Lithospheric shear velocity structure of South Island, New Zealand, from amphibious Rayleigh wave tomography
Ball, Justin S.
Sheehan, Anne F.
Stachnik, Joshua C.
Collins, John A.
MetadataShow full item record
KeywordOBS Rayleigh wave tomography; South Island, New Zealand; Challenger Plateau; MOANA experiment; Convergent tectonics; Mantle lithosphere
We present a crust and mantle 3-D shear velocity model extending well offshore of New Zealand's South Island, imaging the lithosphere beneath the South Island as well as the Campbell and Challenger Plateaus. Our model is constructed via linearized inversion of both teleseismic (18–70 s period) and ambient noise-based (8–25 s period) Rayleigh wave dispersion measurements. We augment an array of 4 land-based and 29 ocean bottom instruments deployed off the South Island's east and west coasts in 2009–2010 by the Marine Observations of Anisotropy Near Aotearoa experiment with 28 land-based seismometers from New Zealand's permanent GeoNet array. Major features of our shear wave velocity (Vs) model include a low-velocity (Vs < 4.4 km/s) body extending from near surface to greater than 75 km depth beneath the Banks and Otago Peninsulas and high-velocity (Vs~4.7 km/s) mantle anomalies underlying the Southern Alps and off the northwest coast of the South Island. Using the 4.5 km/s contour as a proxy for the lithosphere-asthenosphere boundary, our model suggests that the lithospheric thickness of Challenger Plateau and central South Island is substantially greater than that of the inner Campbell Plateau. The high-velocity anomaly we resolve at subcrustal depths (>50 km) beneath the central South Island exhibits strong spatial correlation with upper mantle earthquake hypocenters beneath the Alpine Fault. The ~400 km long low-velocity zone we image beneath eastern South Island and the inner Bounty Trough underlies Cenozoic volcanics and the locations of mantle-derived helium measurements, consistent with asthenospheric upwelling in the region.
Author Posting. © American Geophysical Union, 2016. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Solid Earth 121 (2016): 3686–3702, doi:10.1002/2015JB012726.
Showing items related by title, author, creator and subject.
Pn anisotropy beneath the South Island of New Zealand and implications for distributed deformation in continental lithosphere Collins, John A.; Molnar, Peter H. (John Wiley & Sons, 2014-10-23)Pn travel times from regional earthquakes recorded both by stations on New Zealand and by ocean bottom seismographs deployed offshore indicate anisotropy in the uppermost mantle beneath the region. The largest anisotropy ...
Zietlow, Daniel W.; Sheehan, Anne F.; Molnar, Peter H.; Savage, Martha K.; Hirth, Greg; Collins, John A.; Hager, Bradford H. (John Wiley & Sons, 2014-02-05)New shear wave splitting measurements made from stations onshore and offshore the South Island of New Zealand show a zone of anisotropy 100–200 km wide. Measurements in central South Island and up to approximately 100 km ...
S-wave splitting in the offshore South Island, New Zealand : insights into plate-boundary deformation Karalliyadda, Sapthala C.; Savage, Martha K.; Sheehan, Anne F.; Collins, John A.; Zietlow, Daniel W.; Shelley, Adrian (John Wiley & Sons, 2015-08-30)Local and regional S-wave splitting in the offshore South Island of the New Zealand plate-boundary zone provides constraints on the spatial and depth extent of the anisotropic structure with an enhanced resolution relative ...