If a precariously balanced rock has held its position for 10,000 years without tipping over, it means the land around the stone hasn’t experienced shaking above a certain level in all that time. “The turn of phrase we’re trying to coin is that these precariously balanced rocks, or PBRs, are an ‘inverse seismometer’,” explains Anna. “A normal seismometer records an event that has happened, whereas our PBR is still standing there, and so it records an earthquake that hasn’t happened. Specifically, a large earthquake,” the Imperial College London, UK, researcher tells BBC News. This is really useful information if you want to build a nuclear power station or waste repository; or maybe a major dam or bridge.
BBC 1st Oct 2020 read more »