The earthquake that struck Nepal at mid-day Saturday, killing 4,100 and counting, had not been a surprise. Nor is the death toll.
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Arguably, the entire planet is prone to earthquakes, which are generally caused by plate tectonics – movement by the plates on which the continents and oceans sit. But some places are more prone than others, and two such are the Indian subcontinent, including Nepal, and Israel. Both share another characteristic: Despite being in quake-prone areas, they are not particularly well-prepared.
Just two weeks before the quake, Geohazards International had warned that the people of Kathmandu are about 60 times more likely to be killed in a quake than the people in Tokyo, not least because of the country's poverty.
Even if building codes exist, there is always the question of old buildings constructed before the code applied, and new construction in which the code was not enforced properly.
Chile provides a good contrast: It is extremely prone to enormous quakes. But in some part because of strict building codes and controls, an 8.2-magnitude quake on April 1, 2014, followed by heavy aftershocks, and which caused a tsunami to boot, only killed five people (the government swiftly evacuated the coast as a preventative measure). Four reportedly died of heart attacks.
Not rare after all
The quake to hit Nepal on Saturday struck at mid-day, when many people are out and about, or the death toll might have been even higher as homes and offices collapsed due to the protracted shaking. It was powerful, measured 7.8 on the Richter scale, and was followed, as quakes are, by numerous aftershocks, some quite powerful too.
Among other things, the Saturday quake caused an avalanche on Mt. Everest, which swept through Base Camp and which the Nepal Mountaineering Association has said killed 17 people– the worst single-day toll on the world's tallest mountain. More avalanches on the mountain were reported Sunday as the aftershocks, the most powerful at 6.4, continued to rock the region.
At 7.8 on the logarithmic scale of earthquakes, the Saturday quake was considered powerful, and the Nepalese authorities have also called it "rare." But it wasn't, at least according to geological time-scales.
In the last 100 years there may have been only six quakes in Nepal rating more than 6.0 on the Richter scale, and nine rating more than 5.0. A century is an eye blink in geological terms. That is not "rare." And within that time was the 8.2 shock on January 15, 1934 that flattened Kathmandu, as well as the Indian cities of Munger and Muzaffarpur in the northern province of Bihar (adjacent to Nepal: Saturday's quake was felt there as well). In November 2013 New Delhi itself was rocked by a swarm of earthquakes, albeit mild ones measuring around 3. The writing was on the Nepalese wall.
Geologists calculate that this latest slip happened at a depth of about 9.8 kilometers underground, which is considered quite shallow for an earthquake. The deeper the quake happens, according to the theory, the more rock there is to absorb the shocks, though there are innumerable other parameters that determine how bad a quake is for surface dwellers.
Why Nepal quakes
The mere existence of the Himalayan mountain range, home to Everest, attests to the inevitability of quakes in the region.
The Himalayas, and the Tibetan plateau, were lifted up by the same force causing these quakes. Namely: India, geologically an island sitting on a tectonic plate of its own called the Indian Plate, began colliding with the Eurasian plate.
The question as to when that happened remains contested among the geological set, with some insisting on 55 million years, others a more recent 35 million. In any case, as the plates pressed together, and they have roughly the same density, neither got "over-ridden" by the other, and the planet's crust began to crumple up, folding like an accordion being pressed.
The upshot today is an enormously tall mountain range spanning 2,900 kilometers along the border between India and Tibet; a very thick continental crust where the plates collide; and earthquakes, as the plates are still moving. The Indian Plate is believed to be moving north-west by around 5 centimeters a year.
Thus the Himalayas are rising by about a centimeter and counting each year, though they drop by about as much due to erosion and other weathering forces, say geologists.
Bad land for quakes
So, earthquakes are highly likely in the Himalayan region, and as the Indian Plate presses the Eurasian plate, some of them are going to be nasty.
One serious consequence of these geological processes, as the U.S. Geological Survey puts it, is a deadly "domino" effect: "Tremendous stresses build up within the Earth's crust, which are relieved periodically by earthquakes along the numerous faults that scar the landscape," it writes.
It bears mention however that not all quakes involving the India Plate necessarily involve the Himalayans and the Tibetan Plateau – some involve the plate's other facets.
Among the worse recent quakes involving the southeast part of the Indian Plate, a geologically complicated region, was the 2004 quake just off Sumatra, that triggered tsunamis throughout the Indian Ocean basin. The tidal waves subsequent to the terrible mega-thrust quake, which registered about 9.1on the Richter scale, killed more than 200,000 people in Indonesia alone. That quake was caused by the Burma micro-plate overriding (subducting) the India Plate, say geologists.
In Israel, the reason for the quakes isn't the Indian subcontinent's vagaries but the Great Rift Valley, a crack stretching from Syria through most of Africa, which houses the Sea of Galilee and Dead Sea, too. The region has a history of violent quakes every hundred years or so, which the locals have been tracking the writhing of the land more or less since writing was invented, though it was usually ascribed to divine wrath rather than the molten earth core and plate tectonics. The ancient Israelites thought God was using an earthquake to help them win a battle by frightening the Philistines: "And there was trembling in the host, in the field, and among all the people: the garrison, and the spoilers, they also trembled, and the earth quaked" (Samuel 1, 14:15).
In 2013, a flurry of moderate quakes sent the Home Front Minister into a flurry of his own, warning that Israel was not ready and that a "big one" could kill 7,000. The last local "big one" was in 1927, and killed hundreds of people. In other words, based on statistics and nothing else, another is due any time.