1. Geomagnetism

Inflation and collapse of the Wai’anae volcano (Oahu, Hawaii, USA): implications from rock magnetic properties and magnetic fabric data of dikes

In order to investigate the role of dikes in the volcanic evolution and the triggering mechanisms of catastrophic mass wasting volcanoes, we have sampled for a pilot study, seven dikes within the Wai’anae volc...

Authors: Emilio Herrero-Bervera, Bernard Henry and Mário Moreira

Near-seafloor magnetic mapping of off-axis lava flows near the Kairei and Yokoniwa hydrothermal vent fields in the Central Indian Ridge

The Kairei (KHF) and Yokoniwa hydrothermal fields (YHF) are hosted in mafic as well as ultramafic rocks distributed at an off-axis volcanic knoll of the Central Indian Ridge. Despite intensive investigations, ...

Authors: Masakazu Fujii and Kyoko Okino

Reductive chemical demagnetization: a new approach to magnetic cleaning and a case study of reef limestones

Chemical demagnetization is not preferred as a demagnetizing method in paleomagnetism because strong acids are cumbersome to handle and require considerable time compared to alternating field and thermal demag...

Authors: Chisato Anai, Nobutatsu Mochizuki and Hidetoshi Shibuya

Sources of the lithosphere magnetic field based on magnetic data obtained at different heights

Our investigations are based on the property that the fields of sources, whose depths are numerically equal to survey heights, are most brightly presented in the data of magnetic survey. Therefore, the magneti...

Authors: Yury P. Tsvetkov, Konstantin V. Novikov, Andrey A. Ivanov and Oleg M. Brekhov

A 3D electrical resistivity model around the focal zone of the 2017 southern Nagano Prefecture earthquake (M_JMA 5.6): implications for relationship between seismicity and crustal heterogeneity

Seismic swarm areas below the southeast flank of Ontake volcano, central Japan, provide an important opportunity to study interactions between seismicity, volcanic processes and crustal fluid. On June 25, 2017...

Authors: Hiroshi Ichihara, Junna Kanehiro, Toru Mogi, Koshun Yamaoka, Noriko Tada, Edward Alan Bertrand and Mamoru Adachi

Possible correlation between the vertical component of lithospheric magnetic field and continental seismicity

Recent magnetic satellite missions facilitate new birth of large-scale geomagnetic field models and their applications to tectonics. Here, we directly compare the global geomagnetic field models NGDC-720 with ...

Authors: Yu Lei, Liguo Jiao and Huaran Chen

Paleomagnetic studies on single crystals separated from the middle Cretaceous Iritono granite

Investigations of superchrons are the key to understanding long-term changes of the geodynamo and the mantle’s controlling role. Granitic rocks could be good recorders of deep-time geomagnetic field behavior, ...

Authors: Chie Kato, Masahiko Sato, Yuhji Yamamoto, Hideo Tsunakawa and Joseph L. Kirschvink

Characterization of marine ferromanganese crust from the Pacific using residues of selective chemical leaching: identification of fossil magnetotactic bacteria with FE-SEM and rock magnetic methods

Hydrogenetic ferromanganese crusts (hereafter referred to as “crusts”) on Pacific seamounts are formed by the precipitation of iron–manganese oxides from seawater on volcanic and biogenic substrate rocks. As c...

Authors: Hirokuni Oda, Yoshio Nakasato and Akira Usui

Remanence cycling of 0.6–135 µm magnetites across the Verwey transition

We report zero-field low-temperature cycling of saturation remanence (SIRM) produced at 300 or 10 K for crushed natural magnetites in nine size fractions from 0.6 to 135 µm, one set annealed to reduce stress, ...

Authors: David J. Dunlop and Özden Özdemir

Crustal structure of a young collision zone: the Arabia–Eurasia collision in northeastern Turkey investigated by magnetotelluric data

The northeastern Turkey is located at the intensely deformed east Anatolian Collision Zone that is formed by the collision of the Arabian Plate with Eurasia. The region is one of the best examples of the conti...

