bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gravity and density variations of the tilted Tottabetsu plutonic complex, Hokkaido, northern Japan: implications for subsurface intrusive structure and pluton development
Authors: Kamiyama Hiroyuki , Yamamoto Akihiko , Hasegawa Takeshi , Kajiwara Takanori , Mogi Toru 
Published: August 2014

Abstract
An exposed cross section of the tilted Tottabetsu plutonic complex allows direct evaluation of its original 2-D cross-sectional shape and pretilting vertical density variations in both the pluton and the country rocks, which serves as a strong constraint in gravity modeling that complements information on the ’missing’ pretilting horizontal dimension of this tilted pluton. The pluton is stratified with the uppermost thin granitic unit (≈1-km thick) and the underlying thick gabbro-diorite units (≈9-km thick) that preserve a stratigraphic record of numerous hotter replenishments in the form of alternation of originally horizontal mafic sheets and cumulate layers. Both the pluton and the country rocks show systematic density increase with pretilting crustal depth, but density contrast of the pluton with the country rocks varies between each unit. The 2-D cross-sectional shape and gravity analysis revealed that the pluton had a vertically-elongated shape with vertical side walls before tilting. The vertical side walls, together with the stack of the originally horizontal sheets and cumulate layers, suggests that the pluton grew only vertically by piston mechanism. The very thick, exposed cross section provides unequivocal evidence for development of such a pluton with this unusual shape and mass distribution, which has been inferred elsewhere only by some geophysical studies.
Spatial distribution of F-net moment tensors for the 2005 West Off Fukuoka Prefecture Earthquake determined by the extended method of the NIED F-net routine
Authors: Matsumoto Takumi , Ito Yoshihiro , Matsubayashi Hirotoshi , Sekiguchi Shoji 
Published: August 2014

Abstract
The 2005 West Off Fukuoka Prefecture Earthquake with a Japan Meteorological Agency (JMA) magnitude (MJMA) of 7.0 occurred on March 20, 2005. We determined moment tensor solutions, using a surface wave with an extended method of the NIED F-net routine processing. The horizontal distance to the station is rounded to the nearest interval of 1 km, and the variance reduction approach is applied to a focal depth from 2 km with an interval of 1 km. We obtain the moment tensors of 101 events with (MJMA) exceeding 3.0 and spatial distribution of these moment tensors. The focal mechanism of aftershocks is mainly of the strike-slip type. The alignment of the epicenters in the rupture zone of the main-shock is oriented between N110°E and N130°E, which is close to the strike of the main-shock’s moment tensor solutions (N122°E). These moment tensor solutions of intermediatesized aftershocks around the focal region represent basic and important information concerning earthquakes in investigating regional tectonic stress fields, source mechanisms and so on.
Precise location of the fault plane and the onset of the main rupture of the 2005 West Off Fukuoka Prefecture earthquake
Authors: Takenaka Hiroshi , Nakamura Takeshi , Yamamoto Yosuke , Toyokuni Genti , Kawase Hiroshi 
Published: August 2014

AbstractNear-source strong-motion records of the 2005 West Off Fukuoka Prefecture earthquake have two remarkable features. One is the presence of a relatively long period pulse with large amplitude on the fault-normal component of the velocity and displacement records, which is the result of the forward rupture directivity. The other is that the records show several seconds of small but increasing amplitude arrival (“initial rupture phase”) followed by the onset of the main energy release (“main rupture phase”). We first determined the precise geometry of the fault plane of this earthquake by examining the horizontal particle motion of the mainS-wave portion on the records, as follows: the strike is N304°E, and the dip angle is 87°. The dip direction of the fault plane is northeast, and the surface intersection of the fault plane passes by the eastern coast of Genkai Island. We also obtained the relative location of the onset of the main rupture with respect to the hypocenter, and the mean rupture velocity between them. The distance between them is 5.1 km, the onset of the main rupture is located southeast above the hypocenter. The mean rupture velocity along the straight path is 1.4 km/s. It is found that the main rupture began 3.6 sec later from the origin time, at the central point between the hypocenter and Genkai Island. Our results suggest that Genkai Island directly suffered the strong effects of the forward rupture directivity during the earthquake.
Rupture process of the 2005 West Off Fukuoka Prefecture, Japan, earthquake
Authors: Horikawa Haruo 
Published: August 2014

