12.7. Earthquakes

You just learned about thunderstorm and lightning. These natural phenomena can cause large scale destruction of human life and property. Fortunately, these phenomena can be predicted to some extent. The weather department can warn about a thunderstorm developing in some area.

This chunk introduces earthquakes as a natural phenomenon. Unlike thunderstorms and lightning, which can be predicted, earthquakes currently cannot be forecasted accurately. Understanding this distinction is crucial because it highlights the unpredictability of earthquakes and the potential risks involved.

Think of thunderstorms like an impending storm that you can watch on the news—meteorologists can predict when one might happen. In contrast, an earthquake is more like a surprise party you didn't see coming at all; it can occur without any warning, making preparations crucial.

What is an earthquake? An earthquake is a sudden shaking or trembling of the earth which lasts for a very short time. It is caused by a disturbance deep inside the earth’s crust. Earthquakes occur all the time, all over the earth. They are not even noticed. Major earthquakes are much less frequent. They can cause immense damage to buildings, bridges, dams and people. There can be a great loss to life and property. Earthquakes can cause floods, landslides and tsunamis.

This section defines an earthquake as a sudden shaking of the earth resulting from disturbances in the earth's crust. It points out that while minor earthquakes are common and often go unnoticed, major earthquakes are rare yet potentially destructive, leading to loss of life, damage to infrastructure, and secondary disasters like floods and tsunamis.

Imagine shaking a jar of marbles; when you stop shaking, the marbles settle down, but if you shake too hard, they can break the jar. Similarly, small quakes may occur without us noticing, but a major quake can cause significant havoc, like the waves of a tsunami after a strong tremor.

What Causes an Earthquake? Now we know that the tremors are caused by the disturbance deep down inside the uppermost layer of the earth called the crust. ... The outermost layer of the earth is not in one piece. It is fragmented. Each fragment is called a plate. These plates are in continual motion. When they brush past one another, or a plate goes under another due to collision, they cause disturbance in the earth’s crust. It is this disturbance that shows up as an earthquake on the surface of the earth.

This chunk explains that earthquakes are caused by the movements of tectonic plates that make up the earth's crust. These plates can disrupt each other's positions either by colliding or sliding past each other, resulting in disturbances that we experience as earthquakes at the surface.

Think of tectonic plates like icebergs moving in water. When two icebergs collide or slide against each other, they cause ripples and waves. Similarly, the movement of tectonic plates leads to tremors felt on land when they shift or collide.

The power of an earthquake is expressed in terms of a magnitude on a scale called the Richter scale. Really destructive earthquakes have magnitudes higher than 7 on the Richter scale.

This section introduces the Richter scale, which is used to measure the magnitude of earthquakes. Earthquakes with magnitudes of 7 or more are classified as particularly destructive, emphasizing the need for preparedness in vulnerable areas.

You can think of the Richter scale like a scoring system for a game. Just as higher scores indicate a better performance, higher magnitudes on the Richter scale indicate stronger, more dangerous earthquakes.

We know from the earlier pages that earthquakes cannot be predicted. ... It is advisable to make the structure simple so that it is ‘Quake Safe’. Consult qualified architects and structural engineers.

This chunk discusses the importance of building structures that can withstand earthquakes, especially in seismic zones. It urges consultation with professionals to design buildings that are 'quake safe', thus minimizing damage during such events.

Designing a safe structure is like wearing protective gear when riding a bicycle. Just as a helmet and pads can protect you from falls, quake-safe buildings are designed to absorb shocks and avoid catastrophic failures during an earthquake.

In the event that an earthquake does strike, take the following steps to protect yourself: ... If you are in a car or a bus, do not come out. Ask the driver to drive slowly to a clear spot.

This part provides practical safety precautions for individuals during an earthquake. It details steps based on whether the person is indoors or outdoors, emphasizing the need for calm actions to ensure personal safety.

Imagine being instructed on how to behave during a fire drill. Just like you know to stay low and avoid doors, these earthquake safety tips guide you on how to seek shelter and protect yourself when tremors occur.

--