In this blog post, we will look at the scientific principles of earthquakes and the measures we can take to reduce the damage caused by them.
The powerful magnitude 9.0 earthquake that occurred in Japan in 2011 caused a huge shock across the country, which in turn caused a tsunami that resulted in a large number of casualties and property damage. This earthquake was also linked to the Fukushima nuclear power plant accident, which caused a huge international stir. A similar major earthquake occurred in Chile in 2010. The magnitude 9.5 earthquake was one of the most powerful earthquakes ever recorded in history. Earthquakes are more than just natural disasters; they are one of the disasters that humans have difficulty preparing for. So, what is an earthquake and why does it occur? To understand this, we need to learn about the structure of the Earth’s interior and how it works.
An earthquake is a natural phenomenon that literally means “the earth shakes.” More precisely, it is an earthquake that occurs when the earth’s interior forces suddenly rupture the bedrock and the shock waves cause the earth to shake. The energy generated here is transmitted as seismic waves, and as these waves travel over the ground, people feel the earthquake. There are two main scales used to measure the strength of an earthquake: Magnitude and intensity. Many people often come across the words magnitude and intensity when reading news or articles related to earthquakes, but it is easy to confuse these two concepts.
Magnitude is a measure of the absolute strength of an earthquake. Generally, the Richter scale or the moment magnitude scale is used. The earthquake magnitudes that we often see in the news are mostly based on magnitude. On the other hand, intensity is the relative strength of an earthquake felt in a specific location. The same earthquake feels stronger when it is closer to the epicenter and weaker when it is farther away. This is similar to the way waves spread out when a stone is thrown into the water.
Why do earthquakes occur? To answer this question, we need to understand plate tectonics. The ground we stand on is not fixed, but the huge plates that make up the Earth’s surface are constantly moving. These plates float above the upper mantle and move very slowly but steadily with the movements of the mantle. When the plates collide or push against each other, an impact occurs, which causes an earthquake. The movement of the plates occurs very slowly, so people do not feel it, but when this movement accumulates over a long period of time and suddenly releases, a powerful natural phenomenon called an earthquake occurs.
The shock that occurs when the plate moves is transmitted through seismic waves, which are divided into four types: P-waves, S-waves, L-waves, and R-waves. Among them, the P-wave is the first seismic wave to arrive, which generally does not cause much damage, but the system that detects it can quickly notify of an earthquake. The S-wave arrives next, and this is when major damage begins to occur. In particular, in the case of a powerful earthquake, liquefaction, in which the ground becomes like liquid, can occur, which weakens the foundations of buildings and increases the likelihood of collapse.
An earthquake does not occur all at once, but in several stages. It can be divided into three stages: the foreshock that occurs before the main shock, the main shock that delivers the strongest impact, and the aftershocks that follow the main shock. After the main shock, hundreds of aftershocks can follow, which can also cause additional damage, so caution is required.
Many people say that there are signs that can appear before an earthquake, but there are no scientifically proven signs. For example, animals suddenly moving in groups or unusual clouds are often said to be signs of an earthquake, but these are all stories lacking scientific evidence. To date, there is no reliable way to predict earthquakes, and even in countries like Japan, where earthquakes occur frequently, the emergency earthquake early warning system only detects P-waves and issues warnings as quickly as possible.
So, how should we respond when an earthquake occurs? The most important thing is to protect yourself from falling objects. If you are inside a building, the first thing to do is to protect your head by hiding under a table. In particular, if most buildings in Korea are built with concrete, it may be considered more dangerous to stay inside the building because of the high risk of collapse. However, before leaving the building during an earthquake, there is a high risk of falling objects falling on your head, so it is safer to stay in a safe place until the shaking subsides. It is important to move to a spacious and open area outside the building as much as possible, and it is better to wait for the tremors to stop while protecting your head and not move rashly during an earthquake.
Earthquakes are one of the natural disasters that humanity cannot control, and especially powerful earthquakes have greater destructive power the larger they are. No matter how thoroughly the earthquake-resistant design is, it is difficult to avoid the collapse of a building in an earthquake of magnitude 8.5 or higher. While it is impossible to be completely safe from such disasters, it is essential to take proactive measures and training to reduce damage. Living in a building that is designed to withstand earthquakes and knowing how to respond in the event of an earthquake is the most important way to protect your life from earthquakes.
