bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spatial distribution of static stress drops for aftershocks of the 2005 West Off Fukuoka Prefecture earthquake
Authors: Iio Yoshihisa , Katao Hiroshi , Ueno Tomotake , Enescu Bogdan , Hirano Norio , Okada Tomomi , Uchida Naoki , Matsumoto Satoshi , Matsushima Takeshi , Uehira Kenji , Shimizu Hiroshi 
Published: August 2014

AbstractWe investigated the spatial distribution of static stress drops of the aftershocks of the 2005 West Off Fukuoka Prefecture earthquake, with the aim of assessing the possibility that another earthquake will occur on the SE extension of the earthquake fault. The waveforms from six temporary online telemetry stations installed in and around the aftershock region were measured. Small stress drops were estimated for the aftershocks that occurred relatively distant from the SE and NE ends of the earthquake fault. Conversely, the aftershocks that occurred around the SE end of aftershock region are characterized by large stress drops. These results imply the possibility of a stress concentration at the SE edge of the main shock fault.
Tsunami generated by the 2004 Kushiro-oki earthquake
Authors: Tanioka Yuichiro , Katsumata Kei 
Published: August 2014

Abstract
The 2004 Kushiro-oki earthquake generated a small tsunami that was observed at two tide gauge stations located on the Pacific coast of Hokkaido Province. Analysis of the tsunami waveforms shows that the slip amount of the fault was 2.1 m. The seismic moment was calculated to be 3.1×1019 Nm, which is consistent with the results of previous seismological studies. Tsunami simulation results indicate that a small first wave at Urakawa is caused by large shallow water off Cape Erimo. The tsunami generated from the source area off Kushiro circumvents the shallow area off the cape, propagates through the deep sea, and arrives at Urakawa as a small first wave. Larger tsunamis are propagated through the shallow region slowly and arrive at Urakawa as a later tsunami. These results suggest that a tsunami from a future large Nemuro-oki earthquake will also arrive at the west coast of Hidaka with a small first wave and large later phases.
Dynamical modeling of trench retreat driven by the slab interaction with the mantle transition zone
Authors: Tagawa Michio , Nakakuki Tomoeki , Tajima Fumiko 
Published: August 2014

Abstract
We present the 2-D self-consistent dynamical model of interactions of a subducting slab with the 410-km and 660-km phase boundaries to further our understanding of the relation between the slab stagnation/penetration and the trench migration. Our model takes into account freely-movable plate boundaries and the difference between tensional and compressional yield strengths in the lithosphere. For the case in which the tensional strength is weaker than the compressional one, the negative buoyancy of the subducting slab produces extension of the overriding lithosphere and, accordingly, the trench retreats. Interactions with the 410-km and 660-km phasetransition boundaries further promote the trench retreat, and the dip angle of the slab is substantially decreased. This enhances the resistance of the 660-km phase boundary against the slab penetration. Slab weakening caused by the grain-size reduction in the transition zone may result in a horizontally-lying slab and trench retreat.
Diagenetic effect on magnetic properties of marine core sediments from the southern Okhotsk Sea
Authors: Kawamura Noriko , Oda Hirokuni , Ikehara Ken , Yamazaki Toshitsugu , Shioi Kumi , Taga Shunsuke , Hatakeyama Shinsyo , Torii Masayuki 
Published: August 2014

Abstract
It is well known that magnetic records of marine sediments are affected to a certain degree by early diagenesis, the extent and mode of which are controlled by depositional environments. In order to investigate variations in the effects of early diagenesis, we have analyzed 11 gravity cores estimated to be Holocene in age that constitute a depth transect off the southern coast of the Okhotsk Sea. The rock magnetic parameters have peaks produced by the presence of volcanic ashes, basaltic granules and/or relatively coarser-grained layers. The concentration-dependent parameters display characteristic trends of a rapid decrease within the homogeneous silty clay zone in the middle parts of the cores, assuming that the total amount of magnetic minerals decreases through early diagenesis at this interval. This decrease is found in all of the cores from the transect (from both near-shore and offshore sites). In near-shore sites where larger volumes of organic materials are supplied compared to offshore sites, the depth of the decrease in magnetic minerals is relatively shallow. These results imply that the presence of organic materials accelerates the pyritization through the bacterial reduction of ferric ion, thereby causing the decreases in magnetic minerals to become shallower.
Long-term trends in geomagnetic daily variation
Authors: Macmillan Susan , Droujinina Anna 
Published: August 2014

