bluuebunny/crossref_metadata_2025_split huggingface dataset:
Resistivity imaging across the source region of the 2004 Mid-Niigata Prefecture earthquake (M6.8), central Japan
Authors: Uyeshima Makoto , Ogawa Yasuo , Honkura Yoshimori , Koyama Shigeru , Ujihara Naoto , Mogi Toru , Yamaya Yusuke , Harada Makoto , Yamaguchi Satoru , Shiozaki Ichiro , Noguchi Tatsuya , Kuwaba Yoshihiro , Tanaka Yoshikazu , Mochido Yuji , Manabe Noriko , Nishihara Masanori , Saka Mamoru , Serizawa Masato 
Published: August 2014

AbstractAcross the source region of the 2004 Mid-Niigata Prefecture earthquake, wideband magnetotelluric (MT) survey was performed just after the onset of the mainshock. Owing to the temporal stop of the DC powered railways around the area together with intense geomagnetic activity, we obtain MT records with excellent quality for both short and long period data, as long as 10,000 s. Two dimensional regional strike is evaluated with the aid of the Groom-Bailey tensor decomposition together with induction vector analysis. As a result, N15°W is determined for the strike. This strike is oblique to the local geological trend and also to the strike of the main shock source fault together with aftershock distribution of N35°E. Two dimensional resistivity structure is determined with the aid of an ABIC inversion code, where static shift is considered and estimated. Characteristics of the structure are as follows. (1) About 10 km thick sedimentary layer exists on the top. (2) A conductive body exists in the lower crust beneath the source region. The mainshock occurred at the boundary of the conductive sedimentary layer and a resistive basement beneath it and aftershocks occurred in the sedimentary layer. From geological studies, it is reported that the sedimentary layer was formed in the extensional rift-structure from Miocene to Pleistocene and has been thickened by compressional tectonic regime in the late Quaternary. Interstitial fluids or clay minerals, which reduce the sedimentary layer resistivity, control the reactivation of the normal fault as the mainshock thrust fault and aftershock activity. The second conductive body probably indicates existence of fluids in the depths as well. Such a conductive layer in the lower crust was also revealed by previous MT experiments along the Niigata-Kobe Tectonic Zone and probably plays a main role in concentration of strain rate along the zone.
Electrical conductivity structures estimated by thin sheet inversion, with special attention to the Beppu-Shimabara graben in central Kyushu, Japan
Authors: Handa Shun 
Published: August 2014

Abstract
It is proposed that the Beppu-Shimabara graben (BSG), characterized by the continuous negative Bouguer anomaly, runs NE to SW in central Kyushu. In order to clarify the BSG, the shallow electrical conductivity structure in central Kyushu is obtained by thin sheet modeling using the inversion of a conjugate gradient relaxation method and also using the forward method. The data used are the single-site transfer functions at 75 sites for the periods of 77, 97 and 122 sec. The inverted model indicates three highly conductive areas: these are the Saga-Chikugo plain covered with thick alluvium and the eastern and the western parts of central Kyushu including the BSG. Both end zones of this BSG are highly conductive in our model, which is closely related to conductive layers shallower than about 1 km. In contrast, the central part of the BSG is rather highly resistive. The BSG, thus, is not revealed as a continuous high-conductive belt and seems to be separated into three parts; the eastern and the western high-conductive zones and the central resistive area in our geoelectrical model of the shallow crust.
Crustal analysis of maud rise from combined satellite and near-surface magnetic survey data
Authors: Kim Hyung Rae , von Frese Ralph R. B. , Golynsky Alexander V. , Taylor Patrick T. , Kim Jeong Woo 
Published: August 2014