Authors: Özlem Hacıoğlu, Ahmet Tuğrul Başokur and Elif Tolak Çiftçi

An initial case study to deconvolve natural remanent magnetization of a continuous paleomagnetic sample using the software UDECON

Previous studies have compiled relative paleointensity data for the last 2–3 Ma from individual paleomagnetic records obtained from marine sediment cores. These records have mostly been obtained by pass-throug...

Authors: Yuhji Yamamoto, Toshitsugu Yamazaki and Toshiya Kanamatsu

Rock magnetism of quartz and feldspars chemically separated from pelagic red clay: a new approach to provenance study

Magnetic mineral inclusions in silicates are widespread in sediments as well as in igneous rocks. Because they are isolated from surrounding environment, they have potential to preserve original magnetic signa...

Authors: Yoichi Usui, Takaya Shimono and Toshitsugu Yamazaki

A generating process of geomagnetic drifting field

The geomagnetic field is comprised of drifting and standing fields. The drifting field has two remarkable features. One is predominance of sectorial harmonics when the field is expressed in a spherical harmoni...

Authors: Takesi Yukutake and Hisayoshi Shimizu

Online plotting applications for paleomagnetic and rock magnetic data

This paper describes the development and release of a series of web-based services to generate plots of paleomagnetic and rock magnetic data. All plotting services require a World Wide Web browser as the user ...

Authors: Tadahiro Hatakeyama

Invariant TE and TM magnetotelluric impedances: application to the BC87 dataset

Invariants under rotation of the magnetotelluric impedance tensor relax the directional requirements when fitting data using two-dimensional (2D) models. This happens, for instance, when using the familiar imp...

Authors: Enrique Gómez-Treviño, Yunuhen Muñiz, Mayra Cuellar and Armando Calderón-Moctezuma

A comprehensive model of Earth’s magnetic field determined from 4 years of Swarm satellite observations

The European Space Agency’s three-satellite constellation Swarm, launched in November 2013, has provided unprecedented monitoring of Earth’s magnetic field via a unique set of gradiometric and multi-satellite mea...

Authors: Terence J. Sabaka, Lars Tøffner-Clausen, Nils Olsen and Christopher C. Finlay

A new miniaturized magnetometer system for long-term distributed observation on the seafloor

We have developed a new magnetometer system specialized to multipoint and long-term observations on the seafloor to promote marine or ocean-bottom experiments mainly for the electromagnetic sounding of the Ear...

Authors: Kazunori Ogawa, Tetsuo Matsuno, Hiroshi Ichihara, Kazuo Nakahigashi and Nobukazu Seama

Hybrid finite difference–finite element method to incorporate topography and bathymetry for two-dimensional magnetotelluric modeling

In this research, a new numerical method, called the hybrid finite difference–finite element (hybrid FD–FE) method, is developed to solve 2-D magnetotelluric modeling by taking advantage of both the finite dif...

Authors: Weerachai Sarakorn and Chatchai Vachiratienchai

Comparison of global geomagnetic field models and evaluation using marine datasets in the north-eastern Atlantic Ocean and western Mediterranean Sea

Many models describing the Earth’s magnetic field exist and are maintained by international research organizations. However, no clear general overview of the cross-compared quality of these models is available...

Authors: Jean-François Oehler, Didier Rouxel and Marie-Françoise Lequentrec-Lalancette

Archeointensity estimates of a tenth-century kiln: first application of the Tsunakawa–Shaw paleointensity method to archeological relics

Paleomagnetic information reconstructed from archeological materials can be utilized to estimate the archeological age of excavated relics, in addition to revealing the geomagnetic secular variation and core d...

