New paper published and Disastrous Doctorates symposium

PhD student Jordanka Chaneva has a new paper, ‘Monotonic and cyclic undrained behaviour and liquefaction resistance of a pumiceous, non-plastic sandy silt’ published in the journal Soil Dynamics and Earthquake Engineering. Please contact us if you would like a copy.

This paper is based on her lab work, testing the properties of Tuhua tephra (one of the younger tephra layers in our study). In addition to contributing more broadly to understanding the undrained behaviour and liquefaction resistance of similar soils (pumiceous silts), Jordanka’s work helps us understand the response of Tuhua tephra in the Hamilton Basin lakes to earthquake shaking, by analysing its liquefaction potential.

Many thanks to Ngāti Wairere and the Department of Conservation for field site access, and to MBIE, Marsden, QuakeCoRE, EQC, and Waikato Regional Council for funding.

Jordanka also attended the 2023 Disastrous Doctorates symposium last week, hosted by the Joint Centre for Disaster Research at Massey University, where she presented a three-minute talk about this research.

A group of about 30 people pose for a photograph in a hall. They are all wearing t-shirts with the Disastrous Doctorates logo. a Toka Tu Ake EQC banner and a Resilence Challenge banner are visible on either side.
Attendees of the Disastrous Doctorates Symposium – Jordanka is in the second row, fourth from left.

Tephra Seismites at IAVCEI Scientific Assembly, Rotorua

Two weeks ago, some of the Tephra Seismites group attended the IAVCEI (International Association of Volcanology and Chemistry of the Earth’s Interior) 2023 Scientific Assembly in Rotorua. The conference, with the University of Waikato a major sponsor, was originally scheduled for February 2021. Twice postponed due to COVID, it was a relief that the meeting could proceed (with 860 in-person and 203 virtual participants) despite the wet weather and temporary closure of Auckland Airport.

Photo showing the Events Centre carpark with the old Bath House building in the background. There are IAVCEI conference banners attached to the light poles in the carpark.
IAVCEI 2023 conference banners above the Events Centre carpark

We presented two talks on behalf of the group, in the session ‘Tephrochronology: new methods and applications for chronostratigraphy and beyond’.

The first was a broad overview of the project, covering some of our recently published work, and our work with X-ray CT to identify and characterise tephras and seismites: ‘Tephra seismites preserved in unconsolidated organic lake sediments in the Hamilton lowlands, New Zealand, indicate paleoearthquake activity since 17.6 ka’ (presented by Tehnuka).

The next talk focused on our work at Rotoroa/Hamilton Lake, and findings from Richard Melchert’s thesis: ‘Using ground-penetrating radar and X-ray computer tomography to survey and characterise distal tephras in lake sediments, Hamilton lowlands, New Zealand’ (presented by David).

Tehnuka also gave an ECR (Early Career Researcher) Plenary, showing how we can unravel volcanic gas data to understand both magmatic and non-magmatic processes.

Photograph from the audience of an auditorium with two large screens above the stage. Tehnuka is presenting at the lectern. The screens show a photo of the summit of an ice-covered volcano emitting a blue-white plume against a blue sky, with the title 'Un-mixing messages: finding meaning in volcanic gases'.
Tehnuka presenting her ECR plenary, entitled ‘Un-mixing messages: finding meaning in volcanic gases’.

One of the pre-conference workshops was also tephra-related: ‘From field apps to data repositories: Improving tephra data discoverability, access, and workflows to support next generation research’, organised by Steven Kuehn, Kristi Wallace, Ellen Nelson, Andrei Kurbatov and Kerstin Lehnert. This workshop was a continuation of an ongoing project under the auspices of the Commission on Tephrochronology entitled ‘Community established best practice recommendations for tephra studies—from collection through analysis’, with a milestone paper published last year.

For a field visit and a chance to try out the Strabo app for field data collection, David, Josh, Richard, and Tehnuka arranged an excursion to a tephra outcrop at a nearby pumice quarry. The deposits here include the Rotorua and Waiohau tephras we are familiar with from lake coring around Hamilton, although they are much thicker, since this site is far closer to the source. Our field guide contains more details. Many thanks to the RNL pumice quarry owners for permission to visit.

Tehnuka invited as ECR plenary speaker at IAVCEI 2023 volcanology conference in Rotorua

We are glad to announce that Tehnuka, who is a postdoc in our Tephra-Seismites group, will give an Early-Career Researcher Plenary talk at the volcanology conference of the International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI) 30 Jan-3 Feb 2023.

Although she is currently working with tephras, Tehnuka’s main research area until now has been in volcanic degassing. She is particularly interested in how we can understand volcanic processes and plumbing through gas geochemistry, and in developing methods to collect, analyse, and interpret gas data from active volcanoes. Much of her work to date has used ground-based remote sensing to investigate open-vent volcanism.

The topic of her ECR plenary talk will be “Un-mixing messages: finding meaning in volcanic gases“. Further details and an abstract can be found at https://confer.eventsair.com/iavcei2023/plenary-speakers.”

