bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fault model of the 2005 Fukuoka-ken Seiho-oki earthquake estimated from coseismic deformation observed by GPS and InSAR
Authors: Nishimura Takuya , Fujiwara Satoshi , Murakami Makoto , Suito Hisashi , Tobita Mikio , Yarai Hiroshi 
Published: August 2014

Abstract
On 20 March 2005, the Fukuoka-ken Seiho-oki (the 2005 West off Fukuoka Prefecture) earthquake (MJMA7.0) occurred in northern Kyushu, western Japan. We used coseismic deformation observed by GPS and InSAR to construct a fault model. The uniform slip model of rectangular dislocation in an elastic half-space suggests ∼1.4 m of left-lateral strike slip faulting on a near-vertical fault. The fault strike is 298 degrees and its southeastern edge was strongly constrained by the displacement at a permanent GPS station located on Shikanoshima, which is consistent with the aftershock distribution. We estimated slip distribution on a planar fault and found the maximum slip of ∼1.9 m near the surface. Large slip is concentrated at depths of 0 to 10 km in an along-strike range from the hypocenter to 10 km east-southeast of it.
Source processes of the 2005 West Off Fukuoka Prefecture earthquake and its largest aftershock inferred from strong motion and 1-Hz GPS data
Authors: Kobayashi Reiji , Miyazaki Shin’ichi , Koketsu Kazuki 
Published: August 2014

Abstract
We simultaneously inverted strong motion and 1-Hz GPS data recorded during the 2005 west off Fukuoka prefecture earthquake (M
JMA 7.0) for its source process. The data at a GPS station near the source region provided strong constraint on the fault geometry and asperity area. The resultant slip distribution suggests a single asperity close to the Genkai island, where many houses were severely damaged. The maximum slip is 1.4 m, and the total seismic moment is 1.0 × 1019 Nm (M
W 6.6). We also inverted strong motion data recorded during the largest aftershock (M
JMA 5.8). The resultant slip distribution shows two asperities on the fault plane. The maximum slip in the major asperity is 0.12 m and the total seismic moment is 2.0 × 1017 Nm (M
W 5.5). The main shock and largest aftershock may cause stress change on the Kego fault, which is a major fault running through the city of Fukuoka.
Initial-rupture fault, main-shock fault, and aftershock faults: Fault geometry and bends inferred from centroid moment tensor inversion of the 2005 west off Fukuoka prefecture earthquake
Authors: Ito Yoshihiro , Obara Kazushige , Takeda Tetsuya , Shiomi Katsuhiko , Matsumoto Takumi , Sekiguchia Shoji , Hori Sadaki 
Published: August 2014

Abstract
The 2005 west off Fukuoka prefecture earthquake (M
JMA = 7.0) occurred on March 20, 2005 in northwest Kyusyu, Japan. The fault geometry and rupture propagation of the main shock are investigated by applying the centroid moment tensor (CMT) inversion method to densely-distributed broadband seismic network data. An accurate distribution of small aftershocks is also examined by a double-difference method. The source fault of the main shock whose moment magnitude was 6.6 had a strike of 123°, and the rupture propagated in the southeast direction. We obtain forty-four CMT solutions of the main shock and aftershocks with a moment magnitude greater than 3.5. For the main shock, the fault strike estimated using P-wave first-motion polarities differs from that of the moment tensor solution by 13° in the counterclockwise direction. Some aftershocks with a moment tensor solution similar to the focal mechanism of the main shock derived from the P-wave first motions are distributed north of the epicenter of the main shock. The largest aftershock with a strike of 8° in the clockwise direction, which differs from that of the CMT solution of the main shock, was located south of the main shock. These changes in the fault strike play an important role in the initiation and termination of the rupture process of the main shock.
Source process and near-source ground motions of the 2005 West Off Fukuoka Prefecture earthquake
Authors: Asano Kimiyuki , Iwata Tomotaka 
Published: August 2014

