Today morning while I was deep asleep my phone rang I woke up and answered the call it was one of my buddy asking me “Did you hear the news?”. I asked “What news?”.My Friend told me “There was an earthquake which affected the coastal areas of Tamilnadu severely. As you are from Pondicherry call up your parents and check with them whether they are safe or not”.
Initially it doesn’t strike me hard as I thought it will be one of the minor earthquakes that hit Tamilnadu a month ago. So I switched on the TV started watching BBC News. After watching the news I realized the effect of the catastrophic natural disaster event that took place. I called my parents and spoke with them and found them they are safe and sound.
After finished that call I started thinking about the events that happened. Why this happened?. Why 1000’s of lives lost in this natural disaster?, What should have been done to prevent this massive loss of human life?.
One of the main reasons for this tragedy is this Indian ocean region has never experienced a tsunami wave natural disaster as it is not prone to that. So the basic infrastructure to detect this “tsunami wave” formation is not in place in this region to detect and issue early warnings to the people live in the coastal region of the countries affected.
The other main reason is people in India and other affected countries are not educated in the tsunami wave as they are in cyclone and typhoons and because of this the tsunami wave completely caught them off-guard, which result in massive loss of the human life.
The other thing that confuses me is that the scientists are saying that the Indian ocean fault line is active for the past 18 months and why didn’t they predicated this with all the technologies available to them. Needless to say the power of nature is more than anything else in this world and this proves that.
So I thought of providing some information on Tsunami wave, so that people know more about this thing and take correct precautionary measures in case if they need it in future. The following info about tsunami is taken from the website http://www.geophys.washington.edu/tsunami/intro.html. It has lot of links to the reference materials on Tsunami.
What is Tsunami?
A tsunami (pronounced tsoo-nah-mee) is a wave train, or series of waves, generated in a body of water by an impulsive disturbance that vertically displaces the water column. Earthquakes, landslides, volcanic eruptions, explosions, and even the impact of cosmic bodies, such as meteorites, can generate tsunamis. Tsunamis can savagely attack coastlines, causing devastating property damage and loss of life.
How do tsunamis differ from other water waves?
Tsunamis are unlike wind-generated waves, which many of us may have observed on a local lake or at a coastal beach, in that they are characterized as shallow-water waves, with long periods and wave lengths. The wind-generated swell one sees at a California beach, for example, spawned by a storm out in the Pacific and rhythmically rolling in, one wave after another, might have a period of about 10 seconds and a wave length of 150 m. A tsunami, on the other hand, can have a wavelength in excess of 100 km and period on the order of one hour.
As a result of their long wave lengths, tsunamis behave as shallow-water waves. A wave becomes a shallow-water wave when the ratio between the water depth and its wave length gets very small. Shallow-water waves move at a speed that is equal to the square root of the product of the acceleration of gravity (9.8 m/s/s) and the water depth - let's see what this implies: In the Pacific Ocean, where the typical water depth is about 4000 m, a tsunami travels at about 200 m/s, or over 700 km/hr. Because the rate at which a wave loses its energy is inversely related to its wave length, tsunamis not only propagate at high speeds, they can also travel great, transoceanic distances with limited energy losses.
How do earthquakes generate tsunamis?
Tsunamis can be generated when the sea floor abruptly deforms and vertically displaces the overlying water. Tectonic earthquakes are a particular kind of earthquake that are associated with the earth's crustal deformation; when these earthquakes occur beneath the sea, the water above the deformed area is displaced from its equilibrium position. Waves are formed as the displaced water mass, which acts under the influence of gravity, attempts to regain its equilibrium. When large areas of the sea floor elevate or subside, a tsunami can be created.
Large vertical movements of the earth's crust can occur at plate boundaries. Plates interact along these boundaries called faults. Around the margins of the Pacific Ocean, for example, denser oceanic plates slip under continental plates in a process known as subduction. Subduction earthquakes are particularly effective in generating tsunamis.
What happens to a tsunami as it approaches land?
As a tsunami leaves the deep water of the open ocean and travels into the shallower water near the coast, it transforms. If you read the "How do tsunamis differ from other water waves?" section, you discovered that a tsunami travels at a speed that is related to the water depth - hence, as the water depth decreases, the tsunami slows. The tsunami's energy flux, which is dependent on both its wave speed and wave height, remains nearly constant. Consequently, as the tsunami's speed diminishes as it travels into shallower water, its height grows. Because of this shoaling effect, a tsunami, imperceptible at sea, may grow to be several meters or more in height near the coast. When it finally reaches the coast, a tsunami may appear as a rapidly rising or falling tide, a series of breaking waves, or even a bore.
What happens when a tsunami encounters land?
As a tsunami approaches shore, we've learned in the "What happens to a tsunami as it approaches land?" section that it begins to slow and grow in height. Just like other water waves, tsunamis begin to lose energy as they rush onshore - part of the wave energy is reflected offshore, while the shoreward-propagating wave energy is dissipated through bottom friction and turbulence. Despite these losses, tsunamis still reach the coast with tremendous amounts of energy. Tsunamis have great erosional potential, stripping beaches of sand that may have taken years to accumulate and undermining trees and other coastal vegetation. Capable of inundating, or flooding, hundreds of meters inland past the typical high-water level, the fast-moving water associated with the inundating tsunami can crush homes and other coastal structures. Tsunamis may reach a maximum vertical height onshore above sea level, often called a runup height, of 10, 20, and even 30 meters
Be familiar with the tsunami warning signs.
- Because tsunamis can be caused by an underwater disturbance or an earthquake, people living along the coast should consider an earthquake or a sizable ground rumbling as a warning signal.
- A noticeable rapid rise or fall in coastal waters is also a sign that a tsunami is approaching.
I hope to avoid further tragedies like this the countries in the Indian ocean region will put together a plan to build an early warning system ASAP to detect and warn people in the region about this kind of natural disasters. At the same time I hope they will do a better job of educating the people about this kind of natural disasters and what they have to do when they encounter this kind of things
My Heartfelt prayer goes to the families and friends of all the people who lost their lives in this natural disaster. This blog is dedicated to the people who lost their lives in this tragedy
Jai Hind.