lunes, 10 de junio de 2013

Scientists confirm 'supershear' earthquakes


Image credit: CC 3.0 USDOI


Laboratory experiments have confirmed the existence of an unusual and lethal type of earthquake. Supershear earthquakes are rare events in which the resulting tremors far exceed what would be expected for the given magnitude. Scientists believe this can happen when the rupturing fault breaks more quickly than the seismic waves can travel, producing a seismic mach cone that shoots out the end of the rupture zone, resulting in excessive shaking. Now for the first time scientists have been able to demonstrate that supershear earthquakes can and do happen using experiments in a laboratory.
To do this, they used acoustic sensors to analyze 200 'micro-earthquakes' in a controlled environment to emulate the conditions. "It's like the [seismic] waves are propagating along and all of a sudden it steps on the accelerator," said seismologist Eric Dunham. The inner workings of bizarre and potentially dangerous earthquakes that break the seismic sound barrier creating a sonic boom have been confirmed in laboratory experiments.

source and credit a unexplained-mysteries