A magnetotelluric study of Mount Ruapehu volcano, New Zealand

Ingham, M.; Bibby, H. M.; Heise, Wiebke; Jones, K. A.; Cairns, P.; Dravitzki, Stacey; Bennie, S. L.; Caldwell, T. G.; Ogawa, Yasuo

doi:10.1111/j.1365-246x.2009.04317.x

Cited by 87 publications

(83 citation statements)

References 52 publications

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“…If the lateral model mesh discretization is coarse relative to inter-site distances or to skin depths associated with the highest frequencies used in inversion, it is unclear how successful this approach will be. Heise et al (2008Heise et al ( , 2010, Hill et al (2009), Ingham et al (2009) remove distortion from the transfer functions by a tensor decomposition method described by Bibby et al (2005), arguing that the top-layer cells of the model are too large to properly account for galvanic distortion (Heise et al 2010). Árnason et al (2010) and Cumming & Mackie (2010) attempt to correct static shift of impedances prior to inversion using time-domain electromagnetic measurements.…”

Section: -D Magnetotelluric Inversion Techniquesmentioning

confidence: 99%

3-D joint inversion of the magnetotelluric phase tensor and vertical magnetic transfer functions

Tietze¹,

Ritter²,

Egbert³

2015

Geophys. J. Int.

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S U M M A R YWith advancing computational resources, 3-D inversion techniques have become feasible in recent years and are now a more widely used tool for magnetotelluric (MT) data interpretation. Galvanic distortion caused by small-scale near-surface inhomogeneities remains an obstacle for 3-D MT inversion which so far has experienced little attention. If not considered properly, the effect on 3-D inversion can be immense and result in erroneous subsurface models and interpretations. To tackle the problem we implemented inversion of the distortion-free phase tensor into the ModEM inversion package. The dimensionless phase tensor components describe only variations of the conductivity structure. When inverting these data, particular care has to be taken of the conductivity structure in the a priori model, which provides the reference frame when transferring the information from phase tensors into absolute conductivity values. Our results obtained with synthetic data show that phase tensor inversion can recover the regional conductivity structure in presence of galvanic distortion if the a priori model provides a reasonable assumption for the regional resistivity average. Joint inversion of phase tensor data and vertical magnetic transfer functions improves recovery of the absolute resistivity structure and is less dependent on the prior model. We also used phase tensor inversion for a data set of more than 250 MT sites from the central San Andreas fault, California, where a number of sites showed significant galvanic distortion. We find the regional structure of the phase tensor inversion results compatible with previously obtained models from impedance inversion. In the vicinity of distorted sites, phase tensor inversion models exhibit more homogeneous/smoother conductivity structures.

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Section: -D Magnetotelluric Inversion Techniquesmentioning

confidence: 99%

3-D joint inversion of the magnetotelluric phase tensor and vertical magnetic transfer functions

Tietze¹,

Ritter²,

Egbert³

2015

Geophys. J. Int.

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“…The versatility of MT has also meant it can be used for a wide range of applications, not only within hydrocarbon and mineral exploration but also within the volcanology field as a tool to investigate magma build up (Ingham et al, 2009). However, for investigations to be successful there must be adequate understanding of the geology, including thermal, compositional and structural information.…”

Section: Implications For Magnetotelluric Investigationsmentioning

confidence: 99%

“…By covering many frequencies (i.e. recording short and long wavelengths) it is possible to see shallow crustal features, such as magma chambers (Ingham et al, 2009) with the high frequency (short wavelength) component. Alternatively MT can be used to investigate very deep (100s of km) features, such as the structure of the upper mantle, with the low frequency (i.e.…”

Section: Introductionmentioning

confidence: 99%

Possible compositional effects on the electrical conductivity of olivine: A preliminary study

