Twenty-year Study Yields Precise Model of Tectonic-plate Movements

MADISON – A new model of the Earth, 20 years in the making, describes a dynamic three-dimensional puzzle of planetary proportions.

Created by University of Wisconsin-Madison geophysicist Chuck DeMets and longtime collaborators Richard Gordon of Rice University and Donald Argus of NASA’s Jet Propulsion Laboratory, the model offers a precise description of the relative movements of 25 interlocking tectonic plates that account for 97 percent of the Earth’s surface.

“This model can be used to predict the movement of one plate relative to any other plate on the Earth’s surface,” explains DeMets. “Plate tectonics describes almost everything about how the Earth’s surface moves and deforms, but it’s remarkably simple in a mathematical way.”

Tectonic plates are in constant motion, sliding past one another as they float atop the planet’s molten interior. The collisions and shifts can create mountain ranges or cause earthquakes like the ones that struck Haiti and Chile this year.

“We live on a dynamic planet, and it’s important to understand how the surface of the planet changes,” Gordon says. “The frequency and magnitude of earthquakes depend upon how the tectonic plates move. Understanding how plates move can help us understand surface processes like mountain-building and subsurface processes like mantle convection.”

The new model, dubbed MORVEL for “mid-ocean ridge velocities,” is described in an extensive article available online and slated for the April issue of Geophysical Journal International. The work builds on the collaborators’ 1990 paper on tectonic plate velocities that has been cited more than 2,000 times by other scientists. During the past 20 years, the researchers have incorporated more and higher-quality data to improve the model’s resolution and precision.

About three-quarters of MORVEL’s data come from Earth’s mid-ocean ridges, the undersea boundaries between tectonic plates. At these ridges, new crust forms constantly as magma wells up from beneath the planet’s surface and forces the plates apart.

To judge how fast the plates are spreading, the team analyzed nearly 2,000 magnetic profiles of the crust formed at mid-ocean ridges in all the major ocean basins. The Earth’s magnetic field changes polarity at irregular intervals – most recently about 780,000 years ago – and each time leaves a magnetic mark in the crust akin to a tree ring. Measuring the distances between the marks tells them how quickly new crust is being formed. Most plate boundaries are currently moving at rates of 15 to 200 millimeters per year, DeMets says.

MORVEL also allows scientists to predict future plate movements and identify places where movements have changed over time, areas that are useful for studying the underlying forces that control plate movements.

“Along the boundaries where plates meet there are lots of active faults. It’s useful to know how quickly the plates are slipping across those faults because it gives you some feeling about how often large earthquakes might occur,” DeMets says. “The direction of movement across the faults gives some indication of whether plates are moving toward one another, which gives rise to one kind of faulting and seismic hazard, or slightly away from each other, which gives rise to another kind of faulting and a different type of seismic hazard.”

Higgs Boson Discovery

Physicists working at the Large Hadron Collider (LHC) have announced the discovery of the Higgs boson – or at least a particle that resembles the Higgs. In two special seminars this morning at the CERN particle-physics lab in Geneva, spokespeople for the LHC’s two main experiments – ATLAS and CMS – both reported measurements of the Higgs’ mass at confidence levels of 5σ. Any finding that passes this statistical threshold is generally, but not always, considered a “discovery” among the particle-physics community.

However, today’s announcement of a discovery of a particle that looks like the Higgs is by no means the end of the story, as physicists have yet to understand its complete nature.

Physicists have had the Higgs boson in their sights for nearly 50 years because its discovery would complete the Standard Model of particle physics. The particle and its associated field explain how electroweak symmetry broke just after the Big Bang, which gave certain elementary particles the property of mass. The Standard Model does not, however, predict the mass of the Higgs, and successive experimental programmes at CERN’s Large Electron–Positron Collider (LEP), Fermilab’s Tevatron and now the LHC have tried to measure the particle’s mass.

Presenting the latest results from the CMS experiment, spokesperson Joe Incandela announced that his experiment has discovered the Higgs boson at a mass of 125 GeV/c2 and a statistical significance of 5σ.

Incandela described the result as “A phenomenal effort considering that we stopped taking data two weeks ago.”

Incandela was followed by ATLAS spokesperson Fabiola Gianotti, who says that ATLAS has measured the mass of the Higgs as 126 GeV/c2, which agrees with preliminary results released by CERN in December 2011. The statistical significance of the measurement is 5σ.

“The search is more advanced today than we imagined possible,” says Gianotti. However, she cautioned that “a little more time is needed to finalize these results, and more data and more study will be needed to determine the new particle’s properties”.

Measurements with 5σ from both detectors – combined with previous searches by Tevatron and LEP – leave no doubt that a “Higgs-like” particle has been discovered by the LHC.

“We have reached a milestone in our understanding of nature,” says CERN director general Rolf-Dieter Heuer, who described the new particle as being “consistent with the Higgs boson”.

Speaking in the CERN auditorium immediately after the results had been presented, Edinburgh University particle theorist Peter Higgs congratulated researchers on their finding. “For me, it’s a really incredible thing that it’s happened in my lifetime,” he said.

Keystone XL oil sands pipeline

A new poll shows that 62 percent of registered voters favor approval of the Keystone XL oil sands pipeline, a project Mitt Romney has pledged to greenlight on “day one” if elected but the Obama administration has said needs more review.

The finding suggests that President Obama may be vulnerable to election-season attacks from Republicans and conservative groups, who have bashed him for failing to grant a permit for TransCanada Corp’s pipeline to bring Canadian oil sands to Gulf Coast refineries.

Near Surface Geoscience 2012

Paris has been chosen to host Near Surface Geoscience 2012 – the 18th European Meeting of Environmental and Engineering Geophysics of the Near Surface Geoscience Division of EAGE. The meeting will be held from 3 – 5 September 2012. In conjunction the Remote Sensing Workshop is being organized using the same location.

Clash of Interest?

GeoSearches came across a situation on a project a few days ago which I believe more clients should be concerned about.
GeoSearches was brought in to identify post tension cables and reinforcement within a concrete slab as the client discovered that the same sub contract company was identifying the wire and then also doing the coring.
Is this a class of interest. I believe it is. What do you think?