Severity of earthquake disasters triggered by M_S≥5.0 events: retrospective analysis of 288 cases in China (1991–2020)

The determination of earthquake disaster severity levels facilitates the assessment of loss degree and societal impact caused by earthquake disasters. Metrics such as affected population, fatalities, and direct economic losses are commonly used to quantify earthquake disaster severity. This study collects data on affected population, fatalities, and direct economic losses from M_S≥5.0 seismic events in Chinese Mainland between 1991 and 2020. A computational model for earthquake disaster severity is applied to analyze the severity of 288 M_S≥5.0 earthquake events over the 30-year period. Considering that the losses caused by each earthquake do not include all loss indicators, based on the overall analysis of earthquake disaster severity, this study discusses in detail the severity of earthquake disaster events with only a single loss index, dual loss index, and triple loss index, and compares their consistency with the severity of the entire earthquake disaster event. Key findings reveal that: the severity grading results of earthquake disasters with only a single loss indicator, earthquake disasters with dual loss indicators, and earthquake disasters with triple loss indicators are respectively reduced by 1–3 levels, reduced by 1–2 levels, and increased by 1–2 levels in the overall disaster severity grading results. It reveals that with the increase of earthquake loss indicators, the depth and breadth of the social impact of earthquake disasters have gone from being ignored to being overly concerned. Consequently, comprehensive earthquake disaster severity assessments require multi-dimensional analyses integrating both individual events and holistic frameworks. The findings provide technical support for post-disaster recovery and reconstruction planning in earthquake-affected regions.