There are many earthquakes in tectonically active mountains, so earthquake-induced landslides are a major component of erosion in these ranges. However, many factors influence the balance of uplift and erosion in mountains across the globe. Water and ice, rivers and glaciers, even plants and animals can cause erosion. The effects of earthquakes are nuanced as well. The magnitude of the quake, composition of the rock and dynamics of the watershed all affect the outcomes.
Li has begun investigating these details. He’s curious why the proportion of bedload in the Min River was so high after the 2008 earthquake. The bedload isn’t this high in all mountain rivers in seismically active regions, he explained. For instance, rivers in the Himalayas didn’t seem to experience such a high bedload flux after the 2015 Gorkha Earthquake in Nepal.
Answering this question requires studying the composition of the landslide material itself. Details like the kind of rock a mountain is made of can make an enormous difference in the number of landslides and size of debris, how sediment is transported and how quickly it flows downstream. Li’s team is working to combine data on grain size with advanced models describing how particles will behave as they travel down the watershed.
In science, answers always lead to more questions. And while the authors have their sights on solving a new set of quandaries, they’re quite proud of their contributions so far. As West said, “It’s very satisfying to have been able to quantify something that we’ve struggled to quantify before and that has a wide range of relevance, from hazards to long-term consequences for understanding the evolution of topography over long periods of time.”