What happened in Nepal and how big is the damage?

Seismologists say that the quake happened on what is known as a “thrust fault”. This describes the situation when one piece of the Earth’s crust is moving beneath another piece. In this case, it’s the Indian plate that is moving north at 45 millimetres a year under the Eurasian plate to the north.

United States Geological Survey (USGS) calculations estimate the damage between $100 million and $10 billion. Scientists estimate that more than 105 million people felt moderate shaking during the quake. A UN report says that nearly 6.6 million and 40 percent of the country is affected by the quake.

READ: Nepal earthquake: 3,200 dead and counting


Check here for  fatalities and economic losses estimated by the USGS


What are Aftershocks?

An earthquake that follows a large magnitude earthquake called, “main shock” and originates in or around the rupture zone of the main shock. Generally, major earthquakes are followed by a number of aftershocks, which show a decreasing trend in magnitude and frequency with time.

Around 55 aftershocks occured in Nepal in two days after the massive 7.9 magnitude hit the country on April 25.


Why earthquakes occur?

 
Going by the plate tectonics concept,  the  Indian  plate  is  moving  in  a  north, north-east direction  and  colliding  with  Eurasian  plate  along  the  Himalayan  mountain  range.  This collision is responsible for the formation of faults such as boundary thrust, central thrust in and along  the  Himalayan regions. Almost  all  the  major  earthquakes  in  India  and  its  adjoining  region  occur  along these faults. In brief, earthquakes occur due to forces of geological origin along weak planes called, faults. The earthquakes occurring near plate boundaries such as Himalaya are known as inter-plate earthquakes. Apart  from  earthquakes  from  the  Himalayan  belt,  there  have  been  earthquakes  of relatively lesser magnitude and lesser frequency in the Peninsular region also. Such earthquakes are known  as intra-plate  earthquakes.

   
Classifying earthquakes

    
 

•     Slight Magnitude up to 4.9 on the Richter Scale

•     Moderate Magnitude 5.0 to 6.9

•     Great Magnitude 7.0 to 7.9

•     Very Great Magnitude 8.0 and more

       Nepal earthquake was 7.9, ie. earthquake of great magnitude.

 

Here is a list of significant earthquakes occurred in and around India


Here is a list of largest and deadliest earthquakes occurred around the world

  

With inputs from USGS and IMD