bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the validity of Akasofu’s ε parameter and of the Vasyliunas et al. general formula for the rate of solar wind-magnetosphere energy input
Authors: Aoki Takao 
Published: August 2014

Abstract
The ε parameter of Akasofu and the general formula of Vasyliunas et al. (1982) have been widely used as functions representing the rate of the solar wind energy input into the Earth’s magnetosphere. These two functions have a feature that dependence on the interplanetary magnetic field (IMF) is assumed to be expressed by the combination of B, the magnitude of the IMF, and sin (θ/2), where θ is the clock angle, or by the combination of B

T
= (By
2 + Bz
2)1/2, the magnetic field perpendicular to the Sun-Earth line, and sin(θ/2), not by the Bz component. We check the validity of this assumption by presuming that the AL index has good correlation with the solar wind energy input rate and by applying the regression analysis in a power law form to hourly values of the AL index and of solar wind parameters during the period 1966–1987. We show that Bz generally gives high correlation coefficients and shows higher consistency in exponents than the combination of B (or B

T
) and sin (θ/2). Thus we conclude that the IMF dependence of the rate of the solar wind energy input is described better by Bz than by the combination of B (or B

T
) and sin(θ/2).
An improvement of GPS height estimations: stochastic modeling
Authors: Jin Shuanggen , Wang J. , Park Pil-Ho 
Published: August 2014

Abstract
The results of GPS positioning depend on both functional and stochastic models. In most of the current GPS processing programs, however, the stochastic model that describes the statistical properties of GPS observations is usually assumed that all GPS measurements have the same accuracy and are statistically independent. Such assumptions are unrealistic. Although there were only a few studies modeling the effects on the GPS relative positioning, they are restricted to short baselines and short session lengths. In this paper, the stochastic modeling for IGS long-baseline positioning (with 24-hour session) is analyzed in the GAMIT software by modified stochastic models. Results show that any mis-specifications of stochastic model result in unreliable GPS baseline results, and the deviation of baseline estimations reaches as much as 2 cm in the height component. Using the stochastic model of satellite elevation angle-based cosine function, the precision of GPS baseline estimations can be improved, and the GPS baseline component is closest to the reference values, especially GPS height.
Double-difference relocations of the 2004 off the Kii peninsula earthquakes
Authors: Enescu Bogdan , Mori James , Ohmi Shiro 
Published: August 2014

Abstract
Two large earthquakes (Mw7.3 and Mw7.5) occurred off-shore of the Kii peninsula (Japan) on 5th September 2004. The insufficient station coverage in the area where the large events and their aftershocks occurred led to significant uncertainty regarding their depth location. By using a double-difference approach, we were able to determine more accurate hypocenter locations and better define the main characteristics of the aftershock distribution. The data we used in this study comprise of about 700 earthquakes recorded by the Japanese Meteorological Agency (JMA) from 5 to 12 September 2004. We assume several depth ranges for the initial double difference earthquake locations and select the solution with the smallest rms residual. The resulting hypocenter distribution has two distinctive features: 1) on average the depths are about 20 km shallower than the initial JMA location and 2) the hypocenters are divided into two groups: one shallow (around 12 km depth) and another deep (around 27 km depth). The epicenters of the relocated events define a finer, more clustered structure compared with the epicentral distribution of JMA. The splitting of the earthquake locations into two depth groups is still observed when using a significantly different velocity structure. Our results of the two depth groups for the hypocenters resemble the independently determined hypocentral distribution from the OBS survey.
Recursive travel-time inversion: A tool for real-time seismic tomography
Authors: Ogiso Masashi , Yomogida Kiyoshi , Katsumata Kei 
Published: August 2014

