bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of an automatic procedure to estimate the reflection height of tweek atmospherics
Authors: Ohya Hiroyo , Shiokawa Kazuo , Miyoshi Yoshizumi 
Published: August 2014

AbstractThis paper presents an automated procedure to estimate apparent reflection heighth(from the cutoff frequency for the first waveguide mode,fc), horizontal propagation distanced, and propagation timeTgof tweek atmospherics. Tweek data recorded at the Kagoshima Observatory (31.48°N, 130.72°E), Japan, were used to evaluate the procedure by comparing the results estimated by the automatic method to those read manually by an operator. The two types of results showed differences (automatic–manual) of +0.58 km, −9.9 Hz, and +3058.9 km for meanh,fc, andd, respectively. The difference inh(fc) was less than the resolution of the fast Fourier transform used to obtain the tweek spectra. These comparisons indicate that the automatic estimation procedure of tweek parameters developed in this paper performs well and is a useful tool for studying long-term height variations of the ionosphericDand lowerEregions using very low frequency (VLF) and extremely low frequency (ELF) records observed in Japan over the past 30 years.
Spatiotemporal distribution of very-low frequency earthquakes in Tokachi-oki near the junction of the Kuril and Japan trenches revealed by using array signal processing
Authors: Asano Youichi , Obara Kazushige , Ito Yoshihiro 
Published: August 2014

Abstract
We have developed a signal-processing method for array data recorded at densely and widely distributed tiltmeter stations in Japan and analyzed the data recorded during the last 5 years. Filtered seismograms were analyzed to detect coherent seismic waves and estimate the epicenters. In order to identify very-low frequency earthquakes (VLFEs) with only low-frequency energies only, we selected only events not listed in the earthquake catalogue provided by the Japan Meteorological Agency from all of the detected events. The epicenters of the obtained VLFEs were estimated to be distributed not only along the Nankai Trough, where the events occurred on the reverse faults in the well-developed accretionary prism, but also in Tokachi-oki without accretion. This result suggests that even in such a region, VLFEs can occur on a shallower portion of the plate boundary than the seismogenic region of ordinary earthquakes and/or in a deformed area of the overriding plate along the subduction zone without accretion.
A precise hypocenter determination method using network correlation coefficients and its application to deep low-frequency earthquakes
Authors: Ohta Kazuaki , Ide Satoshi 
Published: August 2014

Abstract
A knowledge of the precise locations of deep low-frequency earthquakes (LFEs) along subduction zones is essential to be able to constrain the spatial extent of various slow earthquakes and the underlying physical processes. We have developed a hypocenter determination method that utilizes the summed cross-correlation coefficient over many stations, denoted a network correlation coefficient (NCC). The method consists of two parts: (1) an estimation of relative hypocenter locations for every pair of events by a grid search, and (2) a linear least squares inversion for self-consistent relative hypocenter locations for the initial centroid. We have applied this method to ten LFEs in the Tokai region, Japan. Statistically significant values of NCC indicate the relative locations for many pairs, which in turn determine the self-consistent locations. While the catalog depths are widely distributed, the relocated hypocenters fall within a 2-km depth range, which implies that LFEs in the Tokai region occur on the plate interface, similar to LFEs in western Shikoku.
Fault models of unusual tsunami in the 17th century along the Kuril trench
Authors: Satake K. , Nanayama F. , Yamaki S. 
Published: August 2014

AbstractGeologic evidence has shown that unusual tsunami deposits are traced as high as 18 m above the current sea level or as far as 1–4 km inland from the shoreline on the Pacific coast of eastern Hokkaido, and that such unusual tsunamis have recurred at about 500 year interval with the most recent event in the 17th century. We computed coastal tsunami heights along the Hokkaido and Sanriku coasts and inundation at five coastal marshes in Hokkaido where the tsunami deposits were mapped. Three types of faults were tested: giant fault, tsunami earthquake and interplate earthquake models. The giant fault model, with the largest seismic moment, yields the lowest tsunami heights and smaller inundation than the distribution of tsunami deposits in Hokkaido, while the tsunami heights are largest in Sanriku. The tsunami earthquake model yields little inundation in Hokkaido and the smallest heights in Sanriku. The interplate earthquake model produces the largest tsunami heights and inundation in Hokkaido, reproducing the distribution of tsunami deposits on the Nemuro coast. The multi-segment interplate earthquake with variable slip (10 m on Tokachi and 5 m on Nemuro segment) can reproduce the distribution of tsunami deposits on the Tokachi coast as well, and considered as the best source model for the 17th century tsunami, although the Sanriku tsunami heights are more than 3 m, exceeding an inferred detection threshold of historical documents. The seismic moment is estimated as 8 × 1021N m (Mw8.5). Comparison with the recent 2003 Tokachi-oki earthquake indicates that the 17th century tsunami source was longer and located further offshore at shallower depth.
Shock equation of state of basalt
Authors: Sekine Toshimori , Kobayashi Takamichi , Nishio Mineyuki , Takahashi Eiichi 
Published: August 2014

