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| Titel |
The influence of the impoundment of Three Gorges Reservoir on the M5.1 Badong earthquake |
| VerfasserIn |
Huihong Cheng, Huai Zhang, Yaolin Shi |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250090410
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| Publikation (Nr.) |
 EGU/EGU2014-4645.pdf |
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| Zusammenfassung |
| The Three Gorges Reservoir constructed on Yangzi River is the world’s largest power station
on installed capacity (39.3x109m3), it extends 660km from the western part of Hubei
province and eastern part of Chongqing municipality. It is a major concern if it can trigger
reservoir earthquakes. After the impoundment of the Three Gorges Reservoir since 7 June
2003, there were many micro-earthquakes in the head segment of the reservoir area including
Badong area. The prior researches had suggested the micro-seismic activity will be weak as
time goes on, even disappear, and the maximum magnitude of earthquake triggered by the
reservoir should not be more than M5.5. However, ten year later, a moderate M5.1
earthquake happened around BaDong Country on 16 December 2013, after the annual
highest water level. The epicenter was about 5.5km away from the Yangzi River
and nearly 100km from the Three Gorges Reservoir dam. The focal depth of this
earthquake was about 5km and the focal mechanism solutions show the NNW-striking
thrust seismogenic fault (www.ceic.ac.cn). So, if this earthquake was related to the
impoundment of the Three Gorges Reservoir? Wouldthispose an important impact on the
earthquake triggered by the Three Gorges Reservoir? In order to quantitatively
analyze these considerations, a three-dimensional fully coupled poroelastic finite
element model is proposed in this study by taking the consideration of the realistic
observation data, such as the high resolution topography, water level fluctuation, flood
zone boundary and water depth variation, fault parameters and etc. The change
of Coulomb Failure Stress (ΔCFS) in correspondence to elastic stress and pore
pressure change induced by fluid diffusion is calculated. Meanwhile, the elastic strain
energy accumulation in reservoir region due to the water-filling load is obtained. Our
primary results indicate that both pore pressure and coulomb stress on the hypocenter
gradually increases with the respect of time while the water level variations. The
magnitude of pore pressure can reach 16kPa when the diffusion coefficient was
selected as 0.2m2/s, which was according to the distribution of small foreshocks. The
maximum surface deformation beneath the of Three Gorges Reservoir is up to 3.6cm
when the water level 135m and the surface deformation near the Badong area is
1.35cm, which well accordance with the GPS measurement. Although the total
elastic strain energy accumulation caused by the impound water load is around
7.3x1011J, the energy density is still insignificant compared to the vast reservoir
inundation area, as it is only less than 3.5 percent of the total seismic wave energy
released by the M5.1 earthquake, which confirms that the tectonic stresses is the major
source for the earthquake and weak fault zone and impoundment of the reservoir
triggered earthquakes. We expect that the pore pressure diffusion in the future may
increase deeper fault instability, therefore reservoir earthquake may still occur instead
of disappear, although the maximam magnitude of triggered earthquakes by the
Three Gorges Reservoir may not exceed M5.5 as suggested by previous researchers. |
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