dc.contributor.advisor |
van Wijk, Kasper |
en |
dc.contributor.advisor |
Spörli, Bernhard |
en |
dc.contributor.author |
Ensing, Josiah |
en |
dc.date.accessioned |
2020-10-11T23:56:18Z |
|
dc.date.available |
2020-10-11T23:56:18Z |
|
dc.date.issued |
2020 |
|
dc.identifier.uri |
http://hdl.handle.net/2292/53212 |
|
dc.description.abstract |
Auckland, New Zealand's most populous region (1.6 million), is situated over an
active volcanic field of at least 53 volcanoes. The mechanism driving volcanism
in the Auckland Volcanic Field is not well understood. We aim to increase knowledge
of the structure of the crust across the Auckland Volcanic Field through
multicomponent ambient noise tomography. We hope this will contribute toward
understanding possible structural controls on volcanism.
We first estimated the orientation of borehole seismometers by polarization
analysis of estimates of the Rayleigh wave Green's function, retrieved from
ambient noise cross-correlation. Knowing the orientations, we then computed
multi-component estimates of Rayleigh wave Green's functions. We performed
frequency-time analysis on the Green's functions to extract Rayleigh wave dispersion
information. We then used Rayleigh wave group arrival times to perform
a reversible-jump Markov chain Monte Carlo inversion for Rayleigh wave speed
maps. We took dispersion curves from the Rayleigh wave speed maps, and performed
a damped inversion of each dispersion curve for a 60-layer 1D shear speed
model. Lastly, we then stitched the 1D models together, creating a pseudo-3D
shear speed model.
The 3D model is a considerable improvement compared to previous tomographic
models, being more robust and having improved resolution. The model
best resolved the upper-most crust but has also been able to resolve some features
as deep as 25 km. One of the main features in the model is a NNW-SSE
boundary slightly east of the Junction Magnetic Anomaly and the volcanic centres
of the AVF. This boundary more clearly defines an eastern high speed region
and a western low speed region in the upper 5 km divided. We interpret the high
speed region as the Waipapa Terrane, and the low speed region as the Murihiku
Terrane. Deeper we see a reversal, with a high speed region west of the boundary
and a low speed region in the east. We interpret the high speed region to be
the continuation of the Dun Mountain-Maitai Terrane, and the low speed region
in the east an effect of metamorphic weakening of lower parts of the Waipapa
Terrane. We identify a long low speed zone along the NNW-SSE boundary, and
other features indicating possible connections to faults and the Takapuna gravity
anomaly. |
|
dc.publisher |
ResearchSpace@Auckland |
en |
dc.relation.ispartof |
PhD Thesis - University of Auckland |
en |
dc.relation.isreferencedby |
UoA99265290712902091 |
en |
dc.rights |
Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. |
en |
dc.rights |
Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. |
en |
dc.rights.uri |
https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm |
en |
dc.rights.uri |
http://creativecommons.org/licenses/by-nc-sa/3.0/nz/ |
en |
dc.title |
Multi-Component Ambient Seismic Noise Tomography of the Auckland Volcanic Field |
en |
dc.type |
Thesis |
en |
thesis.degree.discipline |
Gepphysics |
|
thesis.degree.grantor |
The University of Auckland |
en |
thesis.degree.level |
Doctoral |
en |
thesis.degree.name |
PhD |
en |
dc.date.updated |
2020-08-26T10:54:41Z |
en |
dc.rights.holder |
Copyright: The author |
en |
dc.rights.accessrights |
http://purl.org/eprint/accessRights/OpenAccess |
en |
dc.identifier.wikidata |
Q112951919 |
|