Spatiotemporal characteristics of the energy field and disaster cause of the 2023 Gansu Jishishan <i>M</i> 6.2 earthquake

Anomalies in the seismic energy field and the temporal and spatial evolution characteristics of seismic energy can be used to improve earthquake predictions and rapid seismic hazard assessments. In this study, the seismic energy field was used as a variable with the natural orthogonal function expansion method to analyse the temporal and spatial anomaly evolution characteristics in energy fields and the causes of seismic disasters for the 2019 Xiahe M5.7 and 2023 Jishishan M6.2 earthquakes. The cumulative frequency curves of the earthquakes indicated linear growth, and three anomalous periods deviated from the normal state, coinciding with the anomalous periods of the first four-time factors of the energy field. Strong earthquakes tend to occur near the contours of positive and negative high-value anomalies associated with seismic energy release and accumulation, or around active faults exhibiting hexagonal high-value energy edges. High-energy release regions correspond to areas of severe disaster. Numerical simulations showed that the 2023 Jishishan M6.2 earthquake occurred on the optimal shear stress nodal plane of the tectonic stress field, resulting in severe damage. In contrast, the 2019 Xiahe M5.7 earthquake had relatively low shear stress and insufficient stress release, resulting in reduced damage.