AbstractA large shallow crustal earthquake occurred at the western off-shore of Fukuoka Prefecture, northern Kyushu, Japan, at 10:53 on March 20, 2005 (JST). Source rupture processes of the mainshock and the largest aftershock on April 20, 2005, are estimated by the kinematic waveform inversion of strong motion seismograms. The rupture of the mainshock started with relatively small slip, and the largest slip was observed at the southeast of the hypocenter. The inverted source models showed that both of the ruptures of the mainshock and the largest aftershock mainly propagated to southeast from the hypocenters, and the rupture area of those events did not overlap each other. Three-dimensional ground motion simulation by the finite difference method considering three-dimensional bedrock structure was also conducted to see the spatial variation of the near-source ground motion of the mainshock. The result of the simulation shows that expected groud motions are relatively large in and arround Genkai Island, Shikanoshima Island, and the center of Fukuoka City compared to the other area because of the rupture heterogeneity and the deep basin structure in Fukuoka City.
The generalized Bouguer anomaly
Authors: Nozaki Kyozo 
Published: August 2014

AbstractThis paper states on the new concept of the generalized Bouguer anomaly (GBA) that is defined upon the datum level of an arbitrary elevation. Discussions are particularly focused on how to realize the Bouguer anomaly that is free from the assumption of the Bouguer reduction densityρB, namely, theρB-free Bouguer anomaly, and on what is meant by theρB-free Bouguer anomalyin relation to the fundamental equation of physical geodesy. By introducing a new concept of the specific datum level so that GBA is not affected by the topographic masses, we show the equations of GBA upon the specific datum levels become free fromρBand/or the terrain correction. Subsequently utilizing these equations, we derive an approximate equation for estimatingρB. Finally, we show how to compute a Bouguer anomaly on the geoid by transforming the datum level of GBA from the specific datum level to the level of the geoid. These procedures yield a new method for obtaining the Bouguer anomaly in the classical sense (say, the Bouguer disturbance), which is free from the assumption ofρB. We remark that GBA upon theρB-free datum levelis the gravity disturbance and that the equation of it has a tie to the fundamental equation of physical geodesy.
Geomagnetic effects of high-density plasma with southward magnetic field in the interplanetary coronal mass ejection observed on May 2–3, 1998
Authors: Adachi Haruka , Sakurai Tohru , Marubashi Katsuhide 
Published: August 2014

Abstract
This paper aims to clarify the effect of high-density plasma in interplanetary coronal mass ejection (ICME) observed during the May 2–3, 1998 geomagnetic storm. The examination is performed based on the estimation of Dst index, which is calculated with the observed solar wind parameters of the ICME. The estimated Dst index variation is compared with Dst index variation provided by the World Data Center for Geomagnetism, Kyoto (WDC, Kyoto). From this examination, we find that the trend of the estimated Dst is in good agreement with that of the provided Dst when the thresholds are taken into account for both the solar wind plasma density and the dawn-to-dusk solar wind electric field, as 30 #/cc and 0.49 mV/m, respectively. From the result, we can conclude that the effect of high-density plasma is important on the enhancement of geomagnetic storm as well as the effect of the other solar wind parameters, such as the interplanetary magnetic field (IMF) Bz and solar wind velocity. On the other hand, the solar source of the magnetic field of this ICME is examined. The magnetic field structure of the ICME is examined by fitting the flux rope model to the observed magnetic field and solar wind speed. The results are compared with the magnetic structure of the bases of coronal helmet streamers. From this comparison we can find that the magnetic structure of the interplanetary flux rope is in good agreement with that of the neutral line of the base of coronal helmet streamers. The result suggests that if we look for the causes of geomagnetic storm we should take into account both the plasma structure and the magnetic structure of the base of coronal helmet streamers.
An empirical model of ionospheric foE over Wuhan
Authors: Yue Xinan , Wan Weixing , Liu Libo , Ning Baiqi 
Published: August 2014

