Journal of geomagnetism and geoelectricity最新文献_第9页

Two-Dimensional Inversion of Papua New Guinea Magnetotelluric Data with Smoothness Regularization 巴布亚新几内亚大地电磁资料二维平滑正则化反演

Journal of geomagnetism and geoelectricity Pub Date : 1997-06-20 DOI: 10.5636/JGG.49.869

T. Uchida

引用次数: 4

COPROD2 revisited : Can the B-polarization phase distinguish between single- and multi-body anomalies ? COPROD2重审:b极化相位能区分单体和多体异常吗?

Journal of geomagnetism and geoelectricity Pub Date : 1997-06-20 DOI: 10.5636/JGG.49.745

A. K. Agarwal, K. Macdonald, J. T. Weaver

{"title":"COPROD2 revisited : Can the B-polarization phase distinguish between single- and multi-body anomalies ?","authors":"A. K. Agarwal, K. Macdonald, J. T. Weaver","doi":"10.5636/JGG.49.745","DOIUrl":"https://doi.org/10.5636/JGG.49.745","url":null,"abstract":"The small local minimum in the long-period B-polarization phase responses above the NACP anomaly in the COPROD2 data is re-examined with a view to understanding its role in determining whether the anomaly is a multi-body or continuous conductive structure. It is found by trial-and-error numerical modelling and by further optimization of a model with continuous structure that the B-polarization phase response is not profoundly affected by the NACP anomaly itself, but is extremely sensitive to the resistivity distribution in the sedimentary layer to the extent that quite minor resistivity variations can turn a local minimum into a local maximum and vice versa, without necessarily affecting the short period responses in an unreasonable manner. A further modelling exercise with a multi-body anomaly shows that its response does not necessarily give rise to a local minimum in the phase response, as sometimes claimed. The investigation presented here is not intended to establish whether the NACP anomaly is a continuous or broken conductive structure but it does suggest that the evidence that has been cited in favour of a multi-body anomaly may not be sufficient by itself to settle the question with certainty.","PeriodicalId":156587,"journal":{"name":"Journal of geomagnetism and geoelectricity","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115823843","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 2

A critique of the MTDIW2-PNG data set based on Mohr circles 基于Mohr圆的MTDIW2-PNG数据集的批评

Journal of geomagnetism and geoelectricity Pub Date : 1997-06-20 DOI: 10.5636/JGG.49.807

F. Lilley

引用次数: 3

The BC87 Dataset: Application of Hypothetical Event Analysis on Distorted GDS Response Functions and Some Thin Sheet Modelling Studies of the Deep Crustal Conductor. BC87数据集:扭曲GDS响应函数的假设事件分析应用及地壳深部导体薄层模型研究。

Journal of geomagnetism and geoelectricity Pub Date : 1997-06-20 DOI: 10.5636/JGG.49.757

P. Ritter, O. Ritter

{"title":"The BC87 Dataset: Application of Hypothetical Event Analysis on Distorted GDS Response Functions and Some Thin Sheet Modelling Studies of the Deep Crustal Conductor.","authors":"P. Ritter, O. Ritter","doi":"10.5636/JGG.49.757","DOIUrl":"https://doi.org/10.5636/JGG.49.757","url":null,"abstract":"Galvanic distortion of the regional MT responses was inferred from the analyses of the BC87 dataset presented at the MT-DIW1 in 1992. Since perturbation currents also produce an anomalous magnetic field, the GDS response functions were suspected to be distorted in the long period range. In order to reveal the correct regional strike direction, hypothetical event analysis was applied to the data from all sites. With this technique, common regional information, such as strike and impedance phase, can be recovered from distorted response functions. Although the BC87 GDS data are noisy, and the distortion is more of an inductive than of a purely galvanic nature, the resulting regional strike direction of 60° agrees well with the azimuth suggested from previous MT decomposition methods. Thin sheet modelling studies of the geometry of the deep crustal conductor (L-shaped or oblique) at 1000 s imply that along the BC87 profile induction arrows are generally produced by current concentrations around a resistive region associated with the Nelson Batholith. Comparison of the model induction arrows with those determined from the BC87 data indicates that the model featuring the oblique, NE striking conductor (SABC) may be favoured.","PeriodicalId":156587,"journal":{"name":"Journal of geomagnetism and geoelectricity","volume":"423 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121706482","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 7

One-Dimensional Model Study of the PNG Dataset Using Site-Independent Groom-Bailey Decomposition 基于站点独立grom - bailey分解的PNG数据集一维模型研究

Journal of geomagnetism and geoelectricity Pub Date : 1997-06-20 DOI: 10.5636/JGG.49.843

H. Toh, M. Uyeshima

{"title":"One-Dimensional Model Study of the PNG Dataset Using Site-Independent Groom-Bailey Decomposition","authors":"H. Toh, M. Uyeshima","doi":"10.5636/JGG.49.843","DOIUrl":"https://doi.org/10.5636/JGG.49.843","url":null,"abstract":"Conventional magnetotelluric (MT) analyses of the Papua New Guinea (PNG) dataset reveal that it is a very good two-dimensional (2D) dataset with relatively high S/N ratios up to 10 2 s. However, traditional Swift's angles are unstable at some sites and differ slightly site to site. This implies that weak but significant distortions are present at all sites. Hence, the regional 2D strike angle was sought by minimizing the global X 2 misfits derived from the site- and frequency-independent Groom-Bailey (GB) decomposition at seven selected sites. The other three sites were eliminated by X 2 -test. The strike angle was determined to be 60° west of geographic north. One-dimensional (1D) Monte-Carlo inversion was performed using the Berdichevsky averages of the decomposed 2D principal tensor elements. The 2D model simply based on the 1D inversions was able to reproduce the observed impedances, except for the systematically high values of TM phase in the period range of 10 -1 to 10 s. This indicates that a 1D approximation of the electrical conductivity structure beneath this region is reasonably valid. The 1D models indicated the existence of a thin (up to 2.5 km) resistive layer just below the surface, suggesting the 'single' Darai limestone.","PeriodicalId":156587,"journal":{"name":"Journal of geomagnetism and geoelectricity","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133889910","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 5

