Rainfall-seismic coupling effect induced landslide hazard assessment

Rainfall and earthquakes are the primary causes of landslides. In order to reveal the occurrence mechanisms and spatial differentiations of the rainfall-seismic coupling effect induced landslide, the landslide hazard assessment was carried out in Boshan District as an example. First, the different PGA exceedance probabilities in the next 50 years for 48 sites in Boshan District were calculated using the CPSHA method of the fifth-generation seismic ground motion parameter zonation map in China. The seismic hazard maps of Boshan District were drawn with the Kriging interpolation method. Second, the Green-Ampt infiltration model was improved by the characteristic parameters of the Philip infiltration model, and the formula for the variation of rainfall infiltration depth with rainfall duration was derived. Lastly, on the basis of the above study, the formula of landslide safety factor considering pore water pressure was derived based on the Newmark cumulative displacement model, and the slope cumulative displacement and the landslide probability under the sheer seismic effect and the rainfall-seismic coupling effect were calculated, and the landslide hazard assessment results with different PGA exceedance probabilities and different rainfall recurrence intervals were compared. The research results show that under the effect of PGA with an exceedance probability of 10% in the next 50 years, the maximum slope cumulative displacement is 2.52 cm, and the maximum probability of seismic landslide is 29.6%. The areas with maximum cumulative displacement are the east of Yuanquan Town and the south of Chishang Town. Under the coupling effect of PGA with an exceedance probability of 10% in the next 50 years and the once-in-50-year rainfall, the maximum slope cumulative displacement is 3.76 cm, and the maximum probability of the rainfall-seismic coupling effect induced landslide is 33.2%. The areas with maximum cumulative displacement are the central part of Yucheng Town, the south of Chishang Town and Boshan Town, and the east of Yuanquan Town. As a result of either the sheer seismic effect and the rainfall-seismic coupling effect, the slope cumulative displacement and landslide probabilities with lower PGA exceedance probabilities and higher rainfall recurrence intervals will increase significantly.