Naturally-formed balancing boulders could be used to help scientists to forecast large earthquakes more precisely. Precariously balanced rocks (PBRs) are found throughout the world (characterised by a slender boulder on a pedestal boulder) and have survived earthquake shaking over thousands of years. They can, therefore, indicate the upper limit of earthquake shaking that has occurred since they were first formed – shaking that, were it strong enough, would have caused them to topple.
Earthquake hazard models estimate the likelihood of future earthquakes in a given location. They help engineers decide where buildings should be built and how robust they should be – as well as informing earthquake insurance prices in high-risk areas. Imperial College London researchers have been working on a new approach by counting rare cosmic ray-generated atoms in PBRs and digitally modelling PBR-earthquake interactions.
Anna Rood, from Imperial’s department of civil and environmental engineering, said: “PBRs act like inverse seismometers by capturing regional seismic history that we weren’t around to see.” They found that combining their calculations with existing models reduced the uncertainty of earthquake hazard estimates at the site by 49%, and, by removing the worst-case-scenario estimates, reduced the average size of earthquakes estimated to happen once every 10,000 years by 27%. The team are now using their techniques to validate hazard estimates for southern California – one of the most hazardous and densely populated regions of the United States.
Read the full study at bit.ly/quakestudy