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).
This week we analysed the internal structure of the sediment cores we collected at Rotoroa, Rotokaeo, and Waiwhakareke using a medical CT scanner at Hamilton Radiology. This method provides a first estimation about whether or not seismites (tephras deformed by earthquake activity) are present in the sedimentary record. Next week we plan to cut the cores lengthwise for detailed sediment description and sampling.
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.
Members of the Tephra Seismites group and colleagues from UoW Earth Sciences attended the annual Waikato Regional Natural Hazards Forum at Hauraki District Council, Paeroa, on Friday 20 November. They joined colleagues from district and regional councils, Civil Defence and Emergency Management, and other research institutes to hear about and discuss aspects of natural hazard management and mitigation, with a focus on community engagement.
The Waikato team, including four (post)graduate students, gave a series of short ‘lightning talks’ on current research about newly-discovered faults in Hamilton and the liquefaction potential of lacustrine ash layers.
On Friday, 13th November 2020, paleoseismologists Dr Pilar Villamor and Dr Kate Clark of GNS Science visited the Tephra Seismites team at University of Waikato, to discuss their future collaboration. They will work together to map faults within the Hamilton lowlands, and eventually link the occurrence of fault ruptures to liquefaction observed in lacustrine tephra layers.
Dr Tehnuka Ilanko
School of Science
University of Waikato
Private Bag 3105
+64 7838 4845