Assignment On How Much We Are Prepare For Earthquake

Earthquake is not a common disaster in Bangladesh as compared to flood, cyclone, tornado, draught etc. that cause huge damages of life and property. Among all the frightening things in nature, none is as frightful as an earthquake. The whole world may literally collapses in a few short seconds. At least with cyclones, flood and fire there is some warning. But, with all our advances in science, we can not be able to predict an earthquake. The recent earthquake in Daiichi region about 250 km north east of Tokyo, followed by tsunami and nuclear meltdown, has caused extensive damage in human lives and property. With nuclear radiation leaking from the Fukushima nuclear meltdown, all of Japan now seems to be under a radioactive cloud.

Dhaka has little cause for comfort. In the event of such a major quake, the biggest problem confronting the city population will be that rescue vehicles will get trapped in the maze of narrow lanes in most parts of the city. More alarming, the city's overburdened sewer system might rupture, unleashing deadly germs in the days after the quake. In the older parts of the city, old buildings will collapse onto teeming streets, setting off panic, chaos, devastation and homelessness. Since long Dhaka, Chittagong and Sylhet have been obsessed by the threat of a big earthquake. Located in a major fault zone, experts know another quake will come one day. Worse, Dhaka city and Sylhet are located in a flood plain, and have been built up over the last 100 years over land reclaimed from swamps. Greater Chittagong is dangerously vulnerable to tremors.

Earthquake is a form of energy of wave motion, which originates in a limited region and then spreads out in all directions from the source of disturbance. It usually lasts for a few seconds to a minute. An earthquake is also known as a quake, tremor or temblor is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time. Earthquakes are measured using observations from seismometers. The moment magnitude is the most common scale on which earthquakes larger than approximately 5 are reported for the entire globe. The more numerous earthquakes smaller than magnitude 5 reported by national seismological observatories are measured mostly on the local magnitude scale, also referred to as the Richter scale. These two scales are numerically similar over their range of validity. Magnitude 3 or lower earthquakes are mostly almost imperceptible and magnitudes 7 and over potentially cause serious damage over large areas, depending on their depth. The largest earthquakes in historic times have been of magnitude slightly over 9, although there is no limit to the possible magnitude. The most recent large earthquake of magnitude 9.0 or larger was a 9.0 magnitude earthquake in Japan in 2011 (as of March 2011), and it was the largest Japanese earthquake since records began. Intensity of shaking is measured on the modified Mercalli scale. The shallower an earthquake, the more damage to structures it causes, all else being equal.