Abstract
Long-term changes in the magnetic environment of the Earth are of interest to those studying space weather and climate change, particularly in the upper atmosphere. In this paper we examine long-term changes in daily variation as derived from hourly mean values from 14 geomagnetic observatories around the world. Their time series date back to the beginning of the 20th century. We find that there are similar features in all the records, with peaks in the amplitudes of the daily variation occurring in the 1950s and 1980s, and a small upward trend of 1.3 nT/century corresponding to an increase of over 10%. The extrema coincide with those seen in solar irradiance proxy data, in particular the F10.7 flux density dataset which starts in 1947.
Monitoring global traveling ionospheric disturbances using the worldwide GPS network during the October 2003 storms
Authors: Wang Min , Ding Feng , Wan Weixing , Ning Baiqi , Zhao Biqiang 
Published: August 2014

AbstractThe global traveling ionospheric disturbances (TIDs) during the drastic magnetic storms of October 29–31, 2003 were analyzed using the Global Position System (GPS) total electron content (TEC) data observed in the Asian-Australian, European and North American sectors. We collected the most comprehensive set of the TEC data from more than 900 GPS stations on the International GNSS Services (IGS) website and introduce here a strategy that combines polynomial fitting and multi-channel maximum entropy spectral analysis to obtain TID parameters. The results of our study are summarized as follows: (1) large-scale TIDs (LSTIDs) and medium-scale TIDs (MSTIDs) were detected in all three sectors after the sudden commencement (SC) of the magnetic storm, and their features showed longitudinal and latitudinal dependences. The duration of TIDs was longer at higher latitudes than at middle latitudes, with a maximum of about 16 h. The TEC variation amplitude of LSTIDs was larger in the North American sector than in the two other sectors. At the lower latitudes, the ionospheric perturbations were more complicated, and their duration and amplitude were relatively longer and larger. (2) The periods and phase speeds of TIDs were different in these three sectors. In Europe, the TIDs propagated southward; in North America and Asia, the TIDs propagated southwestward; in the near-equator region, the disturbances propagated with the azimuth (the angle of the propagation direction of the LSTIDs measured clockwise from due north with 0°) of 210° showing the influence of Coriolis force; in the Southern Hemisphere, the LSTIDs propagated conjugatedly northwestward. Both the southwestward and northeastward propagating LSTIDs are found in the equator region. These results mean that the Coriolis effect cannot be ignored for the wave propagation of LSTIDs and that the propagation direction is correlated with polar magnetic activity.
Finite element analysis of crustal deformation in the Ou Backbone Range, northeastern Japan, with non-linear visco-elasticity and plasticity: effects of non-uniform thermal structure
Authors: Shibazaki Bunichiro , Garatani Kazuteru , Okuda Hiroshi 
Published: August 2014

AbstractA finite element analysis with non-linear visco-elasticity and plasticity was carried out with the aim of constructing a model of the slip and deformation processes in the deeper parts of the seismogenic zones of inland earthquakes. Our finite element code is based on the GeoFEM parallel finite element code and was developed using plug-ins to adopt several non-linear functions. We consider the effects of geothermal structures in the crust in a compressional tectonic setting to model the deformation and faulting that occur around the Ou Backbone Range in northeastern Japan. We set an area of high geothermal gradient in the center of the model. The numerical results show that shortening deformation due to non-linear viscous flow occurs in the high-temperature area in the lower part of the crust, which results in shear faulting in the upper part of the crust. In the case where the crust comprises two layers—the upper crust (quartz diorite) and the lower crust (wet diabase)—a weak viscous zone appears in the lower part of the upper crust and a strong viscous or plastic zone appears at the upper part of the lower crust. Our numerical results are able to explain the deformation and faulting that occur around the Ou Backbone Range in northeastern Japan.
Magnitude determination using duration of high frequency energy radiation and displacement amplitude: application to tsunami earthquakes
Authors: Hara Tatsuhiko 
Published: August 2014

