The massive tremors and ensuing tsunami that devastated Japan earlier this month was an order of magnitude more destructive than anything that has hit the continental Unites States in historical times. But seismologists say that a similar event could well strike here. In fact, it’s only a matter of time. And compared to Japan, we’re far less prepared to deal with the consequences.
The danger zone is not California. While Los Angeles and San Francisco suffer frequent damaging quakes, they owe their seismic woes to a relatively shallow phenomenon called a slip-strike fault, caused by two tectonic plates sliding against each other. Sendai was a result of something far more dangerous: a so-called subduction zone, a deep-lying discontinuity caused by one plate slowly burying itself under another.
In both cases, earthquakes are caused by the slow building of pressure as the two plates move relative to one another, but remained locked together at the fault line. The strain increases steadily until the fault gives way, releasing the energy in the form of an earthquake. While strike-slip faults are relatively shallow, a subduction fault is deeper and can release a lot more energy. “One of the signatures of this type of fault,” says Mike Blanpied, associate director of the US Geological Survey’s Earthquake Hazards Program, “is that they sit quietly until they create a giant quake.”And by giant, he means monster. The Sendai event contained more than 30 times the energy of the San Francisco Earthquake of 1906.
Only one such region lies within the Lower 48. Read the rest of this entry »
Filed under: disaster, Cascadia Subduction Zone, disaster, earthquake, Sendai
December 5, 2010 • 10:26 pm
Crazy video, via Mark Frauenfelder at Boing Boing, of Xmas shoppers trampling each other to get at Black Friday bargains at 4am.
Not a proud moment for humanity. But as I’ve written before, this kind of crowd dynamic isn’t unique to the US; in 19th century Russia 1389 people died at a coronation ceremony for Tsar Alexander II of Russia when a rumor circulated through the crowd that souvenirs were in short supply, causing people to rush forward en masse.
Filed under: disaster
Another day, another major earthquake — this time, a magnitude 6.9 tremblor that killed at least 300 people in China’s Qinghai province. I’ve been talking to a lot of seismologists lately, and they all agree that the recent cluster of devastating earthquakes, including the jolt that shook northern Mexico earlier this month, do not point to some planet-wide upheaval; it’s all a statistical coincidence, they say. Well, that may be true, but it sure doesn’t feel that way. It feels like something is up. Not surprising, then, that a few days ago false rumors started proliferating in Southern California that the Big One would strike imminently.
Seismologists’ reassurances would be more soothing if they had a detailed, empirically verified understanding of how earthquakes work. Unfortunately, they’re the result of forces at work deep within the earth that are difficult to gather data on. So the science remains in its early stages. But progress is being made — and soon, you can be a part of the process. As I wrote recently on the Pop Mech website:
As part of their battle to understand and protect against the destructive force of earthquakes, seismologists have gone to extraordinary lengths. They have bored holes deep into the earth’s crust, laid out arrays of sensors hundreds of miles across, and built supercomputers capable of running simulations at teraflop speeds. But the most exciting new effort in cutting-edge seismology involves a piece of instrumentation that’s a good deal less exotic. It’s called an iPhone. Read the rest of this entry »
Filed under: disaster