Authors: Yu Kitahara, Yuhji Yamamoto, Masao Ohno, Yoshihiro Kuwahara, Shuichi Kameda and Tadahiro Hatakeyama

Preliminary paleomagnetic and rock magnetic results from 17 to 22 ka sediment of Jeju Island, Korea: Geomagnetic excursional behavior or rock magnetic anomalies?

Paleomagnetic and rock magnetic investigations were performed on a 64-cm-thick section of nonmarine unconsolidated muddy sediment from the Gosan Formation on Jeju Island, Korea. This sediment was recently date...

Authors: Hyeon-Seon Ahn, Young Kwan Sohn, Jin-Young Lee and Jin Cheul Kim

Cross-validation of independent ultra-low-frequency magnetic recording systems for active fault studies

When working with ultra-low-frequency (ULF) magnetic datasets, as with most geophysical time-series data, it is important to be able to distinguish between cultural signals, internal instrument noise, and natu...

Authors: Can Wang, Chen Bin, Lilianna E. Christman, Jonathan M. G. Glen, Simon L. Klemperer, Darcy K. McPhee, Karl N. Kappler, Tom E. Bleier and J. Clark Dunson

Special issue “Studies on electromagnetic induction in the earth: recent advances”

Authors: Weerachai Siripunvaraporn, Paul A. Bedrosian, Yuguo Li, Prasanta K. Patro, Klaus Spitzer and Hiroaki Toh

Electrical resistivity structure at the North-Central Turkey inferred from three-dimensional magnetotellurics

Magnetotelluric data analyses and three-dimensional modeling techniques were implemented to investigate the crustal electrical structure in the North-Central Turkey, along a 190-km-long profile crossing Çankır...

Authors: Sinan Özaydın, Sabri Bülent Tank and Mustafa Karaş

A paleomagnetic record in loess–paleosol sequences since late Pleistocene in the arid Central Asia

Geomagnetic excursions during Brunhes epoch have been brought to the forefront topic in paleomagnetic study, as they provide key information about Earth’s interior dynamics and could serve as another tool for ...

Authors: Guanhua Li, Dunsheng Xia, Erwin Appel, Youjun Wang, Jia Jia and Xiaoqiang Yang

Geoelectric hazard assessment: the differences of geoelectric responses during magnetic storms within common physiographic zones

Geomagnetic field data obtained through the INTERMAGNET program are convolved with with magnetotelluric surface impedance from four EarthScope USArray sites to estimate the geoelectric variations throughout th...

Authors: Stephen W. Cuttler, Jeffrey J. Love and Andrei Swidinsky

A harmonic spline magnetic main field model for Southern Africa combining ground and satellite data to describe the evolution of the South Atlantic Anomaly in this region between 2005 and 2010

CHAMP satellite and relatively densely spaced ground-based data measured over southern Africa between 2005 and 2010 are combined in a new regional, harmonic spline based, core field model. This new SACFM-2 mod...

Authors: Emmanuel Nahayo, Pieter B. Kotzé, Monika Korte and Susan J. Webb

Time-lapse inversion of one-dimensional magnetotelluric data

We present a new tool for modelling time-lapse magnetotelluric (MT) data, an emerging technique for monitoring changes in subsurface electrical resistivity. Time-lapse MT data have been acquired in various set...

Authors: Dennis Conway, Graham Heinson, Nigel Rees and Joseph Rugari

On the feasibility of routine baseline improvement in processing of geomagnetic observatory data

We propose a new approach to the calculation of regular baselines at magnetic observatories. The proposed approach is based on the simultaneous analysis of the irregular absolute observations and the continuou...

Authors: Anatoly Soloviev, Vincent Lesur and Dmitry Kudin

Source biases in midlatitude magnetotelluric transfer functions due to Pc3-4 geomagnetic pulsations

The magnetotelluric (MT) method for imaging the electrical conductivity structure of the Earth is based on the assumption that source magnetic fields can be considered quasi-uniform, such that the spatial scal...

Authors: Benjamin S. Murphy and Gary D. Egbert

Do ocean tidal signals influence recovery of solar quiet variations?