Abstract
We produced a crustal magnetization model for the Maud Rise in the southwest Indian Ocean off the coast of East Antarctica using magnetic observations from the Ørsted satellite and near-surface surveys complied by the Antarctic Digital Magnetic Anomaly Project (ADMAP). Joint inversion of the two anomaly fields suggests that the magnetic effects due to crustal thickness variations and remanence involving the normal polarity Cretaceous Quiet Zone (KQZ) dominate at satellite altitude (~700 km). The crustal thickness effects were modeled in the Ørsted data using crustal thickness variations derived from satellite altitude gravity data. Modeling of the residual Ørsted and near-surface magnetic anomalies supports extending the KQZ eastwards to the Astrid Ridge. The remaining near-surface anomalies involve crustal features with relatively high frequency effects that are strongly attenuated at satellite altitudes. The crustal modeling can be extended by the satellite magnetic anomalies across the Indian Ocean Ridge for insight on the crustal properties of the conjugate Agulhas Plateau. The modeling supports the Jurassic reconstruction of Gondwana when the African Limpopo-Zambezi and East Antarctic Princess Astrid coasts were connected as part of a relatively demagnetized crustal block.
Utility of aeromagnetic studies for mapping of potentially active faults in two forearc basins: Puget Sound, Washington, and Cook Inlet, Alaska
Authors: Saltus R. W. , Blakely R. J. , Haeussler P. J. , Wells R. E. 
Published: August 2014

Abstract
High-resolution aeromagnetic surveys over forearc basins can detect faults and folds in weakly magnetized sediments, thus providing geologic constraints on tectonic evolution and improved understanding of seismic hazards in convergent-margin settings. Puget Sound, Washington, and Cook Inlet, Alaska, provide two case histories. In each lowland region, shallow-source magnetic anomalies are related to active folds and/or faults. Mapping these structures is critical for understanding seismic hazards that face the urban regions of Seattle, Washington, and Anchorage, Alaska. Similarities in aeromagnetic anomaly patterns and magnetic stratigraphy between the two regions suggest that we can expect the aeromagnetic method to yield useful structural information that may contribute to earth-hazard and energy resource investigations in other forearc basins.
Precise, three-dimensional seafloor geodetic deformation measurements using difference techniques
Authors: Xu Peiliang , Ando Masataka , Tadokoro Keiichi 
Published: August 2014

Abtract
Crustal deformation on land can now be measured and monitored routinely and precisely using space geodetic techniques. The same is not true of the seafloor, which covers about 70 percent of the earth surface, and is critical in terms of plate tectonics, submarine volcanism, and earthquake mechanisms of plate boundary types. We develop new data processing strategies for quantifying crustal deformation at the ocean floor: single- and double-difference methods. Theoretically, the single difference method can eliminate systematic errors of long period, while the double difference method is able to almost completely eliminate all depth-dependent and spatialdependent systematic errors. The simulations have shown that the transponders on the seafloor and thus the deformation of the seafloor can be determined with the accuracy of one centimeter in the single point positioning mode. Since almost all systematic errors (of temporal or spatial nature) have been removed by the double difference operator, the double difference method has been simulated to be capable of determining the threedimensional, relative position between two transponders on the seafloor even at the accuracy of sub-centimeters by employing and accumulating small changes in geometry over time. While the surveying strategy employed by the Scripps Institution of Oceanography (SIO) requires the ship maintain station, our technique requires the ship to move freely. The SIO approach requires a seafloor array of at least three transponders and that the relative positions of the transponders be pre-determined. Our approach directly positions a single transponder or relative positions of transponders, and thus measures deformation unambiguously.
Low latitude Ne and Te variations at 600 km during 1 March 1982 storm from HINOTORI satellite
Authors: Oyama K. I. , Lakshmi D. R. , Kutiev I. , Abdu M. A. 
Published: August 2014

Abstract
This paper presents for the first time a study of HINOTORI satellite measurements of electron density and electron temperature in the topside ionosphere exclusively for magnetic storm departures. Special focus was given to the major storm of 1 March, 1982. While large enhancements in T
e characterize the day time storm response, marked increases in N
e dominate the night time deviations. The night time N
e enhancements which are rather remarkable during 0000–0400 LT are also found to be accompanied by significant T
e increases, by as much as 300 K. The statistical picture that emerges from the study of a large number of storms suggests significant nocturnal T
e enhancements which correlate with the magnitudes of storm intensities. Ring current particles through charge exchange processes seem to be a major source of heat input to thermal electrons, though other sources may also be important.
Transient crustal deformation in Tokai region, central Japan, until May 2004
Authors: Ozawa Shinzaburo , Murakami Makoto , Kaidzu Masaru , Hatanaka Yuki 
Published: August 2014

