Reevaluating the Magnitude of the 1785 Yumen Earthquake through Multidisciplinary Approaches: a Case Study in Western Gansu, China

The 1785 Yumen earthquake represents a significant seismic event in the western Gansu Province, where the Qilian Mountains of the Tibetan Plateau converge with northern foothills. As the sole historically recorded earthquake in this segment of the ancient Silk Road corridor near Yumen—a critical historical hub—this event extends the regional seismic catalog back by approximately 135 years. However, substantial uncertainties persist in its parametric characterization due to limited damage documentation. This study synthesizes previous research while critically examining controversies surrounding intensity assessments and parameter estimations. Through systematic analysis of modern seismicity patterns, we employed seismic density index calculations to delineate persistent aftershock zones. One identified seismic density zone exhibits characteristics consistent with long-lived aftershock activity potentially associated with the 1785 mainshock, providing critical constraints for epicentral localization. Integrating historical accounts with geomorphic evidence, we objectively estimated the earthquake magnitude through intensity attenuation modeling. Our simulations incorporated topographic amplification effects and geological setting considerations to refine magnitude estimates. This investigation establishes a methodological framework linking historical seismic events with contemporary seismotectonic features, offering new perspectives for identifying missing historical earthquakes in poorly documented regions. The findings emphasize the necessity of integrating historical seismology with modern geophysical analysis while highlighting the urgent requirement for supplementary paleoseismic investigations and refined geological surveys to reduce parametric uncertainties. The proposed multidisciplinary approach demonstrates potential for reconstructing seismic histories in tectonically active areas with sparse instrumental records.