The solar quiet (Sq) source morphology changes on a daily basis and becomes disturbed during periods of increased magnetic activity. Therefore, it may be preferable to use single-day magnetic field recordings ...

Authors: Martina Guzavina, Alexander Grayver and Alexey Kuvshinov

Monitoring hydraulic stimulation using telluric sounding

The telluric sounding (TS) method is introduced as a potential tool for monitoring hydraulic fracturing at depth. The advantage of this technique is that it requires only the measurement of electric fields, wh...

Authors: Nigel Rees, Graham Heinson and Dennis Conway

Regularized magnetotelluric inversion based on a minimum support gradient stabilizing functional

Regularization is used to solve the ill-posed problem of magnetotelluric inversion usually by adding a stabilizing functional to the objective functional that allows us to obtain a stable solution. Among a num...

Authors: Yang Xiang, Peng Yu, Luolei Zhang, Shaokong Feng and Hisashi Utada

Electrical conductivity of the global ocean

The electrical conductivity of the ocean is a fundamental parameter in the electrodynamics of the Earth System. This parameter is involved in a number of applications ranging from the calibration of in situ oc...

Authors: Robert H. Tyler, Tim P. Boyer, Takuto Minami, Melissa M. Zweng and James R. Reagan

Core surface sub-centennial magnetic flux patches: characteristics and evolution

Short-term constituents of the secular variation, at inter-decadal (20–30 years) and sub-centennial (60–90 years) time scales, present in observatory data and main field models, are also found in the radial fi...

Authors: C. Stefan, V. Dobrica and C. Demetrescu

Varying Indian crustal front in the southern Tibetan Plateau as revealed by magnetotelluric data

In the southern Tibetan plateau, which is considered to be the ongoing India–Eurasia continental collision zone, tracing of the Indian crustal front beneath Tibet is still controversial. We conducted deep subs...

Authors: Chengliang Xie, Sheng Jin, Wenbo Wei, Gaofeng Ye, Letian Zhang, Hao Dong and Yaotian Yin

Regional electrical structure of the Andean subduction zone in central Chile (35°–36°S) using magnetotellurics

A profile of broadband magnetotelluric stations was acquired between 2009 and 2016 at 35°–36°S in the Southern Volcanic Zone of the Chilean Andes to image the subduction zone and its relation with the volcani...

Authors: Valentina Reyes-Wagner, Daniel Díaz, Darcy Cordell and Martyn Unsworth

Geoelectric structure of northern Cambay rift basin from magnetotelluric data

Broadband and long-period magnetotelluric data were acquired over the northern part of the Cambay rift zone along an east–west profile ~ 200 km in length. The decomposed TE- and TM-mode data were inverted usin...

Authors: Nagarjuna Danda, C. K. Rao and Amit Kumar

Constraints on lithospheric mantle and crustal anisotropy in the NoMelt area from an analysis of long-period seafloor magnetotelluric data

Despite strong anisotropy seen in analysis of seismic data from the NoMelt experiment in 70 Ma Pacific seafloor, a previous analysis of coincident magnetotelluric (MT) data showed no evidence for anisotropy in...

Authors: Tetsuo Matsuno and Rob. L. Evans

Electromagnetic receiver with capacitive electrodes and triaxial induction coil for tunnel exploration

A new type of electromagnetic (EM) receiver has been developed by integrating four capacitive electrodes and a triaxial induction coil with an advanced data logger for tunnel exploration. The new EM receiver ...

Authors: Chen Kai, Jin Sheng and Shun Wang

Depth profiles of resistivity and spectral IP for active modern submarine hydrothermal deposits: a case study from the Iheya North Knoll and the Iheya Minor Ridge in Okinawa Trough, Japan

Submarine hydrothermal deposits are one of the promising seafloor mineral resources, because they can store a large amount of metallic minerals as sulfides. The present study focuses on the electrical properti...

