Alright, good afternoon once again. I am Sir Jude and today I will finish my rediscussion of the only topic that we discussed this week, which is epicenter triangulation, but part two. So the reason why we have part two is because obviously, pag-abing sa gantong lesson na pinaghalong-halong science, mathematics, TLE, even arts, and even AP because of the use of the maps and familiarization with countries, no?
is because, of course, lots of you will be unsatisfied with just one problem. And then, you know, more practice. So, because our first sample problem was situated in the Philippines, we decided that for our second and final problem, we will go to the Philippines.
So, it's an international problem. Let me read it for you. So, three seismic stations in North America detected the body waves earthquake with an unknown intensity and magnitude at around 6 o'clock AM.
Locate the epicenter where the earthquake originated. So let me tell you the description about our paper first. So the stations are CMB, DOG, and PIS.
And here are their P-Wave and S-Wave arrivals. So as you notice, this time to the first set of values in the first video, our set of values specifically in the E and S wave arrivals, they are in the hour, minute, and second format. That means we can't just go straight to computing the log time. We have to analyze the time first.
Okay, so let me start with CMB first. Okay, so let me just... cut to the chase, they all start with 6 o'clock. So our hour is 6. When you subtract each of them, each value, 6 will be cancelled.
So let's rely on the seconds and let's see if we also rely on the minutes. So in CMB, the second here is simply zero for the P wave arrival. For the S wave arrival, The second here is 28 seconds. Now for Dug, the time here, the time of S-Wave Arrival, P-Wave Arrival is 5 seconds while the S-Wave Arrival is 1 minute and 29 seconds.
So it's not equivalent to 129 seconds. We have to do time conversion first. So remember, one minute is equivalent to 60 seconds.
And because we already have 29 seconds here, we have to add 60 and 29 seconds. And it will give you 89 seconds total. Now last, for PAS, the POE variable is 2 seconds.
and the swv variable is 1 minute and 6 seconds. So how do we convert that to simply seconds? So one minute has 60 seconds and the 6 here is already in seconds. So 60 plus 6 will give you 66 seconds.
Alright, so judging by these values alone, we can conclude that out of the three stations The earliest one to detect the body waves is none other than CMV. Because it started at 0 seconds and exactly 6 o'clock AM, it detected the P wave. Now, the latest station to detect and record the seismic wave is none other than DOG because it took 5 seconds out of the 3 stations. So, we now already have the... times all in seconds, so it's time to compute the lag time.
So to solve for lag time, here's the formula. Lag time equals the time of arrival of the S wave minus the time of the arrival of the P wave. Okay, let me start with CM. In CMB, we have 28 seconds.
Sorry, I just changed the color. We have 28 seconds minus 0 seconds, giving you 28 seconds. With DUG, you have 89 seconds minus 5 seconds plus 84 seconds. And lastly for PAS, you have 66 seconds minus 2 seconds giving you 64 seconds. Alright, so because we're done with the first set of calculations, it's time to move on to the distance from the epicenter.
So how do we solve that? the distance from the epicenter. So to solve the distance from the epicenter, all you have to do is multiply the lag time by a constant 12.5 kilometers per second. All right, let me start with CMV. With CMV, you have 28 seconds.
times 12.5 kilometers per second and the product is 350 kilometers. For D-U-G, you have 84 seconds times 12.5 kilometers per second giving you 1050 kilometers. Lastly, for PAS, for PAS, we have 64 seconds times 12.5 kilometers per second and the product is 800 kilometers. Okay, so given the distances, we can assume that out of the three stations, CMB is the nearest to the epicenter because it is only 350 kilometers. And the farthest is DOG because it is 1,050 kilometers.
Okay, but we cannot rely on those values when it comes to drawing the circles on the map because you have limited space on your maps. So I have to scale them down. So on the last set of calculations to solve for the scale distance, all you have to do is simplify the distance by 100 kilometers per centimeter.
Alright, let's start again with C and B. Okay. So, C and D, you have...
kilometers divided by 100 kilometer per centimeter this will give you 3.5 centimeters. For DOG you have 1050 kilometers divided by 100 kilometer per centimeter that will give you 10.5 centimeters and lastly for PIS you have 800 kilometers divided by 100 kilometer per centimeter and the quotient is none other than eight centimeters all right and once you have those values Ready for epicenter triangulation using your map of North America featuring this piece the trance. Okay so again just like in the first video I want to demonstrate to you how to use Home Plus anymore because At this point, we've been here for two days already. So for Day 2, Part 2, and the back, here are some of my representations.
