Myanmar Earthquake: Why the Moment Magnitude Scale Replaced the Popular Richter Scale

The earthquake that struck Myanmar has claimed over 1,000 lives. The quake, which measured 7.7 on the Moment Magnitude Scale and is considered powerful, has caused significant disruption in Thailand’s capital, Bangkok. A multi-story building collapsed in the popular tourist hub, trapping over 43 workers. A state of emergency has been declared in Bangkok, with nine people reported dead and hundreds more missing.

Several countries have extended their support to Myanmar, with India launching Operation Brahma to dispatch the first tranche of 15 tonnes of humanitarian aid.

What is the Moment Magnitude Scale?

The Richter Scale, once used to measure the magnitude of earthquakes, was replaced by the Moment Magnitude Scale in the 1970s.

The Moment Magnitude Scale is now widely used because it can measure earthquakes with magnitudes over 8.

Developed by Charles F. Richter in 1934, the Richter Scale was designed for earthquakes in California and was based on a formula using the amplitude of the largest seismic wave recorded and the distance between the earthquake and the seismometer. Its ineffectiveness in recording large earthquakes and its limitation to California made it obsolete.

In contrast, the Moment Magnitude Scale (Mw) can measure earthquakes of larger magnitudes and is applicable globally. It is based on the total moment release of the earthquake, calculated as the product of the distance a fault moved and the force required to move it. Moment Magnitude estimates are similar to Richter magnitudes for smaller to medium-sized earthquakes. However, only the Moment Magnitude Scale can accurately measure earthquakes with a magnitude of 8 or above.

The Mercalli Scale

Invented by Giuseppe Mercalli in 1902, the Mercalli Scale measures the intensity of an earthquake using observations from people who experienced it and the amount of damage caused.

Modified by Harry Wood and Frank Neumann in 1931, it later became known as the Modified Mercalli Intensity Scale. Although it does not use any equipment to measure seismic activity, the scale has been valuable in understanding the extent of damage caused by major earthquakes.

Also read: First tranche of 15 tonnes of relief material from India lands in quake-hit Myanmar