Foreshocks are known as smaller earthquakes preceding the large mainshock (Jones & Molnar, 1979). Due to the neighboring location and temporal correlation, foreshocks are considered as a possible precursory phenomenon, for example, the success prediction of 1975 M w 7.0 Haicheng earthquake largely relies on the ∼1-day foreshock activity (Wang et al., 2006). Traditionally, two end-member models are proposed to explain the triggering relationship between the foreshocks and mainshock (Dodge et al., 1996): the cascade model and the pre-slip model. The cascade model describes the seismic sequence as the cascade failure of isolated asperities, where each event is triggered by the stress transfer from the previous earthquake (Ellsworth & Bulut, 2018;Felzer et al., 2004;