%0 Journal Article
%@ 0040-1951
%A Lizurek, Grzegorz
%A Leptokaropoulos, Konstantinos
%A Wiszniowski, Jan
%A Van. Giang, Nguyen
%A Nowaczyńska, Izabela
%A Plesiewicz, Beata
%A Van, Dinh Quoc
%A Tymińska, Anna
%A Institute of Geophysics, Polish Academy of Sciences (IG PAS), Poland,
%A Ocean and Earth Science, University of Southampton, UK,
%A Institute of Geophysics, Polish Academy of Sciences (IG PAS), Poland,
%A Institute of Geophysics, Vietnamese Academy of Science and Technology (IGP VAST),,Viet Nam,
%A Institute of Geophysics, Polish Academy of Sciences (IG PAS), Poland,
%A Institute of Geophysics, Polish Academy of Sciences (IG PAS), Poland,
%A Institute of Geophysics, Vietnamese Academy of Science and Technology (IGP VAST),,Viet Nam,
%A Institute of Geophysics, Polish Academy of Sciences (IG PAS), Poland,
%D 2021
%F epos:2321
%I Elsevier
%J Tectonophysics
%K Reservoir-triggered seismicityFocal mechanismStress inversionAnthropogenic seismicityProbabilistic seismic hazard
%P 229121
%T Seasonal trends and relation to water level of reservoir-triggered seismicity in Song Tranh 2 reservoir, Vietnam
%U https://episodesplatform.eu/eprints/2321/
%V 820
%X Reservoir-triggered seismicity (RTS) has the potential to generate disastrous seismic events of M6 and bigger. Song Tranh 2 (STR2) is an artificial water reservoir located in Central Vietnam. High seismic activity has been observed in this area since the reservoir was first filled in 2011. The relation between water level and seismic activity in the Song Tranh area is complex, and previous studies have led to the conclusion that ongoing STR2 seismic activity is an example of the delayed response type of RTS. However, the first phase of the activity observed after impoundment has been deemed a rapid response type. There were three stages of the reservoir filling periods: first, a period of initial impoundment, hereinafter referred to as pre-gap period (from 05/01/2011 to 10/06/2012), then a gap period (from 10/06/2012 to 31/08/2013) where reservoir impoundment stopped and water was drained to minimum exploitation level, and finally, a third post-gap period (from 31/08/2013 to 19/06/2017). In this work, we prove that the gap in the filling of reservoir results to a 2-fold rise of seismicity rate. The re-filling of the reservoir results to a drop of activity rate, roughly equal to the pre-gap period, accompanied by a significant increase of b-value. As a consequence, after the gap, the exceedance probability is significantly lower in comparison to pre-gap and gap periods. We also proved that the seismicity recorded between 2013 and 2016 manifested seasonal trends related to water level changes during wet and dry seasons. The response of activity and its delay with respect to water level changes suggest that the main triggering factor is pore pressure change due to the significant water level changes observed. The findings indicate that water load and related pore pressure changes considerably influence seismic activity and stress orientation in this area.