What are Natural Disaster?A natural disaster is a major adverse event resulting from natural processes of the Earth ; examples include floods ,volcanic eruptions, earthquakes, tsunamis, and other geologic processes. A natural disaster can cause loss of life or property damage and typically leaves some economic damage in its wake, the severity of which depends on the affected population's resilience, or ability to recover. An adverse event will not rise to the level of a disaster if it occurs in an area without vulnerable population. In a vulnerable area, however, such as San Francisco and Nepal, an earthquake can have disastrous consequences and leave lasting damage, requiring years to repair.

A natural disaster can cause loss of life or property damage and typically leaves some economic damage in its wake, the severity of which depends on the affected population's resilience, or ability to recover. An adverse event will not rise to the level of a disaster if it occurs in an area without vulnerable population. In a vulnerable area, however, such as San Francisco and Nepal, an earthquake can have disastrous consequences and leave lasting damage, requiring years to repair.

• . An Earthquake is a sudden movement of the ground that releases the elastic energy stored within the rocks, creating destructive seismic waves. The word "seismic" comes from the Greek word "seismos" meaning an earthquake. These quakes are not isolated events. They come with smaller shocks, called aftershocks, with smaller effects.An earthquake is caused when two sides of a large fracture in the rocks within the earth slide past each other. This fracture is called a fault, which may be microscopic or thousands of kilometers in length, while their width is usually a few millimeters or a few meters in size. The size of an earthquake depends on the area of the fault that ruptured, and the distance through which the rocks on the two sides of the fault slide past one another. Small earth quakes are caused by small faults or small parts of big faults. These last only for a fraction of a second and usually unnoticed, as the rocks on either side of the faults are not displaced much. The larger ones are caused due to faults which are tens to thousands of kilometers long, taking minutes and the displacement of the rocks is around tens of meters.

Earthquakes are caused because the earth is regularly cooling since it was born, the seismic wave being one of its ways to release the elastic energy.Earthquakes are generally categorized into three types: Tectonic, Volcanic and Artificial.

Tectonic earth quakes are the most devastating, and unfortunately the most unpredictable. The volcanic quakes are seldom important or devastative, but they help predict the eruption of volcanoes. The artificial ones are caused due to human activities, like pumping fuels deep into the earth or due to explosives, and several other reasons.

Why Earthquakes Occur?An earthquake is ground shaking caused by a sudden movement of rock in the earth’s crust. Such movements occur along faults, which are thin zones of crushed rock separating blocks of crust. When one block suddenly slips and moves relative to the other along a fault, the energy released creates vibrations called seismic waves that radiate up through the crust to the earth’s surface, causing the ground to shake. What are earthquakes and why do they occur?Earthquakes may last only a few seconds or may continue for up to several minutes. They can occur at any time of the day or night and at any time of the year. They are caused by stress that builds up over time as blocks of crust attempt to move but are held in place by friction along a fault. (The earth’s crust is divided into large plates that continually move over, under, alongside or apart from one another atop the partly molten outer layer of the earth’s core.) When the pressure to move becomes stronger than the friction holding them together, adjoining blocks of crust can suddenly slip, rupturing the fault and creating an earthquake.

The April 2015 Nepal Earthquake

The April 2015 Nepal earthquake (also known as the Gorkha earthquake) killed more than 8,800 people and injured more than 23,000. It occurred at 11:56 NST on 25 April, with a magnitude of 7.8Mw or 8.1Ms and a maximum Mercalli Intensity of IX (Violent). Its epicenter was east of the district of Lamjung, and its hypocenter was at a depth of approximately 15 km (9.3 mi). It was the worst natural disaster to strike Nepal since the 1934 Nepal–Bihar earthquake.

The earthquake triggered an avalanche on Mount Everest, killing at least 19, making it the deadliest day on the mountain in history. It triggered another huge avalanche in the Langtang valley, where 250 people were reported missing.

A major aftershock occurred on 12 May 2015 at 12:51 NST with a moment magnitude (Mw) of 7.3. The epicenter was near the Chinese border between the capital of Kathmandu and Mt. Everest. More than 200 people were killed and more than 2,500 were injured by this aftershock.

Continued aftershocks occurred throughout Nepal within 15–20 minute intervals, with one shock reaching a magnitude of 6.7 on 26 April at 12:54:08 NST. The country also had a continued risk of landslides.

Hundreds of thousands of people were made homeless with entire villages flattened, across many districts of the country. Centuries-old buildings were destroyed at UNESCO World Heritage sites in the Kathmandu Valley, including some at the Kathmandu Durbar Square, the Patan Durbar Squar, the Bhaktapur Durbar Square, the Changu Narayan Temple and the Swayambhunath Stupa.