Abstract
A new recursive inverse scheme is applied to a currently popular problem named seismic travel-time tomography, in order to enhance the efficiency and reliability in obtaining a new velocity model if a small number of new data are added to a large data set in the past. In comparison with conventional inverse schemes in seismic tomography, either least-squares or iterative types, this scheme does not require large amounts of matrix-type computations but utilizes the amount of modification in model parameters responsible for each new data set. We also introduce the computation of a collocation travel time (i.e., from a given station to every grid point) for the reference velocity model inverted by the data for all the past events, using a ray tracing scheme called the Huygens’ method (Saito, 2001), suitable to computations prior to a new event. Combining the above information already stored with the recursive inverse scheme, we can obtain a new or updated velocity model immediately after a new event takes place, because a temporal interval between two events is usually very long in a given local area. Since the model is revised at each recursive step, we perform ray tracings with the updated reference model to get more accurate ray paths and travel times than the conventional inversion schemes that use all the ray tracings for the same reference model. We first showed the validity and stability of the proposed method with synthetic data. We then applied the new approach to the P-wave travel-time data recorded in the Hidaka, south-central Hokkaido, Japan, region, and compared our result with other previous results. Our result shares the overall feature with the previous ones. In addition, a new low-velocity zone is detected in the east of the Hidaka mountains at the depth of 10 km, corresponding to the collision zone of two arcs, due to the use of the updated reference velocity model at each recursive step. We also confirmed that the order of data does not affect the final result, so that the present approach is shown as an appropriate tool for so-called real-time seismic tomography: a updated velocity model is immediately obtained at each time that a new event takes place, in order to monitor temporal variations of model parameters such as velocity structure on the real-time basis.
Source model composed of asperities for the 2004 Mid Niigata Prefecture, Japan, earthquake (MJMA=6.8) by the forward modeling using the empirical Green’s function method
Authors: Kamae K. , Ikeda T. , Miwa S. 
Published: August 2014

AbstractA preliminary source model composed of asperities for the 2004 Mid Niigata Prefecture, Japan, earthquake (MJMA=6.8) was estimated by the empirical Green’s function method. The source parameters for two asperities located on the fault plane were determined from the comparisons of the synthesized broad-band ground motions with the observed ones at several stations including near source. Furthermore, we performed the preliminary nonlinear analysis of the sedimentary soils to reproduce the observed ground motions at NIG019 of K-NET. Resultantly, we pointed out the need of more asperity in northern part on the fault plane and the importance of the quantitative analysis of the nonlinearity of the sedimentary soils at K-NET stations.
Time-dependent earthquake hazard evaluation in seismogenic systems using mixed Markov Chains: An application to the Japan area
Authors: Herrera C. , Nava F. A. , Lomnitz C. 
Published: August 2014

Abstract
A previous work introduced a new method for seismic hazard evaluation in a system (a geographic area with distinct, but related seismogenic regions) based on modeling the transition probabilities of states (patterns of presence or absence of seismicity, with magnitude greater or equal to a threshold magnitude M
r, in the regions of the system, during a time interval Δt) as a Markov chain. Application of this direct method to the Japan area gave very good results. Given that the most important limitation of the direct method is the relative scarcity of large magnitude events, we decided to explore the possibility that seismicity with magnitude M ≥ M
r
m
contains information about the future occurrence of earthquakes with M
M
r
m
> M
r
m
. This mixed Markov chain method estimates the probabilities of occurrence of a system state for M ≥ M
r
M
on the basis of the observed state for M ≥ M
r
m
in the previous Δt. Application of the mixed method to the area of Japan gives better hazard estimations than the direct method; in particular for large earthquakes. As part of this study, the problem of performance evaluation of hazard estimation methods is addressed, leading to the use of grading functions.
Continuous observation of seismic wave velocity and apparent velocity using a precise seismic array and ACROSS seismic source
Authors: Saiga Atsushi , Yamaoka Koshun , Kunitomo Takahiro , Watanabe Toshiki 
Published: August 2014

