Lori Dengler: Japan Reconnaissance - Day 1

Posted on April 28 2011

Friday – Saturday April 29 – 30
A long day in transit but flights were on time, the San Francisco – Narita flight half empty (the flight attendants say a relatively common aftereffect of 3-11) and an easy train trip to Ueno where I’m staying tonight. In the first few weeks after the earthquake, there were major power disruptions and train schedules were chaotic. That seems to be over for the time being. I saw almost no signs of an earthquake en route from Narita to Tokyo. In Ueno, the main sign is numerous tables soliciting donations for relief efforts and lots of anti-nuclear paraphernalia (T-shirts, signs, buttons, satchels, etc.). Tomorrow I take the Shinkansen to Sendai to begin filed work in earnest. Normally I would have flown, but the tsunami caused major damage to Sendai’s airport and access is still limited.

M7 Canterbury New Zealand Earthquake Reconnaissance- Days 7 and 8

Posted on October 03 2010

Tour of northern South Island

Monday 10 – 4

We have had amazing weather during the entire time we have been here. Our trip from Kaikoura to Hanmer was beautiful. It was great to see the Hope fault in Spring with flowers blooming and the trees a vivid green from their new leaves. We drove into Hanmer Springs in the early afternoon. As we crossed the bridge above the Waiau River we saw a man strapped to a bungy cord preparing to jump off the bridge into the gorge below. Not wanting to pass up a good spectacle we pulled across the bridge and watched him go. He came pretty close to hitting the water. I tried to get Paul to try it but he wanted no part of it. We then went to view some trench sites where Rob Langridge, Will Ries and I trenched during our investigation there in 2008. The Hanmer Basin is a large pull-apart valley formed by a right-step of a few kilometers in the dextral slip Hope fault. The northern part of the valley consists of a series of large normal faults upon which the town of Hanmer Springs is built. The faults are active. We have been trying to determine just how active they are and how they relate to the activity of the Hope fault. Hot springs that flow from the faults have been developed into health spas making the town a destination spot.

After spending a couple of hours in Hanmer we headed to Lewis Pass. The road to the pass is amazingly beautiful. Enormous flights of river terraces flank the Waiau and Hope Rivers. In at least one place the Hope fault deforms all but the youngest terraces. We got to Lewis Pass in the late afternoon. This is an exceptional location as the Alpine fault runs through the pass and through a large flight of river terraces. The area has been studied for years and is a favored field trip location for Kiwi geology classes. At this northern location the Alpine fault is starting to dump its strain onto faults of the Marlborough fault system, such as the Hope, Clarence, Awatere and Wairau faults. Thus, individual slip events are somewhat smaller than the 8 to 10 m of horizontal slip that are typical of the central part of the fault. In addition, during each event, there is a small amount (less than 1 m) of vertical slip on the fault. The river terraces exhibit a long history of faulting with older, higher terraces offset greater amounts than the younger, lower ones. We put on our gum boots (rubber boots) and walked through the wet field to see the fault. In the middle of the field a low, long, dark gray wall extends across the fault. The wall was constructed across the fault in the 1970’s in an attempt to document whether the fault creeps. Today, the wall is as straight as the day it was constructed. A sign erected next to the wall proclaims that this is proof that the fault doesn’t move slowly. This proclamation has been a source of debate among geologists. The question exists, did they build the wall long enough to capture the between earthquake deformation of the fault? Is the wall rotating within the fault zone as a rigid beam? New maps have been created recently of the terraced field. Perhaps the story will soon become more clear.

We spent the night in Reefton, a coal and gold mining town on the west coast. We camped in a field, that, turned out, in the morning to be the town rugby pitch. From there we headed down the coast through Greymouth and on south to Franz Joseph. We drove along the eastern Tasman Sea for a few hours. The South Island West Coast is famous for its heavy rains and hard winds. This day was beautiful, sunny and warm. Deep forests and fern bush line the roads except for paddocks that have been cleared for sheep and dairy. The spectacularly steep and white South Alps dominate the view to the east. A few hours later we were in Franz Joseph, the site of the Franz Joseph glacier. During the end of the last glacial maximum the glacier actually extended kilometers west of the current coastline. Now it is retreating rapidly as it has been doing for at least the last 200 years. We took a walk up to a lookout where we could view the glacier coursing through deep native rainforest. It is quite a sight.
We then drove back up the coast and turned inland to go to Jackson’s on the west side of the Alps along the Alpine fault. This is another location that Rob Langridge, Will Ries and I trenched in 2008. The area is surrounded by incredibly steep mountains with huge alluvial fans and debris chutes. It was nearly dark. The mountain “tops” were bright orange. We set up tents at one of the few inhabited places in the area. That night, the sky was amazingly bright from the Milky Way, Mars and Jupiter in the sky. The Magellenic clouds were enormous.