Aftershocks• A major aftershock of magnitude 6.7 Mw occurred on 26 April 2015 in the same

region at 12:55 NST (07:09 UTC), with an epicenter located about 17 km (11 mi) south of Kodari, Nepal. The aftershock caused fresh avalanches on Mount Everest and was felt in many places in northern India including Kolkata, Siliguri, Jalpaiguri and Assam. The aftershock caused a landslide on the Koshi Highway which blocked the section of the road between Bhedetar and Mulghat.

• A model of GeoGateway, based on a United States Geological Survey mechanism of a near-horizontal fault as well as location of aftershocks showed that the fault was an 11° dip striking at 295°, 50 km (31 mi) wide, 150 km (93 mi) long, and had a dip slip of 3 m (9.8 ft). The USGS says the aftershock registered at a shallow depth of 10 km (6.2 mi).

• Assuming that 25 April earthquake was the largest event in this seismic episode, Nepal could expect more than 30 aftershocks greater than magnitude 5 over the following month. As of 25 May 2015, 265 aftershocks had occurred with different epicenters and magnitudes equal to or above 4 Mw.

12 May 2015 earthquake

• A second major earthquake occurred on 12 May 2015 at 12:51 NST with a moment magnitude (Mw) of 7.3Mw 18 km (11 mi) southeast of Kodari. The epicenter was near the Chinese border between the capital of Kathmandu and Mt. Everest. It struck at the depth of 18.5 km (11.5 miles). This earthquake occurred along the same fault as the original magnitude 7.8 earthquake of 25 April but further to the east. As such, it is considered to be an aftershock of the 25 April quake. Tremors were also felt in northern parts of India including Bihar, Uttar Pradesh, West Bengal and other North-Indian States. At least 117 died in Nepal as a result of the aftershock and about 2,500 were injured. Seventeen others died in India and one in China.

CasualtiesNepal

The earthquake killed more than 8,600 in Nepal and injured more than twice as many. The rural death toll may have been lower than it would have been as the villagers were outdoors, working when the quake hit. As of 15 May, 6,271 people, including 1,700 from the 12 May aftershock, were still receiving treatment for their injuries. More than 450,000 people were displaced. The Himalayan Times reported that as many as 20,000 foreign nationals may have been visiting Nepal at the time of the earthquake, although reports of foreign deaths were relatively low. IndiaA total of 78 deaths were reported in India - 58 in Bihar, 16 in Uttar Pradesh, 3 in West Bengal and 1 in Rajasthan. China25 dead and 4 missing, all from the Tibet Autonomous Region. Bangladesh4 dead.

Avalanches on Mount Everest & Landslides in the Lang tang Valley

This earthquake caused many avalanches on Mount Everest. At least 19 died, including Google executive Dan Freedenberg, with at least 120 others injured or missing.In the Lang tang valley located in Lang tang National Park 329 people were reported missing after an avalanche hit the village of Ghodatabela and the village of Lang tang. The avalanche was estimated to have been two to three kilometers wide. Ghodatabela was an area popular on the Lang tang trekking route. The village of Lang tang has been destroyed by the avalanche.

On 4 May it was announced that 52 bodies had been found in the Langtang area, of which seven were of foreigners.

Damage

Thousands of houses were destroyed across many districts of the country, with entire villages flattened, especially those near the epicenter. The Tribhuvan International Airport serving Kathmandu was closed immediately after the quake, but was re-opened later in the day for relief operations and, later, for some commercial flights. It subsequently shut down operations sporadically due to aftershocks, and on 3 May was closed temporarily to the largest planes for fear of runway damage. Many workers were not at their posts, either from becoming earthquake casualties or because they were dealing with its after effects. Flights resumed from Pokhara, to the west of the epicenter, on 27 April.

The top of the Jaya Bageshwari Temple in Gaushala and some parts of the Pashupatinath Temple, Swyambhunath, Boudhanath Stupa, Ratna Mandir, inside Rani Pokhari, and Durbar High School have been destroyed.

DON'T s

• Do not fill the overhead tank completely. • Do not carry out haphazard repairs. • Repairs should be done only under the supervision

of a structural engineer. • Do not put additional supports without the

guidance of an experienced/qualified structural engineer.

• Do not use the lift until it has been checked and certified by the lift company.

DO'S• If any damage is suspected, turn the system off from the main valve

or, switch. • Clean up household chemical spills, toxic and flammable materials to

avoid any chain of unwanted events. • Gather information and necessary instructions from battery operated

radios. • Obey Public safety precautions. • Leave a message stating where you are going if you must evacuate

your residence. • Take your earthquake survival kit with you. • It should contain all necessary items for your protection and comfort. • Check your water and electrical lines for defects.

Presented By-

Srivastava Digvijay Raj 10th F