Station CHUR

Questions for Joe Henton

How did you become a scientist/engineer?

Throughout most of my K-12 schooling, I had a general affinity towards science and math subjects, but I didn't envision a particular career path—perhaps I was having too much fun playing pick-up games of hoops or football. (Although I would put in an honest effort, I was not "academically successful" in any art classes—I did take that as a hint.)

As it became closer to the time for "leaving the nest," I had developed a general interest in the physical and engineering sciences. I decided to attend New Mexico Tech and under a work-study program I was able to work in the earthquake seismology lab under Al Sanford. This hands-on work, coupled with Dr. Sanford's insight on regional seismicity, ultimately cemented my interest in geophysics.

What are you hoping to learn from your research?

I use satellite-based geodesy and absolute gravimetry to investigate the time-evolution of national and regional spatial reference frames and gravity datums as well as the processes driving the observed change. In particular, my research interests include various crustal deformation studies:

• broad-scale glacial isostatic adjustment
• regional earthquake hazard studies
• local monitoring of surficial doming near a CO2 sequestration injection site

My work investigates processes that operate on time scales from long-term secular deformation, to transient geodetic signals that have durations of several weeks (such as Episodic Tremor and Slip), and to "GPS seismology" studying surface coseismic displacements and surface waveforms.

Glacial Isostatic Adjustment

Most of Canada was once extensively covered by the Laurentide Ice Sheet and its huge weight deformed the Earth's surface. During the last peak of glaciation about 20,000 years ago the ice was nearly three kilometers thick in some areas. The mass of the ice caused downward warping of the crust and forced viscous material in the underlying mantle to flow away from ice-covered regions. This effect raised land peripheral to the glaciers. As the glaciers retreated, the process reversed and the land that had been underneath the ice began to rebound. Reaching equilibrium may take 10,000 years or more. This process is called Glacial Isostatic Adjustment (GIA).

GPS data allows us to measure precisely the pattern and rates of vertical deformation here and in other regions experiencing GIA. The overall pattern of uplift and subsidence across Canada can be seen in Figure 2, with a detailed graph of the vertical position change at Churchill in Figure 3.

Spotlight Questions