Sign of Focus or Epicenter..
Hello Friends, welcome to my blog once again. Today I'll be talking about one of the most catastrophic calamities which world faces now-and-then i.e. Earthquakes. Friends many times when a news of an earthquake flashes on the TVs you must have wondered..
- How do these earthquakes occur and how can they be detected?
- Why do they occur?
- What are the possibilities that we can prevent it or mitigate its effects?
- What is the science behind it?
-How and why do Tsunamis occur and there relationship with Earthquakes? ETC..
So people, I will clear all these doubts in my todays article…
Introduction..
Major earthquake zones..
An Earthquake is a trembling, shaking and vibrations of ground caused by passage of energy in the form of waves via breaking of rocks. The most immediate cause of most of the earthquakes is 'Faulting'(breaking and movement of rocks). The actual location of or zone below the earth surface where faulting occurs is known as 'Focus of an earthquake'. This focus lies below the surface but the point just above it is known as 'Epicenter of the earthquake'.
Detection and study of Earthquakes…(Foreshocks, Aftershocks and Swarms)
A large earthquake is preceded by a series of small but measureable tremors, called 'Foreshocks'. These foreshocks are the focus of scientific studies as they contain key to understand the larger earthquakes. Similarly, the tremors that follow the major earthquakes are known as 'Aftershocks'. These are mainly caused because of the periodic release of trapped energy within the rocks after the major wave(earthquake). In some cases the earthquake is followed by 1000s of aftershocks in a day. These aftershocks deceases as the time passes by.
So till now we have learned about two patterns of Earthquakes, the third one is a bit rare kind of pattern found i.e. 'large number of smaller earthquakes occur in a region for months or even years in a series without any major tremor'. For example, In Matsushiro, Japan more than 100,000 smaller earthquakes occurred b/w 1965-67 with zero causalities but huge damage to property in the long run. Such type of earthquake pattern are known as 'Swarms'.
Measurements of Earthquake…
The earthquake is measured in 2 ways i.e. "Intensity and Magnitude". The 'Mercalli Scale'(1-12) is used to determine the "intensity" of damage to life and property where the earthquake strikes. The 'Richter Scale' which is more common and people know about it because the media uses its value to show the havoc caused by the earthquake in an area. It calculates the amount of energy released during the earthquake. Therefore, the former has more of the societal significance and the latter is more for the geographers and scientists. An earthquake with Richter "Magnitude" value of 7.0 or greater is considered the most devastating or catastrophic one.
Earthquakes and the Plate Tectonics…
- 1st of all what is Plate Tectonics?
In the terms of a layman, Our lithosphere is broken up into several plates. Here is the list of different major and minor plates of the earth:-
Rank- Tectonic Plate - Type - Size (Square Km)
1- Pacific Plate- Major- 103,300,000
2- North American Plate- Major- 75,900,000
3- Eurasian Plate- Major - 67,800,000
4- African Plate- Major -61,300,000
5- Antarctic Plate- Major -60,900,000
6-Indo-Australian Plate- Major- 58,900,000
7-South American Plate -Major- 43,600,000
8- Somali Plate- Minor- 16,700,000
9- Nazca Plate- Minor- 15,600,000
10-Philippine Sea Plate- Minor- 5,500,000
11- Arabian Plate- Minor- 5,000,000
12- Caribbean Plate - Minor- 3,300,000
13- Cocos Plate- Minor- 2,900,000
14- Caroline Plate- Minor- 1,700,000
15- Scotia Plate- Minor- 1,600,000
16- Burma Plate - Minor- 1,100,000
17-New Hebrides Plate - Minor- 1,100,000
Source- https://www.worldatlas.com/articles/major-tectonic-plates-on-earth.html
Now, The study of general movement of lithospheric plates with their relative motions and boundary interactions is known as "Plate Tectonics".
Now, the seismic events(earthquakes) are deeply connected with plate tectonics. It fully explains why these catastrophic tremors occur. The plate boundaries are divided into:-
1- Constructive Plate Boundaries(represents diverging plates in which the plate boundaries move away from each other).
2- Destructive Plate Boundaries(where two plates converge and collide against each other and heavier place subdues below the lighter one).