Abstract
Detailed wave profiles for Kinosaki basalt at pressures up to 25 GPa are measured using a laser velocity interferometer in order to determine the dynamic properties. The results indicate a Hugoniot elastic limit of ∼2 GPa and a relationship between shock velocity (U
s) and particle velocity (U
p) approximated by U
s (km/s) = 3.5 + 1.3U
p (km/s) in the low-pressure plastic region (U
p below ∼4 km/s). These data are compared with the known data for rocks with basaltic compositions, and tensile strength of the basaltic rocks was found to be about one tenth of that of compression strength.
Does the 2007 Noto Hanto earthquake reveal a weakness in the Japanese national seismic hazard map that could be remedied with geological data?
Authors: Toda Shinji , Awata Yasuo 
Published: August 2014

AbstractThe Noto Hanto earthquake struck one of the lowest earthquake probability regions on the national seismic hazard map of Japan. To contribute to future updates of the hazard map, we examined the predictability of the 2007 earthquake on the basis of geological data that were available before it occurred. Sonic prospecting profiles of active faulting and the absence of an onshore fault could have limited the potential rupture length to 12–15 km, similar to the 2007 source. Empirical relationships between magnitude and fault length would have given usMj= 6.6–6.8 andMw= 6.3–6.4. The emergence of one marine terrace, which inclines to the south and reaches an altitude of approximately 50 m, can be dated to 120–130 ka and yields an uplift rate of approximately 0.4 mm/year.Mw-displacement empirical relationships and examples of recent blind fault events that have occurred at various locations around the world suggest that the conceivable maximum coseismic uplift of such shocks is 40–70 cm. Together with the uplift rate, we would have obtained an average recurrence interval of 1000–2000 years and, consequently, a 1.5–3.0% time-independent (Poisson) probability for 30 years. In addition, the significant inclination of the marine terraces—3.2 per mille (0.32%)—is better explained by the accumulation of frequent southward tilting as large as that of the 2007 type event with approximately 1600-year intervals, without any significant contributions from other seismic sources. We therefore conclude that the Noto Hanto earthquake source would have been better evaluated and identified if we had taken into account not only major active faults but also the active tectonics of moderate-size faults and their associated scale and rate.
Coastal deformation associated with the 2007 Noto Hanto earthquake, central Japan, estimated from uplifted and subsided intertidal organisms
Authors: Awata Yasuo , Toda Shinji , Kaneda Heitaro , Azuma Takashi , Horikawa Haruo , Shishikura Masanobu , Echigo Tomoo 
Published: August 2014

AbstractThe March 25, 2007 Noto Hanto earthquake (Mj= 6.9,Mw= 6.7) generated vertical crustal movement along the northwestern coast of the Noto Peninsula, central Japan. Soon after the event, we estimated the pattern and amount of coseismic coastal movement based on uplifted and subsided intertidal sessile organisms. Our observations reveal a broad 20-km-wide asymmetric zone of surficial deformation above and across the south-dipping source fault, with a steep north-facing frontal limb and a gentle south-facing back limb. The maximum coseismic uplift was approximately 40 cm at the crest of the zone of deformation. The result of forward modeling suggests that the top of the south-dipping source fault is buried at a depth of approximately 2 km, and that 1.2 m of slip on the fault provides the best fit to our surface observations. Our results demonstrate that traditional field investigations should be combined with modern instrumental observations such as GPS and InSAR to obtain the most effective and reliable spatio-temporal estimates of crustal movement associated with large earthquakes.
Rupture process of the 2007 Chuetsu-oki, Niigata, Japan, earthquake—Waveform inversion using empirical Green’s functions—
Authors: Nozu Atsushi 
Published: August 2014