AbstractDaytime half-hourly values of the critical frequency of the ionosphericE-layer,f oE, obtained at Wuhan Ionospheric Observatory (geographic 114.4°E, 30.6°N; 45.2°dip), China, during the whole interval of 1957–1991 and 1999–2004 have been used to develop an empirical model. The model, including variations with local time, day number and solar cycle, is in agreement with the observations. A comparison between our model and IRI and Titheridge’s model has also been made. Statistically, our model gives a better performance than IRI and Titheridge’s model because data set is obtained with our own station. Both the IRI and Titheridge’s model overestimatef oEespecially in May to September months. Combing with past investigations, we suggest that overestimation of ionospheric parameters by IRI may be a common feature in East Asia. This result is very helpful for both the correction of IRI in East Asia and the development of Chinese Reference Ionosphere (CRI) model.
The Swarm End-to-End mission simulator study: A demonstration of separating the various contributions to Earth’s magnetic field using synthetic data
Authors: Olsen Nils , Haagmans Roger , Sabaka Terence J. , Kuvshinov Alexei , Maus Stefan , Purucker Michael E. , Rother Martin , Lesur Vincent , Mandea Mioara 
Published: August 2014

Abstract

Swarm, a satellite constellation to measure Earth’s magnetic field with unpreceded accuracy, has been selected by ESA for launch in 2009. The mission will provide the best ever survey of the geomagnetic field and its temporal evolution, in order to gain new insights into the Earth system by improving our understanding of the Earth’s interior and climate. An End-to-End mission performance simulation was carried out during Phase A of the mission, with the aim of analyzing the key system requirements, particularly with respect to the number of Swarm satellites and their orbits related to the science objectives of Swarm. In order to be able to use realistic parameters of the Earth’s environment, the mission simulation starts at January 1, 1997 and lasts until re-entry of the lower satellites five years later. Synthetic magnetic field values were generated for all relevant contributions to Earth’s magnetic field: core and lithospheric fields, fields due to currents in the ionosphere and magnetosphere, due to their secondary, induced, currents in the oceans, lithosphere and mantle, and fields due to currents coupling the ionosphere and magnetosphere. Several independent methods were applied to the synthetic data to analyze various aspects of field recovery in relation to different number of satellites, different constellations and realistic noise sources. This paper gives an overview of the study activities, describes the generation of the synthetic data, and assesses the obtained results.
Using global magnetospheric models for simulation and interpretation of Swarm external field measurements
Authors: Moretto T. , Vennerstrøm S. , Olsen N. , Rastätter L. , Raeder J. 
Published: August 2014

Abstract
We have used a global model of the solar wind magnetosphere interaction to model the high latitude part of the external contributions to the geomagnetic field near the Earth. The model also provides corresponding values for the electric field. Geomagnetic quiet conditions were modeled to provide simulated external contributions relevant for internal field modeling. These have proven very valuable for the design and planning of the upcoming multi-satellite Swarm mission. In addition, a real event simulation was carried out for a moderately active time interval when observations from the Ørsted and CHAMP sattelites were available. Comparisons between the simulation results and the satellite observations for this event demonstrate the current level of validity of the global model. We find that the model reproduces quite well the region 1 current system and nightside region 2 currents whereas it consistently underestimates the dayside region 2 currents and overestimates the horizontal ionospheric closure currents in the dayside polar cap. Furthermore, with this example we illustrate the great benefit of utilizing the global model for the interpretation of Swarm external field observations and, likewise, the potential of using Swarm measuremnets to test and improve the global model.
Global lithospheric magnetic field modelling by successive regional analysis
Authors: Thébault E. 
Published: August 2014

Abstract
Present lithospheric field models, like the MF4 and CM4, are produced by least squares estimation using spherical harmonic basis functions with global support. Accounting for the different properties of magnetic data at low and high latitudes, a method that can take regional differences into account is proposed. Using four years of CHAMP satellite data, a detailed lithospheric magnetic field snapshot is obtained at 400 km altitude over the entire sphere by stitching together a dense coverage of regional models. The individual forward models computed on a quasi-regular grid over the Earth are then transformed to spherical harmonics by direct integration. Despite the stitching procedure, the long wavelength lithospheric features are correctly reproduced and small scale features are well resolved. Without regularization, the resulting model is stable to spherical harmonic degree 56. In addition to accounting for regionally varying noise levels, the proposed technique is also well suited to deal with incomplete data coverage issues when combining satellite with near surface data. The method could therefore make an important contribution to one of the main goals of the Swarm mission: to close the spectral gap between satellite and near-surface magnetic surveys.
A reexamination of pitch angle diffusion of electrons at the boundary of the lunar wake
Authors: Nakagawa Tomoko , Iizima Masahide 
Published: August 2014

