bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rupture process of the 2007 Notohanto earthquake by using an isochrones back-projection method and K-NET/KiK-net data
Authors: Pulido Nelson , Aoi Shin , Fujiwara Hiroyuki 
Published: August 2014

Abstract
We estimated the source process of the 2007/3/25 Notohanto earthquake using a new method for source imaging based on an “isochrones-backprojection” of observed seismograms in the source region (IBM). The IBM differs from conventional earthquake source modeling approaches in that no inversion procedures are required. The idea of IBM is to directly back-project amplitudes of seismogram envelopes around the source into a space image of the earthquake rupture. The method requires the calculation of isochrones times at every station used for source imaging, for a set of grids points distributed within the source fault plane. Total grid “brightness” is calculated by adding all observed waveform envelope amplitudes at every station, for every isochrone line crossing the grid, in order to produce an image of the total fault plane brightness distribution. Our source imaging results of the Notohanto earthquake show two large brightness regions; the first region is located 10 km above the hypocenter, and the second region is located at the bottom of the northern end of the fault plane. These regions approximately correspond to large slip areas obtained by a conventional inversion approach. Our method has the capability to quickly map asperities of large earthquakes using observed strong motion data.
Automatic determination of source parameters of the 2007 Noto Hanto earthquake
Authors: Wu Changjiang , Horiuchi Shigeki 
Published: August 2014

AbstractLarge earthquakes have been observed to be caused by the rupture of several asperities. The rapid determination of source parameters is hence of great importance for correctly determining shaking intensities or evaluating the strong motion distribution generated by a large earthquake. This study shows that we can automatically preprocess strong motion data using automaticP- andS-phase pickers, determine the focal mechanism, and identify the fault plane from two nodal planes. A real-time simulation is performed for the 2007 Noto Hanto earthquake. Using our automatic fault plane identificator, we were able to identify one of the nodal planes with a strike of 62° and a dip of 70° within a 30-s interval from the beginning of focal mechanism determination to the end of waveform inversion. Results from automatic inversions showed that the slip was confined to a shallow portion with a maximum slip of about 3 m. The total seismic moment released in 10 s was 2.0×1018N m, which corresponds to a moment magnitude of 6.8.
Temporal variations of crustal structure in the source region of the 2007 Noto Hanto Earthquake, central Japan, with passive image interferometry
Authors: Ohmi Shiro , Hirahara Kazuro , Wada Hiroo , Ito Kiyoshi 
Published: August 2014

AbstractThe passive image interferometry technique is applied to the continuous seismic waveform data obtained around the source region of the 2007 Noto Hanto Earthquake, central Japan. We computed the autocorrelation function (ACF) of band-pass filtered seismic noise portion recorded with each short-period seismometer at several seismic stations for 1 day each. In some stations, comparison of each 1-day ACF shows temporal evolutions of the ACF, which are interpreted as the change of seismic velocity structure in the volume considered. Sudden changes of ACF are detected to be associated with the occurrence of the main shock in one station of the four stations analyzed. Gradual changes of ACFs in the preceding 2 weeks of the main shock are also recognized in two stations, which would be of great importance for understanding the stress state before the occurrence of earthquakes.
Spherical cap harmonic analysis of magnetic variations data from mainland Australia
Authors: Stening R. J. , Reztsova T. , Ivers D. , Turner J. , Winch D. E. 
Published: August 2014

Abstract
Spherical cap harmonic analysis (SCHA) has been applied to geomagnetic data from an array of magnetometers deployed across the Australian mainland during 1989–90 in order to examine features of the ionospheric S
q current system. The external contours, corresponding to ionospheric currents, are generally in good agreement with the data in that the direction of current flow is perpendicular to the measured horizontal magnetic field. The derived internal (induced) current systems are less reliable but exhibit fairly consistent behaviour on some occasions. As the S
q current system whorl passes over Australia, the reversed internal current whorl lags by a bit less than an hour. When the external system moves off the continent into the Indian Ocean, the derived internal system sometimes appears to remain over the continent for about two hours but this is found to be caused by the large coastal effect in the west. The variations obtained from the analysis at particular sites are compared with the original data and give generally good agreement. Internal and external variations at several sites are derived and behave as expected to some extent. In particular we find that the internal component of the vertical element adds to the external component on the west coast but subtracts from it on the east coast. Further analyses are performed using data from the CM4 model. The SCHA gives a separation of internal and external components in good agreement with the original for the horizontal CM4 magnetic fields while the agreement is not so good for the vertical component.
Response of piezoelectric lead zirconate titanate detector to oblique impact with hypervelocity iron particles
Authors: Takechi S. , Onishi T. , Minami S. , Miyachi T. , Fujii M. , Hasebe N. , Mori K. , Nogami K. , Ohashi H. , Sasaki S. , Shibata H. , Iwai T. , Grün E. , Srama R. , Okada N. 
Published: August 2014

Abstract
A cosmic dust detector using piezoelectric lead zirconate titanate (PZT) is currently being developed for use onboard a spacecraft for the BepiColombo mission. The characteristics of the PZT detector were studied by carrying out hypervelocity impact measurements with iron particles supplied by a Van de Graaff accelerator. The measurements with particle velocities of less than 5 km/s showed a linear relationship between the output voltages obtained from the detector and the particle momenta. This linear relationship obtained was almost independent of the impact angle between the particle and the PZT surface.
The intensity of the geomagnetic field in the late-Archaean: new measurements and an analysis of the updated IAGA palaeointensity database
Authors: Biggin Andrew J. , Strik Geert H. M. A. , Langereis Cor G. 
Published: August 2014

