Latest news with #CharlesRichter
LeMonde
30-07-2025
- Science
- LeMonde
How is the strength of an earthquake measured?
How do we measure the strength of earthquakes like the one that occurred off the coast of Russia's Kamchatka Peninsula on Tuesday, July 29? The earthquake was recorded as having a magnitude of 8.8, which made it the most powerful earthquake in the region in nearly 73 years. To understand this phenomenon, two distinct concepts exist, which complement each other: Magnitude measures the strength of an earthquake in terms of the energy it releases, allowing different earthquakes to be compared with each other. Intensity quantifies the effects an earthquake has at the Earth's surface level, including its impacts on buildings and infrastructure. Magnitude Magnitude is a dimensionless quantity specific to each earthquake, unlike intensity, which, for the same earthquake, varies depending on the measured location. An earthquake occurs when a rupture occurs between two tectonic plates: the two blocks slide past each other, moving along the fault line. The energy thus released spreads in the form of seismic waves, which can travel across hundreds of kilometers, moving at speeds of several kilometers per second before eventually fading away. In 1935, the American seismologist Charles Richter (1900-1985), who studied earthquakes in California, developed an equation based on the amplitude of seismograph recordings and using a logarithmic scale to quantify the scale of earthquakes. This became the well-known Richter scale, which has not been in use since the 1960s. "Because his approach was rather imprecise, seismologists gradually defined a magnitude scale based on the physical quantity of energy released by an earthquake, called the 'seismic moment,'" said Jean-Paul Montagner, emeritus professor of seismology at the Paris-Cité University and the Institute of Earth Physics of Paris (IPGP). The seismic moment is "the product of the area that ruptured, the displacement between the two blocks, and a final parameter that depends on the physical properties" of the location. The seismic moment, noted as M 0, is expressed in newton-meters (Nm). To ensure consistency between the old Richter scale and the new method, which is based on measurable physical quantities, "the seismic moment was calibrated to match the Richter magnitude so that, for typical earthquakes, there is no difference between the moment magnitude and the Richter magnitude." In practice, there is a formula that converts the seismic moment (M 0) to the "moment magnitude" (M w, which is a dimensionless quantity). "For example, a magnitude 7 earthquake corresponds to a rupture of 50 kilometers, with a displacement of about 1 meter, over a duration of roughly 15 seconds," said Montagner. This correspondence works well up to magnitude 7, but "not at all for the large earthquakes." On this logarithmic scale, the amount of energy released increases by a factor of 30 with each step up the scale, for example, from 6 to 7. Intensity: A measure of the earthquake's effects Unlike magnitude, which is a physical quantity that characterizes an earthquake and can be measured instantly, an earthquake's intensity corresponds to the effects it produces at the surface level in a given location: the same earthquake can, therefore, have several different intensities depending on the area measured. Intensity is, notably, measured on the Mercalli scale, which records an earthquake's effects on buildings and infrastructure. Partner service Learn French with Gymglish Thanks to a daily lesson, an original story and a personalized correction, in 15 minutes per day. This scale spans from levels I to XII, with each step describing the earthquake's perceived and material consequences in a given region. The first level corresponds to tremors that are not felt, or barely felt, while level XII, the highest, means that almost all of the infrastructure in an area is damaged or destroyed. For example, the 1960 Agadir earthquake was a magnitude 5.9 event, weaker than the earthquake that struck Morocco overnight on September 8, 2023 (magnitude 6.8), but it caused considerable damage: 12,000 deaths, 25,000 injuries and the destruction of the entire city. This discrepancy is explained by the fact that the Agadir earthquake's epicenter was located directly beneath the city, at a depth of just 10 kilometers, whereas the more recent earthquake's epicenter was located farther from densely populated areas (70 kilometers away from Marrakech) and at a greater depth (18.5 kilometers underground). The intensity scale, therefore, not only depends on the earthquake's magnitude and the depth of its epicenter, but also on the local geological structure. According to the United States Geological Survey (USGS), Tuesday's earthquake reached an intensity of VIII at its epicenter, which was located off the coast of Russia's Kamchatka Peninsula. Waves rising between 1 and 3 meters above tide level are likely to sweep across the entire Pacific region, from Japan to Costa Rica, and they could strike many archipelagos, such as French Polynesia, Guam, or Hawaii.
Yahoo
26-04-2025
- Science
- Yahoo
Who is Charles Richter? Meet the Cincinnati native, Richter Scale inventor
April 26, 2025, marks the 125th birthday of Cincinnati native Charles Richter, the inventor of the Richter Scale. The seismologist, aka Earth scientist, invented the critical measurement tool to help better understand the magnitude of earthquakes. Who is Charles Richter? How does the Richter Scale work? Did Richter grow up in Ohio? Here's what to know. Invented by Richter and his colleague Beno Gutenberg, the Richter Scale is a magnitude scale used to measure the intensity of earthquakes. The scale helps assign a numerical value to quantify the amount of seismic energy (the energy of waves that travel through the Earth) released by an earthquake. It is measured on a scale from under one to 10. Here is what the scale looks like: < 2.0: Micro (Micro earthquakes, not felt) 2.0-2.9: Minor (Generally not felt, but recorded) 3.0-3.9: Minor (Often felt, but rarely causes damage) 4.0-4.9: Light (Noticeable shaking of indoor items, rattling noises. Significant damage is unlikely) 5.0-5.9: Moderate (Can cause significant damage to poorly constructed buildings over small regions. At most slight damage to well-designed buildings) 6.0-6.9: Strong (Can be destructive in areas up to about 100 miles across in populated areas) 7.0-7.9: Major (Can cause severe damage over larger areas) 8.0-8.9: Great (Can cause severe damage in areas several hundred miles across) 9.0-9.9: Great (Devastating in areas several thousand miles across) 10.0+: Epic (Earthquakes over 10 have never been recorded) Ohio was hit with an earthquake on April 22 that registered as a 3.1 magnitude on the Richter Scale. Like the Heimlich maneuver or the Cleveland Browns, the invention is probably more famous than the inventor. Charles F. Richter was born April 26, 1900, near Cincinnati in Overpeck, a section of St. Clair Township in Butler County. He later moved to California with his family and studied earthquakes at the California Institute of Technology, earning a Ph.D. in theoretical physics while working at the Seismology Institute. In 1935, he published a paper that described his earthquake magnitude scale, widely known as the Richter Scale, making Richter a household name. The annual Richter Day is celebrated on his birthday, April 26, across the country and at his historical marker in Trenton, Ohio. Richter was 85 when he died in Pasadena, California, on Sept. 30, 1985. This article originally appeared on Cincinnati Enquirer: What is the Richter Scale? Meet the Ohio native who invented it