AbstractWe report the results of continuous monitoring—using a seismometer array—of the travel time of seismic waves generated by an ACROSS artificial seismic source. The seismometer array, which was deployed in a surface vault located 2.4 km from the source, recorded both directP- andS-waves and refractedP- andS-waves that traveled along a velocity boundary between the granite basement and overlying sedimentary rocks. We analyzed temporal variation in differential travel time and apparent velocity for these phases for a period of 1 month and found significant temporal variation in the differential travel time. Most of the variation can be attributed to changes in environmental conditions, such as atmospheric temperature and rainfall. Variation is even observed in the seismogram that is located 50 m from the vibration source, although much smaller variation is observed in the vibration of the foundation to which the source is attached. The spectral study revealed that the effects of temperature and rainfall depend strongly on the frequency range used by ACROSS and that a large variation occurs in the 15- to 20-Hz range, especially between 17 and 20 Hz. The environmental effect on the temporal variation is comparable to the record of refractedSwaves and that of a distance of 50 m, whereas a larger variation was observed in the directSwave. This result shows that the signal is affected by the environmental change near the vibration source. The environmental effect can be drastically reduced when the signal from the 15- to 20-Hz range is eliminated in the analysis.
Upper mantle imaging beneath the Japan Islands by Hi-net tiltmeter recordings
Authors: Tonegawa Takashi , Hirahara Kazuro , Shibutani Takuo , Shiomi Katsuhiko 
Published: August 2014

Abstract
We present a novel receiver-function image of the upper mantle structure around the Japan subduction zone. To increase the amount of available waveform data containing the relatively lower frequency component, we examined whether the Hi-net tiltmeter recordings are usable for imaging the upper mantle discontinuities by comparing them with broadband seismograms in different frequency bands. We found that the two are comparable at a frequency band between 0.02 and 0.16 Hz. To make receiver functions from tiltmeter data, stacked vertical components of broadband seismograms were used as source-time functions. Since such source-time functions may include biases from local structure, we also produced regional stacked source-time functions. The receiver function with the above frequency band does not seem to be affected by local structure. In the images derived from the receiver-function gathers, we were able to visualize both the oceanic Moho and the lower slab boundary, which could be traced down to depths of 400 km and 600 km, respectively. These images also show an uplift of the 410-km discontinuity and a depression of the 660-km discontinuity in the regions that are probably affected by the cold subducting Pacific slab.
Heterogeneous distribution of 60Fe in the early solar nebula: Achondrite evidence
Authors: Sugiura Naoji , Miyazaki Akiko , Yin Qing-zhu 
Published: August 2014

Abstract60Fe-60Ni systematics in quenched angrites and two old eucrites were investigated by secondary ion mass spectrometry. The60Ni/62Ni isotopic compositions were normal within 2σ errors. The inferred initial60Fe/56Fe ratios for quenched angrites was (6±9)× 10−9, and similar upper limit values were also obtained from eucrites. Using the age difference of approximately 5 Ma between the quenched angrites and Ca−Al-rich inclusions, the initial60Fe/56Fe ratio at the start of the solar system was calculated to be approximately (6±9)× 10−8. This initial ratio is significantly smaller than previously published values obtained from chondritic materials, suggesting the heterogeneous distribution of60Fe in the solar nebula.
Aeromagnetic evidence for the arcuate shape of Mahanadi Delta, India
Authors: Nayak Goutam Kumar , Rao Ch. Rama , Rambabu H. V. 
Published: August 2014

AbstractThe stream network comprising Mahanadi and its tributaries, viz. Katjhori, Devi, Koyakhai, Kushbhadra and Bhargavi, cut transversely the ESE-WNW trending basement structure in the Cuttack-Paradip-Puri section and diverge radially from one another near and around Cuttack. The Mahanadi river flows in an ESE-WNW direction, the Katjhori and Devi rivers flow in a NW-SE direction and Koyakhai, Kushbhadra and Bhargavi River in an almost N-S direction. The general southeasterly direction of these rivers and the delta formation was thought to be continued throughout the Quaternary period and the delta was a case of superposition upon the deformational structures derived from the erosional surfaces covered by recent sediments.Analysis of the aeromagnetic anomaly field of the Mahanadi Delta area of the on-shore portion has indicated three prominent structural trends in ESE-WNW, NW-SE and N-S directions along which the rivers Ma-hanadi/Chitratala, Katjhori and Devi, Koyakhai, Kushbhadra and Bhargavi flow, respectively. The tectonic disturbance along the N-S direction, in the western part of Bhubaneswar-Puri section, seems to have been controlling the Koyakhai and Kushbhadra and Bhargavi river system, following the possible trace of 85°E Ridge, whereas the concealed NW-SE trending Mahanadi graben trend is inferred to be the probable cause for the NW-SE flow of the Katjhori river in the middle portion south of Cuttack and the ESE-WNW flow of the Mahanadi and Chitratala rivers in the Cuttack-Paradip section controlled by the Eastern Ghat trend.
Paleomagnetism in Mesozoic rocks of the Northern Andes and its Implications in Mesozoic Tectonics of Northwestern South America
Authors: Bayona Germán , Rapalini Augusto , Costanzo-Alvarez Vincenzo 
Published: August 2014

