The Utah FORGE seismic monitoring plan provides infrastructure for two purposes: first， to continuously monitor seismicity as a part of mitigation strategies for potential seismic hazards associated with fluid injection and migration over the larger FORGE footprint， and second， to monitor during stimulation or injection operations as a diagnostic for mapping and characterizing the fracture systems created and activated for reservoir development。 The former need involves an array of surface and shallow borehole receivers。 The latter need is achieved with deep-borehole， multi-level， high-temperature receiver systems。 Both monitoring systems will provide continuous coverage through all field activities， including before， during， and after all injection operations and flow testing。 For monitoring of potential seismic hazards， the goal is to achieve a magnitude-of-completeness of M 0 with detection capabilities down to M -1。5。 The previous surface network at FORGE was capable of detecting and locating events down to M -1 in the Mineral Mountains 10 km east of FORGE。 Improvement was made by reconfiguring the station placement and supplementing the network with combined broadband accelerometer stations placed in 100 to 150 ft boreholes。 The improved coverage and sensitivity allow: (1) tracking changes in earthquake statistics; (2) tracking event migration within and outside the FORGE footprint; and (3) the analysis of source properties for the larger events。 Placement of the deep monitor wells was guided by modeling efforts to optimize source location accuracy for the initial stimulation plans。 High-temperature， 3-component， borehole receiver strings will be deployed in three wells at or near reservoir depths。 The deep-well receiver strings for monitoring during stimulations will be supplemented with downhole DAS， a new 3-component fiber-optic borehole array， and a high-density array of surface receivers。
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