Turkey Earthquake

Why in news?

A major earthquake struck Turkey and Syria killing more than 2600 people and flattening thousands of buildings.

What is the issue?

• The tremors of the first quake were felt on February 6 with the epicentre located near the city of Gaziantep in south-central Turkey, close to the border with Syria.
• A magnitude of 7.8 was measured on the Moment Magnitude scale.
• At least 40 aftershocks followed the first quake, with some of magnitude as high as 6.7.

What is an earthquake?

Earthquakes

• Earthquakes are caused by a sudden release of stress along faults in the earth's crust.

• The Earth’s crust consists of 7 large lithospheric plates and numerous smaller plates (tectonic plates) that move
  • Towards each other (a convergent boundary)
  • Apart (a divergent boundary) or
  • Past each other (a transform boundary)
• The continuous motion of tectonic plates causes a steady build-up of pressure in the rock strata on both sides of a fault.
• It gets released as waves of seismic energy and propagate through the ground and over its surface and causes shaking as earthquakes.

Types of energy waves

• P waves or primary waves – They are the first waves to be detected.
• These are compressional waves that push and pull as they move through rock and fluids.
• S waves or secondary waves - They are the next waves to be detected.
• These waves move only through solids.
• They move up and down or side to side, perpendicular to the direction in which the wave is moving.
• Surface waves - It follow P and S waves and travel along the surface of the earth and thus cause the most damage.
• Surface waves can be characterized as
  • Love waves - Faster and move the ground from side to side, and
  • Rayleigh waves - Roll like waves on the surface of oceans and lakes

Types of earthquake

• Tectonic - Earthquakes that occur when the edges of the tectonic plates slide against each other in fault zones
• Volcanic - Earthquakes that occur in conjunction with volcanic activity
• Collapse - Smaller-scale earthquakes that result from the subterranean collapse of caverns or mines
• Induced - Quakes caused by human activity, like tunnel construction, filling reservoirs and implementing geothermal or fracking (hydraulic fracturing) projects

Earthquake prone zones

• The regions regularly exhibiting earthquakes include the
  • Circum-Pacific seismic belt - along the rim of the Pacific Ocean
  • Alpide belt - along the southern margin of Eurasia through the Himalayan Mountains, Sumatra, and Java
  • Mid-Atlantic Ridge - along the floor of the Atlantic Ocean

What scales of measurement are available?

Measuring the magnitude

• Earthquake magnitude is a measure of the size or amplitude of the seismic waves generated by an earthquake source.
• Richter Scale (denoted as ML) - Devised in 1935 by Charles Francis Richter, the Richter Scale is a logarithmic scale, where each step represents a tenfold increase in magnitude.
• Thus, an earthquake measuring 7 on the Richter Scale has 10 times the magnitude of one measured 6.
• Moment Magnitude Scale (denoted as Mw) – It is a logarithmic scale which is related to the total energy released in the earthquake.
• This scale provides a more accurate estimate of magnitude.

Measuring the intensity

• The intensity is related to the tangible impact a quake has.
• Intensity scales, like the Modified Mercalli Scale and the Rossi-Forel scale, measure the amount of shaking at a particular location.
• The Modified Mercalli Scale ranks earthquake intensity on a scale of I. (not felt) to XII. (extreme).
• The maximum intensity of Turkey earthquake in Modified Mercalli Scale is IX. (Violent)

What are aftershocks and why do they occur?

• Aftershocks are a sequence of earthquakes that happen after a larger mainshock on a fault.
• Aftershocks occur near the fault zone where the mainshock rupture occurred.
• They can even continue for days, weeks, months, or even years for a very large mainshock.
• Although aftershocks tend to be weaker than the main seismic event, they can cause significant damage.
• In Turkey, reports suggest that significant damage that has followed the original quake has been a result of aftershocks.
• Shallower quakes are generally felt as more intense than deeper quakes due to their proximity from the surface.
• The aftershock in Turkey was extremely shallow, only 10 km deep, which worsens the shaking felt.

What makes Turkey a hotbed of seismic activity?

According to an estimate, almost 95% of the country’s land mass is prone to earthquakes, while about a third of the country is at high risk.

• Turkey is located on the Anatolian tectonic plate, which is located between the Eurasian and African plates.
• On the north side, the minor Arabian plate further restricts movement.
• The North Anatolian fault (NAF) line, the meeting point of the Eurasian and Anatolian tectonic plates is known to be devastating.
• The East Anatolian fault line is the tectonic boundary between the Anatolian Plate and the northward-moving Arabian Plate.
• The Aegean Sea Plate, located in the eastern Mediterranean Sea is also a source of seismic activity in the region.

What makes this one catastrophic in particular?

• Turkey - Turkey’s President Recep Tayyip Erdogan said the earthquake that hit the area around Gaziantep, was the country’s worst disaster since Erzincan earthquake, 1939.
• The impact of the earthquake on the lives of people is worrying.

• Syria - The situation is terrible in Syria, where quake-related destruction has taken hold of both government and opposition-occupied regions as they are facing devastating winter storms that make it difficult for humanitarian resources to reach these areas.

References

1. The Indian Express | Turkey hit by 7.8 magnitude earthquake
2. The Indian Express | ‘Aftershocks’ in Turkey after earthquake
3. The Indian Express | Turkey earthquake
4. The Indian Express | What happened in Erzincan
5. The Hindu | Why Turkey is prone to devastating earthquakes?