AbstractNew paleomagnetic data isolated in Upper Triassic to Aptian rocks exposed in the Colombian Andes and west of the Guyana craton, in conjunction with paleomagnetic data from the Andes of Venezuela and the South American craton, permit the interpretation of along-margin northward translations of Andean Colombian terranes during the Early-Middle Jurassic. Field tests and comparison with reference paleopoles for South America indicate that characteristic components uncovered in red-siliciclastic and igneous rocks are primary, or near-depositional, and they are carried dominantly by hematite, magnetite and Ti-magnetite. Difference in declination values of characteristic components isolated in fault-bounded blocks document counter-clockwise rotations previous to syn-extensional deposition. The Jurassic tectonic scheme proposed here for the northwestern corner of South America shows an Early Jurassic, linear subduction-related magmatic arc evolving to Late Jurassic rift-related setting associated to the opening of the Proto-Caribbean Ocean and westward retreat of the subduction zone. A similar tectonic evolution for the Jurassic has been proposed for southwestern USA and the Nazas arc in Mexico.
Paleomagnetism, rock-magnetism and geochemical aspects of early Cretaceous basalts of the Paraná Magmatic Province, Misiones, Argentina
Authors: Mena Mabel , Orgeira María Julia , Lagorio Silvia 
Published: August 2014

Abstract
The basalts of the Posadas Formation were extruded during the huge continental volcanism that affected the Paraná Basin in the Lower Cretaceous. We have carried out a paleomagnetic and rock-magnetic study on samples collected along a basalt outcrop section in Misiones, Argentina and determined that rocks classified as tholeiitic basalts and andesi-basalts are characterized by a low to intermediate content of Ti. Paleomagnetic and rock-magnetic studies suggest that the main magnetic mineral is low-Ti titanomagnetite of superparamagnetic (SP) to single-domain (SD) sizes, and very low amounts of multi-domain (MD) particles. The stable magnetic remanence enabled us to define characteristic remanent magnetizations (ChRMs) with a maximum angular deviation (MAD) <5° in most cases; and in all the cases, a MAD <10°. The sequence has registered at least two polarity reversions, starting from a normal polarity at the base. The calculated virtual geomagnetic poles (VGPs) present an elongated distribution similar to other distributions of VGPs published for the Paraná Magmatic Province. The elongated distribution of the VGPs could be a real feature of the geomagnetic field at a time of frequent changes of polarity.
Cooling rate corrected paleointensities from the Xitle lava flow: Evaluation of within-site scatter for single spot-reading cooling units
Authors: Morales Juan , Alva-Valdivia Luis M. , Goguitchaichvili Avto , Urrutia-Fucugauchi Jaime 
Published: August 2014

Abstract
The historic Xitle lava, which covers a great part of southern Mexico City, is one of the most studied (magnetically) volcanic unit worldwide. Studies include detailed paleomagnetic and paleointensity investigations, which have documented an enigmatic within-flow variation of absolute paleointensity first recognized in the decade of 1960s. However, attempts to find possible explanations in terms of physical/magnetic parameters or geomagnetic effects have been unsatisfactory. As an effort to understand the over- and underestimating of geomagnetic paleointensity (PI) within the Xitle lava flow, we investigated the relation of the cooling rate upon the acquisition of thermoremanent magnetization (TRM). Contrary to archaeomagnetic investigations, most paleointensity experiments on volcanic rocks do not consider cooling rate effects in a systematic manner. Our results show that the scatter and overestimation of PI values obtained on the single Xitle lava flow are drastically reduced when using the cooling rate correction to raw selected data. The Thellier method combined with cooling rate experiments provide a higher precision compared to conventional Thellier and microwave techniques. The cooling rate effects upon acquisition of TRM in volcanic rocks seem to be as critical as in archaeomagnetic investigations.
Imaging the high b-value anomalies within the subducting Pacific plate in the Hokkaido corner
Authors: Katsumata Kei 
Published: August 2014