Abstract
Velocity distribution of the solar wind electrons injected into the lunar wake boundary is re-examined by using a simple model structure of inward electric field. The electrons that were flowing along the magnetic field lines undergo pitch angle scattering due to the electric field component perpendicular to the magnetic field. The electrons obtain perpendicular speeds twice as much as the drift speed. On the basis of the GEOTAIL observations of the whistler mode waves and strahl electrons, the intensity of the electric field and the thickness of the wake structure are estimated to be 28-40 mVm-1 and less than 20 km, respectively.
GPS measurements of horizontal deformation across the Lai Chau—Dien Bien (Dien Bien Phu) fault, in Northwest of Vietnam, 2002-2004
Authors: Cong Duong Chi , Yun Hong-Sic , Cho Jae-Myoung 
Published: August 2014

Abstract
Global Positioning System (GPS) measurements from Feb. 2002 through Mar. 2004 were used to estimate the recent crustal movement along the Lai Chau—Dien Bien (Dien Bien Phu) fault (LC-DBF) system in the Northwest of Vietnam. Four GPS campaign data were processed to estimate ITRF2000 and local horizontal velocities, as well as extensive and compressive strain rates across the LC-DBF. ITRF2000 velocities are consistent with east-southeastward movement of Sundaland i.e. Indochina. Local velocities did not reveal much left-lateral strike-slip of the fault system and the derived strain rates were insignificantly different from zero at 95% confidence.
Re-estimation of tsunami source of the 1952 Tokachi-oki earthquake
Authors: Satake Kenji , Hirata Kenji , Yamaki Shigeru , Tanioka Yuichiro 
Published: August 2014

Abstract
Previous studies indicate that the source area of the 2003 Tokachi-oki earthquake (M 8.0) was smaller than the comparable 1952 Tokachi-oki earthquake (M 8.2) source. We reinverted the 1952 tsunami waveforms, by adopting higher-resolution tsunami simulation method, and estimating and correcting for clock errors of tide gauges from comparison of the 1952 and 2003 tsunami waveforms. The estimated slip distribution indicates that the 1952 tsunami source area was indeed larger than the 2003 source. The distributions of measured and computed coastal tsunami heights also support this conclusion.
Simulations of SH wave scattering due to cracks by the 2-D finite difference method
Authors: Suzuki Yuji , Kawahara Jun , Okamoto Taro , Miyashita Kaoru 
Published: August 2014

AbstractWe simulate SH wave scattering by 2-D parallel cracks using the finite difference method (FDM), instead of the popularly used boundary integral equation method (BIEM). Here special emphasis is put on simplicity; we apply a standard FDM (fourth-order velocity-stress scheme with a staggered grid) to media including tractionfree cracks, which are expressed by arrays of grid points with zero traction. Two types of accuracy tests based on comparison with a reliable BIEM, suggest that the present method gives practically sufficient accuracy, except for the wavefields in the vicinity of cracks, which can be well handled if the second-order FDM is used instead. As an application of this method, we also simulate wave propagation in media with randomly distributed cracks of the same length. We experimentally determine the attenuation and velocity dispersion induced by scattering from the synthetic seismograms, using a waveform averaging technique. It is shown that the results are well explained by a theory based on the Foldy approximation for crack densities of up to about 0.1. The presence of a free surface does not affect the validity of the theory. A preliminary experiment also suggests that the validity will not change even for multi-scale cracks.
A numerical analysis of seismic waves for an anisotropic fault zone
Authors: Nakamura Takeshi , Takenaka Hiroshi 
Published: August 2014

