Each of us has heard about the dangers that an earthquake poses to the life and health of people. Fortunately, modern seismic instruments are able to predict a possible earthquake, and the authorities have the opportunity to notify the population of an imminent threat, and in some cases to evacuate it from the zone of expected disaster. But how to understand how strong the tremors will be, and what harm they will cause? After all, an earthquake has a hypocenter (a focus in the thickness of the earth's crust), an epicenter (a point on the surface of the earth, under which the hypocenter is located), in addition, the composition of the soil and even the seismic stability of buildings affect the destructiveness of an earthquake. In some cases, tremors can be felt weaker, and in some - stronger. Now, to characterize the force of soil vibrations, the international Richter scale has been adopted, and the magnitude has been recognized as the unit for measuring the strength of seismic shocks.
In fairness, it should be noted that Richter does not own the laurels of the development of an international scale of earthquake intensity. It was developed by the Italian scientist Mercalli, and until the 30s of the XX century it was called “the Mercalli scale”. It consisted of 12 points (most likely, by analogy with the Beaufort 12-point scale evaluating wind speed and strength ). According to Mercalli, the weakest shock (with an intensity of 1 point) is felt only by single people who are sensitive to tremors of the soil, and the strongest (12 points) leads to the complete destruction of buildings and even changes in the landscape. On the Mercalli scale, earthquakes above 6 were considered strong, and below - weak. But the Mercalli scale was not used by all countries: for example, in Japan it was customary to measure earthquakes by a 7-point school, and in some countries they used the 10-point scale of Rossi and Forel. With the advent of globalization, it became necessary to develop an international scale so that seismographs around the world could clearly and clearly explain the degree of impending threat to their neighbors. Such a scale, which has become generally accepted throughout the world, is the Richter scale.
At first, the Japanese scientist T. Valati suggested introducing a logarithmic magnitude scale (in Latin magnitudeo - size, magnitude) to measure the strength of earthquakes, which take into account the total energy of the earth’s vibrations. The American seismograph C. Richter proposed to use the decimal logarithm of the largest amplitude of soil vibrations (which is calculated directly proportional to the ratio of the needle deflection on the seismograph to correct the distance from the epicenter) to measure the magnitude of earthquakes. This scientific explanation does not allow, of course, a simple layman to correctly judge how much the Richter scale will help him to determine the risks in the event of an earthquake.
In Russia, earthquakes that record only seismic instruments, but not people, are estimated at 1 point. If utensils rattle in the cabinet, and chandeliers sway on the upper floors of tall buildings , then the earthquake is estimated at 4 points. Of course, these are only observations of the territory, which can be removed from the epicenter for many hundreds of kilometers, and the Richter scale with these points coincides extremely rarely. But nevertheless, such a Russian characterization of the strength of the shocks has the practical benefit that it allows you to work out the correct action in an earthquake. So, with a shock intensity of 6 points, it is necessary to leave the room (especially the panel and high-rise), and if this is impossible, stay away from windows and closer to the internal walls of the building.
By the way, despite the fact that Richter broke his scale by 12 points, the strongest earthquake, which was observed using instruments, never exceeded the magnitude of 9 points. It was a devastating earthquake that occurred in northeast India on August 15, 1950. It brought the death of one and a half thousand people, but after it new faults and failures formed on the earth, and the Brahmaputra river changed its course.