Introduction
摘要
Several anthropogenic activities, under favourable geological conditions, can trigger or induce earthquakes. These include filling of artificial water reservoirs, mining, geothermal energy production, natural gas and oil production, injection of fluids for enhancing oil/gas recovery, etc. Among these anthropogenic activities, artificial water reservoirs triggered seismicity (RTS) is found to be the most prominent. The deadly M 6.3 artificial water reservoir triggered earthquake occurred in Koyna, India on 10 December 1967, claiming over 200 human lives and causing widespread damage in the Koyna Township. There are at least 4 other sites where RTS events exceeding magnitude 6 have occurred. The magnitude 7 earthquakes that occurred on 17 May 1976 and 19 March 1984 are debated to be associated with the production of oil in Gazli Oil Field. Similarly, it is debated whether the magnitude 7.9 Sichuan, China earthquake on 12 May 2008 was triggered due to the impoundment of the nearby Zipingpu reservoir. For the fear of triggering/inducing earthquakes, several anthropogenic activities had to be curtailed or stopped such as the terminating construction of Auburn Dam in California, USA way back in 1970s. On 15 November 2017 the magnitude 5.5 Pohang earthquake in South Korea, which injured dozens and forced some 17,000 citizens to move to emergency housing, was found to be associated with a geothermal energy production project. One of the latest examples is the fluid injection triggered magnitude 5.5 earthquakes in Oklahoma, USA, which resulted in curtailing/stopping of fluid injection for enhanced oil recovery. The 2 February 2024 magnitude 5.1 earthquake in Oklahoma, USA is also associated with disposal wells.