Mercalli Scale: Understanding Earthquake Intensity Measurement
Planet Earth is never completely at rest, whether through the gentle whispers of the wind or the fearsome earthquakes that shake its core. In the midst of this scenario, a name that echoes throughout history is presented: the Mercalli Scale. It is a tool used to measure the intensity of earthquakes, based on witness reports and observed damage, not just geophysical data.
Created in the 19th century by the Italian volcanologist Giuseppe Mercalli, this scale has gained its place as an indication of how powerful an earthquake can be in human terms. It is based on people’s experience, the damage caused to structures and changes observed in the natural environment, adding practical and tangible meaning to such a devastating phenomenon.
While the Mercalli Scale may seem like just a technical index to scholars, it represents much more. It is a way of humanizing natural disasters, of measuring their impact not only by magnitude, but also by the human eye. Thus, she invites us to explore a unique and in-depth perspective on earthquakes, understanding them beyond simple earthquakes.
What is the Mercalli Scale
The Mercalli Scale is a seismological scale used to measure the intensity of an earthquake. Unlike other scales that measure the energy released by an earthquake (such as the Richter Scale), the Mercalli Scale focuses on the impact felt by humans and the destruction caused to infrastructure and the natural landscape.
It was developed in the 19th century by the Italian volcanologist Giuseppe Mercalli and was modified several times until it reached the version used today, known as the Modified Mercalli Scale (MM). This scale ranges from I (no sense) to XII (total damage), with detailed descriptions for each level of the type of damage and observed effects.
Therefore, the Mercalli Scale is an essential tool for seismologists and geologists around the world, as it provides a practical and humanized view of the effects of an earthquake. Through it, we can better understand not only the strength of an earthquake, but also its real impact on people, buildings and nature.
What is the difference between the Richter and Mercalli scale?
The Mercalli and Richter scales are two of the most commonly used tools by scientists to measure earthquakes, but each has a different approach and focus. The Richter Scale measures the energy released by the earthquake, while the Mercalli Scale seeks to quantify human perception and the damage caused by the event. Both scales are fundamental for the study of seismology, although they have important differences.
Energy Measurement vs. Impact Measurement:
The Richter Scale measures the magnitude of an earthquake, i.e. the total amount of energy it releases. On the other hand, the Mercalli Scale measures the intensity of an earthquake, that is, the impact perceived by humans and the damage caused to structures.
Numerical Values:
The Richter Scale is a logarithmic scale that theoretically has no upper limit. The Mercalli Scale is an arbitrary scale ranging from I (almost imperceptible) to XII (total damage).
Distance Sensitivity:
The magnitude measured by the Richter Scale does not change with distance from the epicenter, while the intensity measured by the Mercalli Scale decreases as you move away from the epicenter of the earthquake.
Equipment Use:
The Richter Scale is based on data collected by seismographs, which are devices that measure seismic waves. The Mercalli Scale, on the other hand, relies largely on eyewitness reports and visual inspection of damage done.
Therefore, although both scales are used to measure earthquakes, they offer different and complementary perspectives on the nature and impact of these geological events.
What does each Mercalli and Richter Scale measure?
The Mercalli Scale and the Richter Scale are two commonly used methods of measuring earthquakes, but they each focus on different aspects of an earthquake.
Mercalli scale:
The Mercalli Scale assesses the intensity of an earthquake based on its observed effects. It considers the impact on people, buildings and the earth’s surface. Its modern version, known as the Modified Mercalli Scale (MM), ranges from I (no sense) to XII (total damage).
Levels I through III are usually only detected by instruments or very attentive observers. From level IV onwards, most people begin to notice agitation. Levels VI to VIII deal increasing damage to buildings and other structures. Levels IX through XII describe damage from very severe to catastrophic, with intensity XII indicating complete destruction of all infrastructure.
Richter scale:
The Richter Scale, on the other hand, measures the magnitude of an earthquake, that is, the amount of energy it releases. It was created in 1935 by seismologist Charles F. Richter and is a logarithmic scale, which means that a magnitude 5 earthquake releases 10 times more energy than a magnitude 4 one.
The Richter Scale does not have an upper limit, which means that it can theoretically measure earthquakes of any magnitude. However, in practical terms, earthquakes with a magnitude greater than 9 on the Richter Scale are rarely recorded, due to the extraordinary amount of energy this would represent.
In summary, the Richter Scale measures the energy released by the earthquake (its magnitude), while the Mercalli Scale measures the intensity of the earthquake based on its impact on people, structures and the natural landscape.
When was Mercalli intensity created?
The Mercalli Scale was created by the Italian volcanologist Giuseppe Mercalli in 1884. However, the original Mercalli version was much simpler than the scale we use today and only had ten levels of intensity.
The scale was later revised and expanded twice in the early 20th century. In 1902, Mercalli expanded its scale to include twelve levels. In 1931, seismologists Harry O. Wood and Frank Neumann again revised the scale, creating what became known as the Modified Mercalli Scale, which is still used today. This version modifies and further details the intensity levels, ranging from I (no sense) to XII (total damage).
Therefore, although the Mercalli Scale was created in 1884, the version we use today was not finalized until 1931.
What was the largest scale of earthquakes in the world?
Earthquakes are powerful and sometimes devastating events that occur around the world. The measurement of these events is done mainly through the Richter and Mercalli scales, which allow scientists to quantify the magnitude and intensity of earthquakes, respectively. Throughout history, several earthquakes have reached impressive magnitudes on the Richter Scale. Here are some of the most notable:
- 1. Chile Earthquake, 1960:
- 2. Alaska earthquake, 1964:
- 3. Indian Ocean Earthquake, 2004:
- 4. Japan Earthquake, 2011:
- 5. Earthquake of Russia, 1952:
Each of these earthquakes had devastating effects and left an indelible mark on human history. They serve as a powerful reminder of the forces that shape our planet.