3.2. EFFECTS OF EARTHQUAKE

Earthquake is a natural hazard. The following are the immediate hazardous effects of earthquake:

(i) Ground Shaking (ii) Differential ground settlement (iii) Land and mud slides (iv) Soil liquefaction (v) Ground lurching (vi) Avalanches (vii) Ground displacement (viii) Floods from dam and levee failures (ix) Fires (x) Structural collapse (xi) Falling objects (xii) Tsunami

Earthquakes can cause a variety of immediate hazardous effects.

1. Ground Shaking - This is the most noticeable effect and occurs as seismic waves travel through the Earth, shaking everything on the surface.
2. Differential Ground Settlement - Different areas may settle unevenly, leading to cracks and damage to structures.
3. Land and Mud Slides - In hilly areas, as the ground shakes, loose soil can slide down slopes, causing destruction.
4. Soil Liquefaction - In saturated soils, the shaking can cause the ground to behave like a liquid, leading to buildings sinking or tilting.
5. Ground Lurching - Sudden movements of the ground can displace land.
6. Avalanches - Earthquake tremors can trigger snow avalanches in mountainous regions.
7. Ground Displacement - The ground can crack or shift, altering landscapes.
8. Floods from Dam Failures - Strong earthquakes can damage dams, leading to flooding.
9. Fires - Gas lines may break, igniting fires during or after the earthquake.
10. Structural Collapse - Buildings not designed to withstand earthquakes may fall, causing injuries and deaths.
11. Falling Objects - Items inside buildings can fall, posing additional risks.
12. Tsunami - If the earthquake occurs under the sea, it may generate a tsunami, leading to widespread flooding in coastal areas. This occurs when the epicenter is beneath the ocean and has a significant magnitude.

Think of an earthquake as a massive, unexpected shaking party. Imagine standing in a room filled with balloons (the buildings). When the music (seismic waves) plays and the ground shakes (ground movements), some balloons may pop (buildings collapse), and others may float to one side (ground lurching), making it hard to keep everything in place. Just like at a party, where the mess can lead to broken items, an earthquake can create severe destruction in its wake.

The first six listed above have some bearings upon landforms, while others may be considered the effects causing immediate concern to the life and properties of people in the region. The effect of tsunami would occur only if the epicentre of the tremor is below oceanic waters and the magnitude is sufficiently high. Tsunamis are waves generated by the tremors and not an earthquake in itself. Though the actual quake activity lasts for a few seconds, its effects are devastating provided the magnitude of the quake is more than 5 on the Richter scale.

Different effects of earthquakes can alter the physical landscape significantly.

• The first six hazardous effects mentioned earlier (like ground shaking and landslides) can reshape landforms instantly. For example, when ground shaking causes landslides, hillsides may lose their stability, leading to the creation of new valleys or cliffs.
• Tsunamis are waves caused by underwater earthquakes. If the epicenter is located beneath the ocean and has enough energy (magnitude above 5), it can create powerful waves that inundate coastal areas, reshaping the shoreline and affecting ecosystems. Although the earthquake itself might last only seconds, the subsequent tsunami can have catastrophic and lasting impacts on coastal landforms.

Imagine you are in a calm pool (the ocean) when suddenly someone jumps in and creates ripples (the earthquake). If that jump is powerful enough, it not only sends ripples across the water but also splashes a lot of water out of the pool, washing away toys and changing where the water meets the land. Just like a tsunami can radically change a coastline, that splash extends far beyond the jump itself.

Though the actual quake activity lasts for a few seconds, its effects are devastating provided the magnitude of the quake is more than 5 on the Richter scale.

Magnitude is a measure of the energy released during an earthquake. Earthquakes with a magnitude of 5 or more on the Richter scale are generally considered significant enough to cause considerable damage, especially in populated areas. The moment of the earthquake itself happens very quickly but can lead to a range of consequential impacts: from structural damage to triggering landslides and tsunamis. Therefore, the magnitude helps predict the potential severity of an earthquake's effects.

Think about a soft drink bottle that you shake vigorously and then open. If you just shake it lightly (low magnitude), the fizz might bubble over a little. But if you shake it hard (high magnitude), the eruption is huge, and everything around it is splattered. Just like that, the larger the earthquake’s magnitude, the more extensive and destructive the possible effects.

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