Explain how induced seismicity from geothermal operations is monitored, and what corrective actions are typically taken when exceeding regulatory thresholds?

Induced seismicity from geothermal operations, which refers to earthquakes triggered by human activities such as fluid injection or extraction, is monitored using a network of seismometers strategically placed around the geothermal field. These seismometers detect ground motion and record the time, location, and magnitude of earthquakes. The monitoring network typically includes both surface seismometers and borehole seismometers, with borehole seismometers providing more accurate measurements due to reduced noise levels. The data from the seismometers is continuously transmitted to a central processing center, where it is analyzed by specialized software to identify and characterize seismic events. The analysis includes determining the location, depth, and magnitude of each earthquake. The data is also used to create a catalog of seismic events, which is regularly reviewed to identify trends and patterns. Regulatory thresholds for induced seismicity are typically defined in terms of magnitude, frequency, and proximity to populated areas. When these thresholds are exceeded, corrective actions are taken to reduce the risk of larger earthquakes. The most common corrective action is to reduce or stop fluid injection. This reduces the pore pressure in the reservoir, which decreases the likelihood of triggering earthquakes. Other corrective actions can include adjusting injection rates, changing injection locations, or modifying the injection fluid composition. Real-time monitoring systems are used to continuously track seismic activity and provide early warning of potential problems. Traffic light systems are often used to communicate the level of risk, with green indicating normal operations, yellow indicating increased monitoring and caution, and red indicating the need for immediate action. In some cases, geothermal operations may be suspended altogether if the risk of induced seismicity is deemed too high. Communication with the public and stakeholders is also an important part of managing induced seismicity. This includes providing regular updates on seismic activity and explaining the measures being taken to mitigate the risks.