While shocked residents continue to sift through the earthquake rubble of Christchurch, New Zealand, geologists have made a stunning discovery: the killer quake occurred along a previously unknown fault line.
Now, as the death toll continues to mount, and the decimated city is wracked with fearful aftershocks, officials believe the number of dead may reach 150 or more.
For years scientists have made best guess about where the most likely killer quakes could strike. Christchurch was always low on their list of possibilities. Most seismologists believed the city was well away from any epicenters, lying more than 80 miles from the nearest fault line.
The concern has been focused on the city of Wellington. That city—like Los Angeles—is built on a major fault that’s expected to produce a great quake sometime in the not-too-distant future. Wellington is literally sitting on top of the fault line.
“Wellington has always been considered much more at risk because it straddles the plate boundary,” Kevin McCue, the Australian Seismological Center director told the UK’s The Independent.
But the first sign the scientist’s calculations were horribly wrong came at at 4:35 am on September 4, 2010. A 7.1 magnitude earthquake struck the South Island of New Zealand causing heavy damage in Christchurch.
Now, after two major quakes and hundreds and hundreds of aftershocks, scientists have abandoned their old theories and believe an overlooked fault—one that may be thousands of years old—has awakened with a fury.
Dr. Roger Musson, head of seismic hazards and archives at the British Geological Society, told The Independent, “It’s not a new fault in the sense that it has only just been created but it is a new fault that has only just been discovered. Some fault lines are very easy to see but the one under Christchurch is covered by sediment and would have been invisible without thorough geophysical searches.”
And that’s the problem. Until a region has been mapped, fault lines can remain invisible until they slip causing earthquakes that can kill people and tear cities apart.
September’s quake was much stronger, yet it did much less damage. Geologists have been trying to map the previously unknown fault ever since.
“This particular fault has probably been still or inactive for the past 10,000 years and we may find that after this burst of activity it will return to an inactive state for another 10,000 years,” Musson said. “The difficultly of disaster management is that, like military planning, you often find yourself using the previous war to prepare for fighting the next one.”
Discovering exactly where a fault lies and how deep it runs is critical to future planning of living areas, utility locations, and their general layout of a growing infrastructure. It also allows scientists to better predict the likelihood and possible intensity of future earthquakes.
A majority of world seismologists believe that certain cities are doomed to major or great quakes that may result in near total destruction and the deaths of thousands, even tens of thousands. Among the cities targeted for destruction sooner or later are such highly populated places as Los Angeles, St. Louis, Lima, Tehran, Istanbul and Karachi. Others that have slightly less risk are scattered around the globe.
Even areas that have not had active faults for millennia might have a quake at any time, although the probabilities are low.
Recently seismological studies of New York and Beijing have been found to be at higher risk of a killer quake than once thought.
New York City built on Manhattan Island. Nearly 20,000 years ago one of the greatest earthquakes ever to occur on North America shook the island.
Geologists have determined the earthquake would have bent seismograph needles with a magnitude of greater than 12-to put that into perspective, that ancient quake was about 1,000 times stronger than the December 26, 2004 undersea megathrust earthquake off the west coast of Sumatra, Indonesia.
If such a superquake were to strike Manhattan today the island would be swept clean.