Abstract
A waveform inversion was conducted to reveal the rupture process of the 2007 Chuetsu-oki, Niigata, Japan, earthquake using near-source strong ground motion records. Based on recent results on the re-location of the aftershocks, a southeast-dipping fault plane was assumed. Aftershock records were used as empirical Green’s functions to avoid uncertainty in subsurface structure in and around the source region for the calculation of Green’s functions. To ensure that the path and the site effects are shared between ground motions from the mainshock and those from the aftershocks, the mainshock fault plane was divided into three domains, each of which was allocated to one of the aftershocks used. Based on the results of the inversion, a major distinctive asperity was identified approximately 20 km southwest of the hypocenter, near Kashiwazaki City. A minor, rather obscure asperity was recognizable between the hypocenter and the major asperity. The rupture continued approximately 10 s. Agreement between the observed and synthetic ground motions is quite satisfactory, not only for the portions used for the inversion but also for the later phases. The rupture of the main asperity, which is close to Kashiwazaki City, may be a primary reason for the large amplitude ground motion and damage in Kashiwazaki City.
Rock magnetic and paleointensity results from Mesozoic baked contacts of Armenia
Authors: Shcherbakova V. V. , Perrin M. , Shcherbakov V. P. , Pavlov V. E. , Ayvaz’yan A. , Zhidkov G. V. 
Published: August 2014

Abstract
Samples were obtained from three baked contacts and one lava flow along the upper Turonian-lower Coniacian Tovuz section, two baked contacts along the upper Coniacian-lower Santonian Paravakar section in the northern part of Armenia, and three baked contacts along the Titonian-Valanginian Kafan section in southern Armenia. A total of 130 samples were studied. Updated mean paleomagnetic poles were calculated for the Upper Cretaceous Tovuz-Paravakar sections (65.6°N, 162.2°E, A95 = 4.3, paleolatitude = 27.0 ± 3.4°) and the Upper Jurassic-Lower Cretaceous Kafan section (61.7°N, 158.9°E, A95 = 4.8°, paleolatitude = 24.7 ± 3.8°). Paleointensity determinations could be estimated from two of the upper Cretaceous and three of the Upper Jurassic-Lower Cretaceous baked contacts, corresponding to a 30% success rate. The mean virtual dipole moments obtained were low (1.7-5.5 × 1022 A m2), which is in agreement with data published by Bol’shakov and Solodovnikov (1981a, 1983) for the same sections (3.0-4.4 × 1022 A m2). Our results support the hypothesis of the Mesozoic Dipole Low, even though the overall data are widely dispersed.
Thermal fluctuation fields in basalts
Authors: Muxworthy Adrian R. , Heslop David , Michalk Daniel M. 
Published: August 2014

AbstractThe thermal fluctuation field (Hf) is central to thermoremanent acquisition models, which are key to our understanding of the reliability of palaeomagnetic data, however,Hfis poorly quantified for natural systems. We reportHfdeterminations for a range of basalts, made by measuring rate-dependent hysteresis. The results for the basalts were found to be generally consistent within the space ofHfversus the coercive forceHC, i.e., the “Barbier plot”, which is characterized by the empirically derived relationship; logHf∝ 1.3 logHCobtained from measurements on a wide range of different magnetic materials. Although the basalts appear to occupy the correct position within the space of the Barbier plot, the relationship within the sample set, logHf∝ 0.54 logHC, is different to the Barbier relationship. This difference is attributed to the original Barbier relationship being derived from a wide range of different synthetic magnetic materials, and not for variations within one material type, as well as differences in methodology in determiningHf. We consider the relationship betweenHCand the activation volume,υact, which was found to beHC∝ υ ***** for our mineralogically homogeneous samples. This compares favourably with theoretical predictions, and with previous empirical estimates based on the Barbier plot, which defined the relationship asHC∝****.
Natural magnetite nanoparticles from an iron-ore deposit: size dependence on magnetic properties
Authors: Rivas-Sánchez M. L. , Alva-Valdivia L. M. , Arenas-Alatorre J. , Urrutia-Fucugauchi J. , Perrin M. , Goguitchaichvili A. , Ruiz-Sandoval M. , Molina M. A. Ramos 
Published: August 2014

