Fig. 3

Histogram of natural time counts is shown along with a demonstration of EPS computation. The dark-green bars are the histograms of the number of small earthquakes (4.5 ≤ M < 6.5) between the large earthquakes (M ≥ 6.5). The purple step-function is the empirical distribution function derived from the histogram values. The dashed blue curve is the best-fit exponential distribution for the present natural time data. Just for demonstration, we show the black solid circle that corresponds to the number of small earthquakes as on November 21, 2020 since the last large earthquake in Palu region. The thermometer-like red bar represents the Earthquake Potential Score (EPS) showing the progression of the earthquake cycle in Palu as on November 21, 2020. However, as the seismicity in Sulawesi exhibits stationary Poisson process, the current level of seismic hazard (risk) is the same for the entire region