Liquefaction structures in Lake Rotoroa (Hamilton Lake)

M.Sc. student Richard Melchert has worked for the Tephra-Seismites group since mid 2021 and assisted with lake coring, sediment description, and other laboratory work. In his recently submitted dissertation entitled “Sedimentology and characterisation of soft-sediment deformation structures within lacustrine successions in 20,400-year-old Lake Rotoroa, Hamilton, New Zealand”, he studied liquefaction structures in Lake Rotoroa, which provide evidence for earthquake activity since the formation of the lake around 20,000 years ago.

Richard used a range of techniques, including X-ray computed tomography (CT), ground penetrating radar (GPR), and grain size analyses. The CT scans enabled him to visualise the liquefaction structures in three dimensions (see figures below).

Vertical flame-like dike penetrating through organic lake sediment (removed during the CT data processing). The dike’s source bed is located within the ~20,000-years-old Hinuera Formation, which underlies the present-day lake sediments.
Five dikes penetrating downwards from a volcanic ash (tephra) layer, having been deposited ~15,600 years ago. The occurrence of these dikes suggest earthquake activity must have happened after the deposition of this tephra layer.
Richard before handing in his dissertation.

Field and lab update

The Tephra Seismites have had a particularly busy couple of months. Our coring fieldwork was completed in September, with cores collected from six further lakes.

Photo of part of a lake. An inflatable boat and pontoon raft are lashed together in the middle of the lake. Three people sit on the boat, facing the raft, where two people are standing, holding a long rod that projects through the centre of the raft into the lake.
Coring at Ngārotoiti. Left to right: Dr Marcus Vandergoes, Henry Gard, Joe Butterworth, Dr Vicki Moon, Dr Tehnuka Ilanko. Photo: D. Lowe.

We have since completed X-ray Computer Tomography (CT) scans of all these new cores. Over the past few weeks, we cut, opened, and described all remaining cores from both of our 2022 field campaigns. This came to a total of 51 separate logs! As well as making detailed descriptions of key tephras and any deformation features, we collected samples for grainsize analyses.

In the coming weeks, will continue labwork on these samples and study the 3D imagery provided by the CT scanning.

A sincere thanks to all those involved with this most recent work, including our GNS Science and Lakes380 colleagues Dr Marcus Vandergoes and Henry Gard for their expert coring support; skipper Joe Butterworth; Ngā Iwi Tōpū O Waipā, private landowners, the Department of Conservation, and Waipā District Council, for fieldwork and access permission; and Nic Ross and Hamilton Radiology for CT scanning.

Participation at QuakeCoRE Annual meeting

Tephra Seismites PhD student Jordanka Chaneva attended the QuakeCoRE Annual meeting in Napier between 29th August to 1st September 2022. She presented part of the on-going triaxial testing research through a poster entitled “Cyclic undrained behaviour and liquefaction resistance of pumiceous, non-plastic sandy silt”. The poster-abstract is now available to read at: http://www.quakecore.nz/wp-content/uploads/2022/08/2022-Abstract-Book-FINAL.pdf

PhD student Jordanka (left) and Prof. Rolando Orense at the annual QuakeCoRE meeting in Napier.

Tephra Seismites group seminars

The Tephra Seismites team at Waikato held a half-day meeting today to present progress on different aspects of the project, and discuss next steps. 

Josh presented preliminary results from paleoseismic trenching and geomorphology of the Te Puninga Fault segment, Hamilton lowlands.

Richard, in his talk on ‘Soft sediment deformation structures (SSDS) in Rotoroa/Hamilton Lake’, presented observations from CT scans, grainsize analyses, and scanning electron microscope imagery of core samples.

Richard presents CT and grain size data from a core taken at Rotoroa.

Danche gave a talk on findings from her labwork, ‘Pumice content quantification of Tuhua tephra using different approaches’, ahead of her presentation at the QuakeCore annual meeting.

In Max’s presentation, ‘Implications of tephra thickness and grain size properties for the occurrence of soft-sediment deformation structures in lacustrine tephra layers, Hamilton lowlands’, he considered the relationship between tephra properties and the occurrence of soft sediment deformation over multiple lakes in the Hamilton Basin. 

Tehnuka discussed computational analysis of core CT scans for estimating volumes of tephra layers and associated soft-sediment deformation structures.

Finally, David’s talk, ‘Origin and development of lakes in the Waikato region’, gave us an overview of different types of lakes according to their formation mechanisms and relationship with the surrounding landscape, illustrated by examples from Waikato. 

Wānanga with Wiremu Puke and CT scanning update

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.

An article about Te Parapara is available on the web, and the abstract is free to read.

The team at Te Parapara, with the whatarangi (storehouse) visible in the background. From L to R: Wiremu Puke, Vicki Moon, Tehnuka Ilanko, Richard Melchert, Danche Chaneva, Toby Kluger (our website designer), and Josh Hughes.

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.

CT scanning at Hamilton Radiology. L to R: Danche, Nic Ross (seated), Max Kluger (standing), Vicki, Richard.