But even with this, earthquakes are transmitted in different ways depending on the ground. To set standards, Richter chose a particular model of seismograph, the Wood-Anderson torsion, and a concrete distance to the epicentre as a reference, 100 kilometres. Logically, the oscillations of the pen were also greater or smaller according to the proximity of the seismographic station to the epicentre. The various models responded differently to the same tremor and could only register nearby movements. But it has obvious limitations, since it was based on the primitive seismographs of the time. The Richter and Gutenberg scale, developed in 1935 and originally called the Local Magnitude scale (M L), served for decades as the standard for rating the power of earthquakes. For Richter, the logarithmic scales were “a device of the devil,” but it worked-the system allowed all earthquakes to be placed on the same scale, bearing in mind that an increase of one integer meant multiplying the violence of the earthquake tenfold. Help came from his colleague and mentor at Caltech, Beno Gutenberg, who proposed converting the linear table into a base-10 logarithmic scale. When comparing the different values to the reference point, the difference in the proportions between strong and weak earthquakes was so vast that it was impracticable to place them on the same linear scale. Inspired by the scale of magnitudes used by astronomers to determine the apparent brightness of stars from Earth, Richter set a minimum base value to which the maximum amplitudes of each earthquake would refer, thus giving a value of magnitude to each quake. This was based on a 1928 work by the Japanese seismologist Kiyoo Wadati, who had represented the oscillations in relation to the distance to the epicentre (the point of the surface directly above the focus of the earthquake). Richter thought of using the amplitude values of seismic movements recorded by the seismograph pen on paper. It was useful as a crude approach, but subjective and of little scientific value. According to the USGS, people based in those regions lived in structures that were largely vulnerable, though some were earthquake resistant.In the 1930s, American seismologist Charles Francis Richter (26 April 1900 – 30 September 1985) of the California Institute of Technology (Caltech) set out to solve an unsettled question in the study of earthquakes-how to compare them according to a standardized method? The Mercalli intensity scale, used at that time, was governed by the levels of destruction observed after an earthquake. It shook the Kashmir region in 2005, sending rugged terrain from the Himalayas down the valley, and leaving more than 80,000 dead.Īt least 250 people were killed in a 6.2 magnitude earthquake across the Italian regions of Umbria, Lazio, and Marche in 2016 - an area that sits above the continental plates. The deadliest earthquake in Pakistan lasted 60 seconds - double the average length of a typical quake. The quake was detected only 6 miles beneath the earth’s surface, therefore causing irreparable damage near the quake’s epicenter in Sichuan province. In 2008, Indian and Eurasian tectonic plates along the Longmenshan fault line in southwestern China collided and moved the earth in two sections. Some of the most dangerous earthquakes have resulted in thousands of casualties and mass displacement, but experts say that the scale of the damage is usually determined by the depth of tremors, how buildings near epicenters are designed, and population density. Smaller earthquakes, like those with a magnitude of 2, happen hundreds of times each day. The more intense the earthquake, the more uncommon it is.
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