So CNB, whose radius is 3.5 cm, is represented by a purple circle. DUG, whose radius is 10.5 cm, is represented by the brown circle. And finally, we have PIS. in which its radius is 8 centimeters and represented by a black circle. So with that, these three circles intersect exactly at this point, the one that I marked with a star, and that star is considered the epicenter of the earthquake.
Now some follow-up questions. Number one, which station is the nearest from the earthquakes to the Earth? epicenter.
So judging by the by the circles, by the map, and even your problem solving a while ago, CMB is the nearest from the Earthquakes epicenter. Number two, which station is the farthest from the Earthquakes epicenter? So again judging by the map and the problem solving, the farthest is none other than TUG. Which station will be the least affected by the earthquake and why?
So the least affected by the earthquake is the one that is the farthest from the epicenter because, of course, the impact is reduced because it's too far away. And that's none other than TUG. While the station that will be the most affected by the earthquake is none other than CMD because it is the nearest to it. If it's close, the impact is strong. Now, additional follow-up questions from the two that we discussed on the first day.
So, is epicenter triangulation 100% effective in locating the exact location of the Earth-based epicenter? If yes, why? If not, why not? So, in the first video, I discussed that only a few students were able to determine the exact location of the epicenter.
alright boys unfortunately is actually inexact but still near to the answer that I'm looking for. So because hindi siya universal for every student, dahil iba-iba tayo with the way that we navigate the compass using our hands, I would say that it is not actually 100% effective all the time. Para yung sabon na panligong and panglinis ng ating katawa is only 99.9%.
In the advertisement, I won't mention any endorsements. They're only 99.9% effective. There is a small chance that at the end of the day, we're not totally 100% clean of our body. There are still impurities in the form of bacteria, dust, dirt, that we can't reach and clean our skin.
In relation to our topic, regardless of how you... beautifully draw the circles, it really depends on the way you use the compass. But realistically, because we're on top of a crust, we cannot determine which specific point in the crust is where the actual epicenter is located, whether it's small or wide. Now, follow up to that is question number two.
Why do seismologists still triangulate the epicenter even if it is not 100% effective in locating its exact location? So to be fair, of course, in this classroom discussion, we don't use seismographs because it's not state-of-the-art and because it's beautiful. And let's say groundbreaking, you're going to use it, of course, in seismic stations.
But still, we rely on epicenter triangulation. For disaster risk and reduction, as the ultimate answer here, because we can't stop earthquakes, we're in the Pacific Ring of Fire. And as we will discuss on the next lesson after your long test, there's a reason why behind the active plates in the Pacific Ring of Fire. So we cannot escape natural disasters.
However, we can prevent it. Alright, especially knowing that we have active faults in the Philippines, you can relocate and evacuate from the most active fault. Especially if you have relatives and loved ones from the other side of the country or other side of the city or whatever, you can alert them, inform them.
So yes, it's not 100% effective all the time but you can still use it, weaponize it for everyone's safety, precaution, and preparation. Now, additional follow-up questions. Please choose.
the words that will make the sentence correct. So the nearer a station is to the epicenter, the earlier or the later it receives the seismic waves, and the lesser or the greater the chance of it being affected by the earthquake. So kung mas malapit ka sa ang stasyon sa epicenter, and therefore mas maaga nitong nare-receive at nadetect ang seismic waves, at mas malakas ang chance nito na maapektohan ng lindol.
So the words that will make the sentence correct in this paragraph, or this sentence rather, are earlier and greater. By contrast, the farther a station is to the epicenter, the later it receives the seismic waves, and the lesser the chances of it being affected by the earthquake. So of course, if you're further away from the epicenter of the earthquake, you'll be late in detecting or recording seismic waves and because of that, the impact you'll have on the wind tunnel is less.
From the wind tunnel. Alright, and there you go. We're done with our lesson about epicenter triangulation.
So, the next phase will be... busy because of the NKAI tri-run and the two-day actual NKAI examination. That means, we'll see you on Monday next week and be ready because we will have your performance task 1.2 by group and your long test 1.2 by pair.
Till then, I'm Sir Judd and have a happy day. Goodbye!