Lanati¹

2018

Preprint

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Abstract:Volatile sensitive probes of the upper mantle, such as magnetotellurics, are being developed to overcome insensitivities in seismic and gravity subsurface mapping as part of an effort to identify the location of deeply buried ore deposits, in addition to more broadly understanding mantle temperature and water contents. An understanding of the conductivity of mantle minerals is an essential prerequisite to the full interpretation of magnetotelluric data. Current proton conduction models for simple mineral systems, such as olivine, show large discrepancies. The material used for these determinations, San Carlos peridotite, is not a single mineral phase and may have compositional variations. This could be one of the origins of these discrepancies. To test this hypothesis, a sample of San Carlos olivine was taken and separated out the mineral components using a combination of electrostatic rock disaggregation, magnetic susceptibility as well as manual separation. The separated fractions were characterised using petrography. Impedance data were collected as a function of temperature and pressure in a multi-anvil press from both the separated olivine material and the original mixture. Comparison of these values with literature data has been made.ii Acknowledgements:I wish to acknowledge the extensive and onerous effort that has gone into this work and the team of people who have taken time from their own work to guide, mentor and advise me. These people not only provided me with an amazing amount of academic help but also showed care and compassion during a personal illness suffered during the course of this thesis.To my supervisors, Associate Professor Simon Clark, Associate Professor Tracy Rushmer, Associate Professor Juan Carlos Afonso, I can never repay the immense amount of time you've given me over the past two years.Simon, I thank you for the guidance and tasks you set for me during the coursework component of this MRes, I do not think I would have anywhere near the grasp of this subject area I currently have without you challenging me. I wish to thank you also for the useful and informative discussion throughout the course of this research project. We may not have always agreed but they certainly helped me to understand how the project was evolving and how impactful and important all aspects of the project can be with a bit more hard work.Tracy, I wish to thank you for meeting with me regularly and helping me through the formalities at the beginning of this year. Your insight specifically into the way which a research project is planned and executed gave me a unique perspective in how I would carry out future work. I want to also thank you for giving me so much time and for the last minute edits that helped me make this thesis much more consistent. This was all while acting as an Associate Dean as well as having other students submitting this year.JC, I want to acknowledge the way you make people think about problems. I truly respect and appreciate the dedication you have to your students and your res...

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“…Although MT profile data often demonstrate the influence of 3-D effects or show deviations from being purely 2-D, 2-D assumptions are usually allowed (e.g., Becken et al 2008b;Ingham et al 2009;Hill et al 2009; among many others). 2-D inversions are then performed to yield 2-D cross-sectional models for profile interpretation.…”

Section: When Is 3-d Inversion Useful? (Advantages Of 3-d Inversion Omentioning

confidence: 99%

“…3-D MT inversions have been used in various studies such as ore deposit exploration (e.g., Tuncer et al 2006;Farquharson and Craven 2008;Türkoglu et al 2009;Xiao et al 2010;Goldak and Kosteniuk 2010), waste characterization (e.g., Newman et al 2003), tectonic studies (e.g., Uyeshima 2007;Patro and Egbert 2008), volcano studies (e.g., Spichak et al 2007;Heise et al 2008Heise et al , 2010Jones et al 2008;Hill et al 2009;Ingham et al 2009), hydrocarbon exploration (e.g., Mackie and Watts 2007;Hautot and Tarits 2009;Zhanxiang et al 2010) and geothermal studies (e.g., Han et al 2008;Newman et al 2008;Á rnason et al 2010;Cumming and Mackie 2010). Improvements in 3-D inversion are likely to continue as long as MT data are still being acquired.…”

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confidence: 99%

Three-Dimensional Magnetotelluric Inversion: An Introductory Guide for Developers and Users

Siripunvaraporn

2011

Surv Geophys

116

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In the last few decades, the demand for three-dimensional (3-D) inversions for magnetotelluric data has significantly driven the progress of 3-D codes. There are currently a lot of new 3-D inversion and forward modeling codes. Some, such as the WSINV3DMT code of the author, are available to the academic community. The goal of this paper is to summarize all the important issues involving 3-D inversions. It aims to show how inversion works and how to use it properly. In this paper, I start by describing several good reasons for doing 3-D inversion instead of 2-D inversion. The main algorithms for 3-D inversion are reviewed along with some comparisons of their advantages and disadvantages. These algorithms are the classical Occam's inversion, the data space Occam's inversion, the Gauss-Newton method, the Gauss-Newton with the conjugate gradient method, the non-linear conjugate gradient method, and the quasi-Newton method. Other variants are based on these main algorithms. Forward modeling, sensitivity calculations, model covariance and its parallel implementation are all necessary components of inversions and are reviewed here. Rules of thumb for performing 3-D inversion are proposed for the benefit of the 3-D inversion novice. Problems regarding 3-D inversions are discussed along with suggested topics for future research for the developers of the next decades.

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A magnetotelluric study of Mount Ruapehu volcano, New Zealand

Cited by 87 publications

References 52 publications

3-D joint inversion of the magnetotelluric phase tensor and vertical magnetic transfer functions

3-D joint inversion of the magnetotelluric phase tensor and vertical magnetic transfer functions

Possible compositional effects on the electrical conductivity of olivine: A preliminary study

Three-Dimensional Magnetotelluric Inversion: An Introductory Guide for Developers and Users

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