Lecture 26

Namaskar, so in the last class we talked about what are the signatures of a fault that creeps and we were talking about the Hayward Fault in the San Andreas Fault System because we had shown here that this fault creeps. So, people live in this area, houses are built, but every time what was happening was that after some time, their subsurface, the underground pipelines were having problems, the gas pipeline was breaking, or the sewer pipeline, or the water pipeline. So, these people were not able to understand what was happening here. So, this is basically what we are talking about, that this fault is creeping, so how did they find out about it? So, when the geologists and scientists were consulted to see if there is any fault here due to which this issue is coming, so I also showed you this photo that usually the pedestrian path is made, the footpath is usually straight, but here it is curved. If we change the color of the pointer a little bit, then it can be made for any reason, but it was not made like this. So, this was made straight, but here this bend has happened. So, when detailed studies were done, it was found that your Hayward Fault is passing from here and its movement is something like this. So, this is one thing they understood. So, its evidence can be seen elsewhere. So, we say that the riddle fractures that are formed, if a fault is passing from here, this fault is actually going from here, it is from here, this is also your branch. So, the cracks that we are seeing on the ground, these cracks are due to the heat, which we mostly see that cracks are formed on the roads, so they are not made due to the heat. So, these fractures that are formed, these typical riddle fractures are formed, which are seen in the strike-strip faults. So, it was found here that this fault is creeping, and because of this, your underground pipelines are breaking. Another evidence was seen at this place. I will tell you the close-up, this is the portion, which clearly indicates that the fault is creeping. So, if you see here, then you have this again, this was straight, but this displacement has happened over the time. So, over time, there was so much displacement in this. So, this portion, your fault is passing from here, if we make it from the red line once, then this fault is coming out from here. So, this portion is like this. So, this is the offset, we call it, this is your offset, and this red line is your fault line. So, we see such deformations like this. So, this earthquake, if there is an earthquake in the future, then it will move more, but now, because energy is not being stored in it, so it is creeping, so in this, it is not so dangerous. But still, if it is seen that if we know such things, then whatever our infrastructure facilities are on the surface, it also affects it. This is the second example. Although, what we were telling in the last, that the pipelines of these people, subsurface or underground pipelines, whatever they are, and either we say that utilities are not there, if there are underground utilities, all this was breaking. So, they have overcome this. Now, how did they do it, we will also talk about this. Although, when we know that this fault will move over time, suppose this is your pipeline, it will move over time. So, what they did for this is that they started taking flexible pipes, which will turn on their own, they will not break. Definitely, after some time, there will be more displacement, so there will be a break, but for some time, what used to happen in the first short period, that will not happen, because these people were saved from it. So, they made a remedy like this. Now, the second thing is that the same fault was passing through a railway track. So, if you look here, this fault is going from here to somewhere. Now, if you look at it carefully, then this pipeline is your railway track, this railway track is going from here to somewhere. So, this pipeline is your railway track, this railway track, some railway tracks are turned, some are not turned. So, if we look at it, these tracks, if you look carefully, then they are slightly turned. Now, if there is so much bending, then this is not good for the railways actually. So, whatever engine or bogies will pass from here, trains will pass, it will affect it, there can be a derailment. So, what they do here is, as soon as they know that there are some parameters, that if it is more than this bending, then they will not allow the trains to move there. So, they make their own new rail tracks. So, this is new, this is older. So, they abandon the older ones. Then they make new ones. So, in this area, they have started a remedial that here, periodically, there is a threshold limit that if it bends more than this, then they will abandon it. So, they keep making new rail tracks and keep shifting. And from here, whatever trains you have to pass, they pass safely. So, this is a very good example, which we understand that if we have identified such features on the surface, then we can save ourselves from it. And we can save ourselves from any big accident, there is less loss. If you look at this clearly, then you can see this bend here. So, this is not done artificially, this is done along the fault. This curve is also the