Reservoir-induced seismicity in connection with large hydropower dams has been well known for at least 60 years, and induced seismicity in connection with ore mining has a history of at least 100 years.
The problems relating to induced seismicity have been known from oil and gas fields since the 1920s, and was 30 years later thoroughly studied at an oil field near Wilmington, California, where the oil production triggered a series of damaging earthquakes. In the last decade a number of examples on earthquake activity related to oil and gas production as well as injection of liquids under high pressure have been observed, although not with as serious consequences as for Wilmington. As of today there is a rapidly increasing number of publications relating to oil and gas field seismicity and to injection induced seismicity.
Induced seismic activity can be divided in two categories:
This group of earthquakes are caused by tectonic stresses. They would probably have occurred sooner or later, but their time-space proximity to human activity indicate antropogenic activity.
This group of earthquakes are purely antropogenic in that stress buildup can be traced directly to human activity. For convenience we use the term induced for both types.
Microseismicity in an exploited reservoir
Induced seismicity can involve large and damaging earthquakes as in Uzbekistan or in California, however, more frequently we observe micro seismicity or `cracking' in an exploited reservoir as shown for an oil field in the figure. The observed micro seismicity reflects the dynamic response both of surrounding rocks and the reservoir itself to exploitation and may as such provide useful information.
NORSAR provides services and research related to induced seismicity.
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