hey guys and welcome to Field Notes. I've
held this video off for another week
because we are continuing today our
earthquake series. If you guys follow the
news at all then you know that there was
another really large earthquake and I
didn't want to seem like I'm trying to
minimize what people there are going
through but at the same time, the
topics that we're going to be talking
about today may help some of you
understand kind of what happens when
there is an earthquake and what you can
really expect when you hear about one,
what sort of things might be happening
in those areas. So today we're going to
be continuing our earthquake series and
we're going to be talking about the
different effects that earthquakes can
have. Not only are there the direct
effects of the seismic waves which we've
talked about before as the shaking of an
earthquake but the shaking almost never
happens in an area that is completely
isolated and effects that are caused by
that shaking are what are known as
secondary effects. There are obviously two
main factors that determine what effects
you're going to see and how strong they
are and those are the local geology of
the area and how close to the epicenter
you are another thing to keep in mind is
that we tend to measure these effects in
terms of how destructive they are to
man-made structures. If there's an
earthquake in the middle of the desert
where there's nobody located we won't
care as much because the destruction to
human lives and human structures aren't
as large.  The first two we're going to
talk about are our direct effects and
that is ground shaking and faulting. Now
ground-shaking is something we've discussed
before in this video, it is the direct
effect of seismic waves but they are
only felt if the earthquake was strong
enough.  Next faulting is only really
present where the actual fault moves so
you have to either be along the fault
zone or at the epicenter to really see
this effect. The movement of a fault can
create what is known as a fault scarp
which we've talked about before. Which in
and of itself is not particularly
dangerous unless you have built your
house directly on top of the fault.  Now
that primary effect of ground shaking
actually causes
most of these others which is why they're
known as a secondary effects.  Landslides
avalanches and rock slumps can also be
triggered by ground-shaking especially
if you have a very unstable section of
rock.  A lot of the time a rockslide or
rock slump is more destructive than the
actual seismic waves.  In 1948 an
earthquake occurred high in the Andes
mountains, south of Quito, and while that
may not have been very destructive due
to the lack of structures that are up
there
it caused a landslide which killed six
thousand people and over a hundred
thousand people lost their homes. Another
one of these secondary effects is
liquefaction.  Liquefaction kind of like
the name suggests is when something
turns more liquid-y the shaking of an
earthquake will stir up groundwater and
soil and turn it more into a quicksand
like consistency this obviously while
also being terrifying, causes
foundations to sink and the building to
collapse.  Like most things this depends a
lot on the local geology, so if you have
very sandy soil or if you have
groundwater that is closer to the
surface you are more likely to see this
occur.
Flooding is another secondary effect
that we see a lot with earthquakes and
can be a little bit confusing because an
earthquake by itself does not really
involve a lot of water unless of course
you're dealing with tsunamis but then
even news and media and whether outlets
tend to call them tsunamis and not
link them back to the original
earthquake. Technically a tsunami is just
a really big wave.  But flooding can be
caused by quite a few other things as
well as the huge tsunami wave.  It could be
caused by a local river or lake but even
if you're not near water, broken water
lines can also be a major cause of flooding.
Now if you do live next to a river or a
lake flooding can occur due to a
phenomenon called a seiche, a seiche is
the technical term for the sloshing
back-and-forth of water.  You can recreate
this oftentimes in a bathtub, and
obviously if the seiche goes higher than
the banks of the river or lake it can
cause flooding. The next couple are
strictly effects of earthquakes because of
the damage to human-made things, one is
fire and these are caused by breaking
electrical and gas lines in fact in the
case of the san francisco earthquake of
1906 it is
estimated that almost ninety percent of
the damage that was done was actually
caused by the fire. So you think of like
maybe one building that really you don't
want affected by earthquakes high up on
that list is going to be a nuclear power
plant but we probably all remember the
Fukushima meltdown that happened in
2011 so nuclear power plants are
not immune to kind of messing stuff up
during an earthquake.  This was dangerous
not only because the nuclear power core
was damaged and unstable but there was a
lot of nuclear waste that was taken out
into civilization by the floodwaters.
there are two final things that I wanted
to mention in kind of the effects.
Earthquakes can sometimes trigger other
earthquakes, earthquakes very rarely happen
in isolated one-off situation a lot of
the times when there is movement along a
fault it is not just one single thing it
is a lot of small and then a larger and
then a lot more small the smaller quakes
afterwards can be very large
the only thing that notes them as
aftershocks is that you have the main
shock and then you continue to have
shocks that were smaller so if the
aftershock was larger than you would
change it to foreshock and main shock.
When these rocks are moving stress is
redistributed along the fault zone and
this can sometimes lead into other
faults in other sections of the fault
zone and cause them to also fault and
this would be what is known as a
triggered earthquake.
I think we think about earthquakes and
we think well ground-shaking isn't
really that dangerous but it is one of
the biggest things that is affecting us
especially in recent years I feel like
we've had a lot of earthquakes. and a lot
of times the secondary effects of
earthquakes are really what are dangerous and
really are what destroy homes and kill
people.
Thank you to everybody who has been
sticking through the series we are
almost done with it if you have missed
any of the other videos i will link the
playlist up here be sure to subscribe
want to keep seeing geology videos.
I try to get one up every other week and i
will talk to you all very soon with
another video
Bye!