offset shown, that how much was there in 2004 and how much in 2006, how much offset was there in a year span. So, they make such measurements clearly. And as I told you last time, that if you have a GPS station, then you can monitor its movement, how much is it slipping throughout the year. So, you can design your house accordingly. So, this is one example, which you can see that this is offset, this is from here, this is broken, this is your drain here, so that is also broken, so at the moment clearly you can see that this portion has come here and this portion has gone here, although when it was made earlier, it was straight, but now it has become like this, so this is the kind of fault lines, which are identified worldwide, this is a robust method and it is also being done in India, but in India it has not been done at the level that it has been done in other countries, it has been done in America, it has been done in Japan, it has been done in New Zealand, so in those places, they have to go to that area. Those areas are also seismically active areas, which are earthquake prone areas, work has been going on there for a long time. In our country, some 4-5 years ago, the government has emphasized it a little and we are doing a project on it, although we have been working on it for the last 10-15 years and we have got very good records and a lot of good mapping has been done. So, this whole thing is being taken from a safety point of view, like we say that earthquakes cannot be stopped, but whatever damage is done by earthquakes, we can minimize it. So, this is another photograph of yours, two photographs, one satellite data is visible on the left-hand side, so it is said that this city, Seattle, this whole city is sitting on top of a fault line, so if it is sitting on top of a fault line, then there is a possibility of an earthquake coming under that city. So, they have this information like this. Now, if we look at India, so in India, like this second thing we were saying that GPS stations, so this has been shown about the Indian plate that we have in some areas, although this portion is of the whole of Nepal. In Nepal, a very close array has been set up of GPS stations, but as you will see in India, this portion is completely empty. There are no GPS stations here, but this is not right, this is an old map, but there are a lot of stations here, but still, we will say that the number of stations that should be placed are not placed closely spaced, there is a need to work more on this. So, from that, we will basically find out that the accumulation of strain, those areas we will find out that where the strain is accumulating more. So, this basically we will be able to identify that where the strain accumulation is occurring, in which fault or in which region. So, from this, we will get an idea that which area this earthquake can produce. So, these things can also be studied by GPS. So, GPS shows its own vector that how the landmass is moving, although you can see from this that this arrow is showing 20 mm per year, but it is more than that, and it is big, so this is what we told you in the last lecture that it is about 45 to 50 mm per year here, its deformation, means it is moving like this. And if you look at the side of China, the part of China is coming out, it is moving towards east. So, we can also find out from these arrows and the velocity arrows. And if we have GPS data, then it is understood that in which area there is more pressure is being created, more strain is accumulating. So, if we look at the forecast and prediction of earthquake prediction, then as I told you that there is not much success, but some success, which we can say that it was very important for earthquakes particularly. So, we usually look at earthquake precursors, how we look, I mean, what is the indication of earthquake precursors. 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Chinese authority used series of four shocks as an warning to anticipate the Haiqing earthquake Chinese authority used series of foreshocks as a warning to anticipate the Haiqing earthquake of 1975. The Chinese authority used series of foreshocks as a warning to anticipate the Haiqing earthquake of 1975. The Chinese authority used series of foreshocks as a warning to anticipate the Haiqing earthquake of 1975. The Chinese authority used series of foreshocks as a warning to anticipate the Haiqing earthquake of 1975. The Chinese authority used series of foreshocks as a warning to anticipate the Haiqing earthquake of 1975. The Chinese authority used series of foreshocks as a warning to anticipate the Haiqing earthquake of 1975. The Chinese authority used series of foreshocks as a warning to anticipate the Haiqing earthquake of 1975. The Chinese authority used series of foreshocks as a warning to anticipate the Haiqing earthquake of 1975. The Chinese authority used series of foreshocks as a warning to anticipate the Haiqing earthquake of 1975. The Chinese authority used series of foreshocks as a warning to anticipate the Haiqing earthquake of 1975. The Chinese authority used series of foreshocks as a warning to anticipate the Haiqing earthquake of 1975. The Chinese authority used series of foreshocks as a warning to anticipate the Haiqing earthquake of 1975.