A review of recent studies of triggered earthquakes by artificial water reservoirs with special emphasis on earthquakes in Koyna, India [Review]

摘要

Triggering of earthquakes by filling of artificial water reservoirs is known for over six decades. As of today, over 90 sites have been globally identified where earthquakes have been triggered by filling of water reservoirs. The question of earthquakes triggered by artificial reservoirs has been addressed and reviewed in a number of papers and books. In the present review, the book "Reservoir-Induced Earthquakes" by Gupta [Gupta, H.K., 1992. Reservoir-Induced Earthquakes. Elsevier, Amsterdam, 364 pp.], which contains all the necessary information on this topic till 1990, has been taken as the base. An effort has been made to add information on this important topic gathered over the last 10 years. Koyna, India continues to be the most significant site of artificial-water-reservoir-triggered earthquakes. During 1990s, two events exceeding M 5 and several smaller. events occurred in the vicinity of Koyna, and recently impounded Warna Reservoir. Detailed studies have addressed the relocation of earthquakes, stress drop, nucleation, migration and other important aspects of these earthquakes. In a unique experiment, twenty-one 90- to 250-m deep borewells have been drilled in the seismically active Koyna-Warna region and the water levels are continuously monitored. Step-like coseismic changes of several centimeters have been observed in some wells associated with a few M greater than or equal to 4 events. Detailed tomographic studies conducted on one of the best recorded triggered earthquake sequence at Lake Oroville in California revealed that this sequence was associated with a southwest dipping structure characterized by low velocity, while in adjacent areas, seismic activity occurs in regions of higher velocity. Similar investigations in Aswan showed that shallow activity is associated with low P-wave velocity. Several new reservoir sites that have triggered earthquakes have been reported during 1990s. The most important being Srinagarind Dam in Thailand, which had an M 5.9 earthquake and the sequence had all the characteristics of triggered earthquake sequences. New theoretical work, particularly the effect of pore fluid pressure in anisotropic rocks and its implication in triggered seismicity is an important development. However, much more needs to be done to fully comprehend the role of artificial water reservoirs in triggering earthquakes. (C) 2002 Elsevier Science B.V. All rights reserved. [References: 148]