Common features of the reservoir-associated seismic activities

Abstract

A detailed examination of the behavior of earthquakes associated with over a dozen artificial lakes shows that, in all cases, the tremors were initiated or their frequency increased considerably following the lake filling and that their epicenters were mostly located within a distance of 25 km from the lakes. Among the factors affecting the tremor frequency are the rate of increase of water level, duration of loading, maximum levels reached, and the period for which the high levels are retained. The study of these reservoir-associated earthquake sequences reveals that the ratio of the largest aftershock to the main shock is high (about 0.9), and the b values are also high in the frequency-magnitude relation, which is contrary to the normal earthquakes of the concerned regions.

Variations in seismic parameters for the earthquakes during loading and unloading periods in the Three Gorges Reservoir area

“…Spatially, the seismicity in the Three Gorges reservoir area is consistent with the common features of reservoir-induced earthquakes 5 . Generally, the reservoir induced earthquakes are basically limited within 10 km of each bank of the reservoir, which is determined by the impact range of the water loading on the reservoir area and the limited seepage range of the reservoir area 5 , 9 . This limited range corresponds to the main area of adjustment of the tectonic stress field 5 .…”

“…In 2003, many micro-small earthquakes instantly occurred due to water impoundment. The b -value during the period exceeded 1.0, which is a typical feature of reservoir induced earthquakes 5 . Later, b -values varied with water level changes.…”

“…Generally, the reservoir induced earthquakes are basically limited within 10 km of each bank of the reservoir, which is determined by the impact range of the water loading on the reservoir area and the limited seepage range of the reservoir area 5 , 9 . This limited range corresponds to the main area of adjustment of the tectonic stress field 5 . In addition, reservoir-induced earthquakes often occur near the intersections of faults, karst cave development areas, and contact zones with different lithologies.…”

“…Especially in recent years, induced earthquakes have been mostly associated with the development of new energy sources such as shale gas, the exploration of geothermal energy, the construction of gas storage facilities, and mining 2 , 3 . Reservoir-induced earthquakes as a kind of induced earthquakes have attracted widespread concern in the early stage 4 , 5 . The construction of large-scale water conservancy and hydropower projects and periodic water impoundment affect the stability of the regional crust and sometimes trigger seismic activity.…”

“…The earliest recorded reservoir-induced earthquake was the Lake Mead earthquake in 1945 4 . In the 1960s, four reservoir-induced earthquakes of M ≥ 6.0 were reported 5 , 6 . Over 140 reservoir-induced earthquakes have been reported worldwide since the 1960s, none of which were above 6 in magnitude.…”