On April 25th
On April 25th, 2015, Gorkha, a city in central Nepal was struck by a magnitude 7.8 Earthquake, being one of the 2 major earthquakes that plagued the country in recent times. It’s epicentre was at the famous Gorkha District but had also reached Kathmandu, leaving behind severe devastations. The Nepal earthquake affected Nepal, India, China and Bangladesh, succeeded by two large aftershocks with magnitudes of 6.6 and 6.7. Only an hour after the main earthquake, there had already been several dozens of small aftershocks which could be felt within the region in the succeeding days.
Nepal sits on the boundaries of the Indian and the Eurasian plate which joined together around 50 million years ago after the Supercontinent Pangea began to break up. The impact of these two plates joining forced the Indian plate downwards while the Eurasian plate was thrusted upwards, creating a convergent boundary. The meeting of these plates is called a thrust fault, which ultimately created the Himalayas (2010, Springer). To this day, it is the source of majority of the most catastrophic earthquakes within the region due to the constant subduction and shifting of both tectonic plates, requiring the created pressure to be released. This was also the reason for the devastating April earthquake, due to the Indian plate sliding beneath the other. The reason is that in subduction, the denser oceanic crust sinks below the continental crust (2015, Oskin). However, in this particular case, the densities of both plates were similarly matched, each having a density of approximately 2.7 grams/cm3, so a constant jostling is created in keeping the Indian plate down (2017, Singh), resulting in the Nepal earthquake. It occurred on the boundaries of the fault, which ran across southern Nepal and through Kathmandu, spanning the approximate length of the Himalayan ranges.
As a result of earthquakes, many hazards are a by-product, including common primary ones such as ground shaking, landslides, surface rupture and collapsing buildings. Ruptures and ground shaking pose as a large threat to many civilians and are often a large contributor to damaging the structural integrity of structures, making them more prone to disintegrating. This ultimately adds to the extra damage and alleviated risks for residents nearby as they are able to trap and bury people underneath. These main effects are a common trait across earthquakes, all leading to increased fatality and loss of lives.
In the Nepal earthquake, it triggered a series of deadly avalanches in Mount Everest, compromising the safety of nearby villages that surrounded the region. The earthquake itself was felt by many other countries which was as a result of the depth of the earthquake, being only at 15 kilometres deep. The shallowness of this disaster meant for more surface shaking and damage, being the culprit for unrepairable infrastructure, landslides and flooding.
However, despite the epicentre originating from the Gorkha District, Kathmandu suffered far more severe effects in death toll and infrastructure damage. Although not all sources confirm this, majority of graphs show that Gorkha had not taken the brunt of the damage from the earthquake. The reason for this is because the fault where the earthquake had come from does not lie in path of Gorkha, instead past Kathmandu, where the fault ran. As a result, due to the seismic waves being emitted from all areas of the focus that travelled near the fault, damage was prevalent in the region. Another reasons is due to the densely populated of Kathmandu, soft surface and looser ground consistency, it was more prone to destruction.
From the seismograph of the Nepal earthquake,
A source has said that the earthquake was 7.9.
The landslides caused by the earthquake erupted over majority of rural areas and the over-populated parts in Kathmandu. Initially, the damage estimates were around $5 billion, however, the numbers rose to a total of more than $10 billion. Ground shaking caused Nepal’s famous landmarks to collapse, including the Taleuju Temple and nine-story Dharhara Tower, which was completely decimated and filled the streets with its remains. The avalanches on Mount Everest also killed an additional 19 climbers, stranding hundreds at base camps on multiple levels of the mountain. At the end of the day, the total confirmed death toll was approximately 9000 people, including the deaths in other affected countries. 21,952 were injured and 2.8 million people were displaced by the earthquake, resorting to shelters with 3.5 million homeless. From a United Nations report, it stated that a total of more than 8 million people, more than a quarter of Nepal’s population, were impacted by the earthquake and the repercussions. 3 years later, over 70% of the earthquake-affected people are still living in shelters or homeless due to the slow recovery of restabilising its economy and rebuilding (2017, Ojha, Baldry and Shresthra).
Following the earthquake and Nepal’s slow road to recovery, new techniques are been attempted to read the record of past earthquakes with greater accuracy (2015, Sandiford, Rajendran, Morell). This is crucial for Nepal and surrounding countries because past tremors allow for scientists to develop better seismic forecast hazards (2016, Newman). Research universities and constitutions from Melbourne, India, Canada and Bhutan are still currently studying earthquake geology within the Himalayan area. Additionally, new technologies such as advanced digital topography datasets are being tested and used as earthquake computer simulation, which helps specifically identify the Himalayan front’s geological makeup (refer to graphic on powerpoint). This allows geologists know where possible plate tectonic movements in the future will be, and help reinforce areas of impact around the danger point.
