How rivers react to large earthquakes: Evidence from central Taiwan

Earthquakes and bedrock river incision are fundamental processes in the evolution of tectonically active landscapes, yet little work has focused on understanding how a bedrock river responds to a single large earthquake. Data from the 1999 M-w = 7.6 Chi-Chi earthquake in central Taiwan show dramatic differences in river response that depend on the proximity to the rupture zone. Near the fault scarp, vertical ground deformation intensifies river incision on a time scale of years to decades, while distal to the fault, landslides induced by the earthquake mantle bedrock on the river bed with sediment, impeding incision for decades to centuries as the material is evacuated. This surprising spatial and temporal variability in bedrock incision caused by earthquakes has implications for the paleoseismic interpretation of bedrock terraces and for the evolution of tectonically active landscapes.