Surely more than once they have heard about the intensity of earthquakes and how important they are to be able to assess the damage they cause. To do this, use the Richter scale. It is the scale that encompasses all the intensities of earthquakes and is used universally.
In this article we are going to tell you everything you need to know about the Richter scale, who was its creator, characteristics and importance.
What is the Richter scale?
The seismic Richter scale, commonly known as the Richter scale or the ML scale, is a logarithmic scale that measures the amount of energy released in the earth's crust during an earthquake or earthquake, named after American seismologist Charles M. Francis Richter (1900-1985), who was its inventor together with the German Beno Gutenberg (1889-1960).
The Richter scale is used around the world to measure the strength of earthquakes. with magnitudes ranging from 2,0 to 6,9, occurring between 0 and 400 kilometers deep.
When the value of the earthquake is 7.0 points or greater, the Richter method is no longer used, but the seismic scale of moment magnitude (Mw) is used, which is more precise for extreme records, and was proposed by Thomas Hanks and Hiroo Kanamori in 1979. Therefore, there can be no earthquakes greater than 6,9 on the Richter scale.
This scale is thought to be a way to distinguish small earthquakes from everyday earthquakes and large earthquakes from sporadic earthquakes. For this, the Wood-Anderson torsional seismometer was used and a preliminary evaluation was carried out in a specific area of southern California (USA).
Despite its proven usefulness and popularity, the Richter scale has the disadvantage of being difficult to relate to the physical properties of the seismic source. For magnitudes close to 8,3-8,5, it presents a saturation effect, which makes it imprecise. Also, limited by the possibility of inventing its seismograph, it requires expansion and other additional scales.
This is why its use was common before the earthquakes with a seismic intensity of 6,9 points, since other matching scales have been used since then, but with greater precision and utility. However, this is unknown and often falsely reported by the media.
Richter scale formula
The scale proposed by Richter uses logarithms, replicating the logic of astronomical magnitude scales. His calculation formula is as follows:
M = logA + 3log(8Δt) – 2,92 = log10 [(A.Δt3)/(1,62)]
Where:
- M = earthquake of arbitrary but constant magnitude releasing the same energy
- A = seismic wave amplitude recorded by seismic waves, in millimeters
- t = time in seconds from the start of the primary (P) to the secondary (S) wave.
Features
The scale is between degrees 1.5 to 12. In fact, before the second level, earthquakes are not usually talked about, because they are micro-earthquakes that humans cannot perceive. Register up to 8.000 movements per day. Earthquakes above magnitude 4 are considered small, usually recorded on seismographs, but go unnoticed and rarely cause damage. Level 4 is not twice as much as level 2, but 100 times more.
The most damage can occur at level 4. Earthquakes are considered moderate earthquakes starting at magnitude 5, with around 800 such earthquakes each year. Earthquakes of this type generally cause damage to poorly constructed buildings and some isolated damage to larger structures.
Level 6 is considered powerful and can cause damage in an area 160 kilometers in diameter. To understand the magnitude of this magnitude, it is enough to remember the magnitude 6,9 earthquake that devastated Italy, which killed 294 people and left 50.000 people homeless. Level 4 is not twice as much as level 2, but 100 times more.
This scale is "open", so there is no theoretical maximum limit, beyond the limit given by the total energy accumulated in each plate, which would be a limit on Earth, not a limit on the scale. A Roman numeral rating system may be used. This is proportional so that intensity IV is twice that of II.
scale degrees
- Grade I: Very few people feel the shock of the first order under particularly favorable conditions.
- Grade II: Level 2 vibrations are only felt by a few people at rest, especially on the upper floors of buildings. Suspended objects can swing.
- Grado III: The magnitude 3 tremor was clearly felt indoors, especially on the upper floors of buildings, and many people did not associate it with the earthquake. Parked motorized vehicles may move slightly. Vibrations, such as those caused by the passage of heavy vehicles. Estimated duration.
- Grade IV: During the day, many people feel it indoors and few outdoors. Vibration of cutlery, windows and glass doors; creaking walls. It feels like a heavy vehicle hitting a building and parked motorized vehicles swaying noticeably.
- XNUMXth grade: Almost everyone feels it. Many wake up with broken pottery, glass, etc., very few crushes and cracks, falling unstable objects. Disturbances are observed in trees, power poles and other tall objects.
- Grade VI: many frightened people run outside. Some heavy furniture changes places; there are some fallen or damaged chimneys. Minor injuries.
- Grade VII: People flee abroad. Minor damage to well designed and constructed buildings. Minor damage to ordinary well-built structures; considerable damage to weak or badly situated people; breakage of some chimneys.
- Grade VIII: Minor damage to particularly well-designed structures; considerable in ordinary buildings with partial collapse; falling from chimneys, product falls in factory warehouses, pillars, monuments and walls. Heavy furniture tips over. Small amounts of sand and mud sprayed. Changes in the level of well water. People who drive motor vehicles lose control.
- Grade IX: Severe damage to well designed structures; extensive damage to solid buildings, partial collapse. Buildings fall from their foundations. The ground is clearly cracked. Explosion of underground pipes.
- Grade X- Destroy some well-built wooden structures; most of the armored and masonry structures are completely destroyed along with the foundations; cracks in the ground. The rails twist. There are quite a few landslides on the banks of the rivers and steep slopes. The river water invades its banks.
- Grade XI: destroyed bridges. Cracks in the ground. Settlement and slides on soft soil foundations. Big turn of the rails.
- XNUMXth grade: total destruction. Visible ripples on the ground. Level elevation disturbances (rivers, lakes and seas). Objects thrown in the air upwards.
I hope that with this information you can learn more about the Richter scale and its characteristics.