Earthquake Magnitude vs Intensity
Earthquake Magnitude vs Intensity
Earthquake Magnitude and Intensity are two dimensions of the earthquake. Earthquakes are natural disasters that take place in different parts of the world causing much devastation and loss of property and lives. These earthquakes are a result of movement of tectonic plates beneath the earth’s crust. Because of the motion of these plates, breaking or bending of earth takes place that causes an upheaval that is felt in the form of trembling of earth. Earthquakes are unpredictable and occur without any warning. Seismologists study of their frequency of occurrence at different places and calculate the probability of their taking place in future. Magnitude and intensity are two characteristics of earthquakes that tell a lot about them. Many people are often confused regarding the difference between the two. This article intends to find the difference between earthquake magnitude and intensity so that people can have a better understanding of earthquakes. Seismologists, when talking about earthquakes, make use of magnitude and intensity quite often hence it makes sense to understand what they mean by these two words.
Magnitude of an earthquake is a value that tells a reader the amount of seismic energy released by it. It is a single value and is not dependent upon distance from the epicenter of the earthquake. It is calculated by measuring the amplitude of the seismic waves (through a seismometer). The scale which is used to measure magnitude of an earthquake is called Richter magnitude scale. This is a logarithmic scale and assigns values from 1-10 to the magnitude of any earthquake. So it is obvious that the devastation power of an earthquake is directly proportional to the value assigned on the Richter scale. As it is logarithmic, an earthquake of value 5.0 has shaking amplitude ten times greater than an earthquake measuring 4.0 on the scale. Richter magnitude scale has today given way to moment magnitude scale that yields similar but more accurate results than Richter scale.
Intensity of an earthquake is its property that indicates the effects and damage caused by it. Of course intensity varies as we go farther from the epicenter of the earthquake. It can be determined by taking stock of the devastation in the areas affected by the earthquake. The scale used to describe the intensity of earthquakes is called Mercalli, as it was developed by Giuseppe Mercalli in 1902. Today upgraded versions of this scale are used at any place to talk about the intensity of the earthquake at that place.
Difference between Earthquake Magnitude and Intensity
Thus it is clear that magnitude is a fixed value independent of distance from the epicenter of the earthquake, whereas intensity varies and is measured differently at different places depending upon its distance from the epicenter. Intensity decreases as we move farther from the epicenter. Assigning a value of intensity is dependent upon the perception of the local populace, and their felt responses are taken into consideration when intensity is calculated. On the other hand, magnitude is an independent value that measure seismic energy released and is always fixed.
The two recent earthquakes happened in 2011 were in New Zealand and Japan. The magnitude of the earthquake in Japan was 8.9 and the magnitude of the earthquake in New Zealand was 6.3. But the intensity of the earthquake was more in New Zealand than in Japan. This is because the Japan earthquake was centered in the Pacific Ocean 80 miles away from the closest Japanese city, Sendai while the epicenter of the New Zealand earthquake was only six miles from the center of Christchurch, which was devastated by the earthquake. The vast devastation in Japanese city Sendai was due to the subsequent Tsunami that was created by the monstrous earthquake.