Abstract
The frequency-magnitude distribution (b-value) for seismicity within the Pacific plate is not definitely homogeneous. An anomaly of b-value higher than 0.9 is detected within the descending Pacific plate in the Hokkaido corner. In the western Hokkaido, the anomaly exists at a depth of about 150 km, which is directly beneath active volcanoes. In the eastern Hokkaido, the anomalies exist at approximately 200 and 300 km depths, which is tens of kilometers sideways from active volcanoes. The results obtained in this paper are more reliable than previous studies on b-value heterogeneity within descending plates, since I used a catalog homogeneous, both in time and space, which was obtained through re-examination of all seismograms and relocation of hypocentral parameters based on arrival times from fixed seismic stations.
A computer simulation study on the mode conversion process from slow X-mode to fast X-mode by the tunneling effect
Authors: Katoh Yuto , Iizima Masahide 
Published: August 2014

Abstract
The mode conversion process from slow X-mode waves to fast X-mode waves by the tunneling effect has been studied by means of computer simulation. On the basis of the new approach by the simulation, we have confirmed that the mode conversion to the fast X-mode waves is especially effective in the case where the width of the evanescent layer which exists between the local UHR frequency and the local fast X-mode cut-off frequency, is of the order of the wave length of the incident slow X-mode waves. In space plasmas, this type of mode conversion process becomes important for the case where the different plasmas form a sharp boundary or a discontinuity at their contact boundary with a scale size of the order of the wave length of the incident slow X-mode waves.
Coseismic slip distribution of the 2005 off Miyagi earthquake (M7.2) estimated by inversion of teleseismic and regional seismograms
Authors: Yaginuma Tadashi , Okada Tomomi , Yagi Yuji , Matsuzawa Toru , Umino Norihito , Hasegawa Akira 
Published: August 2014

Abstract
A large earthquake (M7.2) occurred along the plate boundary off Miyagi Prefecture (Miyagi-Oki), northeastern Japan, on August 16, 2005. In this area, large earthquakes (~M7.5) have occurred repeatedly at intervals of about 37 years, and more than 27 years have passed since the last event occurred. To estimate the relationship between this earthquake and the previous events, we determined coseismic slip distribution by this 2005 Miyagi-Oki earthquake by adopting the seismic waveform inversion method of Yagi et al. (2004) and compared it with that of the previous 1978 Miyagi-Oki earthquake. We performed two cases of the inversions; inversion using only far-field seismograms and that using far-field seismograms and local seismograms simultaneously. Both results show that a large slip occurred near the hypocenter and rupture extended to the westward deeper portion. Considering that the rupture area of the 2005 event partly overlapped with the southeastern part of that of the 1978 event, suggests this result the possibility that plural asperities exist which cause the sequence of Miyagi-Oki earthquakes and that the 2005 event ruptured one of such asperities, although the previous 1978 event ruptured all the asperities at one time.
Small repeating earthquakes and interplate creep around the 2005 Miyagi-oki earthquake (M=7.2)
Authors: Uchida Naoki , Matsuzawa Toru , Hirahara Satoshi , Hasegawa Akira 
Published: August 2014

AbstractTaking advantage of the feature that creep around an asperity is necessary for the recurrent rupture of the same small asperity (small repeating earthquakes), we have estimated the spatio-temporal distribution of quasistatic slip (creep) around the 2005 Miyagi-oki earthquake (M=7.2) using the distribution of small repeating earthquakes. The creep was detected mainly outside of the coseismic slip areas for the 2005 Miyagi-oki, 1978 Miyagi-oki (M=7.6) and 2003 Fukushima-oki (M=6.8) earthquakes. The creep rates estimated from the recurrence intervals and slip amounts of small repeating earthquakes for 21 years were almost constant for the areas near the western limit of the interplate earthquakes but they varied temporally in the areas nearer to the Japan trench. The changes in the creep rates before and after the 2005 Miyagi-oki earthquake were not significant with the exception of small slip accelerations in some areas near the Japan trench. These results suggest that the plate boundary around the source area for the 2005 earthquake is still mostly locked.