3- Conservative Plate Boundaries(here two plates slide against each other without any collision).
All these are associated with earthquakes the constructive boundary has low earthquake activity(for example the "Mid-oceanic ridge" in Atlantic ocean) while the other two are associated with huge earthquakes(For example, the earthquakes of "mid-continental belt" along the Alpine-Himalayan chains are caused due to collision of Eurasian plate with African and Indian plate). This example also explains the recent earthquake activities in Nepal region, as the Indian plate is sinking under the Eurasian plate the earthquake occurs due to collision of rocks beneath the ground. The other examples are the "Pacific Ring of Fire" region which is most prone to volcanic and seismic activities in the world also follows the same mechanism. A little different pattern is followed by the "Transform fault or the Conservative fault" of the California, USA; another zone prone to heavy earthquakes.
Subduction Zone is the area where most intense and widespread earthquakes occur. These are found at the meeting point of the convergent boundaries. Luckily for us this region is much below the earth surface and the seismic waves becomes almost negligible till they reach the earth surface, these earthquakes are also known as "Plutonic Earthquakes". Therefore, we can conclude that the most intense earthquakes which bring havoc on the earth surface are found near the lithospheric and upper mantle zones and not deep into the lower mantle or core.
The concept behind the Earthquakes and its havoc…
Shadow Zones of Seismic Waves..
The discovery of seismic waves(19th century) transformed our knowledge of Geomorphology and took it to a next level. It not only provided us important data for earthquake studies but also helped us in properly figuring out the internal structure of our Earth. For example, the discovery of Asthenosphere b/w lithosphere and upper mantle was made possible only due to seismic experiments as the velocity of seismic waves decrease when it passes through it. The seismic waves are mainly of 3 types i.e. P-waves(Primary), S-waves(Secondary) and L-waves( Love and Rayleigh). The P-waves are the fastest among all. They are longitudinal waves that can traverse both solid and liquid mediums in the earth's interior. The S-waves are comparatively slower and can only pass through solid medium(therefore, helped in the discovery of Asthenosphere mentioned above). All the waves start from the similar point known as focus or epicenter but P-waves are the 1st one to reach the earth surface. The L-waves starts traveling once both the waves have passes through the planet. Now, both the L&S waves are destructive in nature and are main reasons why the earthquakes bring calamities with them. When an earthquake occurs the P-waves travel much faster and to every corner of planet but the S-waves which are destructive in nature cannot travel through liquid medium and due to outer-core they do not reach the opposite side of the world from where epicenter lies as shown in the diagram. Here we have some "seismic shadow zones of P&S waves" where the earthquake has no effect.
Tsunamis…
The Mechanism of Tsunami..
Many of my friends here have a perception that Tsunamis are a disaster which occurs because of some kind of sea or oceanic disturbances. But in reality these are strongly related to earthquakes. The Tsunamis(means Harbor Waves in Japanese) are triggered by high magnitude Earthquakes in the ocean floors or by violent volcanic eruptions. The origin of tsunami starts with an earthquake which has its focus under the sea floor and when the energy is released the waves start piling up one over the other because the depth of ocean starts decreasing and the Tsunami wave as it moves towards the shore line the wave momentum gets shattered by the shallow shores and beaches. Therefore, it strikes the land with great destruction and havoc to life and property. The Tsunamis are nothing but the "Deep-sea Earthquakes". A typical Tsunami can be 100km high or even more which travels at a speed of more than hundreds of Kilometers per hour. Normally, when we travel over the ocean via ships, there are many tsunamis that form and die due to the small intensity earthquakes going on in the divergent plate boundary area of the deep sea ridges but we ignore them like some normal high tides. The point to be noted here is that the tsunamis if remains within the ocean and stays away from shore line it will cause negligible damage where as if it moves towards the shore and strikes the landmass it is the most destructive calamity found on earth because where ever it strikes everything turns into ocean. It barely leaves any survivors or any property.
Some of the prominent examples of furious Tsunami waves in 20th century are:-
1- Aleutian Tsunami.
2- Kamchatka Tsunami.
3- Chilean Tsunami.
4- Alaskan Tsunami.
