Earthquakes management

GS-Paper-1 Geography- Earthquake (PT)

According to a recently published study, researchers have developed a new way to improve the prediction of earthquakes.

Seismic Waves

Vibrations from an earthquake are categorised as P (primary) and S (secondary) waves. They travel through the Earth in different ways and at different speeds. They can be detected and analysed.

- P-waves:
  - These are the first waves detected by seismographs (instruments used to detect and record earthquakes).
  - These are longitudinal waves which means they vibrate in the same direction as they travel.
  - Other examples of longitudinal waves include sound waves and waves in a stretched spring.
- S-waves:
  - These waves arrive at the detector after primary waves.
  - These are transverse waves which means they vibrate at a right angle to the direction in which they travel.
  - Other examples of transverse waves include light waves and water waves.
Both types of seismic waves can be detected near the earthquake centre but only P-waves can be detected on the other side of the Earth. P-waves can travel through solids and liquids (since they are longitudinal waves) whereas S-waves can only travel through solids (as they are transverse waves). This means the liquid part of the core blocks the passage of S-waves.
The earthquake events are scaled either according to the magnitude or intensity of the shock.
- The magnitude scale is known as the Richter scale. The magnitude relates to the energy released during the earthquake which is expressed in absolute numbers, 0-10.
- The intensity scale or Mercalli scale takes into account the visible damage caused by the event. The range of intensity scale is from 1-12.

Earthquakes:

Earthquakes usually occur along faults (fractures between rocks which can range from a few millimetres to thousands of kilometres). When two blocks of earth slip past one another, seismic waves are generated in a short span of time and earthquakes occur. The waves travel to the surface causing destruction and are difficult to predict, making it challenging to save lives.

Earlier Attempts

Scientists have attempted to recreate the faults and their sliding in laboratories to try and understand the conditions in them during earthquakes.

However, the actual conditions are so complex that it is difficult to recreate them with full accuracy which makes the prediction of earthquakes difficult.

New Method:

Researchers have now used a different approach for earthquake prediction by trying to predict the frictional strength of phyllosilicates.
Frictional Strength: It is the force required to cause movement along a fault.
Phyllosilicates: Minerals in the form of thin plates are found along the weakest part of the faults where earthquakes occur.
The researchers analysed artificial fault zones on a microscopic scale to identify processes that occurred during the experiment.
A set of equations were then formulated to predict how the frictional strength of phyllosilicate changes, along with a change in conditions such as humidity or the rate of fault movement.
This made it easier for modellers to simulate fault movement in natural conditions, including earthquakes.
The new model predicts that movement along phyllosilicate-rich fault zones becomes more difficult as it becomes faster and this has been consistent with experiments.
This behaviour of movement becoming more difficult prevents earthquakes and suggests minerals other than phyllosilicates play an important role in causing earthquakes.
However, more work and research are needed to clearly explain it and to understand the relation between the force that holds a fault together and the force needed to move the fault.

Source: DTE

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