Abstract: According to the theory of seismic stress triggering, triggering relationship exists between adjacent large earthquakes. In 2020, two earthquakes with M_W>7.5 occurred in the subduction zone of Alaska an M_W7.8 earthquake on July 22 and an M_W7.6 earthquake on October 19, which provides an opportunity for us to study the triggering effect of double-shock earthquakes. Using the near-field GPS coseismic displacement and far-field seismic waveform data, and with different fault parameters, four slip rupture models of M_W7.8 earthquake are obtained by inversion; combined with the initial rupture model, the Coulomb stress changes caused by the earthquake at the epicenter of the later M_W7.6 earthquake are estimated. The results show that the stress changes calculated by four of the five models far exceed the triggering threshold 0.01 MPa, indicating that the former earthquake has an obvious triggering effect on the latter one. Based on the variation of locking ratio on both sides of the seismogenic fault of the M_W7.6 earthquake and the plate subduction rate in the region, it is estimated that the former earthquake caused the latter earthquake to occur 32 years earlier.

Key words: Alaska earthquake, Earthquake triggering, Coulomb stress, Locking ratio