A modified gravity model integrated with a social vulnerability index: a case study of the 2008 Wenchuan Earthquake

In the context of global climate change and frequent natural disasters, the impact of sudden disasters such as earthquakes on population migration is becoming increasingly significant. Taking the 2008 Wenchuan Earthquake as a case study, this study explores the impact mechanism of earthquake disasters on population migration by combining the modified gravity model and the social vulnerability index. By collecting seismic data for earthquakes of of magnitude 5 or higher in China and its surrounding areas from 2011 to 2023, combined with population density information, this study first visualized the seismic events and revealed the spatial distribution characteristics and potential impacts of seismic activities. Subsequently, based on the socioeconomic data before and after the Wenchuan Earthquake, the social vulnerability index was constructed to quantify the impact of the earthquake on population migration. Finally, a model based on the traditional gravity model, social vulnerability, the gross domestic product (GDP) of the place of migration, and the place of migration is introduced. The results show that the GDP of the place of migration and the places of migration have a significant impact on population migration, while the social vulnerability index has a relatively small impact on intraprovincial migration. The goodness-of-fit of the model reached 0.9927, indicating that the modified gravity model could effectively explain the variability of population migration. This study provides a new quantitative evaluation method for managing post-disaster population migration, and provides a scientific basis for future disaster risk management and urban planning.