Abstract
An analysis of Global Positioning System (GPS) data reveals a continuation of the transient crustal deformation that was first reported by Ozawa et al. (2002) in the western Tokai region. Kalman filtering following the time-dependent inversion shows a slow-thrust slip occurring on the plate boundary in the western Tokai region, with its center around Lake Hamana, which is adjacent to the anticipated Tokai earthquake source area. The moment release from the Tokai silent earthquake was observed to be continuous surpassing Mw 7.0 in May 2004, with relative slip increases to the northeast and north of Lake Hamana from 2002. The moment release rate decreased in 2002, and then increased in 2003, reaching the rate observed in 2001.
Propagation of the 2001–2002 silent earthquake and interplate coupling in the Oaxaca subduction zone, Mexico
Authors: Franco S. I. , Kostoglodov V. , Larson K. M. , Manea V. C. , Manea M. , Santiago J. A. 
Published: August 2014

AbstractThe aseismic slow slip event of 2001–2002 in Guerrero, Mexico, with an equivalent magnitudeMW~ 7.5, is the largest silent earthquake (SQ) among many recently recorded by GPS in different subduction zones (i.e. Japan, Alaska, Cascadia, New Zealand). The sub-horizontal and shallow plate interface in Central Mexico is responsible for specific conditions for the ~100 km long extended transient zone where the SQs develop from ~80 to ~190 km inland from the trench. This wide transient zone and relatively large slow slips of 10 to 20 cm displacements on the subduction fault result in noticeable surface displacements of 5–6 cm during the SQs. Continuous GPS stations allow one to trace the propagation of SQs, and to estimate their arrival time, duration and geometric attenuation. These propagation parameters must be accounted in order to locate source of slow slips events and to understand the triggering effect that they have on large subduction earthquakes. We use long-baseline tiltmeter data to define new time limits (onset and duration) for the SQs and continuous records from 8 GPS stations to determine the propagation of the 2001–2002 SQ in Central Mexico. Data from the CAYA and IGUA GPS stations, separated by ~170 km and located along the profile perpendicular to the trench, are used to determine that the surface deformation from the 2001–2002 SQ started almost instantaneously. It propagated parallel to the coast at ~2 km/day with an exponential attenuation of the horizontal surface displacement and a linear decrease of its duration with distance. Campaign data obtained yearly from 2001 to 2005 at the Oaxaca GPS network have been modeled according to a propagation of the 2001–2002 SQ step-like displacement anomaly. This modeling shows that the SQ ceased gradually in the central part of the Oaxaca segment of the subduction zone (west of Puerto Angel, PUAN) and then it apparently triggered another SQ in SE Oaxaca (between PUAN and Salina Cruz, SACR). The estimated horizontal velocities for inter-event epochs at each GPS site are used to assess an average interplate coupling in the Central Oaxaca subduction zone.
The central Philippine Fault Zone: Location of great earthquakes, slow events and creep activity
Authors: Besana G. M. , Ando M. 
Published: August 2014

AbstractThe central Philippine Fault Zone is found to be the locus of great earthquakes, a transition zone with slow slip and creep activity. This is based on the analysis and correlation of seismic historic data and detailed documentation of recent seismic events in the region. Based on this study the Guinyangan fault is defined to be the northern locked portion with recurrence interval of as short as 65 years. The Masbate fault is the central part with large and medium earthquakes accompanied by unusually large ground rupture. The north Central Leyte fault and the south Central Leyte fault, on the other hand, are characterized by aseismic creep and medium-sized events, usually with clusters of foreshocks, respectively. Unusual seismic activity both on the Masbate fault and Central Leyte fault somehow correlates well with the behavior of known slow events and creep activity. Further investigation of this region could lead to deeper understanding of impending major earthquakes, especially along the Guinyangan fault, which usually produces larger damaging events, and for further understanding of the impact of slow events and creep on the adjoining active structures.
Strong S-wave anisotropy in the aftershock region of the 2000 Tottori-ken Seibu, Japan, earthquake (Mw6.6)
Authors: Nakamura Takeshi , Takenaka Hiroshi , Suzuki Sadaomi 
Published: August 2014

