New technique dates faults near earth's surface

July 11, 2001

ANN ARBOR---A new approach developed by scientists at the University of Michigan and ExxonMobil Upstream Research Company allows direct dating of faults---surfaces along which rocks break and move---near Earth's surface. A report on the work appears in the July 12 issue of the journal Nature.

Dating shallow faults is essential to understanding the evolution of Earth's crust, the interactions among the plates that make up Earth's surface, and the processes by which faults are activated and reactivated, explains Ben van der Pluijm, professor of geological sciences at U-M.

For some time, scientists have been able to directly determine the ages of deeper rocks, but until now the age of shallow crustal faults could only be inferred through indirect dating methods---by studying the ages of fossils in associated deposits, for example.

Such estimates can suggest only a broad age range spanning many million years, not a precise age. The technique described in Nature, however, narrows down the age to within a couple of million years---practically pinpoint accuracy in geologic terms.

The researchers used the new method, which combines several approaches, to carefully analyze clays from near-surface faults in the Canadian Rocky Mountains. "That's an extremely well-studied area geologically, but there have been few reliable absolute ages on the faulting," says van der Pluijm. As a result, "we have not been able to get a firm handle on how fast processes like mountain building occur, when old faults stop being active and when new ones kick in, and the link between global plate tectonic processes and their surface expression," he says.

That kind of information has more than academic value, says van der Pluijm: "If you remember the stories about earthquakes in California, they often occur along faults we hadn't really seen active before. It's not because they weren't there; they just hadn't been activated in recent record." While the new method probably never will help scientists predict exactly when earthquakes will strike again at a specific fault, it should provide more general insights into the fault processes involved.

"If we understand more about the rates of these processes, we'll understand more about recurrence in general, and we'll get a better understanding of the mechanical behavior of the outer part of Earth," says van der Pluijm. "So we might ultimately get a better handle on the activation and reactivation of faults."
Van der Pluijm collaborated on the research with U-M research scientist Chris M. Hall, and Peter J. Vrolijk, David R. Pevear and Michael C. Covey of ExxonMobil Upstream Research Co. in Houston, Texas.

The work was supported by the National Science Foundation and Exxon Production Research Co.

University of Michigan

Related Faults Articles from Brightsurf:

New evidence for geologically recent earthquakes near Portland, Oregon metro area
A paleoseismic trench dug across the Gales Creek fault, located about 35 kilometers (roughly 22 miles) west of Portland, Oregon, documents evidence for three surface-rupturing earthquakes that took place about 8,800, 4,200 and 1,000 years ago.

A scalable method of diagnosing HVAC sensor faults in smart buildings
Heating, ventilation and air-conditioning (HVAC) systems are the biggest consumers of energy in a building.

Researchers develop new explanation for destructive earthquake vibrations
High-frequency vibrations are some of the most damaging ground movements produced by earthquakes, and Brown University researchers have a new theory about how they're produced.

Upper-plate earthquakes caused uplift along New Zealand's Northern Hikurangi Margin
Earthquakes along a complex series of faults in the upper plate of New Zealand's northern Hikurangi Subduction Margin were responsible for coastal uplift in the region, according to a new evaluation of local marine terraces.

Machu Picchu: Ancient Incan sanctuary intentionally built on faults
The ancient Incan sanctuary of Machu Picchu is considered one of humanity's greatest architectural achievements.

Faults' hot streaks and slumps could change earthquake hazard assessments
For more than a century, a guiding principle in seismology has been that earthquakes recur at semi-regular intervals according to a 'seismic cycle.' In this model, strain that gradually accumulates along a locked fault is completely released in a large earthquake.

New map outlines seismic faults across DFW region
Scientists from SMU, The University of Texas at Austin and Stanford University found that the majority of faults underlying the Fort Worth Basin are as sensitive to forces that could cause them to slip as those that have hosted earthquakes in the past.

Many Dallas-Fort Worth area faults have the potential to host earthquakes, new study finds
A study led by The University of Texas at Austin has found that the majority of faults underlying the Fort Worth Basin are as sensitive to changes in stress that could cause them to slip as those that have generated earthquakes in recent years.

Models suggest faults are linked through California's Imperial Valley
New mechanical modeling of a network of active strike-slip faults in California's Imperial Valley suggests the faults are continuously linked, from the southern San Andreas Fault through the Imperial Fault to the Cerro Prieto fault further to the south of the valley.

Catalog of north Texas earthquakes confirms continuing effects of wastewater disposal
A comprehensive catalog of earthquake sequences in Texas's Fort Worth Basin, from 2008 to 2018, provides a closer look at how wastewater disposal from oil and gas exploration has changed the seismic landscape in the basin.

Read More: Faults News and Faults Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to