Washington, August 11: Scientists have revealed that underground water plays a key role in triggering powerful earthquakes, an insight they claim could help seismologists to save human lives.
An international team has examined the role of water crushed out of the Earth’s crust deep below the surface in triggering powerful earthquakes, changing the dynamics of the fault and eventually causing volcanoes to form.
According to lead scientist Grant Caldwell of New Zealand, “In actively deforming regions like New Zealand, deformation will promote electrical inter-connection of any fluid present in the rocks below the depth at which the rocks are hot enough to become slightly ductile or soft.
“Thus localised ductile shear zones containing small amounts of fluid will be conductive compared to their surroundings. Measurements of the low frequency electro magnetic waves produced by solar activity and worldwide thunderstorm activity allow us to see electrically conductive zones deep within the earth.
“A line of these measurements (known as magnetotelluric or MT soundings) across the northern part of the South Island show that localised zones of high electrical conductivity occur about 15 km below some of the major faults in Marlborough.”
The results support the idea that the high conductivity zones observed below major strike-slip faults in New Zealand and elsewhere (eg the San Andreas Fault in California) mark ductile shear zones.
“This provides information on the deformation occurring beneath the part of the fault that breaks in large earthquakes and insight into the mechanisms that ultimately cause earthquakes,” Caldwell said.
The findings are published in the ‘Nature’ journal.
–Agencies