Earthquakes are quite literally quaking of the earth. This has happened
over thousands of years and people in the past have thought of many different
ways this is caused. When tectonic plates move, giant plates of rock push and
pull and slide and overlap; this is where friction and compression and pressure
increase until it is released. This releases all the energy contained. Now,
since waves are the most efficient way energy goes from point A (disturbance)
to point B (any other medium of matter), a wave is how the energy will travel.
The wave we are talking about is a mechanical wave, so it can only travel along
a medium (basically solids, liquids and gasses). Now, in this situation the
plates are transforming (like rubbing hands together) and the jolt sends out a
longitudinal wave quickly followed by a transverse wave, since longitudinal
waves are quicker than transverse. When the energy enters a building (buildings
are a medium), it vibrates because all that movement energy is being forced
into something barely containing the energy inside. The energy leaves the
building into the air (air is also a medium). If the building was strong enough
or flexible enough, it will survive the energy entering and leaving. If not,
the energy reduces the building to rubble. This is because the energy is pure
movement energy, and it comes from a large source: the Earth’s plates.
Now, as well
as knowing what caused them and where, they wanted to know how to stop
earthquakes from destroying their homes or at least getting a heads up before
everything they had was destroyed. Over years, people devised many methods such
as the frogs in a circle with their mouths open to catch a golden sphere from a
dragon’s mouth. The way this would work is a wave came from a direction and the
wave movement caused the golden sphere to fall and land in one of the frogs’
mouths. The frog that had the sphere showed which way the first wave came from
and then safety procedures built off that. This was quite efficient.
The next
step would be to locate the earthquake. To do this, they needed to find how
powerful the disturbance was from at least 3 different locations. A disturbance
is where matter is disturbed and this causes waves from friction, compression
and rarefaction. To help locate the disturbance, scientists measure the
frequency of the waves caused by the disturbance. They can find the speed of
the wave based on frequency, wavelength, and amplitude. After finding the
speed, they can tell how far away an earthquake was by how long the wave took
to get from the initial disturbance to one of 3 locations. After getting the
general distance for each point, scientists get a map of the area including all
three locations, and draw circles (the centre being one of the 3 locations)
representing the distance of the disturbance in all possible ways. Where all
three circle edges overlap in one spot, that shows just where the disturbance
happened.
The following step to safety was to
create a way to either get the people aware and away from anything possible of
collapsing, or to build things designed to withstand an earthquake. While some
of this is done, a major part of the system (monetary) wants people to buy new
stuff which has a “low life time” so you can buy more. This can lead to badly
made buildings that look nice but will collapse as soon as look at you or just
badly made buildings. Since option number one looked better (and more
profitable with all the “buy more earthquake detector kits which will last 3
days before getting boring”), the scientists started designing systems which
would warn everyone of an earthquake (and potentially monitor people’s every
move) and send off large annoying alarms blaring in everyone’s ear telling them
“GET A MOVE ON SLOW POKE OR YOU DIE!”.
One system
used is the Quake Guard, and it is used by several countries that lie either
right next to or on top of a fault line; such as Japan, Taiwan and Mexico. Quake
Guard is an automated system which basically turns a country into a giant nervous
system complete with automated brain. When a nerve ending (earthquake detector)
receives a painful hit (earthquake) it sends an alarm of sound and electrical
signals (literal giant blaring alarms and equally blary light) through the nervous
system(wire system) and ensuring the automated computer (brain) does what it
needs to do (tell everyone to RUN [not what the human body does]). The Quake
Guard also sends out a message to everyone in the country via internet/phone/TV
(sort of creepy how they have all phone numbers and email addresses). This
system is one of many used around the world. It might save your life one day.
