The earthquake that shook the center of the Iberian Peninsula today can make us doubt what it really is and how this meteorological phenomenon occurs that so many times has been the protagonist of the news.
Step into the eye of the earthquake with me to learn more about it.
What is it?
Earthquakes are a geological phenomenon that is caused by a shaking of the earth's crust due to the friction of tectonic plates. These plates, although invisible, shape the surface of our planet, and their movement can generate a release of energy that manifests as an earthquake. The Earth's crust is composed of several tectonic plates floating on the magma layer, and the places where these plates interact can create everything from mountains to faults. The San Andreas Fault in North America is a famous example where plate movements have caused some of the most devastating earthquakes.
These places are prone to record very high intensities, even reaching to have a magnitude of 7.2 on the Richter scale. Speaking of scales, let's take a deeper look at how earthquakes are measured and the importance of measurement of these phenomena.
How are earthquakes measured?
The best known scale for measuring the magnitude of an earthquake is the Richter scale, developed by American seismologist Charles F. Richter in 1935. This scale measures the magnitude of the phenomenon but does not provide information on the damage caused. For this purpose, experts also use the Mercalli scale, which assesses the effects of an earthquake on the environment, and the seismological scale at the moment, which considers factors such as the stiffness of the rock and the distance it has moved.
On this map you can see the intensity that earthquakes can have if they touch the Spanish soil according to the Richter scale. The categories are as follows:
- Intensity of 3 or less: It is not usually felt and does not cause noticeable damage.
- Intensity from 3 to 6: It is noticeable, it can cause minor damage.
- Intensity from 6 to 7: It can cause serious damage to entire cities.
- Intensity from 7 to 8The damage is very significant, potentially devastating an area of more than 150 km.
Earthquakes that reach or exceed 8 degrees on the Richter scale can cause significant material losses over large areas. However, there is no record of earthquakes of this magnitude having been recorded in Spain.
The Richter scale and other scales
As we mentioned earlier, the Richter scale measures the magnitude of an earthquake based on the amplitude of seismic waves. Each increase of one on this scale implies an increase of about 32 times the energy releasedThus, a magnitude 7 earthquake is approximately 32 times more powerful than a magnitude 6 earthquake. This method has been fundamental to understanding the magnitude of earthquakes, although it is not without limitations.
Eg Mercalli scale Provides a subjective assessment of an earthquake, graded in Roman numerals from 1 to 12, depending on the observed effects on the population and structures. This assessment addresses how the earthquake was felt in different locations, the damage it caused, and people's reactions. This analysis can vary considerably depending on proximity to the epicenter and the characteristics of the terrain. For more information on this topic, see the article on the seismogram.
How are earthquakes classified?
Earthquakes are classified according to different scales:
- Less than 3.5: Machines register them, but the population does not notice them.
- Between 3.5 and 5.4: They are noticeable but usually cause minor damage.
- Between 5.5 and 6.0: They may cause slight damage to buildings.
- Between 6.1 and 6.9: They are dangerous in highly populated areas and can cause serious damage.
- Between 7.0 and 7.9: It is considered a major earthquake that can cause severe damage over large areas.
- 8 or more: Major earthquake causing total destruction in nearby communities.
On the other hand, the scale of Moment Magnitude (Mw) has become more common in recent decades as measurement technology has advanced. This method is based on the energy released at the moment of an earthquake and considers variables such as the fault surface and the amount of displacement. A single-digit increase in magnitude on this scale indicates that the energy released is about 32 times greater than that of a lower magnitude earthquake. This means that a magnitude 6 earthquake releases 32 times more energy than a magnitude 5 earthquake, and so on.
What instruments are used to measure earthquakes?
The most commonly used instruments for measuring seismic movements are: seismographsThese devices detect the Earth's vibrations and produce a visual record known as seismogramSeismographs have evolved over time, and modern ones are capable of recording earthquakes in real time, providing valuable information for early warning.
A typical seismograph consists of a sensor that moves when an earthquake occurs. This sensor is connected to a recording system that graphs ground movements, allowing scientists to analyze the strength, duration, and other aspects of an earthquake. precision and location of seismographs are also critical factors influencing the quality of the accurate data obtained. In addition, it is essential to understand the geological context in which these phenomena occur.
Why is it important to measure earthquakes?
Understanding how earthquakes are measured is vital for several reasons. First, it helps assess the risks in earthquake-prone areas, allowing communities to plan and prepare for potential disasters. Precise measurements allow engineers to design buildings and structures that are more resistant to earthquakes, safeguarding human lives and reducing property damage.
Furthermore, earthquake research and measurement contribute to the development of early warning systems that can provide valuable seconds or minutes of warning to people before seismic waves reach their location. These seconds can mean the difference between life and death.
Interpreting earthquake data involves not only measuring the magnitude of an earthquake, but also analyzing patterns and trends over time. This can provide insight into seismic activity in specific regions and help predict future earthquakes. Click this link to learn more about how earthquakes relate to other natural phenomena such as volcanic eruptions in the article on earthquakes. relationship between earthquakes and volcanic eruptions.
The study of earthquakes and their measurement is a complex discipline that combines geology, engineering, and technology. As measurement technology advances, so does our understanding and our ability to protect society from seismic risks.
