Sunday, May 13, 2012

Hitting the Tundra

It has been cloudy in the last couple of days. Jonathan Ajo-Franklin from LBNL joined the spirited gang of Arctic geophysicists and with his arrival the seismic acquisition has started. Surely the lemmings and the inhabitants of the quiet tundra have noticed our new activity.
Alessio hits the ground with the sledgehammer while Jonathan carefully observes the seismic wave being recorded by the geophones. Glen, our great bear guard, learns about seismic too. 
 For the entire day we have been repeatedly hitting the tundra with a 30 lbs sledgehammer. Today, we swung the sledgehammer approximately 600 times to introduce seismic energy into the subsurface. The seismic energy traveled in the frozen ground and was recorded by a number of little geophones, which were accurately buried within the snowpack.We are carrying out both surface refraction and MASW (multi-channel analysis of surface waves) methods.
It is time to move the seismic line. The team digs the geophones out from the snowpack. 
 The seismic experiment will allow us to measure the seismic velocities within the permafrost. This is a precious information that can be used to discern the physical properties of the subsurface. As with all the other methods we have applied in this campaign, it allows us to interrogate the  permafrost without really directly touching it.

We have now two more days left until the end of this very intensive geophysical campaign in which we collected a tremendous amount of information.
We have all learned a lot  - about geophysics, about the tundra, about the North, and about each other. 
John patiently completes the GPR survey while the rest of the team focuses on the seismic and the electromagnetic methods.
Written by Alessio Gusmeroli (UAF)