and I modify the clock and try several ways to improve the quality of
the pen / writing surface. End up soldering an additional arm to the min
hand so that the paper is supported fully. This works much better.
take all the equipment to the quarry about an hour away from the sawmill
and set up the seismograph on the road. The two quarry men who are looking
after us drill two large holes in the ground and we fit the base of the
seismograph to these holes using two metal poles rammed in. Set up the
pendulum and the clock and try a test run – but with no earthquake!
The clock chart recorder makes a beautiful line and we know that everything
is working very well, in fact the best it has worked so far.
Ellen has made up
a really nice shelter for the seismograph consisting of a wooden structure
to hold a homemade roof.
Then the Helicopter
with the two Mikes comes over and drops them off with us so that we can
film the end of the program sequence at the quarry. As the helicopter
comes in the air blast moves the seismograph pen clean off the chart recorder
very spectacular!! The Two Mikes look tired but very happy they obviously
had a great time up on the mountain.
All of us get together
for the official blasting and testing of the seismograph. The quarry men
set up a charge some distance from the instrument and we huddle far off
at the end of the wire detonator. As Kate turns the key to explode the
charge there is a great blast, we feel the air blast in our stomachs and
the rumblings continue for sometime as the sound echoes from hill and
mountain to hill and mountain. Then we run off down to the instrument
to see what it has recorded.
and I are amazed, in fact everyone is amazed – there is absolutely
nothing registered on the seismograph just a nice straight line!! We have
made the most insensitive device that you can imagine!! So what's
going on? We do another charge and the same thing happens!
Then we question the
quarry men as to how they are setting up the charge and they tell us that
they laid the dynamite on the rock surface rather than into a hole into
the rock. The results now seem to make sense as this situation would make
a lot of noise but not expect to move the rock much. So they drill a hole
near to the instrument and load a charge into it. Now finally in this
test we manage to record something – a tiny blip on the chart recording!
Evidently it is much harder to make the earth move than you might think!!
this does make sense. An earthquake really does move the earth by cm's
even many kilometers from the source of the quake. A little stick of dynamite
would not be expected to move such a large amount of rock. But then I
heard stories that even blasting going on in other quarries far off set
their seismographs moving, how so? Well most modern day instruments work
on similar principles to ours but they have electronics to amplify the
sensitivity many 1000 of times. Our machine registers mm's of movement
on the rocks, which is not very likely but amplify this so that you can
measure millionth of a meter and you would detect all sorts of vibrations
and natural earth movements even many kilo meters away. So our instrument
did work but it was not sensitive enough to detect dynamite only earthquakes!
A spectacular but
also slightly un eventful end to TV3.