Far to the north of a Himalayan valley, a modest tremor in Tibet has become entangled with a catastrophe to the south, and the entanglement says something about how mountains and water answer to one another. Scientists examining the Nepal flood now suspect that the seismic trace they recorded was not the cause of disaster but its echo, the sound of a glacier's ice and rock surrendering to gravity and rushing into the valley below. The story is still unfolding, with hundreds dead, many more missing, and the precise chain of events still waiting to be proven.
Magnitude 5.0 Tibet Quake Reported Without Damage as Scientists Question Its Link to Nepal Flood
The related Nepal flood killed over 362 people and left more than 1,500 missing, including around 300 Indians; the Tibet quake itself caused no reported casualties.
The seismic signal may have been produced by the landslide itself
Mark
Why does a quake in Tibet get linked to a flood in Nepal at all?
Mimi
Timing. The flood hit Wednesday, and a magnitude 5.0 quake followed late Thursday, according to the German Research Centre for Geosciences. People naturally wonder if one caused the other.
Luke
But the epicentre was hundreds of miles north of the flood regions. Distance alone makes a direct link a stretch.
Mark
And the scientists say the seismic signal might have come from the landslide itself?
Mimi
One group does. The USGS also said a 5.2 event near Kodari, Nepal, was a landslide, not an earthquake. Daniel Shugar of the University of Calgary told CNN it was probably seismic energy from a landslide.
Luke
Note the hedging, though. Probably. May have. The glacier-collapse account is a working hypothesis, not a finding.
Mark
What is the hypothesis, in short?
Mimi
A big section of glacier broke away and fell into the valley. A rock landslide may have followed, forming a fast mixture of ice and rock that gathered sediment and water downstream during the monsoon.
Luke
And it has a hole. Shugar himself said the huge volumes of water in the videos are hard to reconcile with it. Weeks of work lie ahead.
Mark
What about the human toll?
Mimi
Over 362 dead, more than 1,500 missing, around 300 of them Indians. The Tibet quake itself caused no reported harm.
Luke
Worth saying the death toll figure is as reported in this coverage, and the missing count may shift as searches continue.
The Pulse
- A magnitude 5.0 tremor in northern Tibet registered on seismic instruments in the late hours of Thursday, yet no one reported injury or ruin.
- Hundreds of miles south, a violent flash flood tore through parts of Nepal and China, leaving hundreds dead and more than 1,500 unaccounted for.
- Investigators are challenging the obvious story: the quake may not have triggered the landslide, and the landslide may instead have generated the seismic signal.
- A possible glacier collapse, followed by a fast-moving mass of ice and rock gathering sediment and monsoon water, is being tested against the sheer volume of floodwater seen in footage.
- Researchers say weeks of analysis may be needed, and the search for missing people, including around 300 Indians, continues while the picture remains incomplete.
Far to the north of a Himalayan valley, a modest tremor in Tibet has become entangled with a catastrophe to the south, and the entanglement says something about how mountains and water answer to one another. Scientists examining the Nepal flood now suspect that the seismic trace they recorded was not the cause of disaster but its echo, the sound of a glacier's ice and rock surrendering to gravity and rushing into the valley below. The story is still unfolding, with hundreds dead, many more missing, and the precise chain of events still waiting to be proven.
Late on Thursday, the German Research Centre for Geosciences recorded a magnitude 5.0 earthquake in northern Tibet, at a shallow depth of about 10 kilometres. No deaths or property damage have been reported from it.
The quake's location is significant because of what came the day before. On Wednesday, a devastating flash flood struck parts of Nepal and China, hundreds of miles south of the epicentre. Hundreds have died, and more than 1,500 are missing, including roughly 300 Indians. One figure in the coverage places the confirmed dead at over 362.
The natural question is whether the two events are linked. Some scientists investigating the disaster doubt the obvious answer. They believe the seismic signal did not set off the landslide that devastated Nepal, but may instead have been produced by it. The United States Geological Survey has drawn a similar distinction, attributing a seismic event near Kodari, Nepal, to a landslide rather than an earthquake.
Daniel Shugar, a geologist at the University of Calgary, told CNN that the recorded signal was probably seismic energy released by a landslide. The working theory is that a large section of glacier broke away and fell into the valley, mixing with rock into a fast-moving slurry that gathered sediment and water during the monsoon season.
The account is not yet complete. Shugar said it could take weeks to establish exactly what happened, and he pointed to the enormous volumes of water visible in the flood footage as a detail the current explanation does not yet fully account for.
For now, a large block of ice breaking from a Himalayan glacier may have helped set off the flooding in Nepal, while the Tibet quake has so far caused no reported harm. What comes next is the scientists' continuing analysis, and the search for those still missing.
Late on Thursday, the German Research Centre for Geosciences recorded a magnitude 5.0 earthquake in China's Tibet region. The centre put its depth at 10 km, in the northern part of the region. As of the latest reporting, no deaths and no property damage had been reported.
The location matters because of what happened a day earlier. On Wednesday, a devastating flash flood hit regions of Nepal and China, and the quake's epicentre lay hundreds of miles north of them. The flood killed hundreds of people. More than 1,500 are missing, among them around 300 Indians. One figure in the coverage puts the confirmed dead at over 362.
The obvious question is whether the two events are connected, and one group of scientists investigating the disaster is skeptical of the obvious answer. They believe the seismic signal did not trigger the landslide that devastated Nepal. They suggest the reverse: the landslide itself may have produced the signal.
The United States Geological Survey has made a similar distinction. It said that a 5.2 seismic event near Kodari, Nepal, was caused by a landslide and was not an earthquake.
Daniel Shugar, a geologist at the University of Calgary in Canada, told CNN the recorded event was probably seismic energy released by a landslide. The scientists' working picture is that a huge section of glacier broke away and fell into the valley. A rock landslide may then have produced a fast-moving mixture of ice and rock. That mass would have picked up more sediment and water as it moved downstream, during the monsoon season.
The account is not yet complete. Shugar said it could take weeks to establish exactly what happened. He pointed to a piece that does not yet fit: the enormous volumes of water visible in what he called absolutely horrific videos of the flood. In his words, those volumes are hard to reconcile with the explanation as it stands.
For now, the assessment suggests that a large block of ice breaking from a Himalayan glacier may have helped set off the flooding in Nepal. The Tibet quake, by contrast, has so far produced no reported casualties or damage. What to watch is the scientists' continuing analysis over the coming weeks, and the search for the people still missing.
Notable Quotes
Probably seismic energy released by a landslide.— Daniel Shugar, geologist, University of Calgary, to CNN
What is hard to reconcile is the gargantuan volumes of water that we see in these absolutely horrific videos.— Daniel Shugar, University of Calgary
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