AbstractThe 2005 West off Fukuoka Prefecture, Japan, earthquake (MS 6.7) is a moderate-size crustal event. The rupture process of this earthquake was inferred from strong motion data. It is observed regardless of epicentral distance and azimuth that the initialP-wave with a small amplitude continued for 2.5–4 s, suggesting prominent initial rupture. The duration of the initial rupture was estimated to be 3.3 s from travel time analysis. Inversion analysis shows that the initial rupture continued for 3.5 s and the overall rupture finished within 10 s. An area of large slip with two peaks of slip amount appeared to the southeast of the hypocenter, and the location of the large-slip area is consistent with the origin of the main rupture inferred from travel time analysis. Small amount of slip was found at and around the hypocenter, and the rupture velocity was slow there. The seismic moment of this earthquake was estimated to be 5.7 × 1018 Nm (Mw6.4). The maximum stress drop calculated from the derived slip distribution exceeded 10 MPa. An area of negative stress drop expanded, corresponding to the distribution of small slip. Forward modeling of the observed waveforms suggests that the negative stress drop is not fully attributable to poor resolution of inversion analysis for small amount of slip. Since dynamic stress drop should be positive around the hypocenter so that rupture propagates over the entire fault, it is plausible that the negative stress drop appeared after healing.
Simulation of strong motions in Fukuoka City during the 2005 West Off Fukuoka Prefecture Earthquake with special reference to thick Quaternary sediments around the Kego fault
Authors: Satoh Toshimi , Kawase Hiroshi 
Published: August 2014

AbstractWe simulate velocity records at two stations in the building damaged area near the Kego fault in Fukuoka City by 1-D wave propagation theory during the 2005 West Off Fukuoka Prefecture Earthquake, Japan. Here we use the pre-Tertiary bedrock wave deconvolved from the record observed at a K-NET station outside of the damaged area. The observed velocity waveforms and pseudo velocity response spectra in the period range from 0.7 to 10 seconds in the predominant direction (N20°E) components are reasonably reproduced. Velocity pulses with a period of about 1 to 2 seconds in observed velocity waveforms at two stations are found to be amplified by the Quaternary sediments above the pre-Tertiary bedrock. After we confirmed the validity of our approach through the simulation, we predict the peak ground velocity (PGV) distribution around the Kego fault by considering 1-D response of Quaternary sediments at each site. The predicted PGV distribution of N20?E components is largest (about 80 cm/s) in the northeast side of the Kego fault and agrees well with the building damage distribution. Our result shows that the 1-D site responses of Quaternary sediments mainly contributed to the difference of PGVs inside and outside of the damaged area in Fukuoka City.
Stress change prior to the major events in the 1989 earthquake swarm off the eastern Izu Peninsula, Japan
Authors: Kawakata Hironori , Ogasawara Hiroshi , Sekiguchi Shoji , Uyama Shizuka , Mino Kazuo 
Published: August 2014

AbstractWe investigate a temporal change in a stress parameter of earthquakes that occurred in the 1989 swarms off the eastern Izu Peninsula in Japan. We use the energy index (EI), which have been monitored in deep South African gold mines for predicting major events, as an estimate of apparent stress that is proportional to the ratio of seismic energy (E) to seismic moment (Mo).EImeasures an excess or shortage inEwith respect to the empirical relationship betweenEandMo. We check thatEIis almost proportional to the apparent stress for the ranges ofMoand frequency for our analysis, althoughEis underestimated due to the artifact of limited frequency band of monitoring. The largest events (M= 5.2 and 5.5) took place off the tip of a vertical crack, which opened associated with magma intrusion. While the opening continued to load the source areas of theM5.2 and 5.5, we find significant decrease inEIprior to the events. Based on the experimental result that the stress decreases when yielding takes place prior to final failure, we interpret this observation as yielding in the vicinity of the large earthquake hypocenters, following a rapid increase in stress caused by magma intrusion.
Statistical studies of fast and slow Z-mode plasma waves in and beyond the equatorial plasmasphere based on long-term Akebono observations
Authors: Nishimura Y. , Ono T. , Iizima M. , Shinbori A. , Kumamoto A. , Oya H. 
Published: August 2014

