Wallace and the Study of New Zealand's Subduction Zones
The geological stability of New Zealand is governed by the complex interactions of tectonic plates. To better understand these movements, researcher Wallace has dedicated her career to monitoring the land and seafloor, utilizing advanced technology to track shifts that are often invisible to the human eye. Her work focuses on the Hikurangi subduction zone, a critical area where one tectonic plate slides beneath another, posing significant geological risks to the region.
Monitoring Land Movement with cGPS
To capture the minute shifts of the Earth's crust, Wallace helped design a network of 150 continuous Global Positioning System (cGPS) reference stations across New Zealand. These stations allow scientists to study local geophysics by measuring land movement on a millimeter scale, providing a high-precision map of how the region is shifting over time.
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The Discovery of Slow Slip Events
In 2002, Wallace became the first researcher to demonstrate slow slip events at the Hikurangi subduction zone east of Gisborne. Unlike traditional earthquakes that release energy in seconds, slow slip events are gradual movements that occur over approximately two weeks, causing up to 20 cm of displacement along the New Zealand and Pacific Plates.
Through her research, Wallace determined that these events follow five-year cycles and occur at depths reaching 50 km. Crucially, she discovered that some of these events are shallow enough to allow for sample collection and analysis. Her findings revealed that slow-slip events can trigger ruptures in the shallower parts of a fault—the same areas responsible for generating devastating earthquakes and tsunamis.
The HOBITSS Project
To further investigate these phenomena, the Hikurangi Ocean Bottom Investigation of Tremor and Slow Slip (HOBITSS) project was launched. Utilizing the R/V Tangaroa, the team deployed a network of seafloor instruments capable of measuring vertical movement. This technology enabled high-resolution mapping of seafloor areas that were previously inaccessible to researchers.
Sub-Seafloor Observatories and Te Matakite
Expanding her research into the deep ocean, Wallace led the installation of sub-seafloor observatories off the coast of Gisborne in 2018. This initiative was a collaboration with the Australian and New Zealand Integrated Ocean Drilling Program (IODP) Consortium.
One of the most significant installations was Te Matakite, the first observatory in New Zealand located directly at a subduction plate boundary. Deployed from the Hawke's Bay coast, these instruments provide critical data on plate interactions. However, the project faced a setback in 2020 when it was reported that five of the thirty instruments, valued at $30,000, could not be located.
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Key Facts
- cGPS Network: 150 stations used to measure millimeter-scale land movement.
- Slow Slip Events: Occur on five-year cycles, lasting about two weeks and moving plates up to 20 cm.
- Depth: Slow slip events can occur at depths of up to 50 km.
- Te Matakite: New Zealand's first subduction plate boundary observatory.
- Risk Factor: Slow-slip events can cause ruptures in shallow fault zones, potentially leading to tsunamis and earthquakes.
Research Summary
| Project/Award | Focus/Achievement | Key Detail |
|---|---|---|
| cGPS Network | Local Geophysics | 150 reference stations |
| HOBITSS | Seafloor Vertical Movement | Deployed via R/V Tangaroa |
| Te Matakite | Subduction Plate Boundary | First of its kind in NZ |
| McKay Hammer Award | Contribution to Geology | Awarded in 2018 |
Professional Recognition
Wallace's contributions to science have been widely recognized. In 2018, she was elected to the Royal Society Te Apārangi and received the Geoscience Society of New Zealand McKay Hammer award for the most meritorious contribution to geology. Additionally, she is a member of the East Coast Lab, a scientific collective dedicated to understanding and communicating the risks of natural hazards.
Frequently Asked Questions
What are slow slip events?
Slow slip events are gradual movements along tectonic plate boundaries that occur over several days or weeks, rather than the sudden rupture seen in typical earthquakes.
Why is the Hikurangi subduction zone significant?
It is one of New Zealand's most significant geological hazards because it has the potential to generate major earthquakes and tsunamis.
What is the purpose of the Te Matakite observatory?
Te Matakite is designed to provide data from a subduction plate boundary that is otherwise invisible to human observation, helping scientists monitor plate interactions.
How does cGPS help in studying geophysics?
Continuous Global Positioning System (cGPS) stations allow researchers to track the movement of land at a millimeter scale, providing precise data on tectonic shifts.
What is the relationship between slow slip events and tsunamis?
Wallace's research indicates that slow-slip events can cause the shallower sections of a fault to rupture, which are the areas typically involved in the creation of earthquakes and tsunamis.