Page 22 - GeoPRISMS_Newsletter_Spring2018_Neat

“It does not do to leave a live dragon out of your calculations, if you
live near him.” – Gandalf the Wizard (The Hobbit by J.R.R. Tolkien)

Sizing up the Taniwha: Seismogenesis at

Hikurangi Integrated Research Experiment

(SHIRE)

Jeff Marshall (Cal Poly Pomona) and

Jessica Pilarczyk (University of Southern Mississippi)

“A Live Dragon” Beneath the Sea
In Māori culture, the Taniwha is a dragon-like beast that lives beneath the water, sometimes protecting
seafarers, while at other times wreaking disaster on coastal communities (King, 2007). Māori lore tells of
Taniwha that cause sudden upheavals and changes in the coastline, altering the shape of the land-ocean
interface. In the wake of New Zealand’s 2016 Mw7.8 Kaikōura Earthquake, the Taniwha was evoked as a
supernatural force behind coastal uplift, tsunami, and landslides (Morton, 2018). For New Zealand, the
Hikurangi subduction margin is a formidable Taniwha, a “live dragon” lurking just offshore, ready to
unleash powerful forces locked within its seismogenic zone. With multiple collaborative research efforts
now underway, geoscientists are shedding light on the habits of this secretive dragon, revealing new
understandings of the earthquake and tsunami hazards that threaten New Zealand’s coastline.

The SHIRE Project
REU student Stephen Mitchell
with grad student Thomas The Hikurangi margin along the east coast of New Zealand’s North Island (Fig. 1) provides an optimal
Kosciuch (USM) surveying venue for investigating megathrust behavior and controls on seismogenesis (e.g., Wallace et al., 2009
sediment sampling sites, and 2014). Along-strike variations in multiple subduction parameters, such as interface coupling, fluid
Ahuriri Lagoon.
flow, and seafloor roughness, can be linked to observed differences in megathrust slip behavior (seismic
vs. aseismic), forearc mass flux (accretion vs. erosion), and upper-plate deformation (contraction vs.
extension). Much of the forearc is subaerial and therefore ideal for geodetic and geologic studies, while
the submarine areas are easily accessible for geophysical imaging and monitoring. The SHIRE Project,
funded by the NSF Integrated Earth Systems (IES) Program, is a four-year, multi-disciplinary, amphibious
research effort involving a team of investigators at five US institutions, as well as multiple international
collaborators from New Zealand, Japan, and the United Kingdom. This project is designed to evaluate
system-level controls on subduction thrust behavior by combining both on and offshore active-source
seismic imaging, with onshore paleoseismic, geomorphic, and geodetic investigations. The project results
will be meshed with existing geophysical and geological datasets, and analyzed through the lens of state-
of-the-art numerical modelling. The overarching goal is to develop an integrated perspective of the
physical mechanisms controlling subduction thrust behavior and convergent margin tectonic evolution.

22 • GeoPRISMS Newsletter Issue No. 40 Spring 2018