Everest and the Toenail
One Day The Earth Will Drop Kathmandu – Earthquake Risk in Nepal
Nepal: Japan-size earthquakes, Haiti-like infrastructure.
Notes on a talk given by John Galetzka (Tectonics Observatory, CALTECH).
Presented by the Cultural Studies Group of Nepal
Last year I experienced a 6.6 earthquake here in Kathmandu, a few weeks earlier a 5.6 magnitude earthquake in Northern Virginia. Some years ago sitting outside in Malawi I watched the surface of the pleasant grass covered earth move towards me like an approaching wave. Those are my limited experiences of earthquakes. What follows is my interpretation of an absorbing talk given by John Galetzka. Any errors are mine and not his!
At this point the wonderful, hard continuous surface of planet earth feels more like a series of blocks of jelly, wobbling in constant motion. The two tectonic plates that concern us here in the Kathmandu valley are the Indian Plate — an Oceanic plate sliding on rock that is more dense than the Eurasian Plate above it. The Indian plate has an interesting history John illustrated in a rapid motion animation. About 100 million years ago it was cast adrift from the Antarctic Plate and began it’s voyage across what is now the Pacific Ocean. Essentially all alone on a long, very slow ocean voyage. Then it met and collided with the Eurasian Plate and is still subluxing (moving beneath) it. If I were sitting watching you in Northern India I could see you moving towards me at about 18mm – 22mm a year – hence the name of my blog for those that don’t know. That movement is faster than a toenail grows. This rate of movement is measured from a number of GPS stations that record not just horizontal but vertical movement of the earth’s surface. On one island in the Pacific the locals, having experienced a quake moved their village and rebuilt it around the GPS station so as to be safe. On another island John found all the cables had been cut and carried away because the local people thought George W. Bush was pushing a button in Washington and through the GPS device causing the ground to shake.
Kathmandu sits in the middle of the crush zone (which stretches to Russia) between the two plates. The city is built on top of the Main Himalayan Thrust plane – the direction the plate is moving in. Deep in the earth the rock moves smoothly, unnoticed, closer to the surface friction slows the rock, bending the Eurasian Plate (with the Himalaya Mountain Arc on top of it) causing the leading edge of the plate to bend backwards against the flow, rather like a ratchet on a clock against a cog. Closer to the surface the plates are locked and not moving. The plate flexes, creeping forward in the lock zone. Tension builds, the fault pops and cracks and then from time to time the fault line unzips and there is incomprehensible and unimaginable explosive release of energy. In geological time a minute advances on the clock. Tick, tock, bang.
There are millions of quakes every year throughout the world as plates jostle and move. Most of these nobody feels. In KTM I can feel minor vibrations from time to time and don’t notice them anymore — was that a truck going past? Ever so slightly the building is shaking, almost unnoticed. Fortunately the higher the intensity, the less frequent a major event.
Each step in the measurement of the magnitude of an earthquake represents a 33-fold increase in the release of energy. A magnitude 7 (close to that we experienced here last year – epicenter about 160 kms away and 20 kms down beneath the surface) releases the equivalent of 25 nuclear bombs – about half a million tons of TNT. A magnitude 9 quake in comparison (that which hit Japan) released the equivalent of 25,000 nuclear bombs – some 500 billions of tons TNT. The largest recorded earthquake occurred in Chile and registered 9.5. on Dr. Charles Richter’s Scale.
Some remarkable changes occur to the rock hard surface of the earth when there is an earthquake. In western Nepal there is evidence of a 15 meter (almost 50 foot) vertical displacement in the earth’s surface caused by an earthquake. John showed us a picture of a new 8 meter tall waterfall caused by a 7 magnitude quake. An 8.5 earthquake in the Pacific raised an entire an island up 3 meters. Where the ships used to dock there is now dry land.
