Geothermal brines in the Salton Sea Geothermal Field (SSGF), Southern California, offer abundant geothermal energy and significant amounts of dissolved lithium, both of which can be harvested to support the ongoing clean-energy transition. Harvesting these resources, however, could induce earthquakes in the seismically active Brawley Seismic Zone. To support responsible development of SSGF resources, we retrospectively correlate 50 years of seismic history in the SSGF (1972-2022) with 40 years of contemporaneous geothermal power plant operations (1982-2022). We conclude that the background seismicity rate in the SSGF is directly proportional to production and injection rates at geothermal wells during the period 1982-1996, and that this proportionality relationship weakens between 1996 and 2005, and nearly vanishes after 2005. After 2005, the background seismicity rate remains elevated above the pre-production rate; however, production and injection rates offer marginally more predictive power than assuming a simple constant background seismicity rate. These observations motivate development of more sophisticated models for understanding the relationship between geothermal power plant activity and seismicity in the region. We hypothesize that the Brawley Fault may act as a hydraulic barrier inhibiting fluid migration between the eastern and western portions of the field, thus imposing first-order constraint on the field's overall geomechanical response to plant activity. We suggest that refined modeling efforts take this structural constraint into consideration.