Good afternoon everyone, Sergius here and today I will be rediscussing the lesson of the capital disc. So let's start our session with picture analysis. So at the top left portion you see Makati students undergoing an earthquake drill.
On the top right picture you see an aftermath of a landslide. On the bottom left picture you see an aftermath of a tsunami. And on the bottom right picture you see a seismograph and a seismograph.
So all these pictures collaborate to form a bigger picture in which all of them are connected to a certain natural disaster, which is the earthquake. So starting from this lesson, we will now be revolving around earthquake. And earthquake is referred to as the shaking of the Earth's lithosphere, releasing potential energy.
Now, if I'm not mistaken, earthquake was first introduced to you when you were studying... in grade 8, so that was two years ago. So we will just recap the four major parts of an earthquake.
So both epicenter, seismic waves, as well as focus and hypocenter. Now of the four arrows here, earthquake begins at the from the bottom. So the bottom is the point where the stored energy is release and that is the focus or the hypocenter.
Because we human beings and other living organisms reside above the crust, that is the point where we feel the earthquake. So the point on the surface directly above the globus pertains to the epicenter. Sometimes, due to the severity or the intensity and the magnitude of an earthquake, some crusts, blocks, or plates begin to crumble or break.
So the third part of the earthquake referred to as large cracks is what we call the fog. And finally, the reason why we feel the waves of the earthquake is because of the vibrations caused by them, also known as the seismic or seismic waves. Alright, so in this video recap, let's point the parts of the earthquake to the diagram on the right.
Let me just adjust my screen. Okay, let's start with the focus or the hypocenter. So focus or the hypocenter again is the point at the bottom where the earthquake originates releasing stored energy.
red dot here is the focus or the hypocenter. The epicenter is the point on the surface just directly above the focus. So this red point here, red mark just above the focus on the surface is the epicenter.
Now originally these two blocks are supposed to be together. So fault is marked by the truss or the point of separation between these two blocks or crusts or plates. So this region here, this curved line corresponds to the fault.
And finally, seismic waves are the vibrations caused by the earthquake. So they're represented by concentric red circles here. All of them here.
These are the seismic waves. Alright, so of the four parts of the earthquake, in this week we will focus solely on the seismic waves. Because this topic is too long, I decided to divide this into two parts.
Today is part one, tomorrow will be part two. Now in this illustration, aside from the major parts of the earthquake, all of the four types of seismic waves are also here. And these are the four types of seismic waves. First we have the T wave followed by the S wave. Both are found at the the bottom of the cross.
Then on the third, The Love Wave and the fourth is the Rayleigh wave. So both Love and Rayleigh are found at the top of the crust or at the surface of the crust. Now let's differentiate the four seismic waves according to the type of seismic wave. Okay so there are two types of seismic wave. We have body waves wherein they travel within the Earth's interior.
So in Tagalog, paloob. and surface waves wherein they travel on the Earth's surface. So prior to this slide, I mentioned that both P and S waves are found at the bottom of the crust. So that means they propagate and traverse the areas that they traverse within the Earth. So movement lies most of the time downward.
So both primary and secondary waves are classified as body. On the other hand, both love and Rayleigh waves are found on the surface. That's why both love and Rayleigh are surface waves.
So just to recap, P which stands for primary wave is a body wave. S which stands for secondary wave is also a body wave. L which stands for love is a surface wave. while R, which stands for Rayleigh, is another surface wave. The second point of comparison among the four seismic waves is the wave propagation.
So we have three types of wave propagation. The first is what we call longitudinal, in which the wave propagates or moves back and forth. Now, second is transverse. Transverse has two types.
One that moves or propagates up and down and the other one is side by side. And the third and last one is elliptical wherein it is a combination of both longitudinal and transverse waves. So let's look into them one by one by starting with primary winds.
So P or primary wave as you can see is back and forth. So as a consequence, we classify P or primary waves as Dongyitudinal. On the other hand, if you look at how S-wave propagates, so it moves in an up and down direction. So that means S-wave propagates transversely, specifically up and down.
Now, you want to love? So as you can see, love is almost similar to how S-waves propagate. The only difference here is love waves propagate side by side.
So because love and secondary are almost identical with each other. Love wave's propagation is also transverse but specifically it moves side by side. And finally in Rayleigh wave, if you look at the blue Through Mark Arrows there, it moves in an elliptical fashion, which is a combination of long E to the N. transverse wave. So that means the Rayleigh wave is classic or propagates elliptically.
All right. So to distinguish the four seismic waves according to wave propagation, we have primary propagating longitudinally back and forth. Second is secondary propagating transversely, specifically in an up and down manner. Third is love which propagates also transversely but this time side by side like a snake.
And the last one is really which propagates elliptically there's a combination of longitudinal and transverse. Alright now the last point of comparison among the four seismic waves is the media When we say the verse in Tagalog, It's dinadaanan or dinadagos. I think it's better if we have this view instead. Okay, so speaking of media traverse, we will only choose among solid, liquid, and gas, the three basic states of matter.
