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Lessons Learned From Monitoring of Reservoir Triggered Seismicity in Tectonically Stable and Seismically Active Areas of Vietnam

Description: 

Water reservoirs play important role in energy production in Vietnam. Numerous dams were designed and built for hydropower plants and water storage. We conducted seismic monitoring and research on two sites: first, the tectonic active area of Lai Chau (North Vietnam) and the relatively stable area of Song Tranh in Central Vietnam. We observed different seismicity patterns in these areas. The area of Lai Chau was less active in terms of reservoir triggering, while the almost aseismic area of Song Tranh was highly active after reservoir impoundment. The latter activity was related to seasonal water level changes in the reservoir. Moreover, a low water period during service works was proved to be more active and with significantly higher seismic hazard than during the production regime. It suggests that a decrease in water level and following pore-pressure change destabilize minor faults being closer to failure than main faults in the area. It is confirmed by finding multiplets triggered on minor normal faults. Seismic activity in the area of Lai Chau was observed on both existing active strike-slip faults and minor normal faults. However, the difference between seismic activity parameters before and after impoundment except for spatial distribution directly after the first filling didn’t differ substantially. Moreover, the influence of the reservoir filling was very limited in short distances from the reservoir in terms of Coulomb stress changes due to water level variations. We can conclude, that in a stable tectonic setting triggering effect is clear and related to pore-pressure changes caused by reservoir water level fluctuations. On the other hand in active seismic area reservoir influence seems to be too small to significantly change seismic activity in the long term.

This work was supported by the research project no. 2021/41/B/ST10/02618, funded by the National Science Centre, Poland under the agreement no. UMO-2021/41/B/ST10/02618.

Session: Understanding and Managing Induced Seismicity

Type: Oral

Date: 4/19/2023

Presentation Time: 11:30 AM (local time)

Presenting Author: Grzegorz Lizurek

Student Presenter: No

Invited Presentation: 

Authors