Abstract
Recently, we developed a new method to determine earthquake magnitudes using durations of high frequency energy radiation and the maximum displacement amplitudes, which can be measured from processing of first arriving P-waves. In the present study, we applied this method to the 1992 Nicaragua, 1994 Java, 1996 Peru, and 2006 Java earthquakes which have been suggested to be “tsunami earthquakes.” Our magnitude estimates for these earthquakes are consistent with the moment magnitudes in the Global CMT catalog, which demonstrates that our method is applicable to tsunami earthquakes. The analyzed tsunami earthquakes are characterized in our method as those with longer source durations and smaller displacement amplitudes.
A numerical study on magnetic polarity transition in an MHD dynamo model
Authors: Takahashi Futoshi , Matsushima Masaki , Honkura Yoshimori 
Published: August 2014

Abstract
Magnetic polarity transitions in a Takahashi-Matsushima-Honkura dynamo model are analyzed. Distinctive differences in behavior of the axisymmetric poloidal magnetic field are found among a polarity reversal and excursions, including short polarity events. At the beginning of magnetic polarity transitions, the magnetic field with the reversed polarity is generated by anti-cyclonic convection columns deep within the outer core. In the case of excursion, it is soon advected by the radial flow toward a shallow interior of the core, and the transition can be detected at the core surface. However, the same process retrieves the original polarity from the deep interior, and the reversed field eventually vanishes. In the case of polarity reversal, on the other hand, the reversed polarity field is persistently generated deep within the core. It is then advected toward a shallow interior of the core, while the generation process of the reversed field occurs successively. The reversed polarity field near the core surface is collected by the downwelling flow associated with convection columns, as is the case for the original polarity field. The polarity reversal is completed by the advection process, the duration of which is consistent with the flow speed in the core.
Paleomagnetism of Unzen volcano: A volcanic record (Senbongi excursion) of the Iceland Basin event and the Brunhes VGP distribution for Japan
Authors: Shibuya Hidetoshi , Iwasaki Yuki , Tanaka Hidefumi , Hoshizumi Hideo 
Published: August 2014

Abstract
A paleomagnetic study was carried out on volcanic rocks from Unzen volcano: samples were collected from a total of 69 sites with 19 sites in pyroclastic flows and 50 sites in lava flows. Ages for the flows were determined either by K-Ar methods or detailed field surveys, and indicate that all of the flows were deposited during the Brunhes chron. After demagnetization 10 pyroclastic and 48 lava flows had stable site-mean directions. One lava flow in the Senbongi area with a K-Ar age of 197±17 ka had an intermediate virtual geomagnetic pole (VGP) at 8.3°N, 21.6°E. The age and VGP position apparently correlate with the Iceland Basin event, suggesting that it is a record of the event on volcanic rocks. Our study added 53 Brunhes-aged VGPs to the overall collection for Japan, increasing it by 40% to a total of 175 VGPs. After excluding all site-mean directions having α95 > 10° and VGP latitude < 50°, the remaining 148 VGPs have a mean pole at 89.7°N, 40.9°E (A
95 = 2.2°) showing no significant deviation from the geographic pole. The angular standard deviation (ASD) was calculated as 15.2° ± 1.2° (N = 148), which is compatible with paleosecular variation models from the literature. However, the data set was found to deviate from a Fisher distribution. The actual meaning of the ASD value after removing the intermediate VGPs needs to be reconsidered.
Geomagnetic 100-ky variation extracted from paleointensity records of the equatorial and North Pacific sediments
Authors: Yokoyama Yukiko , Yamazaki Toshitsugu , Oda Hirokuni 
Published: August 2014

