In an article titled Sobering alarm for cities on faultline; the Press (NZ), Nov. 2, 2011, describes some unusual geologic conditions and sounds and alarm for cities on faultlines. In the report, it quotes Erol Kalkan, manager of the United States Geological Survey’s national strong-motion network, said the February earthquake was “remarkable on several counts”. Some quotes from the report:
“The ground motion was much larger than previously recorded, the high intensity of shaking was greater than expected, particularly for a moderate-size earthquake, and the liquefaction-induced damage was extensive and severe within the central business district of Christchurch.
“Many urban areas are built over soft sediments and in valleys or over basins, for example the San Francisco Bay area and Los Angeles metropolitan. These are urban areas that sit atop geological features that may exaggerate or amplify ground motion, just as Christchurch experienced.
“The question is how to apply or account for such significant, higher-than-expected ground motions, as seen in Christchurch.” The Christchurch quake would have a long-lasting and significant impact on engineering practices and provided a huge opportunity to fuel scientific knowledge, Kalkan said.
GNS Science’s John Callan said the quantity and quality of data collected during the quake was “almost unprecedented internationally”. “Analysis of this data is already having a significant impact on seismology worldwide.”
Another related article from Our Amazing Planet, Nov. 1.