Figure 2

(a): Seismicity in the study area (blue rectangle in Fig. S1) since 1981, from the Southern California Seismic Network catalog. The black dots and red stars indicate earthquake magnitudes \(< 3\) and \(>=3\), respectively. Black lines and gray surfaces are faults from the SCEC CFM 6.1 model. (b): Expanded view of the seismicity across the Fontana fault (orange rectangle in panel a) within the upper 10 km of the crust. The magenta rectangle shows the area of the 2019 Fontana earthquake sequence, shown in more detail in Fig. 6.