20 April 2005

Induced Earthquakes

I'm reading about earthquakes this week and came across a reference to earthquakes that have been caused by dams. The most obvious examples of this are from the Hoover Dam, the Aswan High Dam, the Kariba Dam on the Zambia/Zimbabwe border, and the Koyna Dam in India. Earthquakes have also occurred at the Hsin-feng-chiang Dam in China, the Kremasta Dam in Greece, and the Nurek Dam in Tajikistan and in a variety of other places.

However, most reservoirs do not cause earthquakes. It is theorized that earthquakes will only be caused where there was already stress and faults that are set off by the increased pressure from the reservoir. Usually the earthquakes occur as the reservoirs are filling or if water levels are lowered significantly; they are often small. However, some can be fairly large.

The area around the Hoover Dam has been experiencing increased small earthquakes as a result of lower water levels in Lake Mead. The Koyna Dam has caused some large earthquakes (a magnitude 6.4 earthquake in 1967 killed 200 people) and recently experienced another.

Of course, many are not convinced that reservoirs can cause earthquakes. (search for 3.9.1. Reservoir induced seismicity (RIS))

1 comment:

Anonymous said...

This has been the explanation so far that dams -some of them- cause quakes locally. Now new research has unveiled that Indian dams are causing waves of earthquakes in tune with the South West monsoon and the dry season of water withdrawal. See my URL:
http://monsoonquakes.rediffblogs.com
They decide the when,where,how, what depth and what magnitudes the quakes shall have. For example, the coming monsoons including the ongoing one in India will see a series of strong to big earthquakes including those above 8.0 MM inresponse to the dry season great quake of 9.4 MM in the Andaman Basin on December 26 2004 which caused the tsunami which devastated many parts of Asia and some even in Africa.