Lake sediments record cycles of sediment flux driven by large earthquakes on the Alpine fault, New Zealand

Abstract

Large earthquakes in mountain regions commonly trigger extensive landsliding and are important drivers of erosion, but the contribution of this landsliding to long-term erosion rates and seismic hazard remains poorly understood. Here we show that lake sediments record postseismic landscape response as a sequence of turbidites that can be used to quantify erosion related to large (moment magnitude, Mw > 7.6) earthquakes on the Alpine fault, New Zealand. Alpine fault earthquakes caused a threefold increase in sediment flux over the ~50 yr duration of each postseismic landscape response; this represents considerable delayed hazard following earthquake-induced strong ground motion. Earthquakes were responsible for 27% of the sediment flux from the lake catchment over the past 1100 yr, leading us to conclude that Alpine fault earthquakes are one of the most important drivers of erosion in the range front of the Southern Alps. © 2012 Geological Society of America.