4/25/15 Nepal Quakeupdated 5/15/15
The 7.8 Magnitude earthquake hit Nepal April 25, 2015 at 06:11 UTC (11:11 AM local time). The epicenter was 50 miles NW of Kathmandu. It was the worst quake in Nepal in 81 years. Over 8,000 have been confirmed dead, over 11,000 injured, 450,000 internally displaced and over 100,000 have been left homeless. Many older buildings were destroyed. Some modern buildings seem to have fared better. However a number of newer buildings have been built quickly without regard to building codes. These buildings have not stood up so well to the quake. In the countryside, many areas are were cut off by landslides and avalanches. Reports that have been received from villages suggest widespread devastation with most of the buildings destroyed by the quake or the landslides that followed. Resources are stretched thin as the government struggled to rescue survivors and provide aid. Rebuilding will take a long time due to the extent of the damage
Areas that are normally a 2 or 3 days trip from Kathmandu were completely cut off for days. The army was mobilized to help in the rescue effort. International relief is being flown into the country. The airport was been closed intermittantly due to aftershocks. As is usual for a quake of this size, there have been frequent aftershocks.
On May 12, 2015 the worst aftershock yet with 7.3 Magnitude hit at 7:05 UTC (12:35 pm local time). Its epicenter was 50 miles east of Kathmandu. The USGS classified the second quake as an aftershock because it occurred right at the eastern edge of the slip zone of the original quake. At least 48 people were killed in Nepal from this second quake and possibly another 17 in India, according to the BBC.
An avalanche on Mt Everest killed 18 people at the 18,000 ft high Base Camp, where climbers begin the climb. Survivors are being airlifted off the mountain. Over 100 climbers were stranded above the avalanche. Helicopters were able to rescue them from Camp 1 at 20,000 ft.
Seismic activity in this area is driven by the same forces that raised the Himalaya mountains. This area is feeling the effects of the collision between the Indian tectonic plate and the Eurasian plate. (See the Plate Tectonics page for more information on this process). Over the past few millions of years the Indian plate traveled across the Indian Ocean, finally slamming into Eurasia with enough power to crumple the landscape and push the Himalaya mountains 5 miles above sea level. This collision is still occurring. Stresses in the earth's crust continue to produce earthquakes. See the USGS report on the original quake. And the USGC report of the major aftershock of May 12.
Earthquakes are the result of pressure building up at a fault. When one section of the fault ruptures, it relieves the pressure in that section but can increase pressure in a neighboring section that didn't move. That leads to a subsequent quake to relieve that pressure. It can take many years for this to happen. The previous large quake in this area was in 1934 to the east of both of these recent quakes. The May 12 aftershock was located between the 1934 quake and the April 25 one, which increased the pressure likely triggering the May 12 shock.
News Stories about the quake:
Nepal Earthquake fears grow for remote villages as over 4,000 confirmed dead (The Guardian 4/27/2015)
Villages near the Nepal earthquake epicenter are desperate as death toll tops 4,000 (New York Times 4/27/2015)
A scene of destruction after ice thunders into Everest Base Camp (New York Times (April 27, 2015)
Nepal Earthquake Happened Right on Schedule, Scientists Say (Huffington Post April 27, 2015)
Fallen: Nepals Historic Landmarks After the Quake (CNNApril 27, 2015)
Nepal Earthquake Death Toll Hits 5,000 as Aid Starts Flowing (NBC 4/28/15)
Dozens die in new tremor near Everest (BBC 5/12/15)