M7 Canterbury New Zealand Earthquake Reconnaissance- Day 3

Telegraph Road Surface Rupture, Jumping Rocks in Christchurch, Structural and Geotechnical Engineering Meeting at Canterbury University

Tuesday 9-28

Rob Langridge flew back to Wellington this morning leaving the Americans to roam freely about the Canterbury Plains. Paul and I headed west this morning to look at some of the larger horizontal displacements at Telegraph Road. The road has been offset about 3 to 4 m in a right-lateral sense. A paddock (field) to the east of this large offset displays complex surface rupture. A house at the far end of the paddock was directly in line with the rupture. The house was completely shattered by the 3 m of rupture that went through it. The house has been sheared with the concrete slab foundation rotating and breaking into small, discrete blocks. We met with the homeowner who stated that it was just a bit of bad luck that he built his house directly over an unmapped fault. He stated that his paddock was nearly flat prior to the earthquake and had no idea there was a fault. New Zealand has national earthquake insurance coverage that is under the guidance of the Earthquake Commission (EQC). Their website and FAQS about the coverage can be found at http://www.eqc.govt.nz The homeowner said that his house is covered and now he has to go through the bureaucratic process to get paid.

We headed back to Christchurch to meet with Dr. Kevin Furlong (Penn State University) and a Canterbury University Ph.D. student, Nargas (I will get her last name tomorrow, apologies). We went to the rim of the large, extinct Miocene volcano that flanks the southern end of Christchurch. Trekkers found large rocks (up to 1.5 m diameter) along the crest that appear to have been thrown in the air during the earthquake. Nargas will likely map these rocks and analyze the potential high seismic accelerations that produced these jumping rocks. These rocks were truly amazing. It is hard to imagine what it might have been like to be on the ridge as rocks were literally bouncing in the air. As the earthquake occurred at about 4:30 in the morning it is unlikely there were any human witnesses.

We then went to Canterbury University with Kevin where he showed us some of the data that have been collected from the event. It promises to be an earthquake that will prove invaluable for seismic hazard studies. 

We then attended a joint special meeting of the New Zealand Geotechnical Society and New Zealand Society of Earthquake Engineering regarding the engineering aspects of the Canterbury earthquake. GNS Science and Canterbury University scientists and engineers described the strong motion aspects of the earthquake, the hazard issues posed by the event and the engineering aspects associated with strong motion. I was especially impressed by the amount of liquefaction that has occurred in the area. As it turns out Christchurch is built on marsh deposits and river deposits which are notorious for liquefying under cyclic shaking. One thing that became evident from the discussions at the meeting was that many houses are built on unreinforced concrete slabs that float when subjected to liquefaction or break up when vertical deformation occurs. There is great interest in what adjustments the New Zealand government might make to the building codes to address this issue.

Paul and I are pretty exhausted but are so energized by the amazing geology and incredible work being done around here that we will likely be up again at 5 am to get going. Tomorrow is another busy day. We will be meeting with Mark Stirling, GNS Science to look at rupture and evidence for large accelerations at the western end of the event. We will work our way back along the rupture toward Christchurch. We also hope to look at some of the impressive liquefaction evidence that occurred on the outskirts of the city.