Abstract: Image-based deformation analysis has emerged as a critical technique for slope instability monitoring,early warning,and indoor physical experiments.However,its applicability and reliability in analyzing dynamic deformations of slopes under seismic conditions remain insufficiently explored.Based on multi-condition sandy slope earthquake model tests under single factors such as water content,water coverage,particle gradation,and slope angle,this study systematically investigates deformation modes,failure characteristics,and influencing factors,and evaluates the reliability and applicability of image analysis methods.Research has found that:the studied conditions exhibit four primary deformation modes:sliding,shear sliding,sliding-collapse,and no failure,with their deformation triggering conditions and failure modes influenced by a combination of multiple factors.Slopes with 5% water content transition from shallow sliding to internal shear sliding compared to dry counterparts;slopes with half and full water coverage display top sliding and sliding-collapse failure characteristics,respectively.Particle gradation and slope angle have significant impacts on the triggering conditions and modes of slope deformation.As the fine particle content decreases and the slope angle increases,both slope instability and the scale of sliding bodies augment.For small deformations,PIVlab and RG-DIC methods effectively analyze slope deformations,with average peak errors of 13.5% and 9.2%,and maximum peak errors of 24.7% and 19.6%,respectively.Errors occur in PIVlab and RG-DIC during slow small deformations and instantaneous large deformations,respectively,indicating that enhancing the applicability and reliability of multi-scale deformation analysis is a crucial issue in the current development of image deformation methods.The established data and conclusions provide guidance and reference for the prevention and control of slope earthquake disaster risks and the development of image-based deformation analysis methods.