Cascadia's Fault - Jerry Thompson [148]
Little more than a month later, on February 27, 2010, another big subduction earthquake struck the coast of Chile. At magnitude 8.8 it released approximately five hundred times more energy than the Caribbean shock yet it killed far fewer—roughly seven hundred lives were lost in Chile compared with the 200,000 in Haiti. Observers commented that construction quality in Chile was definitely better because building codes have been strictly enforced ever since their last big quake in 1960—at magnitude 9.5 still the largest rupture ever recorded.
The February jolt occurred on the same fault, twenty-two miles (35 km) beneath the sea floor, and apparently picked up right where the last one stopped. It ripped the next four-hundred-mile (640 km) segment of the subduction zone and probably relieved most of the remaining stress built up in the system. That was the good news. But there was more.
Because the 1960 quake did not rip the entire fault, scientists expected the next segment to go at any time. So several groups of researchers had installed an extensive array of GPS monitors to keep track of the strain build-up. Computer models (including one by Kelin Wang at PGC on Vancouver Island) then made predictions of how much the fault would move when the last segment finally did break.
On February 27 the predictions turned out to be right on the money. Almost ten feet (3 m) of nearly instantaneous horizontal motion was measured by GPS instruments at Concepción. The land lurched sideways nearly nine feet, just like Wang’s model projected. Which is the same kind of movement Herb Dragert and Mike Schmidt expect to see in Victoria when Cascadia rips loose. Scientists can now be fairly confident in predicting which part of a fault is likely to break, how far it will move, and how large the jolt will be.
But in Chile other positive factors were at work as well. One of them was a higher level of public awareness. Because enough people remembered 1960, they knew what to do when the ground started to rumble. Those living in danger zones near the beach immediately ran to higher ground without waiting for someone in authority to issue an evacuation order. According to Kelin Wang, “Numerous lives were saved by this kind of self-evacuation ... The importance of educating the public far exceeds that of warning buoys.”
And then it happened again. On Tuesday, February 22, 2011, a strike-slip fault near Christchurch, New Zealand, ruptured in a magnitude 6.3 earthquake that killed more than a hundred people outright and buried hundreds of others in rubble. This time two tectonic plates ripped past each other horizontally, like the San Andreas plates had done. So it wasn’t a subduction quake like the ones in Chile or Alaska or Cascadia (no heaving up of the ocean floor and no tsunami), but it was a rupture in another corner of the Pacific region’s infamous Ring of Fire.
Less than a month later, on Friday afternoon, March 11, 2011, another segment of the Ring of Fire tore apart in a magnitude 9 earthquake that did jack up and shift the ocean floor off the northeast coast of Japan near the city of Sendai. The shockwaves lasted between three and five minutes and caused skyscrapers in Tokyo—231 miles (373 km) away—to sway like trees in a strong wind. The tsunami was seen around the world almost instantly, covered live by Japanese television crews in breathtaking and heartbreaking detail for hours on end. We were all able to witness immediately the apocalyptic extremes of seismic chaos.
Rolling balls of flame and thick smoke billowed from ruptured tanks at an oil refinery. A farm family’s home burned furiously as it was carried away—floating atop a tangled mat of splintered lumber and logs, twisted sheets of metal from busted barns and sheds—all of it swept across the coastal lowlands on a thirty-foot (10 m) wave, a churning tsunami gumbo of black soil and seawater. Large commercial