The 6.3 magnitude earthquake that struck Christchurch, New Zealand on Feb. 22 demonstrates the vulnerability of urban centers with important lessons for the US. And a 30 million ton block of ice sheared off a New Zealand glacier just minutes after the violent earthquake there. Civil engineer Thomas D. O’Rourke says, "Some reasons for the serious damage are the many unreinforced masonry buildings in Christchurch and the occurrence of soil liquefaction throughout the city."
Soil liquefaction is the transformation of saturated granular soil into a liquid-like substance from high groundwater pressures triggered by strong shaking. The soil liquefaction in Christchurch has damaged many miles of underground water mains, sewers, and electric power cables, and damaged several bridges. Many US cities in areas vulnerable to earthquakes have many unreinforced masonry buildings, like those in Christchurch, and are founded on liquefiable soils." The New Zealand quake was actually an aftershock associated with the 7.1 magnitude Darfield earthquake that occurred west of Christchurch on Sept. 4, 2010. Since then, aftershocks have been occurring on the Greendale Fault, the causative fault, and progressing toward the Christchurch central business district. The relatively shallow depth of the earthquake below the city shows that even 5 to 10 seconds of strong shaking can have devastating effects.
Researcher Denis Callesen says everyone in New Zealand had been expecting an iceberg to "calve" from the glacier for the past month, but the event was finally caused by the earthquake. Yahoo.com news quotes him as saying, "Within about a minute of (the earthquake), the staff at the lake heard from five kilometres away (from the glacier) a sound that sounded like a rifle shot and then over the next two minutes all the events started to unfold. I have absolutely no doubt in my mind that the earthquake was the trigger." Yahoo quotes local official Richard McNamara as saying, "You could argue whether the earthquake precipitated it or not–the fact is that the terminal face was about due to carve anyway."
Thank goodness there has never been an earthquake in sunny Nashville, where we’re holding our Dreamland Festival in June. We expect to have a lot of fun as well as some amazing experiences, so we hope you’ll join us–the number of people we can accommodate is EXTREMELY limited, so don’t delay, get your tickets today!
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