Abstract
We report on the discovery of magnetite nanoparticles ranging in size from 2 to 14 nm in the mineralized zones of the Pe~na Colorada iron-ore deposit, southern Mexico. Micrometric scale magnetite was magnetically reduced and divided into distinct size ranges: 85-56 μm, 56-30 μm, 30-22 μm, 22-15 μm, 15-10 μm, 10-7 μm and 7-2 μm. Nanometric-scale magnetite in the size range 2-14 nm was identified. The magnetite was characterized by X-ray diffraction, transmitted and reflected light microscope, high-resolution transmission electron microscopy (TEM), high angle annular dark field, Mossbauer spectroscopy and its magnetic properties. Crystallographic identification of nanostructures was performed using high-resolution TEM. Characteristic changes were observed when the particles make the size transition from micro- to nanometric sizes, as follows: (1) frequency-dependent magnetic susceptibility percentage (χFD%) measurements show high values (13%) for the 2-14 nm fractions attributed to dominant fractions of superparamagnetic particles; (2) variations of χFD% < 4.5% in fractions of 56-0.2 μm occur in association with the presence of microparticles formed by magnetite aggregates of nanoparticles (< 15 nm) embedded in berthierine; (3) Mössbauer spectroscopy results identified a superparamagnetic fraction; (4) nanometric and 0.2-7 μm grain size magnetite particles require a magnetic field up to 152 mT to reach saturation during the isothermal remanent magnetization experiment; (5) coercivity and remanent magnetization of the magnetite increase when the particle size decreases, probably due to parallel coupling effects; (6) two-magnetic susceptibility versus temperature experiments of the same 2-14 nm sample show that the reversibility during the second heating is due to the formation of new magnetite nanoparticles and growth of those already present during the first heating process.
Palaeosecular variation for 0.1-21 Ka from the Okataina Volcanic Centre, New Zealand
Authors: Tanaka Hidefumi , Komuro Naoyuki , Turner Gillian M. 
Published: August 2014

AbstractStudies of palaeodirections and palaeointensities were carried out on mainly rhyolitic lavas and pyroclastics from the Okataina Volcanic Centre, New Zealand, which has erupted during the past 32 kyr. Of the 17 sites studied, 14, spanning the period 0.1-21 Ka yielded good mean palaeodirections, while three carried unstable natural remanent magnetizations. Of 49 specimens from 7 sites, on which Thellier palaeointensity experiments were carried out, 21 specimens gave successful results, yielding 3 site mean palaeointensities for 1886 AD, 5 Ka, and 7.5 Ka. When the new palaeodirections, together with previously reported archaeo and volcanic data, were compared with sedimentary records from New Zealand and eastern Australia for the last 10 kyr, good agreement was obtained in inclination but discrepancies were observed in declination. The new 7.5 Ka and 5 Ka palaeointensities are moderately high and relatively low, respectively, and are concordant with the global trend. The mean palaeointensity obtained for 1886 AD is, 11% higher than the IGRF1900. The difference is scarcely significant, but might indicate a small bias toward high values. Although the sedimentary directional curves show excellent agreement with the prediction from CALS7K, the fit of the palaeointensity data to model values was relatively poor over the wider Pacific region. Further reliable palaeointensity data are needed to solve the discrepancy.
Resistivity and density modelling in the 1938 Kutcharo earthquake source area along a large caldera boundary
Authors: Ichihara Hiroshi , Mogi Toru , Hase Hideaki , Watanabe Tomonori , Yamaya Yusuke 
Published: August 2014

Abstract
We present the crustal structure around the fault zone pertaining to the 1938 Kutcharo earthquake (M 6.0), northern Japan, to consider why large earthquakes have occurred around calderas. The study was based on gravity anomalies and magnetotelluric and direct-current (DC) electrical-resistivity survey data. The density structure obtained from gravity anomalies indicated that the fault plane corresponded to the main depression boundary of the Kutcharo caldera. The resistivity section, based on audio-frequency magnetotelluric surveys, indicated that the estimated fault plane was located along the boundary of resistivity blocks, which also corresponded to the depression boundary. A detailed resistivity section in the ruptured zone revealed by a DC electrical-resistivity survey showed a discontinuity of layers, implying cumulative fault displacements. These results indicate that the 1938 earthquake was an abrupt slip along the main depression boundary of the Kutcharo caldera. The most likely hypothesis pertains to fluid intrusion along the depression boundary. However, additional seismic and geodetic studies are required to identify other feasible earthquake mechanisms.
Waveform inversion for slip distribution of the 2006 Java tsunami earthquake by using 2.5D finite-difference Green’s function
Authors: Okamoto Taro , Takenaka Hiroshi 
Published: August 2014

