Studying the seismicity triggeringresponse of fault systems to periodic stress fluctuations can improve ourunderstanding of earthquake nucleation, rupture failure processes, and localstress states. Geothermal fields are well known to be susceptible totriggering, as the injection and extraction activities change the local stressand fluid flow conditions. Here, we examine the modulation of earthquakes byEarth tides within California's Coso geothermal field (CGF) and its vicinity.To maximize our resolution to detect modulation of small earthquakes, we takeadvantage of the new Quake Template Matching catalog in southern California,which has nearly twice as many events in the Coso region as the standardcatalog and is complete down to about magnitude 0.3. We observe strong tidaltriggering of earthquakes within the CGF, even though the fluctuations of tidalstresses are small (∼2 kPa). The tidally-triggered earthquakestend to occur near the time of maximum tensile tidal stress. The signal isstrongest near the edges of the zone of new production wells, suggestingfluid pressuregradients encourages triggering at tidal periods.