5- Japanese Tsunami.(2011- latest)
The article may sound a bit technical to the non-geography or non-science background people but still i have tried my best to explain each and everything very leniently. If u have got some good information from my blog then please let me know in the comments section and if u have any correction, suggestions or additions please feel free to leave your ideas in comments.
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This is important to address the conceivable harming impacts related with blame movement. These ongoing occasions are a reminder for all inhabitants of the Philippines to prop for conceivable seismic tremors that may strike the nation somewhere else, whenever.
WOW, Nice blog with great information about how #earthquake happens some of the things I did not really know. Keep doing this type nice post regularly.
thankyou so much for the valuable comment..
Wow is very good information, however, we can not challenge nature, but if we get such information we can reduce the accidents in the future.
Yess sure..
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An earthquake is triggered by two parts of the earth’s crust sliding past each other in a jerky, rather than a smooth way. Despite the huge impact that large earthquakes have on society, the causes of the transition from smooth to jerky movement are still poorly understood. The above information is crucial if we are to improve the models that forecast the size, location and timing of future earthquakes.
Thanks for the nice comment..
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Really good blog learnt new things
Check out my post
https://steemit.com/bitcoin/@gurumetras/what-are-etf-s-and-how-they-can-pump-bitcoin-and-crypto-market-to-the-moon
Awesome information about Earthquake
Many thing to understan to this post bro amazing post bro @devsingh
Nice blog with great information about how earthquake happpens
thankyou..
Very good information, but the thing is how accurate these signals are... As per my view as soon as we anticipate an earthquake, there should be a system that can dilute the effect...
We may not have such system now, but soon can expect .
yes the evolution of Disaster Risk Reduction is at slow pace but still lets hope that some day we can dilute the effects of earthquake and get ready for it before it strikes..
The information about the Tsunami was new to me as I used to think of them as oceanic disturbances.... Thanks pal!
welcome..!
Woah, some of the things I did not really know.
@devsingh
Very good blog.Informative blog.
I like your post brother
Thankyou bhai..
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very nice artical bro very impressive.
keep it
Thanks bhai...
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Dr Sushil Kumar From Wadia Institute of Himalayan Geology said that :-
scientists studied a total of 423 earthquakes in the year 2004 to 2013 and the conclusion came is 8 richter earthquake can occur in india .,can't say the exact site but Uttarakhand and Himalaya range is the most sensitive zone
Yes the himalayan region is the most sensitive zone because the Indian Plate is sliding down under the Eurasian plate and this region has the trough of this collision...it also explains the continous occurence of Nepal Earthquakes in this region...
i know its all science but still we can just pray to god that it can't be done
Truee..
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Good news related earthquack
Wow you really work on your blog ,one can easily through your content .em new here trying my best too
Yes i have seen ur blogs..they are nice and well written
Thanks
So nice. This is really so good article . You capture very well and explain a topic very well . Your effort is so good. Keep doing.
Thankyou ji.. ☺
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Plate tectonics plays a crucial role in quakes.
i didn't knew india have a different plate for itself, really new to this fact, plus great to see you going good through bots my man :)
Thankyou so much..bhai
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@devsingh Great and detailed article my friend. Looks like you have know very dip stuff about this. Keep sharing good stuff like this my friend.
Thankyou @flash
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Wow bro. Superb article. I have learned some new things from your post. Thanks for sharing this with us
Thankyou bro..
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Excellent, living in a sismic country as Chile I need to be very informed. Just living here since a year ago and have experienced one 6.8 earthquake, and that's nothing compared to what have happened in here! Please don't stop doing science communication.
Thankyou for the apritiation sir...
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very useful information you given thanks for sharing ...
Thankyou mam..
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Woww!! This is mind blowing! Thanks for this piece
This is very useful information thanks for shearing
Welcome bro..
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Nice research
Thankyou sir..
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Hello bro,
You seems to be scientiest
No bhai m not.. ☺ just a student👍
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Himalaya high risk zone
Thats really a good article. Thanks for letting us know about the mechanism of earthquakes.
Earthquake ka name he Bura hai.
very good information your blog is going rocket sky keep it up my friend
thankyou bro..
Nice article man....it's not possible to predict about earthquake early...bt we can do something to negotiate it's effect so that there is no much loss
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STOPThis is a very interesting article I must say.