Earthquakes have long been regarded as one of the major triggers of ice avalanches (IAs). However, their role in IA initiation remains controversial. Here, we compiled 169 IA events that occurred between 1941 and 2022 together with their associated earthquake records, and found that only 9 IAs occurred on the same day as the earthquake. This indicates a pronounced delayed response of IAs to seismic forcing. Taking the Hailuogou, Yanzigou, and Dagongba glaciers on Mt Gongga as examples, and using the 5 September 2022 Luding earthquake as the dividing point, we analysed glacier surface velocities during September-December 2021 and September-December 2022. The results show that glacier motion reached its maximum 1 month after the earthquake. By comparing meteorological data from the pre- and post-earthquake periods, we excluded climate variability as the primary cause of the observed glacier acceleration, thereby confirming the statistical pattern of delayed earthquake-induced IAs. We further propose a new contact model showing that seismic loading can transiently enhance the strength of ice. This strengthening effect is interpreted as the fundamental reason for the delayed occurrence of IAs after earthquakes. This study provides a new theoretical framework and fresh insights into the failure mechanism and hazard mitigation of earthquake-induced IAs.