Abstract
In order to investigate spatial and temporal variations of fast and slow Z-mode waves frequently observed in the equatorial plasmasphere, statistical studies have been performed by using plasma wave observation data obtained by the Akebono satellite within a period from 1989 to 1995. It has been clarified that fast and slow Z-mode waves are intensified within ±5° of geomagnetic latitudes in an altitude range from 6000 km to the apogee (10500 km) of the satellite without obvious local time dependence. Long-term averaged intensity of fast Z-mode waves has almost the same orders of magnitude as that of slow Z-mode waves. These results indicate that significant part of fast Z-mode waves are not produced by the linear mode conversion process from slow Z-mode waves, but excited by more direct process. Furthermore, the region of intensified fast and slow Z-mode waves has been spread in a wider geomagnetic latitude range of ±10° during geomagnetic storms. These evidences suggest that one of the possible free energy sources is ring current particles injected into the equatorial region of the plasmasphere during geomagnetic storms.
3-D electromagnetic induction studies using the Swarm constellation: Mapping conductivity anomalies in the Earth’s mantle
Authors: Kuvshinov Alexei , Sabaka Terence , Olsen Nils 
Published: August 2014

Abstract
An approach is presented to detect deep-seated regional conductivity anomalies by analysis of magnetic observations taken by low-Earth-orbiting satellites. The approach deals with recovery of C-responses on a regular grid and starts with a determination of time series of external and internal coefficients of the magnetic potential. From the coefficients, time series of the magnetic vertical component and of the horizontal divergence of the horizontal components are synthesized on the grid and the C-responses are determined by means of signal processing of the corresponding time series. For validation of the approach, 3 years of realistic synthetic data at simulated orbits of the forthcoming Swarm constellation of 3 satellites have been used. To obtain the synthetic data for a given 3-D conductivity Earth’s model a time-domain scheme has been applied which relies on a Fourier transformation of the inducing field, and on a frequency domain forward modelling. The conductivity model consists of a thin surface layer of realistic conductance and a 3-D mantle that incorporates a hypothetic deep regional anomaly beneath the Pacific Ocean plate. To establish the ability of the approach to capture the geometry of the mantle heterogeneities used in the forward approach, numerical experiments have been undertaken using various satellite combinations, sampling periods of the resulting time series, and numbers of internal coefficients. The possibility of the approach to map anomalies in the mantle using satellite data that contain contributions from the core and lithosphere, from the magnetosphere and ionosphere (and their Earth-induced counterparts), as well as payload noise has been investigated. The model studies have shown that C-responses obtained on a regular grid might be used to map regional deep-seated conductivity anomalies. Moreover, it has been demonstrated that these C-responses are successfully recovered from magnetic data collected by the proposed Swarm constellation of 3 satellites.
Modeling and analysis of solar wind generated contributions to the near-Earth magnetic field
Authors: Vennerstrom S. , Moretto T. , Rastätter L. , Raeder J. 
Published: August 2014

Abstract
Solar wind generated magnetic disturbances are currently one of the major obstacles for improving the accuracy in the determination of the magnetic field due to sources internal to the Earth. In the present study a global MHD model of solar wind magnetosphere interaction is used to obtain a physically consistent, divergence-free model of ionospheric, field-aligned and magnetospheric currents in a realistic magnetospheric geometry. The magnetic field near the Earth due to these currents is analyzed by estimating and comparing the contributions from the various parts of the system, with the aim of identifying the most important aspects of the solar wind disturbances in an internal field modeling context. The contribution from the distant magnetospheric currents is found to consist of two, mainly opposing, contributions from respectively the dayside magnetopause currents and the cross-tail current. At high latitudes the field-aligned component is of partidular interest in connection with internal field-modelling. In the altitude regime of 400–800 km (typical for low Earth orbit satellites) the ionospheric currents are found to contribute significantly to the disturbancance, and account for more than 90% of the field-aligned disturbance. The magnetic disturbance field from field-aligned currents (FACs) is basically transverse to the main field, and they therefore contribute with less than 2% to the disturbance in total field intensity. Inhomogeneity in ionospheric conductance is identified as the main cause of main-field disturbance in the field-aligned direction. These disturbances are associated with the ionospheric Pedersen currents, and may introduce systematic errors in internal field models.
Curl-B technique applied to Swarm constellation for determining field-aligned currents
Authors: Ritter Patricia , Lühr Hermann 
Published: August 2014

