Earthquakes might have regions more prone to landslides well into the future, research by scientists at Cardiff University suggests.
Their study speculates that this is because damage can reside in the side of mountains after an initial earthquake, and that the consequences of this damage may only be felt when a second earthquake hits.
The work, published in the journal Earth Surface Dynamics, has implications for disaster management and prevention, as predictive models for landslides currently in use do not consider historical occurrences of previous earthquakes.
“This could potentially be a significant gap in our understanding of the factors that lead to landsliding,” said Dr Robert Parker, lead author of the paper, from Cardiff University’s School of Earth and Ocean Sciences.
After this year’s Nepal earthquakes, a program called ShakeSlide, developed by Dr Parker, was used to predict areas affected by landslides and assist in post-disaster efforts. These new findings may lead to improved predictions, through models that consider the legacy of past earthquakes.
The study analysed data from two individual earthquakes that occurred in close-proximity to each other, in 1929 and 1968, on the South Island of New Zealand.
The epicentres of the two earthquakes were around 21 kilometres apart and both triggered landslides over a large area.
The researchers firstly analysed the influence that standard factors, such as the strength of the earthquake and the gradient of hillslopes, had on the distribution of landslides. Where the results were unexplained by these standard factors, the researchers investigated whether the results could be attributed to the legacy of previous events. Their results suggested that hillslopes in regions that experienced strong ground motions in the 1929 earthquake were more likely to fail during the 1968 earthquake than would be expected on the basis of the standard factors alone.
“Our results suggest that areas that experienced strong shaking in the first earthquake were more likely to produce landslides in the second earthquake than would be expected based on the strength of shaking and hillslope characteristics alone,” said Parker.