Richter

We still often hear about “an earthquake measuring so many degrees on the Richter scale” in the news or when reading about an earthquake. This is incorrect for one or more reasons.. To understand why, we must delve into what the Richter scale is, when it is used and, above all, when it is not. What is the Richter scale The Richter scale is a scale used to measure the magnitude of an earthquake. According to defines the National Geological Institute (IGN), the magnitude of the earthquake is “a measure of the energy released by an earthquake and is determined from the signal recorded in a seismogram.” There are several magnitude scales for earthquakes, since earthquake waves can vary in their characteristics. Among them, the best known to the public is that of local Richter magnitudeor simply ML for “local magnitude.” Local, in this answer, refers to the fact that this scale is used to measure earthquakes that have been captured from close range. Specifically, it is used for those captured at less than 600 kilometers, according to the IGN. Who was Charles Francis Richter The name “Richter scale” refers to the American seismologist Charles Francis Richter. Born in 1900 in the state of Ohio, this American physicist and seismologist would leave as a legacy the first scale of its kind, a systematic way of measuring the strength of an earthquake. The seismographs They had been used for decades as a way to measure earthquakes, but it was in 1935 when Richter brought up the idea to establish a magnitude with which to measure these events. Starting from this idea, Richter would have the help of the German-American seismologist Beno Gutenberg to put it into practice. Charles F. Richter died in 1985 in the US state of California. The scale And how are the magnitudes calculated? The scale It is based on the logarithm of the amplitude of seismic waves. That is, the magnitude of an earthquake is proportional (logarithmically) to the height reached by the waves drawn by seismographs. The calculation must be “corrected” to, among other things, adjust it to a “type seismograph”. What we measure with the Richter scale, and what we don’t We pointed out before that the Richter scale, or ML, is used locally. And for seismologists, “local” refers to earthquakes originating no more than 600 kilometers of the seismograph that must measure it. But not all earthquakes that occur in “local” contexts are the same, so they are not all measured using this scale. The use of the ML scale is also limited with respect to the magnitude earthquake: it is only used to measure earthquakes of small or moderate magnitude (magnitudes between 2 and 6.5). The objective of measure the magnitude of an earthquake It is to get an idea of ​​its strength. To do this, scales such as the Richter scale use the waves generated by the earthquake, as captured by seismographs. The problem, as the experts realized, is that waves in large earthquakes do not always allow extrapolation of the magnitude using the Richter scale: sometimes the magnitude thus calculated overestimates the strength of the earthquake and sometimes the opposite occurs. Come on, although there are two earthquakes less than 600 kilometers from where they have been recorded with a seismograph, this scale is not always accurate for both. Sometimes this scale is fine, but other times the actual strength of the earthquake is higher or lower than what it measures. To compensate for the shortcomings of ML, geologists created different scalessuch as body wave magnitude (Mb) or surface wave magnitude (Ms). Each of these scales works in its own context, but the problem arises because none are universally applicable. To solve this, we then had to create the Mw scale, which we will talk about below. Magnitude and intensity To avoid confusion, we have to have clear concepts such as earthquake intensity. The intensity of an earthquake has its own scalebut it does not measure the strength of the earthquake but its impacts. The European Macroseismic Scale graduates in a scale from I to XII earthquakes based on the damage caused. The ML scale and the Mw scale As explained by the United States Geological Survey (USGS), the limitations of the existing scales implied the need to create a new scale that would serve to cover these limitations. This is how the seismographic moment magnitude scale, or Mw, would have been born. This scale, although it is adjusted to “coincid” with the local magnitude scale where the latter is applicable, is based on a very different principle. Where the Richter scale converts recorded seismic waves into a magnitude, the Mw scale uses geological properties of tectonic movement. To do this, we start from the measurement of seismic momentthe product of the area traveled by the fault that has moved, the distance traveled in this displacement, and a measure of the stiffness of the rock that makes up the fault. This measurement is transformed through a logarithmic formula to obtain the magnitude of the moment (Mw) of the earthquake. Here, we can say that this scale is the closest thing to a universalsince it was created to be used in all earthquakes, even those with a magnitude greater than that supported by the Richter. Thus, it is currently the most used today to measure earthquakes, although in the news we will continue to hear about Richter’s. By saying degrees when they are magnitudes Other common mistake When talking about earthquakes and their scale, we talk about degrees, for example if we said “an earthquake measuring 5.5 on the Richter scale.” The origin of this common error is not clear, but some attribute it to the fact that there are scales (such as the one used to study the intensity of earthquakes) in which degrees are used. In Xataka | 0.2 magnitude points and 70 years of disaster preparedness: what differentiates the deadly tsunami of 1952 from the one that occurred … Read more