Pacific Earthquake: Why is the Richter Scale outdated for measuring the intensity of this earthquake?

An earthquake was recorded this Wednesday, July 30 , off the Russian peninsula of Kamchatka. The earthquake triggered numerous tsunami alerts in several countries , including Japan, China and Peru.

The magnitude of the earthquake was 8.8 on the Richter scale , named after the American seismologist Charles Richter. This measurement, proposed in 1935, is no longer considered accurate enough.

At the time of its introduction, the principle of the Richter scale was to measure the maximum amplitude of seismic waves captured by a seismograph, often around a hundred kilometers from the epicenter of the earthquake, the place on the surface closest to the broken zone of the earth at depth.

But this method of calculation poses a real problem. While the Richter scale works well for small, shallow earthquakes, it loses precision for larger earthquakes, such as the one that occurred on the Kamchatka Peninsula in Russia.

Its limit: it saturates from a magnitude of about 7. An underestimation mainly linked to the measuring devices. This scale uses seismographs. These are devices that record seismic waves. Except that this technique has its limits, and during violent earthquakes, the power released is so great that it exceeds the measuring capacity of the instruments.

The lesser-known moment magnitude scale, abbreviated "MW" by scientists, is favored by scientists. Developed in the 1970s, this scale is much more robust than the Richter scale because it does more than just measure the amplitude of waves.

This scale calculates the total energy released by an earthquake, via three elements: the size of the fault that moved, the average displacement of the rock block along this fault and the rigidity of the rocks that broke and moved.

This magnitude is universal and applies to all types of earthquakes, whether shallow or deep, nearby or distant. If the Richter scale is still used today, except by scientists, it is for reasons of habit. The term has been in common use for years, so it is easily understood by the entire population.