Context: A powerful earthquake of magnitude 7.7 struck Myanmar, with the epicenter located approximately 17.2 km from Mandalay (city in Myanmar). This quake of magnitude 7.7 was the strongest one anywhere in the world in the last two years.
Relevance of the Topic : Prelims : Earthquake, Sagaing fault, location of Mandalay.
Sagaing Fault
- Myanmar is vulnerable to earthquakes, largely due to its location along the Sagaing Fault.
- Sagaing Fault is a major tectonic fault line between the Burma and Sunda plates. The fault runs approximately 1,200 kilometres (north to south) through the country and has a history of significant seismic activity.
Recent Myanmar Earthquake:
- Myanmar sits directly on top of the Sagaing Fault. In this region, the Indian and Sunda tectonic plates move in opposite directions at a speed of 49mm per year.
- When these plates slide past each other horizontally, stress builds up due to friction. This vast reserve of energy is then released in a violent 'slip-strike' earthquake.
- The earthquakes from this fault are violent and extremely shallow, meaning they have the potential to cause enormous damage in nearby population centres.
How do Earthquakes originate?
- An earthquake is a violent and abrupt shaking of the ground, caused by movement between tectonic plates along a fault line in the earth’s crust.
- The earth’s outermost surface (crust) is fragmented into tectonic plates.
- These plates continuously move at a slow pace, colliding, sliding, or moving past each other.
- The edges of these plates, known as plate boundaries, are irregular and get stuck due to friction.
- When the plates move far enough, the edges suddenly unstick, releasing the stored energy in the form of seismic waves.
- This release of energy causes the ground to shake, resulting in an earthquake.
Key Facts related to Earthquakes:
- The point where the energy is released is called the focus of an earthquake or hypocentre. The point on the surface, nearest to the focus, is called epicentre (directly above the focus).
- The earthquake events are scaled either according to the magnitude or intensity of the shock. The magnitude scale is known as the Richter scale. Mercalli scale is used to measure the intensity of an earthquake. It assesses the effects and damage caused by an earthquake at a specific location.
- Earthquakes are divided into three zones: shallow, intermediate, and deep, based on their depth which range between 0 – 700 km.
- Shallow earthquakes have a focus 0 – 70 km deep
- Intermediate earthquakes have a focus 70 – 300 km deep
- Deep earthquakes have a focus 300 – 700 km deep.
- Shallow earthquakes are usually more dangerous because they release more energy when they reach the surface. In contrast, deeper earthquakes lose some of their energy as they travel a longer distance to the surface.