Abstract
The 2000 Tottori-ken Seibu earthquake (Mw6.6) occurred in Tottori prefecture, western Japan on October 6, 2000. We conducted aftershock observation and analyzed S-wave anisotropy using the aftershocks M
jma2.0 to 3.5 observed at two stations near the aftershock region. The fast S-waves are polarized to almost E-W direction, which corresponds to the P-axis direction of the mainshock. The delay time of the split S-waves ranges between 20 and 100 ms. The crack density inside and outside the aftershock area is estimated from the delay time. The distribution of crack density shows a strong spatial variation and depends on the ratio of the path length inside the aftershock region against the whole path length. Assuming a uniform distribution of anisotropy inside and outside the aftershock region, the crack densities inside and outside are 0.017 and 0.007, respectively. It thus seems probable that in the aftershock region the distribution of cracks is intensive and cracks are opened due to the presence of fluids in seismogenic layers. This considerable spatial variation of anisotropy between inside and outside the aftershock region suggests that the aftershock region may have different mechanical properties from the surrounding area.
Sharply concentrated cosmic-ray excess fluxes from heliomagnetospheric nose and tail boundaries observed with neutron monitors on the ground
Authors: Nagashima K. , Kondo I. , Fujii Z. 
Published: August 2014

Abstract
Two kinds of sharply concentrated excess flux of cosmic rays from heliomagnetospheric nose and tail directions (right ascension α ∼ 18 hours and ∼ 6 hours) are found by the analysis of sidereal daily variation of neutron intensity (median energy Em ∼ 20 GeV) on the ground. These fluxes do not show any response to the polarity reversal of solar magnetic field at the north pole and is contradictory to the simulation of the solar modulation of galactic anisotropy, which produces sidereal variation at the Earth greater in the negative polarity state than in the positive state. This indicates that they are not of the galactic origin and would be produced on the heliomagnetospheric nose and tail boundaries where it is considered that the interaction between the galactic and solar magnetic fields could produce the cosmic-ray acceleration. The acceleration mechanism producing the polarity-independent sidereal variation against solar modulation will be discussed.
The BGS magnetic field candidate models for the 10th generation IGRF
Authors: Lesur Vincent , Macmillan Susan , Thomson Alan 
Published: August 2014

Abstract
In this paper we describe the derivation of the BGS candidate models for the 10th generation International Geomagnetic Reference Field. Our data set comprised quiet night-time data from the Èrsted and Champ satellites spanning 1999.2–2004.6 and observatory hourly means spanning 1999.0–2004.0. To improve the secular variation estimates for 2005.0–2010.0, predictions based on application of linear prediction filters to long series of observatory annual means were also used. These data were fitted by a spherical harmonic “parent” model with an internal field of maximum degree 36, a quadratic dependence on time up to degree 8, a linear dependence on time up to degree 12, an external field of maximum degree 2 with linear dependence on time, annual and semi-annual variations, and Dst dependence for degree 1 terms. Additionally for the external field, non-zonal degree 1 coefficients in the Geocentric Equatorial Inertial reference frame with annual variations and dependence on the Interplanetary Magnetic Field Y-component are included. The candidate models were then based, for the main field, on an extrapolation to 2005.0 of the truncated parent model, and for the secular variation, on its extrapolation to 2007.5. This latter set of coefficients was then used to generate a synthetic data set at the Earth’s surface and this set was augmented with long term linear predictions of observatory annual means, to produce the final candidate secular variation model at 2007.5.
A global distribution of sporadic E events revealed by means of CHAMP-GPS occultations
Authors: Garcia-Fernandez M. , Tsuda T. 
Published: August 2014