Abstract
We have analyzed three sets of paleointensity series varying in duration from 300 to 1600 ka to confirm the existence of paleosecular variation on a 100-ky time scale. The data series are from sediment cores in the equatorial and North Pacific regions. We transformed the three time series into wavelet space and found characteristic variations in a 100-ky time scale. We also calculated wavelet correlation between the series of the paleointensity and rock magnetic parameters of each core to assess the efffect of rock magnetic properties on relative paleointensity. The wavelet correlation coefficients of the three cores are small, so the change in the paleointensity in each core is concluded to be independent of magnetic properties. In order to confirm the cause of the paleointensity variation, we calculated the wavelet correlation among the three cores. The relative intensity variations of the three cores are significantly correlated, while rock magnetic parameters are not, indicating that there are differences in rock magnetic variations among the cores, although they appear to occur on similar scales. On the other hand, all sets of relative paleointensity have synchronous variations. Such paleointensity variations observed over a wide area are considered to originate from changes in the Earth’s magnetic field.
Early Miocene magnetostratigraphy and a new palaeomagnetic pole position from New Zealand
Authors: Turner Gillian M. , Michalk Daniel M. , Morgans Hugh E. G. , Walbrecker Jan O. 
Published: August 2014

Abstract
We report palaeomagnetic results from a 26.5 m sequence of early Miocene sediments in NW Nelson, New Zealand. Analysis of the strong, stable characteristic component of natural remanent magnetization has yielded an important record of the part of Chron 5 from ca. 18.5 to 16.5 Ma, including positive identification of the cryptochron or “tiny wiggle” C5Dr-1, and a pole position ([{«mbda _k} = {78.4^ circ }]; [{☎i _p} = {283.0^ circ }]; dp = 2.2°; dm = 2.8°) for NW Nelson that is indistinguishable from the contemporaneous published pole for the Australian Plate. We infer that this portion of NW Nelson has undergone negligible rotation with respect to the main part of the Australian Plate over the past 17.5 Myr.
Sulfur abundance of asteroid 25143 Itokawa observed by X-ray fluorescence spectrometer onboard Hayabusa
Authors: Arai Takehiko , Okada Tatsuaki , Yamamoto Yukio , Ogawa Kazunori , Shirai Kei , Kato Manabu 
Published: August 2014

Abstract
The Japanese Hayabusa spacecraft successfully carried out in situ observations of S-class asteroid 25143 Itokawa, including the surface major elemental analysis with the X-ray fluorescence spectrometer (XRSHayabusa). Our previous results for the X-ray experiments (Okada et al., 2006a) indicated that major elemental ratios of Mg/Si and Al/Si on the surface of Itokawa resemble ordinary LL- or L-chondrites more than any other meteorite analogues. In the NEAR Shoemaker observations of S-class asteroid 433 Eros, the results of X-ray fluorescence observations indicated the depletion of sulfur, probably reflecting impact-induced volatilization, photoor ion-induced sputtering at the surface, or the loss of FeS-rich materials due to partial melting. Here, we determined the elemental abundance of sulfur (S) on the surface of Itokawa, in addition to that of Mg, Al, and Si, and its regional variation using XRS-Hayabusa observations. In particular, we carefully corrected the fluctuation of solar X-rays, variation of surface geometry, and sensor response function in this analysis, and thus we believe that the results are more accurate than those of our previous report. In this study, the upper and lower limits for Mg/Si, Al/Si, and S/Si overlap those of meteorite analogues for ordinary chondrites or primitive achondrites. In terms of the major elemental composition, Itokawa is best classified as a ordinary chondrite or a primitive achondrite. Our models do not include the mineral mixing effects. With the effects, the abundance of sulfur is expected to be 30% lower than our results. Hence, we conclude that the abundance of sulfur on the surface of Itokawa is almost equal to or even lower than the average abundance in ordinary chondrites. Although the abundances for Mg and Si are globally homogeneous, best-fit or upper limits of mass fraction for Al and S vary in local areas. There is a negative correlation (−0.92) for Al/Si vs. S/Si in ten facets. In particular, the area with the lowest sulfur, accompanied with enriched aluminum, is found in Arcoona, close to a cratered area. Therefore, aluminum enrichment and sulfur depletion features may support events of partial melting on the parent body of Itokawa or aluminum-rich material impacts on the surface of Itokawa. In some areas, Itokawa has a brighter geometric albedo and color variation. Little altered, fresh material may be exposed in these portions of the surface. The sulfur abundance on the surface appears to vary between little and highly altered areas by space weathering. Thus, the sulfur regional variation in our result may reflect the heterogeneity of a surface altered by space weathering.
The 2004 Las Campanas/Lowell Observatory Itokawa campaign: I. Simultaneous visible and near-infrared photometry of the Hayabusa mission target
Authors: Thomas-Osip J. E. , Lederer S. M. , Osip D. J. , Vilas F. , Domingue D. , Jarvis K. , Leeds S. L. 
Published: August 2014