In here, we're going to detect if any of these waves can traverse solids, liquids, and gases. Let's start with P waves. Okay.
So the best way to compare the perversion of the TNS waves is by recapping the major parts of the Earth's atmosphere. So first we have the crust here, the only habitable layer, which is solid, followed by the magma reservoir on the Mandel, which is also solid. And then here, the blue, the one represented by a sky blue shade, we have the outer core, which is technically the only liquid layer in the Earth's lithosphere. And finally, we have the pothos layer, the inner core, also solid, containing several metals.
Now, let's look into P waves first. For P waves, it's clear that all these black lines, which represent P waves, they can traverse across all layers of the Earth's sphere. The cross, which is solid, the mantle, which is also solid, the outer core, which is liquid, and the inner core, which is solid.
So that means primary waves can traverse solids, liquids, and it can be said gases. Now let's move on to the secondary waves. In secondary waves, they can only traverse on cross and mantle both of which are solid layers. Unfortunately, it stops traversing beginning at the outer core which is a liquid layer. So that means secondary or S-waves can only traverse in solids only.
Unlike primary which can traverse in basically any medium. For both love and Rayleigh waves, they have no other medium to traverse other than solids only. Alright, so to recap the media to which these seismic waves traverse.
So for primary, it traverses all media, solids, liquids, and gases. While the remaining three, secondary, love, and really, they only traverse through solid, medium, only. So to make sense of how the diversion of seismic waves are applied in real life, let's analyze the problem on the next slide.
Okay, so in this problem, you have a fisherman on the sand on the left side of the picture and a tourist swimming in the sea, the right side of the picture, are shocked by an earthquake. The fisherman shouted that the earthquake is strong, but the tourist is not that concerned because for him, it is weak. So it is obvious that both of them felt the earthquake. The only difference is that the fisherman felt the intensity or the magnitude of the earthquake.
strongly while for the swimmer tourists he found it kind of weak so because both of them are witnesses and they have their testimonies all of their uh all of their complaints are valid but what waves did the fishermen feel on the sand and the tourists in the sea. So you have to remember where the fishermen and the tourists are located. So the fisherman is standing on the sand and as we know, sand is a solid medium. On the other hand, the tourist is swimming in the sea and as we know, sea is a liquid medium. So going back to the table of comparison from the previous slide, we can deduce that the fisherman felt all the seismic waves because primary, secondary, love and rain all passed through solid.
Yeah that's why the fisherman was able to detect and feel that the earthquake was strong. So for him it was strong because he felt four waves. However for the tourist swimmer he only felt three waves because the P wave is the only seismic wave that can travel through liquids.
That's why for the tourist swimmer, the earthquake was weak. So there you go. That's why when there is an earthquake, you have to rely on someone who is standing or who is staying in a solid medium. Not on liquids and not on gases.
because the people who stayed in the solid video, they're the ones who can feel all the vibrations of the seismic waves. Okay, now, so basically we're done with our discussion. But before I end, let's have our review end. Pick a picture and identify the type of wave based on the videos provided. I want to start with this railway system which is kind of disjointed.
Alright, so using these three clues, we have to identify what type of seismic wave is being described. So is it primary, the B wave, secondary, the S wave, or low, the L wave, and R, the Rayleigh wave. So here are the clues.
Number one, it moves side by side. Number two, it reverses solids only. And number three, it travels on the Earth's surface. So the strongest claim here is that this wave moves side by side.
And there is no other wave doing that other than the love or the L wave. All right, let us go back to the selection. Let me pick the accordion.
Take. So in the accordion picture, here are the three clues. Number one, this wave moves back and forth.
Number two, it can traverse solids and liquids. And number three, it travels beneath the Earth's crust down to its inner core. There is no other way of moving back and forth or propagating longitudinally other than the primary or the P wave.
Let's go back to our menu. Next, this woman exercising using two pieces of rope. Okay.
In this setup, first, we have the clue stating that this wave traverses on its own. It moves up and down vertically, and it travels also beneath the Earth's crust. There's no other wave propagating transversely in an up and down motion other than the secondary or S-wave.
Now, based on how I analyzed the given groups, it is better to distinguish them using their wave propagation because each of their movement is very unique and distinct. Alright, so the last one we have rolling pins and we are the clues. This cis-weak wave traverses solids only, travels on the Earth's surface, and is a combination of longitudinal and transverse wave. So meaning its wave propagation is elliptical.
And there's no other wave propagating elliptically other than the Rayleigh or R wave. Alright, so basically we're done with the first one of Sysweek Wave. Going back to the first slide, to give you a sneak peek of what we're going to tackle tomorrow, you see the picture at the bottom right of this picture analysis?
That's what we call the seismograph and the printed vibrations are the seismograph. So using the printed images from the seismograph and the seismogram, how we're going to detect which are P waves, S waves, L waves and R waves? Which is faster?
Which is the fastest? Which is the slowest? Which is the most destructive?
And which is the least destructive? So all of those questions will be answered tomorrow. In the meantime, I'm Sir Jude. Thank you and...