We awoke to the “whump-whump” sounds of Wekas (chicken-sized flightless birds) and their chicks exploring around our tents. Bell birds and Tuis were singing loudly; what an amazing alarm clock. The morning was grey and damp. We attempted to dry our tents so they could make the flight home. A short drive to the west brought us to the beautiful Arthur’s Pass. This is the area where the troupe in Lord of the Rings made it through the high peaks. At the top of the pass we stopped to view the Keas (pronounced Kee-Ahs). They are large alpine parrots. These are amazingly beautiful and mischievous birds that show no fear of people. They fly right up to you and pose for photos. If you are not careful they will also fly to your car and pull your windshield wipers and antenna off the car.

We are now sitting in Christchurch airport about to board the first leg of a long flight home. We’ll take our first flight to Auckland where we’ll catch a 12 hour flight to San Francisco and then Arcata. Our flight from here leaves on Monday at 4:30 pm. If all goes as scheduled we will arrive home at 4:56 pm on Monday. So, we should only travel for 26 minutes. You have to love the International Dateline.

Now will be days of catching up on things that have been ignored for the past 10 days. We have learned an incredible amount from this earthquake. I think this has proven to be a great learning experience for Paul. We’ve made great contacts with fellow researchers from GNS Science, Canterbury University and Penn State. Thank you again to all who have made this trip possible.

M7 Canterbury New Zealand Earthquake Reconnaissance- Day 6

Posted on October 01 2010

We’ve now left Canterbury and driven north to Kaikoura where the Hope fault meets the Pacific Ocean. This is a truly magical area with snow-capped peaks running straight to the water. The Hope fault is the southernmost of the Marlborough fault system, a series of right-lateral strike-slip faults that strike northeast. The Alpine fault, the big dextral slip fault that forms the backbone of the southern Alps and has most of the Pacific-Australian plate converge rate across it begins to lose its slip to the north and apparently shunts that motion onto the Marlborough system. The Hope fault probably takes on the majority of that motion according to GNS folks such as Kelvin Berryman and Robert Langridge.

We camped near the beach last night and saw amazing stars. The Milky Way was a bright band in the sky, constellations were unrecognizable, familiar constellations were missing. The most amazing sights in the southern sky are the Magellanic Clouds, two dwarf galaxies that are prominent. Nothing like them exists in the northern hemispheric sky.

Today we head southwestward along the Hope fault. We’ll look for evidence for large-scale right slip displacement. We’ll stop in Hanmer Basin, a large pull-apart basin that Rob Langridge and I worked on a couple of years ago. From there we’ll head to Lewis Pass and across the Alpine fault.

All is good.

Cheers

M7 Canterbury New Zealand Earthquake Reconnaissance- Day 5

Posted on September 30 2010

Visit to site of massive liquefaction at Kaiapoi and Avondale; Downtown Christchurch destruction

Thursday 10-1

Day 5, we joined Mark Stirling (GNS Science) to visit Kaiapoi, a river town north of Christchurch that was heavily affected by liquefaction (seismic liquefaction is the result of uncompacted materials (usually sand) that is saturated becomes shaken and looses its strength). Kaiapoi is located in a low-lying area, near the coast, that is a former delta/estuary of the Waimakaririri River. Materials there include sands, silts and peats. The downtown is quaint with river walks, pedestrian bridges across the streams and neighborhoods that range from older, generally single story dwellings on established blocks to newly-constructed multi-story houses.