Abstract
In 2004, Asteroid 25143 Itokawa made its final close approach to the Earth prior to its encounter with the Japanese spacecraft Hayabusa. This apparition was superb with Itokawa reaching magnitude 12 (two magnitudes brighter than the 2001 apparition and the brightest since its discovery in 1998) and covering a large range of observable solar phase angles. An extensive visible and near-infrared observing campaign of Itokawa was undertaken at Las Campanas and Lowell Observatories to obtain full rotational coverage and cover the largest possible range of solar phase angles (4–129°). Unresolved global color mapping over the complete light curve (best fit synodic period of 12.118 hr) shows no sign of rotational color variability with upper limits of a few percent across the full U-thru-K spectrum. These combined multi-wavelength (UBVRIJHK) rotational light curves allow for the concrete deconvolution of shape from albedo variation in the rotational models and as required for Hapke modeling presented in Paper II (Lederer et al., this issue), permits the removal of the rotational light curve effects from the solar phase curve. Furthermore, these derived solar phase curves can be fit with the IAU H,G magnitude system (Bowell et al., 1989) thus allowing the calculation of geometric albedos (p
v = 0.23 ± 0.02) as well as an estimate of the asteroid’s elongated shape (a/b = 1.9 ± 0.1) via the amplitudephase relationtionship (Zappalà et al., 1990). Results derived from the extensive ground-based campaigns are compared and contrasted with the much higher spatial resolution in situ measurements made by the Hayabusa spacecraft. The ‘ground-truth’ provided by the Hayabusa mission results shed light on the inferences that can begin to be made for the general asteroid population.
Tsunami generated by the 2007 Noto Hanto earthquake
Authors: Namegaya Yuichi , Satake Kenji 
Published: August 2014

AbstractTsunami numerical simulations of the 2007 Noto Hanto earthquake are carried out for three models based on the coastal vertical movements, the GPS observations, and the strong-motion data. The three fault models produce similar tsunami waveforms at five tide gauge stations around the source. Comparisons with the observed tsunami waveforms indicate that the fault model based on the coastal movements shows the best agreement but that a slightly smaller fault area with a larger slip amount would make the agreement better. At three tide gauge stations in Toyama Bay, unusual oscillatory waves were recorded before the expected tsunami arrival. The spectral analysis of the observed records indicates that they represent characteristic oscillation of Toyama Bay, and modal calculations show that they can be reproduced by the water displacement in the mouth of Nanao Bay generated by a possible extension of the mainshock fault toward the southeast or a possible landslide source at a steep part of ocean bottom.
Rock magnetic and geochemical analyses of surface sediment characteristics in deep ocean environments: A case study across the Ryukyu Trench
Authors: Kawamura Noriko , Kawamura Kiichiro , Ishikawa Naoto 
Published: August 2014

Abstract
Magnetic minerals in marine sediments are often dissolved or formed with burial depth, thereby masking the primary natural remanent magnetization and paleoclimate signals. In order to clarify the present sedimentary environment and the progressive changes with burial depth in the magnetic properties, we studied seven cores collected from the Ryukyu Trench, southwest Japan. Magnetic properties, organic geochemistry, and interstitial water chemistry of seven cores are described. Bottom water conditions at the landward slope, trench floor, and seaward slope are relatively suboxic, anoxic, and oxic, respectively. The grain size of the sediments become gradually finer with the distance from Okinawa Island and finer with increasing water depth. The magnetic carriers in the sediments are predominantly magnetite and maghemized magnetite, with minor amounts of hematite. In the topmost sediments from the landward slope, magnetic minerals are diluted by terrigenous materials and microfossils. The downcore variations in magnetic properties and geochemical data provided evidence for the dissolution of fine-grained magnetite with burial depth under an anoxic condition.