas high Q P and Q S are found both at deep layers and at shallow layers in regions other than the main river area. We inferred that the rocks beneath the main rivers are infiltrated by substantial water and water infiltration reaches 4∼7 km deep, and the ranges of water infiltration vary by region. Specifically, the zone of high water content is estimated to extend up to 10 km away from the Buliu river in the reservoir dam area where water depth in the reservoir reaches maximum, and the extent of water infiltration in rocks can only be about 5 km around from the Hongshui river and the Youla river. Low Q P and high Q S indicate that the carbonate rocks in the east of the Bala fault area may be saturated with water. Earthquake clusters are mainly concentrated on the low-Q P and low-Q S zones, indicating that water infiltration beneath the main rivers possibly plays an important role in inducing earthquakes in the Longtan reservoir area.

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“…For example, soon after water storage in the Xinfengjiang reservoir of Gunagdong Province in 1959, the seismic station began to record small quakes (Ding, 1989). Similarly, seismic activities were increasing after the impoundment of Longtan reservoir of Guangxi Province, with three events of magnitude greater than 4.0 (Zhou et al, 2012). While, some other reservoirs showed opposite characteristics, where seismicity remained quiet a few years or even a dozen years.…”

Section: Introductionmentioning

confidence: 97%

Comprehensive Understanding of the Zipingpu Reservoir to the M_S8.0 Wenchuan Earthquake

Zhang

2015

Chinese J of Geophysics

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Since the 12 May 2008 Wenchuan earthquake, whether this massive event was triggered by the impoundment of the nearby Zipingpu reservoir has attracted wide attention in international academic community. In addition to qualitative discussions, many scholars have made calculations on this issue. However, due to the different results, they draw very different conclusions. In this paper, we take the disputes from different teams in the quantitative calculation of Zipingpu reservoir as the starting point. Based on the basic principle of quantitative calculation of the stress changes after the impoundment of the reservoir, we analyze all kinds of influence factors to find out the key factors during the numerical simulation. The results show that the calculation methods, dimension of models, diffusion model, diffusion coefficient and focal mechanism are the main factors that resulted in the differences, especially the diffusion coefficient of the fractured rock mass. The Coulomb failure stress changes of the epicenter of the Wenchuan earthquake attained from the 2D model is about 3 times of that of the 3D model. And it is not reasonable that only considering the fault permeability or homogeneous isotropic rock mass permeability. The different focal mechanisms also could dramatically affect the Coulomb failure stress changes, of which the differences can research 2∼7 times. And the differences of Coulomb failure stress changes can reach several hundred times when selecting different diffusion coefficients. According to existing research that the magnitude of Coulomb failure stress change is about several kPa, we can not rule out the possibility that the Zipingpu reservoir may trigger the Wenchuan earthquake. However, for the background stress is not clear and Coulomb failure stress change is too small, we are not sure there must be a connection between the reservoir and earthquake. In the future work, we should target on the basis of field surveys and indoor experiments, improve the model and develop high‐performance simulation. Based on these calculation methods, we can compare more typical reservoir‐triggered earthquakes with different mechanisms both in China and elsewhere in the world to explore the mechanism of reservoir‐induced earthquakes.

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Three-Dimensional V P and V P /V S Structure in the Longtan Reservoir Area by Local Earthquake Tomography

Cited by 10 publications

References 21 publications

Influence of the impoundment of the Three Gorges Reservoir on the micro-seismicity and the 2013 M5.1 Badong earthquake (Yangtze, China)

Influence of the impoundment of the Three Gorges Reservoir on the micro-seismicity and the 2013 M5.1 Badong earthquake (Yangtze, China)

Inferring water infiltration in the Longtan reservoir area by three-dimensional attenuation tomography

Comprehensive Understanding of the Zipingpu Reservoir to the M_S8.0 Wenchuan Earthquake

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Three-Dimensional V P and V P /V S Structure in the Longtan Reservoir Area by Local Earthquake Tomography

Cited by 10 publications

References 21 publications

Influence of the impoundment of the Three Gorges Reservoir on the micro-seismicity and the 2013 M5.1 Badong earthquake (Yangtze, China)

Influence of the impoundment of the Three Gorges Reservoir on the micro-seismicity and the 2013 M5.1 Badong earthquake (Yangtze, China)

Inferring water infiltration in the Longtan reservoir area by three-dimensional attenuation tomography

Comprehensive Understanding of the Zipingpu Reservoir to the MS8.0 Wenchuan Earthquake

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Product

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Comprehensive Understanding of the Zipingpu Reservoir to the M_S8.0 Wenchuan Earthquake