Today the BBC called Christchurch “a city destroyed.” A report from the city opens with footage of buildings continuing to crumble as people run panicked in the streets. The count is 65 dead so far, with many more still trapped under rubble. The clock is ticking.
It’s a far cry from the result of a much bigger earthquake last September. Yesterday’s quake was magnitude 6.3; the one last year was 7.0. The older quake had seven times more shaking power, yet there was very little property damage and no deaths. Why was yesterday so different?
This is why:
I plugged the coordinates of the two quakes into Google Earth, and then took some measurements. Last September’s much stronger quake was centered 65 km (40 miles) from the center of Christchurch. Yesterday’s, however, was just 9.5 km (6 miles) away from the city center. To make matters worse, it was only 5 km (3 miles) deep.
Unless the fault line ran directly beneath City Hall, you really can’t get much closer than that. This may have been a much smaller earthquake in terms of magnitude, but because it was so close to a major population center, the perceived shaking and physical consequences were huge. On top of that, last year’s quake probably stressed the buildings of Christchurch in ways that could not be seen. That made them more vulnerable to yesterday’s much, much closer earthquake. It’s not a surprise that so many of them crumbled.
I know there are several readers of this blog who live in New Zealand. I fervently hope they, and their loved ones, are safe today.