Abstract
The constellation of the Swarm satellites provides for the first time the opportunity to determine field-aligned currents in the ionosphere uniquely. This is achieved by employing the curl-B relation of Ampere’s law directly to measurements of a satellite pair flying side-by-side. The new technique is applied to a set of consistent magnetic field and current data generated by a global magnetospheric model. Using a realistic Swarm constellation the current distribution is determined along the orbit from the synthetic magnetic field data. The resulting currents are tested against the input currents. The agreement between input model and recovered field-aligned currents is excellent and much improved compared to the single-satellite estimates. Due to the spatial separation of the sampling points, only the distribution of large-scale field-aligned currents can be determined. These investigations demonstrate one important aspect of the broad capabilities provided by the upcoming space mission.
Two-layer Q
s
structure of the slab near the southern Kurile trench
Authors: Maeda Takahiro , Sasatani Tsutomu 
Published: August 2014

Abstract
We estimate Q
s values (quality factor for S-wave) of the slab near the southern Kurile trench by using seismic data observed at ocean bottom seismometer (OBS) stations from selected local earthquakes. The seismic rays pass mainly through the slab and this enable us to directly estimate the slab Q
s values. The spectral inversion and coda normalization method are applied to these data. The estimated Q
s values from the two methods are nearly the same and increase with frequencies. However, these Q
s values are not high enough to explain the abnormal distribution of ground motion that has been recognized as abnormal distribution of seismic intensities at the Japanese arc. Thus we propose a two-layer Q
s structure of the slab to explain the both facts, our slab Q
s values and the abnormal distribution of ground motion. The two-layer Q
s structure consists of the upper layer with not so high Q
s values (39f
1.0) and lower layer with very high Q
s values (500f
1.0); the upper layer has a thickness of about 50 km. Seismic activity is restricted only within the upper layer of the two-layer Q
s structure. This may mean that the two-layer Q
s structure reflects the different material property between the upper and lower layer of the slab.
A study of the storm event on October 21–22, 1999 by the MHD simulation
Authors: Park K. S. , Ogino T. 
Published: August 2014

Abstract
We carried out a high resolution three-dimensional magnetohydrodynamic (MHD) simulation of the interaction between the solar wind and the Earth’s magnetosphere during a strong magnetic storm on October 21–22, 1999. The input to the simulation was from WIND solar wind observations. As the IMF is strongly southward (−20 nT to −30 nT) for 6 hours, the geomagnetic field lines in the dayside magnetopause are eroded to the geosynchronous orbit (GEO) region by reconnection. The associated magnetic flux is transferred from the dayside magnetosphere to the tail. The reconnection region still appears near GEO region on the dayside magnetopause, even though the IMF B
z component becomes small or northward, because of the influence of the strong IMF B
y (30 nT). IMF lines can successively reconnect with the naked and large geomagnetic field line in the dayside flank regions. Thus, the cross polar cap potential is maintained to be large value and convection in the ionosphere is enhanced. The cross polar cap potential is governed by IMF B
y as well as B
z (ф ≈250 kV for B
z ≈ −20 nT and ф ≈ 300 kV for B
z ≈ − 30 nT), and it saturates during the strong southward IMF. A large energy flux enters the ionosphere at very low latitudes (50°) and the inner edge of the plasma sheet becomes very close to the Earth X = −3.2 R
E for a strong magnetic storms. The open-closed boundary extends to 60° latitudes on the nightside, 72° on the dayside, 62° on dawn, and 66° on dusk. Enhanced energy flux appears at low latitudes (50°) on the nightside in simulation. Moreover, the energy flux in the dusk region (19 MLT) appears down to 55° latitude in simulation, which is consistent with the low latitude boundary of the 0.02-20 keV particles detected by TED of the NOAA-15. A convective electric field, which is penetrating to the Earth-side of the NENL, is almost comparable to that of the solar wind. The present MHD simulation study give reasonable results even for extreme conditions and thereby its usefulness is demonstrated as a physical model for space weather studies.
Time scheduling of magnetic surveys in mid-latitudes with respect to forecasting geomagnetic activity
Authors: Hejda Pavel , Bochníček Josef , Horáček Josef , Nejedlá Jaroslava 
Published: August 2014