AbstractIn this study we examine the effects of anisotropy on the seismic wavefield in a fault zone from computation of the synthetic seismograms for a simple fault zone model and a variety of seismic wave sources. The fault zone is modeled by a homogeneous vertical layer with transverse isotropy, induced by cracks, sandwiched between isotropic half-spaces (host rocks). The symmetry axis of the transverse isotropy is horizontal and perpendicular to the fault zone strike. We calculate the synthetic seismograms for this anisotropic fault zone model using a semianalytical method, the propagator matrix method. The synthetic seismograms show a later phase arriving after the main shear-wave in the horizontal component perpendicular to the fault zone strike at most stations near the fault zone. It is the slower shear-wave (qS2) and its reverberation. The amplitude of this phase and the time delay from the main shear-wave arrival are proportional to the degree of anisotropy, which suggests that observing such phase in field measurements may imply the presence of an anisotropic fault zone. We also perform the shear-wave splitting measurements by applying the cross-correlation method to the synthetic seismograms for various sources. For a strike-slip source, the synthetic seismograms show that the wavefield is more affected by the velocity structure than by the degree of anisotropy, which makes it difficult to estimate the anisotropic (shearwave splitting) parameters. For normal and dip-slip fault sources with the strike parallel to or striking against the fault zone, the effects of anisotropy is so dominant that the anisotropic fault zone can be detected. These results suggest that the determination of the anisotropic properties in the fault zone would require an appropriate station deployment and the source type information.
One-dimensional spherical elementary current systems and their use for determining ionospheric currents from satellite measurements
Authors: Juusola Liisa , Amm Olaf , Viljanen Ari 
Published: August 2014

Abstract
The method of 1D spherical elementary current systems (SECS) is a new way for determining ionospheric and field-aligned currents in spherical geometry from magnetic field measurements made by a low-orbit satellite. In contrast to earlier methods, the full ionospheric current distribution, including both divergence-free and curl-free horizontal currents, as well as field-aligned currents, can be determined. Placing infinitely many 2D SECSs of identical amplitudes at a constant latitude results in two types of 1D SECSs, which are independent of longitude, and by superposition can reproduce any ionospheric and field-aligned current system with the same property. One type of the 1D SECSs is divergence-free and toroidal with a poloidal magnetic field, and the other type is curl-free and poloidal. Associated with the divergence of the curl-free type are radial currents. The magnetic field of the combined curl-free 1D SECS and field-aligned currents is toroidal and restricted to the region above the ionosphere. Ionospheric currents are determined by placing several 1D SECSs at different latitudes and choosing their amplitudes in such a way that their combined magnetic field as closely as possible fits the one measured by the satellite. The 1D SECS method has been tested using both modeled and real data from the CHAMP satellite, and found to work excellently in 1D cases.
Measurement quality estimation of proton-precession magnetometers
Authors: Denisov A. Y. , Denisova O. V. , Sapunov V. A. , Khomutov S. Y. 
Published: August 2014

Abstract
A method for calculating quality estimation of the magnetic field value measured by proton-precession magnetometers from data of single measurement is presented. This method is appropriate for frequency measurement algorithms which process time-series of signal’s zero crossing. Expressions for measurement error estimation are obtained taking into account signal decay and correlated noise. Presented formulas allow a result reliability to be estimated immediately in single measurement and give an opportunity for complex control of a device performance. Correlation and relaxation corrections are given. It was experimentally tested that the standard deviation of measurements is in a good qualitative agreement with presented error estimation.
Influence of magnetic field variations on measurements by magnetometers using averaging algorithms
Authors: Denisova O. , Sapunov V. , Denisov A. 
Published: August 2014

Abstract
The article is devoted to features of modulus magnetic field measurements by means of proton magnetometers. Inertial characteristics of the magnetometers and dynamic errors of variable magnetic field measurements are discussed. Three basic magnetometers averaging algorithms, processing zero crossing times of free precession, are compared. Theoretical and some numerical estimations of the algorithms work are presented for the linear, square and harmonic variations of magnetic field.
Modelling of spatial-temporal changes of the geomagnetic field in Japan
Authors: Ji Xiaoli , Utsugi Mitsuru , Shirai Hiroki , Suzuki Akira , He Jinlan , Fujiwara Satoshi , Fukuzaki Yoshihiro 
Published: August 2014

Abstract
A geomagnetic regional model is constructed to provide a spatial-temporal variation of three orthogonal components (X, Y, Z) in Japan. In order to obtain a high temporal and spatial resolution, Natural Orthogonal Components (NOC) analysis and Spherical Cap Harmonic (SCH) analysis were employed to produce a spatial-temporal model based on the observed data from geomagnetic observatories and continuous geomagnetic stations. Using this model, we calculated the secular variation between 1999 and 2004 in Japan. The root mean square (RMS) scatter of the model is less than 3 nT, which indicates a good agreement between calculated and input data.