We're in the seismology lab here at BGS. This is where we setup all our
seismic instrumentation and sensors that record earthquakes in the UK and from
all around the world.
and, the sensors are incredibly sensitive devices.
This is one here
and they're sensitive to ground vibrations of
thousandths of a millimeter
and whenever there's an earthquake
the seismic waves travel through the Earth
and the’re picked up by the sensors and we use that to work out exactly where and
when earthquakes occur.
We record them
on computer systems, and this is one here, and what we see here is data coming in
from a number of seismic stations. So each wiggly line on the screen here
is the signal
from a seismic station somewhere around the world.
and were using that again to pick up exactly where,
when and how big earthquakes are.
On the top here
We’ve got and instrument that we are testing at the moment. It’s just down on the floor at
my feet here
and if I stamp
like that.
We’ll see the signal appears on the screen up here.
So obviously the instruments are
Sensitive to any vibrations not just earthquakes. So when a car drives past or
when somebody walks past the sensor the signal is picked up as well. So we need
to be able to discriminate between those kind of vibrations and the vibrations that
result from earthquakes themselves.
We need to understand why we get earthquakes, where they occur, how big they might be
and what places are a hazard from earthquakes. So we use the earthquake monitoring work
that we do to build picture of
where earthquakes are and how big they are
and how likely they are in different parts of the world and all that feeds into our
understanding of what’s called seismic hazard. That really is just a probability
of getting earthquakes of a certain size in different places.
Now in the UK we're in a country of fairly low seismic hazard, but
nevertheless there still is a potential to get earthquakes.
Many people feel earthquakes on an annual basis. We get about
20 to 30 earthquakes every year, even in this country, that are felt by
people and of course around the world seismic hazard is very high.
Earthquakes are one of the most destructive
natural phenomena that we know about and we really need to understand them.
Okay so what we're looking at is the signal
from a seismic sensor
being played back. So it has been speeded up about 128 times, so this
is much faster than it would normally be recorded.
It's from a sensor down in Eskdalemuir which is where
our seismological observatory is in the UK.
At the moment we are just looking at background signals,
but here you see the signal from an earthquake,
then another part of the same earthquake signal.
So these are probably body waves. This is probably a shear wave coming in here.
This is from a magnitude 7
earthquake in Vanuatu,
which is in the South Pacific.
So the signals from that earthquake took about 20 minutes to reach us, maybe
15 to 20 minutes to reach us.
And as we keep on going,
we’ll see that the earthquake returns to background noise.
Say, somebody wanted to build a tall building in an earthquake prone country.
That building would need to be constructed to withstand the expected
ground vibrations from earthquakes in that place. So, the kind of work that we do
provides information on expected ground vibration and that allows planners
and engineers to construct buildings so that they can best withstand the type
earthquakes that might occur in those type of places.
We use lots of different seismic sensors to record earthquakes.
We use some that are kind of
a low gain sensor to record strong ground motions from very large earthquakes.
And we also use ones a bit like this one
to record weaker motions from
earthquakes at much larger distances
We tend to put them out together,
so that if there is an earthquake very close to a seismic station
it will remain on scale.
And then
they are both buried
in a hole in the ground somewhere
and they will be well coupled with the earth and it will be very sensitive.
What my research is about at the moment is really about understanding
driving forces for earthquakes in this country.
So although the UK is a country of low seismic hazard we still get earthquakes.
But, why we get earthquakes in certain parts of the UK and not in others is still a real
mystery and but nobody really understands.