At the start of June, the team met at Hamilton Gardens for a wānanga led by Wiremu Puke (Ngāti Wairere, Ngāti Porou). This began with an introduction to mātauranga Māori in geosciences research – particularly as it relates to Ngāti Wairere, as mana whenua for much of the area in which we are working. Wiremu also shared some of the history of Ngāti Wairere, and took us on a tour of Te Parapara Garden. We were lucky to have Wiremu, as one of the leaders of its planning, and construction, explain the significance of the garden design and layout, especially to the direct descendants of Ngāti Wairere, as well as visitors.
We have also completed CT scanning of all remaining cores from our March field campaign, with the help of Nic Ross at Hamilton Radiology. This means we can identify tephras and avoid cutting through them when we begin the next stage – opening and describing the cores. Masters student Richard Melchert has already been working on the cores from Rotoroa (Hamilton Lake). When we look at the CT scan images in more detail, they will show us the structures of any tephra seismites in 3D. We remain very grateful to Nic and Hamilton Radiology for their generous support.
Tephra Seismites PhD student Jordanka Chaneva attended two conferences in Sydney earlier this month: the International Young Geotechnical Engineers Conference (7iYGEC), and the 20th International Conference on Soil Mechanics and Geotechnical Engineering (ICSMGE). As well as presenting a paper at 7iYGEC, she participated in a victorious debate between ‘Young’ and ‘Experienced’ engineering teams on the future of geotechnical engineering!
The Tephra Seismites team has had a busy month, with successful field campaigns conducting ground-penetrating radar (GPR) at Rotoroa/Hamilton Lake with Dr Andrew Lorrey and John-Mark Woolley (NIWA), and sediment coring at seven Hamilton Basin lakes with Dr Marcus Vandergoes and Henry Gard (Lakes380 and GNS Science).
This follows fieldwork with Dr Pilar Villamor and Genevieve Coffey (GNS Science) in February to continue investigating Te Puninga Fault, also using GPR.
Thank you to our collaborators, and all those who helped with fieldwork permission and access.
While we plan for fieldwork later this summer, some of our team members have also been busy in the lab with triaxial testing to characterise the mechanical properties of pumiceous sands and tephras. These tests will tell us more about the conditions under which the tephras in our lake cores have liquefied.
In recognition of having submitted the first of our papers from the project, and a lot of hard work thus far, our group and supporters met for a special lunch last Friday (13 Aug).
Triaxial tests in the lab, led by Danche, got underway earlier this week – though these are now on hold with the latest lockdown! There is plenty to do from home, however. The team are working on abstracts for the forthcoming Geoscience Society of NZannual conference at Massey University (Palmerston North) later this year, and on the first report to our Marsden funders. As we head into spring, we are also looking forward to resuming our fieldwork.
Late last month, the Tephra Seismites team went to visit one of our field sites and collect tephra samples for lab testing, to better understand how and why they might liquefy in an earthquake.
We found Tuhua (Mayor Island) tephra (7.6 cal ka) and Mamaku tephra from the Okataina caldera (8.0 cal ka), which are the upper and lower tephras respectively in the photo below. Jordanka will be using these in her geomechanical tests.
We are looking for a doctoral student to join our team, for a project on characterising and using liquefied lacustrine tephra layers to evaluate paleoearthquakes and seismic hazard in the Hamilton lowlands.
The PhD project will involve (1) lake coring; (2) interpreting CT and micro-CT images of liquefaction of tephra layers in lake cores; (3) developing methods to characterise the liquefied tephra layers (tephra seismites) quantitatively in 3D (geometric morphometrics); (4) analysing spatial patterns of the seismites; and (5) evaluating paleoseismicity and hazards in and beyond Hamilton.
More information is available through the University of Waikato website here.
From the week beginning 15 February, 2021, we have been taking part in a joint project investigating the newly discovered Te Puninga Fault near Morrinsville. This fault is the closest to the Hamilton Basin and so we are trying to work out if activity on the Te Puninga Fault may have impacted on Hamilton Basin, where we suggest the liquefaction of lacustrine tephra layers (tephra seismites) has been caused largely by activity on one or more of the local Hamilton Basin faults. By studying the Te Puninga Fault we plan to test this idea.
The work on the Te Puninga Fault is jointly funded by an EQC project entitled “Paleoseismology of the newly discovered Te Puninga Fault, Hauraki Plains”, and our Marsden Fund project associated with paleoseismicity of the Hamilton lowlands.
Directed by palaeoseismologist Dr Pilar Villamor (GNS Science), three large trenches were opened on two different strands of the fault scarp that runs essentially north-south (roughly parallel to SH 27) a few kilometres to the northeast of Morrinsville. Others involved in the trenching work included Drs Kelvin Berryman and Kate Clark (GNS Science) along with Waikato-based geoscientists David Lowe, Vicki Moon, Alan Hogg, and Joshua Hughes. Joshua has joined the tephra seismites team to work on the Te Puninga Fault as part of his University of Waikato graduate studies (2021-22).
Last month, the Tephra Seismites group teamed up with our colleagues at Lakes380, who are also studying lake sediments, to collect the first of our core samples. More details about our joint fieldwork are available on the full press release here.
Dr Tehnuka Ilanko
School of Science
University of Waikato
Private Bag 3105
+64 7838 4845