Fig. 3: Temporal evolution of cumulative seismic activity and b-values at different distances from M_W 7.8 epicentre.

a Cumulative seismic activity per km² was calculated for different epicentral distances from the M_W 7.8 mainshock (excluding quarry blast clusters Q5, Q6 and Q8). Dashed and solid lines represent the entire and complete catalogues (M_C > 1.5) in each zone, respectively. The seismicity rates accelerated within the last 8 months before the mainshock within 50 km radius mostly due to clusters C1 and C2 (Supplementary Fig. 1). b The b-value (with error bars showing 95% c.i.) displays a transient significant decrease within a 50 km radius around the epicentre and a 8-month period before the mainshock that is primarily attributed to C1 and C2, and a subsequent recovery is visible. This transient decrease is overlain with a long-term decrease in the b-values in the broader region 50 < R < 90 km. Transient drops in b-value observed in 2017 and 2019 for 50 < R < 130 km are attributed to scattered seismic activity in the Osmaniye region (see Fig. 1 for location) that do not display comparable clustering.