Reservoir-induced earthquakes and engineering policy

Abstract

In numerous parts of the world today, including some of the most highly developed countries, many dam designers and operators have tended to close their eyes to the engineering problems posed by reservoir-induced earthquakes. One sometimes hears these kinds of defensive argument: 1) no convincing correlation has yet been demonstrated between earthquakes and reservoirs; 2) since the natural seismicity at a given site is low, the danger of reservoir-inducement is therefore also low; 3) the geology at a given site is different from that at localities where major reservoir-induced events have occurred; 4) only 3 or 4 out of some 11 000 large dams worldwide have experienced significant induced earthquakes, and one should therefore not worry about a given site; and 5) no dam has yet failed disastrously because of a reservoir-induced earthquake, and the danger is thus grossly exaggerated. While many of these arguments have some elements of truth to them, they are essentially evading the primary issues: Virtually every careful study has concluded that there is indeed a cause-and-effect relationship between some earthquakes and some reservoirs, and two dams (Koyna, India, and Hsinfengkiang, China) have in fact come uncomfortably close to disastrous failure during such events. Furthermore, it is precisely in the regions of low natural seismicity where the major existing problems lie, because in areas of high seismicity dams are usually designed for substantial earthquake resistance anyway.