Two-Dimensional Inversion of Oklahoma EMAP Data with Smoothness Regularization 基于平滑正则化的俄克拉荷马州EMAP数据二维反演

Journal of geomagnetism and geoelectricity Pub Date : 1997-06-20 DOI: 10.5636/JGG.49.791

T. Uchida

引用次数: 2

The Albanian Geomagnetic Repeat Station Network at 1994.75 阿尔巴尼亚地磁重复站网1994年4月75日

Journal of geomagnetism and geoelectricity Pub Date : 1997-05-20 DOI: 10.5636/JGG.49.701

M. Chiappini, O. Battelli, S. Bushati, G. Dominici, B. Duka, A. Meloni

引用次数: 8

Intrinsic Bias in Averaging Paleomagnetic Data 平均古地磁资料的固有偏差

Journal of geomagnetism and geoelectricity Pub Date : 1997-05-20 DOI: 10.5636/JGG.49.721

P. Arason, S. Levi

引用次数: 1

Studies of the E-Region Neutral Wind in the Auroral Ionosphere Using Two Long-Run Data 利用两个长期资料研究极光电离层e区中性风

Journal of geomagnetism and geoelectricity Pub Date : 1997-05-20 DOI: 10.5636/JGG.49.641

S. Nozawa, A. Brekke, R. Fujii

{"title":"Studies of the E-Region Neutral Wind in the Auroral Ionosphere Using Two Long-Run Data","authors":"S. Nozawa, A. Brekke, R. Fujii","doi":"10.5636/JGG.49.641","DOIUrl":"https://doi.org/10.5636/JGG.49.641","url":null,"abstract":"EISCAT data obtained in the auroral ionosphere have been analyzed in terms of the E-region neutral wind behavior at three heights of 101, 109, and 119 km. We have analyzed two extended CP-1-H runs conducted over four consecutive days each for 21-25 September 1987 and 16-20 March 1988. Mean winds as well as tidal amplitudes and phases derived by both Fast Fourier Transform (FFT) and least square fit (LSF) methods are compared with those of corresponding seasonal winds from the quiet-time statistical study by Brekke et al. (1994). During 21-25 September 1987 the mean zonal wind derived by FFT with filling in zeroes in the data gaps blows eastward with a maximum of ∼20 m s-1 between 101 and 119 km and its direction is consistent with the average quiet-time fall wind. The directions of mean meridional and vertical winds, however, are opposite to those of the fall wind. The amplitudes and phases of the tidal winds are in reasonable agreement with those found. for fall quiet time. At 119 km the zonal wind shows a large enhancement during the very geomagnetically disturbed period between 16 UT on 22 September and 05 UT on 23 September and also for about 5 hours after the end of the disturbed period. During 16-20 March 1988 the amplitudes of the mean meridional and vertical winds are very small while the mean zonal wind blows eastward with a maximum of less than 18 m s-1 between 101 and 119 km, which is about half as large as that of the average quiet-time spring wind. Most diurnal meridional and semidiurnal horizontal wind amplitudes between 101 and 119 km are also about half of those found for spring quiet time. The height profiles of phases for most components are much the same as those of the spring wind. Comparisons are made with results obtained by the Sondre Stromfjord IS radar and model predictions, and geomagnetic disturbance effects on the wind are discussed.","PeriodicalId":156587,"journal":{"name":"Journal of geomagnetism and geoelectricity","volume":"88 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127526978","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 2

Propagation Parameters of Sea Surface Waves Inferred from Observations from Two Closely Spaced Vector Magnetometers 由两个紧密间隔的矢量磁力计观测推断的海面波传播参数

Journal of geomagnetism and geoelectricity Pub Date : 1997-05-20 DOI: 10.5636/JGG.49.709

J. Watermann, A. Magunia

{"title":"Propagation Parameters of Sea Surface Waves Inferred from Observations from Two Closely Spaced Vector Magnetometers","authors":"J. Watermann, A. Magunia","doi":"10.5636/JGG.49.709","DOIUrl":"https://doi.org/10.5636/JGG.49.709","url":null,"abstract":"The alternating magnetic dynamo field of sea surface waves, a consequence of their Lorentz electric field, has been observed with a pair of simultaneously operated, closely spaced tri-axial magnetometers. Measurements from a magnetometer located in the centre of a tiny, uninhabited island served to compensate measurements from a near-shore magnetometer for magnetic pulsations of ionospheric origin, leaving the water wave dynamo field, effective close to shore only, as the dominant residual magnetic field. Amplitude and frequency of waves and swell were recorded with a vertical accelerometer (wave rider buoy), floating on the sea surface. The wave rider data are in good agreement with those obtained from the magnetometers. Amplitude and phase relations between the three vector components of the magnetic oscillations yield a sea surface wave vector which is consistent with the swell propagation direction usually found in that area. The magnetic field data further demonstrate that the water mass motion close to shore was not confined to a vertical plane (as would be the case for freely propagating gravity waves in the open ocean). The motion rather took place in a plane inclined at about 40° from the horizontal, which is roughly twice the inclination of the island flanks. We conclude that the magnetometer measurements yield a reasonably accurate description of the surface wave water motion within about one wavelength from shore.","PeriodicalId":156587,"journal":{"name":"Journal of geomagnetism and geoelectricity","volume":"64 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132107716","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 4