Authors: Shogo Komori, Yuka Masaki, Wataru Tanikawa, Junji Torimoto, Yusuke Ohta, Masato Makio, Lena Maeda, Jun-ichiro Ishibashi, Tatsuo Nozaki, Osamu Tadai and Hidenori Kumagai

Electrical conductivity of a locked fault: investigation of the Ganos segment of the North Anatolian Fault using three-dimensional magnetotellurics

This study attempts to reveal the fault zone characteristics of the locked Ganos Fault based on electrical resistivity studies including audio-frequency (AMT: 10,400–1 Hz) and wide-band (MT: 360–0.000538 Hz) m...

Authors: Mustafa Karaş, Sabri Bülent Tank and Sinan Özaydın

Electrical conductivity of old oceanic mantle in the northwestern Pacific I: 1-D profiles suggesting differences in thermal structure not predictable from a plate cooling model

Seafloor magnetotelluric (MT) experiments were recently conducted in two areas of the northwestern Pacific to investigate the nature of the old oceanic upper mantle. The areas are far from any tectonic activit...

Authors: Kiyoshi Baba, Noriko Tada, Tetsuo Matsuno, Pengfei Liang, Ruibai Li, Luolei Zhang, Hisayoshi Shimizu, Natsue Abe, Naoto Hirano, Masahiro Ichiki and Hisashi Utada

The afternoon counter-electrojet current system along the 75°E meridian during the IEEY

In the present study, the technique of principal component analysis (PCA) is applied to analyze the hourly mean values of geomagnetic field components D, H, and Z along an Indo-Russian chain of stations during...

Authors: S. K. Bhardwaj and P. B. V. Subba Rao

Statistical evaluation of global geomagnetic field models over Southern Africa during 2015

Global geomagnetic field models using spherical harmonic basis functions are important in space physics research, space weather and applications like navigation and mineral resources exploration. These models ...

Authors: P. B. Kotzé

Use of ssq rotational invariant of magnetotelluric impedances for estimating informative properties for galvanic distortion

Several useful properties and parameters—a model of the regional mean one-dimensional (1D) conductivity profile, local and regional distortion indicators, and apparent gains—were defined in our recent paper us...

Authors: T. Rung-Arunwan, W. Siripunvaraporn and H. Utada

Automatic selection of Dst storms and their seasonal variations in two versions of Dst in 50 years

A computer program is developed to automatically identify the geomagnetic storms in Dst index by applying four selection criteria that minimize non-storm-like fluctuations. The program is used to identify the ...

Authors: N. Balan, S. Tulasiram, Y. Kamide, I. S. Batista, J. R. Souza, K. Shiokawa, P. K. Rajesh and N. J. Victor

Effect of a huge crustal conductivity anomaly on the H-component of geomagnetic variations recorded in central South America

We describe here an analysis of the H-component of the geomagnetic field recorded in several temporary stations operating simultaneously in the central–eastern region of Brazil during nighttime pulsation even...

Authors: Antonio L. Padilha, Livia R. Alves, Graziela B. D. Silva and Karen V. Espinosa

Utility of Slepian basis functions for modeling near-surface and satellite magnetic anomalies of the Australian lithosphere

The utility of frequency- and space-limited spherical harmonic Slepian basis functions for magnetic anomaly modeling over restricted spherical patches of the Earth was investigated using combined near-surface ...

Authors: Hyung Rae Kim and Ralph R. B. von Frese

Generation of billow-like wavy folds by fluidization at high temperature in Nojima fault gouge: microscopic and rock magnetic perspectives

Microscopic billow-like wavy folds have been observed along slip planes of the Nojima active fault, southwest Japan. The folds are similar in form to Kelvin–Helmholtz (KH) instabilities occurring in fluids, wh...

Authors: Tomohiko Fukuzawa, Norihiro Nakamura, Hirokuni Oda, Minoru Uehara and Hiroyuki Nagahama