Hot Fluids and Deep Earthquakes

May 08, 2007

Fluids in the Earth's lower crust are an underlying force in shaking things up where continental plates slip under each other, according to a study recently published in Nature. Donna Eberhart-Phillips, a UC Davis researcher in geology, collaborated on the study with Martin Reyners from GNS Science, New Zealand, and Graham Stuart from the University of Leeds, England.

Eberhart-Phillips said that these findings contradict the existing model for explaining earthquakes in the lower crust, which assumed that the lower crust had to be cold and brittle for earthquakes to occur. The new study shows that the presence of hot fluids can also weaken the crust from below.

"Rifting is caused not just by properties of the crustal material, but of the mantle below it where fluids are being released," Eberhart-Phillips said.

The study focused on the Taupo Volcanic Zone (TVZ), an active continental rift that cuts across the face of New Zealand's North Island. Located where the Pacific continental plate slips under the Australian plate, the TVZ is the most active and productive volcanic system on Earth. Eberhart-Phillips said that earthquakes in this area are deeper than average and occur in swarms, which is characteristic of fluids present at depth. Swarms consist of several small quakes occurring simultaneously, as opposed to a large quake followed by aftershocks.

The researchers used three-dimensional imaging to map the decrease of energy released from more than 1,600 seismic events in the TVZ. Their seismic velocity readings penetrated 200 miles through the Earth's crust and into the mantle, the layer below the crust.

"The thing that is unique about our study is the combination of the 3-D attenuation image of the whole region, and looking within that at the swarm earthquakes in detail," Eberhart-Phillips said.

Of particular interest to the researchers was the end of the subduction zone, where expected volcanic action does not occur. Three-dimensional imaging data suggests that thick crust chokes off the fluids at this end. Fluids appear to flow laterally along the TVZ, which may contribute to its high magma production.

The work was published in the April 26 issue of the journal Nature.

Source: UC Davis

Explore further: NASA's HS3 mission continues with flights over Hurricane Gonzalo

add to favorites email to friend print save as pdf

Related Stories

Cassini caught in Hyperion's particle beam

27 minutes ago

Static electricity is known to play an important role on Earth's airless, dusty moon, but evidence of static charge building up on other objects in the solar system has been elusive until now. A new analysis ...

Gypsies and travellers on the English Green Belt

37 minutes ago

The battle between Gypsies, Travellers and the settled community over how land can be used has moved to the Green Belt, observes Peter Kabachnik of the City University of New York.

Opportunity rover gets panorama image at 'Wdowiak Ridge'

39 minutes ago

The latest fieldwork site for NASA's Mars Exploration Rover Opportunity, which has been examining a series of Martian craters since 2004, is on the slope of a prominent hill jutting out of the rim of a large ...

Recommended for you

NASA image: Fires in the Egypt River Delta

6 hours ago

This NASA satellite image is of the Egyptian River Delta. Actively burning areas, detected by MODIS's thermal bands, are outlined in red. Each hot spot, which appears as a red mark, is an area where the thermal ...

Terra Satellite sees Tropical Storm Ana over Hawaii

6 hours ago

Tropical Storm Ana made a slow track west of the Hawaiian islands over the last couple of days, and by Oct. 20 was moving westward away from the main Hawaiian islands and heading toward the northwest Hawaiian ...

User comments : 0