Abstract
With the advent of the GPS/MET mission, the atmospheric sciences were given a new tool to enhance studies related to global and seasonal variations of different atmospheric parameters. In particular, it has proof valuable for the study of the ionospheric irregularities in the E layer, which before were performed basically on a local basis by ground based instruments. Using similar techniques applied to GPS/MET data to process the 50 Hz sampling rate GPS data to study the E layer electron density distribution, this work shows the global and seasonal distributions of the ionospheric irregularities of electron density, during high solar activity, by using the CHAMP satellite GPS data from January 1st 2002 to May 31st 2004. As pointed out by several theories on the E layer and previous studies with ground based data, the results presented here show that these irregularities have strong geographical and seasonal dependence, with enhancements in the auroral regions, in mid-latitudes and during the summer season.
Nighttime enhancement of the amplitude of geomagnetic sudden commencements and its dependence on IMF-Bz
Authors: Araki T. , Keika K. , Kamei T. , Yang H. , Alex S. 
Published: August 2014

Abstract
We present a statistical study of the diurnal variation of the occurrence frequency of geomagnetic sudden commencements (SCs) observed at Kakioka (geomagnetic latitude, θ = 27.4°). SCs with an H-component amplitude (ΔH) larger than 40 nT occur more frequently in the nighttime than the daytime, while those with smaller amplitudes (ΔH < 39 nT) occur more frequently in the daytime. Three large amplitude SCs (ΔH = 85, 117 and 145 nT at Kakioka) were analyzed in detail. All three exhibited larger amplitudes during the nighttime at all low latitudes except those near the dayside equator. A statistical study reveals that the averaged amplitudes are slightly larger in the daytime at Alibag (θ = 10.2°) but considerably larger in the nighttime at three higherlatitude Japanese stations, Kanoya (θ = 21.9°), Kakioka and Memambetsu (θ = 35.4°). Case studies of two moderate amplitude SCs which occurred at the same UT indicate that nighttime SC amplitudes at low latitudes are slightly (considerably) larger than daytime amplitudes when the interplanetary magnetic field (IMF) points northward (southward). We suggest that the diurnal variation of SC amplitudes can be explained by a combination of field aligned and resultant ionospheric currents produced during the main impulse of SCs.
Simulation of the high-degree lithospheric field recovery for the Swarm constellation of satellites
Authors: Maus S. , Lühr H. , Purucker M. 
Published: August 2014

Abstract
A primary objective of the Swarm constellation mission is to resolve the lithospheric magnetic field with the best achievable accuracy in order to bridge the spectral gap between satellite and airborne/marine magnetic surveys. In a series of end-to-end simulations, the possibilities of high degree field recovery were investigated. The proposed constellation consists of a higher and a lower pair of satellites. It was soon found that a constellation as such does not yet guarantee improved high degree field recovery. Of crucial importance is the orbit constellation of the lower pair of satellites. If the lower satellites follow each other, as investigated in Constellation 1, the gain of a constellation turns out to be marginal, compared to a single satellite. For Constellation 2, the lower satellites were separated in the E/W direction. In this setup, one can use the instantaneous E/W magnetic field gradient between the satellites, as well as the N/S along track gradients. Incorporating this vector gradient information results in significantly improved field resolution. Indeed, the final simulation suggests that the envisaged Swarm constellation will enable the recovery of the lithospheric field to beyond spherical harmonic degree 130.
Introducing localized constraints in global geomagnetic field modelling
Authors: Lesur Vincent 
Published: August 2014

AbstractA set of functions is defined that can be used for modelling the internal part of the geomagnetic field. These functions are represented in term of spherical harmonics of a given maximum degreeLand are centred at specific latitudes and longitudes. The number of functions needed and the positions of their centres are such that any potential field of maximum spherical harmonic degreeLcan be modelled. Formulae are obtained to transform between the potential field representation using these functions and a classic spherical harmonic representation. The shape of these functions can be optimized to make them reasonably localized, and from there it is shown how a localized constraint can be applied to an internal geomagnetic field model. The technique is demonstrated by means of models built from a few months of the Swarm mission synthetic data set.