Abstract
We first incorporate the large effect of near-source heterogeneity on teleseismic body waveforms in the inversion of the slip distribution of the 2006 Java tsunami earthquake. We incorporate the effect by computing the response of an assumed “2.5D” model structure of the Java trench by a 2.5D finite-difference method. Based on a simulation of inversion, we suggest that intense smearing is possible when we apply 1D Green’s functions in the analysis, and that it may obscure the slip pattern. In the inversion of real data, we confirm macroscopic features, such as a long duration (∼ 165 s) and a slow rupture velocity (∼ 1.25 km/s). The region of the initial rupture is found to be isolated from the eastern broad region in which we further identify a heterogeneous slip distribution. Most of these regions are likely to be at the sedimentary plate interface where the accreted sediment and the subducting plate are in contact. In particular, the nearly “isolated” feature of a shallow slip region suggests a possible faulting in the shallowest part of the sedimentary plate interface without being strongly enforced by the rupture propagated from the deeper part of the fault. Such heterogeneity suggests a highly variable frictional behavior at the sedimentary plate interface.
Seismic structure of the northern end of the Ryukyu Trench subduction zone, southeast of Kyushu, Japan
Authors: Nishizawa Azusa , Kaneda Kentaro , Oikawa Mitsuhiro 
Published: August 2014

Abstract

P-wave velocity models related to the Philippine Sea plate subduction have been obtained from seismic explorations at the northern end of the Nansei-Shoto (Ryukyu) Trench. Both multi-channel seismic reflection and ocean bottom seismographic records provide clear images of the rough seafloor topography and irregular P-wave velocity structure of the northwestern extension of the Kyushu-Palau Ridge and Amami Plateau below the landward trench slope. Low velocity (V

p
≤ 4–5 km/s) and thick (>7 km) materials above the plate boundary characterize the landward trench slope structure. An exception to this is found where the subducting plate contacts higher velocity (V

p
> 5 km/s) materials of the landward plate at the estimated position of the seismic asperity of 1968 Hyuganada earthquake (M
w 7.5).
DC railways and the magnetic fields they produce—the geomagnetic context
Authors: Lowes F. J. 
Published: August 2014

Abstract
DC electric railways produce magnetic fields, not only from the intended traction currents, but also from unintended earth-leakage currents; these fields, particularly those from the leakage currents, are becoming an increasing problem for geomagneticians. This paper introduces the relevant properties of DC-railway traction-power circuits, and the various ways in which earth-leakage currents are produced, and discusses models of how these leakage currents vary along the track and with train position. It describes the geometry of the resultant magnetic fields, and gives the formal algebra for calculating the magnetic field when these leakage currents are known, but also suggests some simple approximations that could be used when the current distribution is not known in detail. This paper also summarises previous relevant papers.
Stress field in the source region after the 2007 Mw 6.6 Niigataken Chuetsu-oki earthquake deduced from aftershock focal mechanisms: Implication for a pre-mainshock stress field
Authors: Imanishi Kazutoshi , Kuwahara Yasuto 
Published: August 2014

AbstractStress fields in the source region before and after the 2007Mw6.6 Niigataken Chuetsu-oki earthquake were investigated using aftershock focal mechanism solutions. We have attempted to determine aftershock focal mechanisms usingP-wave polarity data as well as body wave amplitudes because this earthquake occurred offshore, where observation station coverage is poor. This approach enabled us to obtain 76 well-determined aftershock focal mechanisms. Although the stress field in the studied area is known to be generally characterized by a reverse-faulting regime, the application of a stress tensor inversion method to the aftershock focal mechanisms revealed that the stress field spatially varied on a scale smaller than the fault dimension of the mainshock, with a mixture of strike-slip and reverse faulting regimes. The post-mainshock stress field estimated by the stress tensor inversion was compared with the theoretical stress field computed using an observed non-uniform slip distribution of the mainshock and variously assumed pre-shock stress fields. The results of this comparison suggest that the pre-mainshock principal stress in the WNW-ESE direction was dominant and that the magnitudes of the other two principal stresses were similar.