GS3 - Disaster Management
Understanding the Impact
Shallow earthquakes are seismic events that occur near the Earth's surface, typically at depths of fewer than 50 kilometers. These earthquakes are known for their potential to cause significant destruction, often surpassing the impact of deeper ones. The key factor contributing to their destructiveness is the behavior of seismic waves as they approach the surface.
Seismic waves generated by deep earthquakes lose some of their energy as they travel upwards, leading to a decrease in their destructive potential. In contrast, shallow earthquakes release their energy closer to the surface, resulting in more intense shaking and a higher potential for damage to structures and communities.
Furthermore, shallow-focus earthquakes have a distinctive characteristic of generating numerous aftershocks. These aftershocks can continue for an extended period after the initial earthquake, adding to the overall impact and challenges faced by affected regions.
It's worth noting that the majority of earthquakes that occur worldwide are shallow, making them a common and significant geological phenomenon. This prevalence underscores the importance of understanding their characteristics and potential consequences.
Examples of Shallow Earthquakes
Two notable examples highlight the impact of shallow earthquakes on communities and infrastructure. In 2016, Italy experienced a magnitude 6 earthquake that caused widespread devastation. Despite having a similar magnitude to an earthquake in Myanmar around the same time, the Italian earthquake resulted in significantly more damage. This difference in impact can be attributed to the shallow depth of the Italian earthquake, which allowed for more intense seismic waves to reach the surface.
Another example occurred near Cianjur in West Java, where an earthquake with a shallow depth of only 10 kilometers struck. This relatively shallow earthquake led to the loss of 268 lives and extensive damage to 22,000 buildings. Shallow earthquakes, especially in inland areas like Java, can be particularly devastating due to their infrequent occurrence, catching communities unprepared for their destructive potential.
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Morocco Earthquake  The most powerful earthquake in Morocco's history, with a magnitude of 6.8, struck on September 8th, 2023, near Marrakech. The earthquake was caused by the convergence of the African and Eurasian plates along a complex plate boundary. The faulting mechanism was classified as "oblique-reverse," indicating movement along the fault plane. The earthquake occurred at a relatively shallow depth beneath the Earth's surface, contributing to its destructive potential. Morocco is situated on the convergence plate of Africa and Eurasia, two major tectonic plates that create mountains, volcanoes, and earthquakes. The Atlas Mountains in Morocco are a result of the collision between these plates. |
Why are Shallow Earthquakes dangerous?
Shallow earthquakes are more dangerous than deeper ones due to their greater energy release closer to the Earth's surface, causing stronger ground shaking and increased damage to structures and casualties, compared to deeper earthquakes which lose energy as they travel to the surface. The sound and impact will be much louder and stronger if someone hits the drum very closely to the top surface. Similar to this, a shallow earthquake shakes the ground more violently because it is closer to the surface, making it more dangerous because it can harm people and cause more property damage.
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Earthquake Earthquakes are natural events that cause the shaking of the Earth and generate seismic waves that travel in all directions. The location below the Earth's surface is called the hypocenter, and the location directly above it is called the epicenter.
The depth at which an earthquake occurs is referred to as the depth of focus or focal depth in seismology.
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What can be done?
To improve building practices, focusing on enforcing existing building codes and introducing minimum standards for protection. These standards should cover basic aspects like concrete strength and reinforcement quality. Additionally, cultural change and increased expectations from customers about earthquake resilience are needed to ensure compliance with codes and promote investment in earthquake-resistant construction.
India's efforts to be earthquake-ready
India has established building codes and standards for earthquake-resistant construction, which must be strictly enforced. Older buildings can be retrofitted or reinforced to improve seismic performance. Emergency response planning, research, and land-use planning are crucial for minimizing earthquake impact. Investing in these areas can improve understanding of earthquakes and develop better methods for predicting and mitigating their impact.
The National Disaster Management Authority (NDMA) is implementing a project to improve earthquake-resistant construction in India, involving awareness raising, model building bye-laws, capacity building, training, and collaboration.
Conclusion
Shallow earthquakes represent a significant geological phenomenon with far-reaching consequences. These seismic events, occurring within the Earth's upper crust, can cause substantial damage to infrastructure, pose threats to human lives, and alter the landscape. It is imperative that we continue to advance our understanding of shallow earthquakes through scientific research, improve early warning systems, and implement resilient building practices to mitigate their impact. By doing so, we can better prepare for and respond to these natural events, ultimately safeguarding our communities and minimizing the devastation they can bring.
