Geology and Earth Structure

The 2001 Gujarat earthquake occurred on January 26, 2001, India's 51^st Republic Day. The epicentre was about 9 km southwest of the village Chobari in Bhachau Taluka of Kutch district of Gujarat, India. The earthquake reached a magnitude of between 7.6 and 7.7 on the moment magnitude scale.

Volcanoes are generally found where tectonic plates are diverging or converging. A mid-oceanic ridge, for example: the Mid-Atlantic Ridge has examples of volcanoes caused by divergent tectonic plates pulling apart. The Pacific Ring of Fire has examples of volcanoes caused by convergent tectonic plates coming together. By contrast, volcanoes are usually not created where two tectonic plates slide past one another.

The 2004 Indian Ocean earthquake was an undersea megathrust earthquake that occurred at 00:58:53 UTC on Sunday, 26 December, 2004, with an epicentre off the west coast of Sumatra, Indonesia. The resulting tsunami was given various names, including the 2004 Indian Ocean tsunami, South Asian tsunami, Indonesian tsunami and the Boxing Day tsunami. With a magnitude of MW 9.1–9.3, it is the third largest earthquake ever recorded on a seismograph. The earthquake had the longest duration of faulting ever observed, between 8.3 and 10 minutes.

The San Andreas Fault is a continental transform fault that runs a length of roughly 810 miles (1,300 km) through California in the United States. It forms the tectonic boundary between the Pacific Plate and the North American Plate. On September 28, 2004, at 10:15 A.M. PDT, a magnitude 6.0 earthquake struck California on the San Andreas Fault. It was felt across the state, including the San Francisco Bay Area.

The Alpide belt is a mountain range which extends along the southern margin of Eurasia. Stretching from Java to Sumatra through the Himalayas, the Mediterranean and out into the Atlantic, it includes the Alps, the Carpathians, the mountains of Anatolia and Iran, the Hindu Kush and the mountains of Southeast Asia. The Alpide belt is being created by ongoing plate tectonics namely the process of collision between the northward-moving African, Arabian and Indian plates and the Eurasian plate. The most seismically active zone in the world is the Pacific Ring of Fire. Alpide Belt falls on the second position behind it in terms of seismicity.

The epicentre is the point on the Earth's surface that is directly above the hypocenter or focus, the point where an earthquake or underground explosion originates. Thus, focus and hypocentre are synonymous terms, whereas epicentre is a related but distinct concept.

The moment magnitude scale (abbreviated as MMS; denoted as MW or M) is used by seismologists to measure the size of earthquakes in terms of the energy released. The magnitude is based on the seismic moment of the earthquake, which is equal to the rigidity of the earth multiplied by the average amount of slip on the fault and the size of the area that slipped. The MMS is the scale used to estimate magnitudes for all modern large earthquakes by the United States Geological Survey. The Richter magnitude scale (often shortened to Richter scale) was developed to assign a single number to quantify the energy released during an earthquake.

Megathrust earthquakes occur at subduction zones at destructive plate boundaries (convergent boundaries), where one tectonic plate is subducted (forced underneath) under another. Due to the shallow dip of the plate boundary, which causes large sections to get stuck, this type of earthquakes are the planet's most powerful. Since 1900, all six earthquakes of magnitude 9.0 or greater have been megathrust earthquakes. The 2004 Indian Ocean earthquake was an undersea megathrust earthquake.

No, the inner most layer of the earth is called inner core. The Earth's inner core is made up of iron and nickel. It has trapped gases and hot liquids under great pressure. Sometimes these gases burst out and explode outside the crust as volcanoes.

It is mentioned in the 2^nd line.

The intensity scale (range varies from 1-12) takes into account the visible damage caused by the event and is named after Mercalli, an Italian seismologist.

These volcanoes outpour highly fluid lava that flows for long distances. There can be a series of flows with some flows attaining thickness of more than 50 m. Individual flows may extend for hundreds of kilometres.

Core is made up of very heavy material mostly constituted by nickel and iron. That is why, it is sometimes referred to as nife layer.

India is supposed to have started her northward journey about 200 million years ago at the time when Pangaea broke.

Caroline plate is located between Philippine and Indian plates (North of New Guinea). Nazca plate lies between South America and Pacific plates.