Abstract
The quality of magnetic surveys is essentially influenced by the geomagnetic activity. As the in situ measurements are usually limited to very short time period, they must be compared with observatory continuous registrations. When reducing measurements one makes an assumption that diurnal variations of the magnetic field are identical at both the station and the reference observatory. During magnetically quite periods, this assumption is satisfied to an acceptable extent. However, under high geomagnetic activity, the error may easily exceed the acceptable limit. Our analysis indicates that, in mid-latitudes, magnetic surveys should not be made, if some of the Kp values are over 5. Long-term and medium-term forecasts of geomagnetic activity are based on known periodicities (11-year, half-year and 27-day). Short-term forecasts are based on the knowledge of the actual conditions on the Sun, in the solar wind and in the interplanetary magnetic field. Regional Warning Centres, associated in the International Space Environment Service (ISES) deal with forecasts of geomagnetic activity. Links to all 12 centres can be obtained through http://www.ises-spaceweather.org/about_ises/index.html.
Geomagnetic survey and geomagnetic model research in China
Authors: Gu Zuowen , Zhan Zhijia , Gao Jintian , Han Wei , An Zhenchang , Yao Tongqi , Chen Bin 
Published: August 2014

Abstract
The geomagnetic survey at 135 stations in China were carried out in 2003. These stations are with better environmental condition and small magnetic field gradient (<5 nT/m). In the field survey, the geomagnetic declination D, the inclination I and the total intensity F were measured. Ashtech ProMark2 differential GPS (Global Positioning System) was used in measuring the azimuth, the longitude, the latitude and the elevation at these stations. The accuracy of the azimuth is 0.1′. The geomagnetic survey data were reduced using the data at geomagnetic observatories in China. The mean standard deviations of the geomagnetic reduced values are: <1.5 nT for F, <0.5′ for D and I. Using the geomagnetic data which include the data at 135 stations and 35 observatories in China, and the data at 38 IGRF (International Geomagnetic Reference Field) calculation points in China’s adjacent regions, the Taylor polynomial model and the spherical cap harmonic model were calculated for the geomagnetic field in China. The truncation order of the Taylor polynomial model is 5, and its original point is at 36.0°N and 104.5°E. Based on the geomagnetic anomalous values and using the method of spherical cap harmonic (SCH) analysis, the SCH model of the geomagnetic anomalous field was derived. In the SCH model, the pole of the spherical cap is at 36.0°N and 104.5°E, and the half-angle is 30°, the truncation order K= 8 is determined according to the mean square deviation between the model calculation value and the observation value, the AIC (Akaike Information Criterion) and the distribution of geomagnetic field.
New Slovak geomagnetic repeat station network
Authors: Valach Fridrich , Vaczyova Magdalena , Dolinsky Peter 
Published: August 2014

Abstract
Six geomagnetic repeat stations were established over the territory of Slovakia. The locations of the observation points were chosen in a way to provide long time series of geomagnetic measurements at the same places (or nearly the same ones). Thus the series start in the middle of the 19th century. In this paper, the long time series of three geomagnetic elements D, H and I are reviewed. Results of the last geomagnetic measurements at the six observation points (reduced to the 2004.5 epoch) are presented and linear models of the distribution of geomagnetic elements and of their secular variations are shown.