[Just to note, we are not doing anything associated with the liquefaction analysis other than observing its effects. Much of the work documenting and analyzing the earthquake-induced liquefaction in Canterbury is being conducted by Canterbury University Department of Civil and Natural Resouces Engineering Associate Professor Misko Cubrinovski and his students. He presented impressive documentation of their work at the New Zealand Geotechnical Society Special Meeting we attended on 28 September. A link to the the geotechnical aspects of the event can be found at http://quake.canterbury.ac.nz ]

The ground failure through this area was wide-spread and devastating. The recently-renovated New World supermarket (think scale of Safeway or Kroger) will have to be torn down. Several older downtown business buildings looked to be complete losses and were red-tagged. Those areas adjacent to the river had suffered liquefaction and also large scale lateral spreads. In some locations the extension cracks are large enough to stand and extend for 10‘s to 100‘s of meters parallel to the river bank. Many of the pedestrian bridges that cross the smaller tributaries to the Waimakaririri River were pleasant thoroughfares in town. The lateral spreads caused them to shorten and compress causing the bridges to become bent like pretzels.

The largest impact to the area is likely the damage to the residential structures. Walking through the neighborhoods is eerie as houses are abandoned, many with contents emptied. Work crews are removing sand and silt that flowed up on the ground, in places to depths greater than 0.5 m thick. Remnants of sand volcanoes peak out around the foundations of houses, many of which are now tilted. Numerous garages and houses have become disarticulated. It appears that, in some cases, roads were built on gravel beds that floated during the liquefaction process; meanwhile, the houses along the road placed heavy loads on the soils and sank. The result is that we are walking along streets and looking into yards that have depressions of about 0.5 to 1 m deep centered around a sunken house. It became clear, from the discussions with geotechnical folks, that a big problem, aside from building on liquefiable materials, is that many of the foundations consist of unreinforced concrete slabs. Steel in the concrete would have kept the houses from self-destructing. That wouldn’t have prevented that subsidence problem though.

Another issue that was obvious as we first arrived in the neighborhood is that utilities are completely shattered by liquefaction. Port-a-loos (Porta-potties in US-speak) line the streets as all sewage lines were severed. Likewise, water and electrical lines have been disrupted. The infrastructure repair and replacement process will take a long time.

We also found neighborhoods that appeared almost unaffected by liquefaction aside from few, scattered sand spouts and cracks. We didn’t have construction plans for these neighborhoods but Mark Stirling was under the impression that some of the newer neighborhoods were built on reclaimed land that had been engineered. They seemed to perform well.

I left Kaiapoi knowing that there are communities in the Humboldt area that have similarities in construction practice and geologic setting. We have documented some liquefaction during recent earthquakes there but have not experienced the extensive, community-wide devastation that we observed in Canterbury. Certainly, a factor is the amount and duration of ground motion. The poorly consolidated, sandy materials were prone to liquefaction. It leads one to question whether these areas should be developed. The question that will be paramount to Kaiapoi for the future is what will be done with the town. Materials that are prone to liquefaction and have liquefied in the past, remain liquefaction hazards. Without substantial geotechnical engineering or structural foundation design, the town will likely continue to have these problems in future earthquakes.

We completed the afternoon by walking through downtown Christchurch in the area that received all of the international press with collapsed brick building façades and smashed cars. The main destruction occurred on Manchester Street, an area of older unreinforced masonry (URM) buildings near Victoria Square. The Kiwis are quite efficient in taking care of these hazards. Instead of letting a damaged building partially stand behind a temporary fence for months like I’ve seen happen in California they pulled the buildings down with diggas (excavators) within days of the earthquake. This has a two-fold effect, first, the regional council or city council, in conjunction with engineers, declares the building finished and it is destroyed. This eliminates future hazards (especially with the significant aftershocks that continue, even now, a month later). Second, there is a sense that the city is not going to sit on its hands but is ready to move forward.

So, Manchester Street is now the site of vacant lots scattered between undamaged modern steel and concrete buildings and reinforced brick buildings. One thing we found as we worked our way into the city is that many of the brick buildings that seemed untouched by the earthquake had been retrofitted with steel. It seemed to work! Another thing we noticed, which is typical for most large earthquakes, is that for the most part the city appears untouched by the earthquake. You have to go looking for damage which is localized and not citywide. The media tries to make the devastation look widespread and total which is not the case. As we walked through Christchurch we were impressed with how vital the area looks as Spring is just kicking in with flowers blooming, fruit trees blossoming and people going about their everyday business.