When there is a massive earthquake the more developed the infrastructure the lower the loss of life. Maybe an obvious statement, but the facts are telling. The 7.0 quake that devastated Haiti recently killed 222,750 people, whereas the 9.0 quake that struck Japan killed 15,703 people — mostly as a result of the Tsunami. Japan is nearly back on it’s feet. In Haiti people are still living in tents and extremely vulnerable. Why? Because building codes are not only set but enforced in Japan. In the recording of the Japanese quake below had that been in a building in Kathmandu (where at best — and who knows how well built the houses are built — a house should withstand a magnitude 7) it would have been reduced to rubble. In Tokyo some hundreds of miles south of the main quake the building retained its structural integrity.
In Kathmandu where a 9.0 quake on a level with Japan is a distinct and enduring possibility given it’s location, the infrastructure is that of Haiti, the effect of a 9.0 quake on Kathmandu is hard to exaggerate. Sitting where we are, moving towards China, is one thing. Sediment amplifies seismic waves. Rock doesn’t vibrate as much. Kathmandu is built on sediment, surrounded by 2000 meter hills, in effect a wonderful way for nature to amplify the S waves that will shake and drop the majority of the buildings in this beautiful city to the trembling ground in a few short minutes, killing countless thousands, maybe a million people — hard to quantify. The process is called liquefaction where particles become suspended in liquid. The very ground will turn fluid. Most massive quakes occur under the ocean. In Nepal they occur beneath our feet, so a quake map like the one shown below of the last earthquake would be entirely deep red and over Kathmandu.
There is no sensible or known way to predict when an earthquake will happen. There are, however, ways of predicating in what region a quake will happen and the possible severity. In the movie below the P wave arrives first and gives tens of seconds notice for the arrival of the S wave. The P wave is fast and not that destructive, it is what comes next that inflicts the damage. If the fault unzips beneath Kathmandu there will be no advanced warning, the P and S waves arriving almost simultaneously. If it happens some 100 of kms away to the west or east there will be some warning.
So why are people building high rise apartment blocks in Kathmandu and tall office blocks with walls of glass? There is no manpower to enforce the building codes, even if they are adequate. Cultural problems exist in that less senior government officials will not pass up information that is problematic to their superiors. Preparation, advance warning, as seen in the Japanese video, is non existent here. Such preparation and education can allow the population to ride out an earthquake. If it is a mother of a quake it will devastate northern India too, so no aid will come from there. With no airport, no roads, a shattered infrastructure, Kathmandu feels remote.
When will it happen? All that is known is that it will. How big? Magnitude 8 or 9. A sure thing. Today, tomorrow, next week, next month, next year? The tension beneath Nepal builds as I type, incrementally it builds and builds. Irresistible forces propel us towards the sacred Himalayas. One day the plates will simply slip and unzip one or more devastating shifts in the structure of the ground beneath our feet and where shall Nepal be? What is the government doing about educating and preparing it’s people? It could prove to be too late to act. The Americans, however, following Haiti, beat a path to John’s door and have exhibited a level of preparedness that is at once pragmatic and admirable as was his excellent and riveting talk. John always travels with a ‘go bag’ of emergency supplies. Never stays above the first floor in a hotel (now he has a daughter) and from his lips today came words of wisdom presented not to create panic but to lay out the facts. It is for embassies and the government to begin serious and concerted preparations for what is occurring not in front of our eyes but beneath our feet.
Education, preparedness and early warning are the way forward. Make sure you have go bags in your house, car and office, keep walking boots (and socks) by the bed and a trunk full of equipment (ropes, sleeping bags, tents, pick axes, dry food, etc.) handy outside the house along with supplies of water and medications. Have photocopies of all your key documents. Know who your warden is and make sure that your embassy has the GPS location of your house.
The Last Ten Seconds: https://www.youtube.com/watch?v=n-FMpNBfna8
The Last Ten Seconds: https://www.youtube.com/watch?v=n-FMpNBfna8
