Submarine technology helps earthquake researchers

Gravity sensor is intended to reveal structures below the San Andres fault

San Andreas Fault in California © USGS
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Geoscientists are looking into the depths of the San Andreas Fault in California this week in an experiment conducted for the first time in this form. Using technology developed for military purposes during the Cold War, they investigate the "furrow zone" of the fault, a region two to three kilometers deep, where the constant movement of the earth's plates has crushed the rock to pebble size.

Very little data has been collected on the deep structures below the fault lines, as it is very laborious and expensive to drill so deep and to install corresponding measuring instruments so far below the surface. The scientists around Manik Talwani of the American Rice University now want to remedy this dilemma by scanning the area from an aircraft using an extremely sensitive gravity sensor. The measurements cover an area of ​​about 100 square kilometers in the San Andreas Graben near Parkfield. Scientific drilling will also be carried out here as part of the international Continental Deep Drilling Program, so that the data obtained can be compared with the results of the drilling cores.

"If this technology works, it will open the door to an affordable way for geoscientists to acquire data on fault and other subsurface areas, " explains geophysicist Talwani. "In addition, these flights will provide us with a reference measurement that will allow us to compare future studies to see how things in the shallow crust change beneath the surface of the fault."

The experiments use the fact that gravity at the surface of the earth changes slightly depending on the nature of the subterranean rocks and sediments. Using the highly sensitive sensors originally developed for the navigation of nuclear submarines, researchers can measure the gravity gradient, the smallest changes from place to place, along the fault.

(Rice University, 08.09.2004 - NPO) Display