Magnetotelluric sounding of the Hikurangi Margin, New Zealand

Ingham, M.; Whaler, Kathy; McKnight, Don

doi:10.1046/j.0956-540x.2000.01330.x

Cited by 22 publications

(30 citation statements)

References 41 publications

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“…Similar features have been noted in other subduction systems (e.g., Kurtz et al 1986Kurtz et al , 1990Wannamaker et al 1989a, b;Fuji-ta et al 1997). Ingham et al (2001) also reported a perpendicular MT transect ( Fig. 1, AA ) running along the length of the margin, which penetrated into the Wairarapa region at its southern end.…”

Section: Introductionsupporting

confidence: 55%

“…2). Data at 10 of the sites were collected over the summer of 1998/99, while 4 sites were occupied in conjunction with the study reported by Ingham et al (2001). Two of the sites (MGN, KAI) lie to the west of the Wairarapa Fault on the Mesozoic greywacke rocks that make up the main axial ranges of the North Island.…”

Section: Magnetotelluric Datamentioning

confidence: 99%

“…Two of the sites (MGN, KAI) lie to the west of the Wairarapa Fault on the Mesozoic greywacke rocks that make up the main axial ranges of the North Island. A further site, PIGB, Sites with three-letter acronyms were recorded with the Victoria University MT system, which has a nominal period range of 0.002-300 s. Data at sites with four-letter acronyms were collected using a SPAM Mark III system (Ritter et al 1998) and have a nominal period range of 0.007-1000 s. At all sites, data were recorded for between 24 and 48 h. The compatibility of data recorded by the two separate systems has previously been demonstrated by Ingham et al (2001). The recorded data were processed to obtain robust estimates of the impedance tensor relating the horizontal electric and magnetic field variations.…”

Section: Magnetotelluric Datamentioning

confidence: 99%

“…Presented in this paper are the results of a second MT transect across the Hikurangi margin located some 100 km southwest of that reported by Ingham et al (2001) and crossing the Wairarapa region. The main aim of the study was to determine if the conductive zone detected to the north was also present farther south along the strike of the Hikurangi margin.…”

Section: Introductionmentioning

confidence: 99%

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A magnetotelluric transect of the Wairarapa region, New Zealand

McLoughlin

Ingham

Whaler

et al. 2002

New Zealand Journal of Geology and Geophysics

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Magnetotelluric (MT) soundings have been made at 14 sites along a traverse of the Wairarapa region at the southwest end of the active Hikurangi margin. Joint inversion of direct current resistivity soundings and the MT data indicates that the MT data are unaffected by static-shift. Analysis of the dimensionality of the data suggests that the transverse electric (TE) mode data (derived from an electric field parallel to the strike of the margin) may be distorted by 3D effects arising from the presence of Cook Strait and the non-continuity of structure along the margin. 2D inversion of the more robust transverse magnetic (TM) mode responses has therefore been used to derive a model of electrical resistivity structure beneath the transect. This shows the existence of two depressions containing lowresistivity sediments separated by a more resistive region which is inferred to correlate with a spur of Mesozoic greywacke extending north from the Aorangi Mountains. The same features were previously identified from gravity data. The thickness of sediments adjacent to the Wairarapa Fault is of the order of 3-4 km, whereas that in the western arm of the Wairarapa trough is c. 2-3 km. The resistivity structure of the southwest end of the Hikurangi margin is more complex than the structure determined farther north along the margin.

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Section: Introductionsupporting

confidence: 55%

Section: Magnetotelluric Datamentioning

confidence: 99%

Section: Magnetotelluric Datamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A magnetotelluric transect of the Wairarapa region, New Zealand

McLoughlin

Ingham

Whaler

et al. 2002

New Zealand Journal of Geology and Geophysics

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“…The application of Mohr circles in MT interpretation was introduced by Lilley (1976). Nowadays, this simple technique is used to display the dimensionality of a structure and to infer the regional strike angle (Lilley, 1993(Lilley, , 1998aMakris et al, 1999;Ingham et al, 2001). By simply rotating and then plotting specific rotated components of the measured impedance tensor (e.g.…”

Section: Galvanic Distortion Analysis Of the Ioannina Mt Impedance Esmentioning

confidence: 99%

A magnetotelluric study of the sensitivity of an area to seismoelectric signals

Balasis

Bedrosian

Eftaxias

2005

Nat. Hazards Earth Syst. Sci.

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Abstract. During recent years, efforts at better understanding the physical properties of precursory ultra-low frequency pre-seismic electric signals (SES) have been intensified. Experiments show that SES cannot be observed at all points of the Earth's surface but only at certain so-called sensitive sites. Moreover, a sensitive site is capable of collecting SES from only a restricted number of seismic areas (selectivity effect). Therefore the installation of a permanent station appropriate for SES collection should necessarily be preceded by a pilot study over a broad area and for a long duration. In short, a number of temporary stations are installed and, after the occurrence of several significant earthquakes (EQs) from a given seismic area, the most appropriate (if any) of these temporary stations, in the sense that they happen to collect SES, can be selected as permanent. Such a long experiment constitutes a serious disadvantage in identifying a site as SES sensitive. However, the SES sensitivity of a site should be related to the geoelectric structure of the area that hosts the site as well as the regional geoelectric structure between the station and the seismic focal area. Thus, knowledge of the local and regional geoelectric structure can dramatically reduce the time involved in identifying SES sites. In this paper the magnetotelluric method is used to investigate the conductivity structure of an area where a permanent SES station is in operation. Although general conclusions cannot be drawn, the area surrounding an SES site near Ioannina, Greece is characterized by: (1) major faults in the vicinity; (2) highly resistive structure flanked by abrupt conductivity contrasts associated with large-scale geologic contacts, and (3) local inhomogeneities in conductivity structure. The above results are consistent with the fact that electric field amplitudes from remotely-generated signals should be appreciably stronger at such sites when compared to neighboring sites.

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Modeling Geoelectric Fields and Geomagnetically Induced Currents Around New Zealand to Explore GIC in the South Island's Electrical Transmission Network

et al. 2017

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Transformers in New Zealand's South Island electrical transmission network have been impacted by geomagnetically induced currents (GIC) during geomagnetic storms. We explore the impact of GIC on this network by developing a thin‐sheet conductance (TSC) model for the region, a geoelectric field model, and a GIC network model. (The TSC is composed of a thin‐sheet conductance map with underlying layered resistivity structure.) Using modeling approaches that have been successfully used in the United Kingdom and Ireland, we applied a thin‐sheet model to calculate the electric field as a function of magnetic field and ground conductance. We developed a TSC model based on magnetotelluric surveys, geology, and bathymetry, modified to account for offshore sediments. Using this representation, the thin sheet model gave good agreement with measured impedance vectors. Driven by a spatially uniform magnetic field variation, the thin‐sheet model results in electric fields dominated by the ocean‐land boundary with effects due to the deep ocean and steep terrain. There is a strong tendency for the electric field to align northwest‐southeast, irrespective of the direction of the magnetic field. Applying this electric field to a GIC network model, we show that modeled GIC are dominated by northwest‐southeast transmission lines rather than east‐west lines usually assumed to dominate.

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Magnetotelluric sounding of the Hikurangi Margin, New Zealand

Cited by 22 publications

References 41 publications

A magnetotelluric transect of the Wairarapa region, New Zealand

A magnetotelluric transect of the Wairarapa region, New Zealand

A magnetotelluric study of the sensitivity of an area to seismoelectric signals

Modeling Geoelectric Fields and Geomagnetically Induced Currents Around New Zealand to Explore GIC in the South Island's Electrical Transmission Network

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