The setting is idyllic: a rock-strewn, mossy hill above a classic West Coast vista, where the setting sun silhouettes craggy trees and turns the sea below peach-hued.

And amid this beauty, there it sits — a short, dome-topped concrete cylinder.

To the east, 434 kilometres away in a locale almost as scenic, sits a similar sentinel-like structure.

Each is a Global Positioning System (GPS) station.

And each is made up of an antenna mounted on a “monument” anchored into the bedrock below.

Inside, out of sight, a GPS receiver silently transmits a continuous stream of high-speed data to Natural Resources Canada scientist Herb Dragert and his team of researchers at the Geological Survey of Canada in Sidney, British Columbia.

A federal scientist since 1976, Dr. Dragert was born in Yugoslavia and educated at the University of Toronto, the University of British Columbia and Göttingen’s Institute of Geophysics.

“These two strategically located GPS stations — with 15 others — are collectively known as the Western Canada Deformation Array which also serves as the northern portion of the Pacific Northwest Geodetic Array (PANGA),” explains Dr. Dragert. “Spanning the most seismically active and most densely populated regions of western Canada and the U.S., together, they give us some wonderful new insights into how our planet works.”

The “obelisk” on the left — at Ucluelet — has moved 21 millimetres closer to the one on the right — at Penticton — since January 2005. That’s an average rate of 9 millimetres a year, very fast in geological terms.  Award-winning Natural Resources Canada research scientist Dr. Herb Dragert knows the reason. PHOTO CREDIT: Michael Schmidt, Natural Resources Canada

That’s putting it mildly.

Using space-based technology, this network of automated GPS stations is continually monitoring the minuscule movements of the earth’s surface.

Already, the network has detected that the station at Ucluelet on the west coast of Vancouver Island is moving eastward toward the one at Penticton at a rate of nine millimetres a year.

That movement would never have been noticed by the standard surveying tools of 30 years ago, which at any rate were difficult and costly to use in misty mountainous regions.

Why is the earth moving?

“What we’re observing is the surface of the earth being subtly deformed,” says Dr. Dragert. “Far below the surface, a piece of the earth’s crust, known as the Juan de Fuca Plate, is slowly sliding under another plate moving in the opposite direction.”

By monitoring and modelling the buckling and squeezing of the Earth's surface, Dr. Dragert and other geoscientists at Natural Resources Canada are gaining a better understanding of the processes that result in earthquakes. And with this and other information, they are collecting clues as to where and when the next major earthquake is likely to occur.

This research is clearly of the greatest interest and importance, and it has not gone unnoticed. Recently, the Canadian Geophysical Union recognized Dr. Dragert for his decades of meticulous work monitoring crustal deformation to improve our understanding of earthquakes.

It awarded him its highest honour, the J. Tuzo Wilson Medal.

This prestigious award recognizes not only Dr. Dragert’s significant contributions to the field of crustal geodynamics but, in particular, his role as the driving force behind the creation of the Western Canada Deformation Array and his discovery of a surprising plate behaviour now known as Episodic Tremor and Slip.

"Offshore and at great depths, the Juan de Fuca Plate converges relatively steadily toward the North America plate margin, except at the shallow interface where it remains locked for centuries until it finally ruptures in a huge earthquake,” says Dr. Dragert. “The part of the plate interface immediately down-dip from this locked zone, formerly thought to be moving continuously, appears to be getting snagged for about 15 months and then releases over a two-week period. That slow release is what we call a slip or silent earthquake, and because it transfers stress to the shallow locked zone, such a slip could conceivably trigger 'the big one.' "

This unexpected finding quickly became recognized as one of the most important advances in our understanding of earthquake mechanisms. It has gone on to open up an entire new area of research, not only for NRCan scientists but also for researchers in other seismically active parts of the world.

“Herb’s findings spurred us to seek similar slip events in Japan, and we ended up finding occurrences accompanied by low-frequency tremors,” says Takeshi Sagiya of Nagoya University.

Dr. Dragert’s contributions are also appreciated by other specialists in his field.

“Herb is one of the most careful, conscientious observers applying satellite positioning to plate boundary and seismic problems today,” says William Prescott, past president of UNAVCO, a consortium of research institutions committed to supporting Earth science by advancing high-precision techniques for the measurement and understanding of crustal deformation.

Dr. Dragert is already looking forward to the next technological innovation that will further enhance the measurement and monitoring of crustal deformation and its effects on the earth’s surface.

“I don’t know how it will be done, exactly. But 30 years ago we thought identifying a location on the surface to within 10 metres accuracy was acceptable. Now, it’s 1 millimetre; next, it could be 0.1 millimetre!”

He likens the improvement to a photograph — the less coarse the data, the sharper the image.
“I’m sure then we’ll be able to see phenomena that we haven’t been able to monitor before.”

Source: NRCAN News Room