The Richter scale: On a scale of 1 to 10
Some earthquakes go unnoticed. Others cause houses to shake and a book or two, a vase, or figurine to all of the bookshelves. Still, others destroy whole cities and landscapes.
Seismologist, the scientist who study earthquakes use a scale to describe their force or intensity
A pendulum type instrument called a seismograph measures the intensity of an earthquake. The scale is known as the Richter scale. The scale was devised by Charles Richter and Beno Gutenberg. It measures the earthquake on a scale of 1 to 10 with one (1) the least and the Ten (10) the most powerful.
The base of the instrument is fixed firmly on the ground or bar rises from the base their weight hangs from the top of the shaft when shock wave moves through the earth the weight swings leaving marks on the paper. That instrument is so sensitive that it can pick up movements from earthquakes thousands of miles away.
Earthquake magnitude scale is divided into 10 in number, 1 to 10 is are the damages caused by an earthquake.
Richter intensity number
2 to 3. 4 mostly unnoticeable and occur every year 800000 time/year
- 5 to 4. 2 barely felt 30000 times/year
- 3 to 4. 8 felt by most humans 4800 times/year
- 9 to 5. 4 felt by all 1400 times/year
- 5 to 6.4 damaging 500 times/year
- 2 to 6.9 serious damage 100 times/year
- 0 7. 3 very serious dramas 15 times/year
- 4 to 8.4 catastrophic 4 times/year
- 0 +near total damage 1 times/year
The intensity depends on some factor. the intensity and the earthquake magnitude are not the same things.
The intensity can be explained by the light illumination area coverage by an electric bulb. Suppose, a 100w power bulb is lighting the area, the more the distance an object less light can be illuminated. Hence, the intensity of the earthquake is the same idea as the illuminating power with a distance people. The more the distance from the epicenter the less the intensity caused by the earthquake.
The factors responsible for the intensity increase or decrease
- Earthquake magnitude; the higher the magnitude the higher intensity to damage the localities.
- The hypocenter depth; The deeper the hypocenter the less the intensity and the less damage
- The distance from the epicenter; the more the distance the less the damage or shaking felt by the people.
Earthquake is caused by the movement of the plate tectonics and the eruption of volcanoes and some of the factors are responsible for the earthquake.
Earthquake can happen anytime, the history of the earthquake disaster is very remarkable and we can mitigate this disaster by observing the previous destructive earthquake interval.
The most severely damaged earthquake in the earth history is as below
- 1906 San Francisco earthquake magnitude 8. 3 total death is 503.
- 1906 Chile earthquake total death 20000 magnitudes 8. 6
- 1920 China earthquake 100000 magnitudes 8. 6
- 1923 Yokohama, Japan earthquake total death 200000 magnitudes 8. 3
- 1927 China earthquake 200000 magnitudes 8. 3
- 1934 Nepal earthquake 10700 people death magnitude 8. 4
- 1939 Chilean earthquake 28000 people death magnitude 8. 3
- 1946 Honshu, Japan earthquake 2000 death magnitude 8. 3
- 1964 Alaska earthquake 131 magnitudes 8. 4
- 1976 China earthquake total date 240 000
How Does an earthquake occur?
An earthquake occurs at the plate boundary. The forces push against the blocks of crust on both sides of a fault friction prevents the block from sliding smoothly past each other then, forces push over a period of thousands of years bend and twist the rocks out of the fault, at last, the force becomes so great that the Rocks suddenly break loose the slide past each other causing an earthquake.
Most earthquakes like 80% as well as volcanic eruptions the Ring of Fire is a narrow bend land on the edge of the Pacific Plate. About 900 earthquakes occur every hour most of these are very minor and probably cannot be felt by humans. The earth most earthquake-prone area is Japan Chili and the country located around the Ring of Fire ocean. Scientist discovered a very sensitive earthquake wave detective device and still, the scientist is walking on that. Like other countries, Bangladesh is one of the most earthquake risk and vulnerable country in the world. If an earthquake occurs at Dhaka City approximately 70000 highest building will collapse and the destruction is miserably caused by the 7. 0 magnitude earthquake at or near the Dhaka City. So, this is the high time to educate the people and make awareness among the people what to construct the new building with the earthquake resilience building and retrofit the existing old building.