We met with Kevin Furlong again last night for dinner and a beer. We had great discussions about New Zealand and western US tectonics. We were in the old town in a brewpub with brick walls (that had been retrofitted)…how soon we begin trusting the engineers and architects again… Thanks to Kevin for his generosity in time and resources as we invaded in the middle of an extremely busy time!
We just saw the GNS Science geodetics crew pull out of the motel to head back to Wellington. They said they got tons of data and now have days of post-processing. It was great getting a chance to see them again. Mark Stirling headed back yesterday. It has been a bittersweet return to New Zealand. It has been great to see all of my friends that Eileen, Ethan and I made when we lived here two years ago, unfortunately it had to be a damaging earthquake to bring me back. We’ll definitely be heading back soon.

We leave Canterbury to do some touring of the big South Island faults. I can’t bring Paul to New Zealand without getting him onto the Hope and Alpine faults. We’ve brought tents and sleeping gear so, we’re just going to do a route up the east coast to Kaikoura and then travel to Hanmer Springs, across the Alpine faut at Lewis Pass and onward to the West Coast. From there we’ll head to Hokitika, then across Arthur’s Pass again at the Alpine fault then back to Christchurch to depart on Monday.

We’ll keep blogging…

M7 Canterbury New Zealand Earthquake Reconnaissance- Day 4

Posted on September 29 2010

Reconnaissance of Western end of Surface Rupture at Hororata and GreenDale

Wednesday 9-20

It’s hard to believe but this is Day 4 of the reconnaissance. The weather has turned a bit as we have some winds coming out of the west along with a bit of moisture. We can only hope that it will hold out a bit so that we can stay in the field and, more importantly, so that these fragile features are preserved for awhile.

Today we met with my good friend Mark Stirling, GNS Science, to head to the west end of the surface rupture in the vicinity of the Selwyn River and community of Hororata. This portion of the fault had large accelerations during the earthquake.

We first visited several locations along the fault were roads and fence lines have been offset. Due to the enormous number of roads, fences, hedgerows and plow lines, there are tremendous opportunities to measure the amount of surface displacement along the rupture. The fault did not have uniform displacement along its length, but, instead had portions with large slip (> 4.5 m) and others that had along a fraction of that. We wanted to observe this range of slip if possible.

At Highfield, Kivers and Telegraph Roads the slip ranges from 3 to 4 m in a right lateral sense. Additionally, there appears to be vertical displacement on the order of up to 1 m. Near Hororata and the Selwyn River, horizontal displacements appear to be less than 1 to 2 m and vertical slip appeared negligible.

We visited the St. John’s Anglican church in Hororata. The church, built in 1910, was a beautiful, large cut-stone structure with a wooden frame ceiling and slate roof. Large accelerations from the earthquake toppled the bell tower into the alter portion of the church. We have heard it said many times while on South Island that it was good fortune that the earthquake didn’t occur during services because tons of stone crashed through the ceiling and destroyed the church.

We then travelled to Greendale where the highest accelerations (that means the ground accelerating, much like a car suddenly moving from a dead stop) were recorded for the event. The vertical accelerations have been reported at 1.25 g (that is 1.25 times gravity). If the ground moves upward at 1.25 g then it becomes airborne which is a frightening thought. It should be noted that this only the highest REPORTED acceleration. The accelerometer is located in a power station that was displaced by the fault. To the credit of the engineers and builders of this power station it suffered little damage and was providing electricity not long after the earthquake.

We finally travelled eastward closer to the area of the fault where we GNS Science has been conducting the detailed LIDAR surveys. Near Courteney Road we observed a road that has about 4.5 m of displacement. A landowner invited us to look at the deformation on her farm and stated that they have observed the fault still moving after almost three weeks. We found that the paddock had a large (1 to 1.5 m-high linear mound on it with numerous fractures and faults that trended oblique to the mound. The landowner said that the cracks on the mound have been expanding fairly continuously. It appears that this may be the result of after slip, a phenomenon where the surface portion of the fault didn’t slip as much as the fault at depth but is slowly catching up.

Aftershocks are a still a common occurrence. M 3 + earthquakes have been occurring several times a day since we’ve been here.

Tonight geodesists from GNS Science including John Beaven and Susan Ellis, bearing take-out Indian food and beer came to our motel room for dinner. They are reoccupying monuments all across the fault zone to try to measure its post-earthquake motion.

Tomorrow we will head into the area of Kaiapoi where significant liquefaction and lateral spreads from shaking-induced soil failures occurred. We also plan to travel into downtown Christchurch to observe the structural damage to buildings.

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