A 7.9 magnitude earthquake has just hit 80km west of Pokara in Nepal, with reports of damage to many buildings in Kathmandu. The quake was felt heavily in Delhi, and across much of the Himalayan region. Reports of casualties are yet to come in, but comparisons with recent similar quakes would indicate we could expect thousands of fatalities.
Initial social media reports suggest that more modern reinforced concrete buildings have fared reasonably well, though there has been significant damage, the buildings have not completely collapsed. The 19th century Bhimsen Tower appears have have been completely destroyed, and there are reports of the non-engineered homes being heavily damaged and collapsing.
Information is coming out of Kathmandu, but there is currently less news from Pokara and the towns in the Kathmandu valley, both closer to the epicentre of the quake and where there are significantly more non-engineered buildings, and thus we would expect more casualties.
The possibility of a quake in Kathmandu has long been anticipated, and there are plans in place for this event. Records indicate a major earthquake around once every 75 years, with the last major earthquake in 1934 (81 years ago). The Kathmandu Valley earthquake Risk Management Plan (http://geohaz.org/projects/kathmandu.html) completed in 1999 assessed the risks and aimed to mitigate the damage to the region.
Earthquake resistant construction techniques were taught (and known about prior to the inception of the project), and I must presume that many of the buildings constructed more recently will have behaved adequately in this earthquake. The older building stock may not have been so resistant to an earthquake of this magnitude.
Now is the time to focus on the emergency works, to first rescue survivors, then to provide Water, food, sanitation and safe shelter to those who require it.
Once these priorities are met, the international community must look to retrofit of existing buildings, or to the demolition of buildings which would be unsafe in an earthquake of this magnitude. This process is well underway in New Zealand, following the 2011 Christchurch earthquake, it is costly and painful, but ultimately the assessment and improvement of earthquake prone buildings will save many thousands of lives.
Disclaimer: I wasn't involved in the Kathmandu project, but I have visited this region. I'm a structural engineer working in New Zealand, with an expertise in mud brick construction.
Durbar Square in Central Kathmandu
Durbar Square in central Kathmandu
Durbar Square in central Kathmandu in happier times