Abstract
We firstly present the results of a detailed palaeointensity study performed on 54 samples from 9 volcanic units of late Archaean age (2724-2772 Ma) from the Pilbara Craton, Western Australia. These results were severely affected by magnetomineralogical alteration occurring during the laboratory heating process necessitating the application of a correction procedure. The correction allowed results from three lavas to pass strict selection criteria but we deem that only one of these exhibits sufficient internal consistency to be considered moderately reliable. It yields a virtual dipole moment of 47±6 ZAm2which is 60% of the present-day value. We combine this determination with a filtered dataset from the updated IAGA (International Association of Geomagnetism and Aeronomy) palaeointensity database, PINT08. Directional secular variation has recently been shown to have changed fundamentally since the Archaean, probably as a consequence of inner core growth since that time. However, here we argue that it is still unclear whether this evolution was accompanied by a single long timescale change in average poloidal field intensity. While the distribution of Precambrian palaeointensity determinations as a whole is significantly lower than that for the last 300 Myr, we show that this finding largely reflects data from the Proterozoic aeon. The distribution of more ancient measurements from the late Archaean-earliest Proterozoic is indistinguishable from that of the last 300 Myr which might suggest that a ‘Proterozoic dipole low’ period existed between two periods of higher field intensity. Were this pattern of long-term geomagnetic intensity variation to be supported by the addition of new data in the future, then it could indicate a related three-stage evolution in core dynamics, namely: vigorous thermal convection caused by high core-mantle heat flux early in the Earth’s history, weaker thermal convection later as the heat flux fell, and finally, strong compositional convection since the inner core nucleated.
Cenozoic and Mesozoic basalts from Egypt: a preliminary survey with a view to paleointensity
Authors: Perrin M. , Saleh A. , Alva-Valdivia L. 
Published: August 2014

Abstract
Numerous phases of igneous activity took place in Egypt during the Mesozoic and the Cenozoic but no paleointensity results have ever been published from these rocks. Therefore a preliminary survey was conducted in the northern part of Egypt and in Sinai to test the suitability of these basalts for paleointensity determinations. Three Oligo-Miocene sites have been sampled north of Cairo: Abu Zaabal, Qatrani, and 6th of October City. In Sinai, we sampled Jurassic basalts in Wadi Budra and Oligo-Miocene rocks from Wadi Nukhul. The main magnetic carriers of these rocks are titanomagnetites with varying Ti content. Large secondary components are present in most middle Jurassic basalts and discrepancies remain in the directional analysis so this sill cannot be used for paleointensity experiments and the associated poles should not be considered for paleomagnetic reconstructions either. Directional analysis of the Oligo-Miocene basalts is very straightforward and updated mean VGPs have been calculated from the Cairo area (68.9°N, 91.3°E; Kappa = 274; A95 = 3.7) and from Wadi Nukhul (72.7°N, 13.4°E; Kappa = 528; A95 = 5.4). Pseudo-paleointensity results obtained as well from stable Egypt as from Sinai are promising, with values lower or similar (between 29 to 58 μT) to present-day field intensity.
First archeointensity results from Portuguese potteries (1550-1750 AD)
Authors: Hartmann Gelvam A. , Trindade Ricardo I. F. , Goguitchaichvili Avto , Etchevarne Carlos , Morales Juan , Afonso Marisa C. 
Published: August 2014

Abstract
Geomagnetic field variations at archeomagnetic timescales can be obtained from well-dated heated structures and archeological potsherds. Here, we present the first archeointensity results obtained on Portuguese ceramics (1550 to 1750 AD) collected at Brazilian archeological sites. The results are compared to those obtained from Western Europe and currently available geomagnetic field models. Continuous thermomagnetic and IRM acquisitions curves indicate that Ti-poor titanomagnetite is responsible for the remanence in these ceramic fragments. Five fragments (24 samples) out of twelve analyzed yielded reliable intensity estimates. The row archeointensity data were corrected for TRM anisotropy and cooling rate effect. The mean dipole moments are obtained for three different age intervals: 1550±30 AD, 1600±30 AD and 1750±50 AD. Mean intensities vary from 37.9±4.2 μT to 54.8±7.6 μT in agreement with the previously reported data for 1550 AD and 1750 AD. Relatively weaker, but still highly dispersed, values were obtained for 1600 AD ceramics.
Controlled atmosphere vibrating thermo-magnetometer (CatVTM): a new device to optimize the absolute paleointensity determinations
Authors: Poidras Thierry , Camps Pierre , Nicol Patrick 
Published: August 2014

Abstract
The laboratory of paleomagnetism of Montpellier (France) has developed a new one-axis vibrating thermal magnetometer dedicated to the study of physical properties of natural rocks remanence. Among its key characteristics, this apparatus allows both measurement of the magnetization moment on the interval from room temperature to 700°C with a precision of 2 × 10-9 A m2 and acquisition of a total or a partial thermo-remanent magnetization using a steady field from -100 up to 100 μT. Another point that is worth noting is that one can apply a controlled atmosphere by means of argon flux to prevent oxidation of the studied sample during heating. We report here a technical description of this new instrument and review some specific applications in absolute paleointensity surveys.
Low-temperature magnetic properties of andesitic rocks from Popocatepetl stratovolcano, Mexico
Authors: Kosterov Andrei , Conte Gennaro , Goguitchaichvili Avto , Urrutia-Fucugauchi Jaime 
Published: August 2014

Abstract
To contribute to the growing database of magnetic properties of rocks and minerals at cryogenic temperatures, we have measured magnetization, low-field susceptibility, and hysteresis loops as a function of temperature between 2 K (10 K for hysteresis) and 300 K for twelve representative samples from a suite of volcanic rocks of predominantly andesitic composition erupted by the Popocatepetl stratovolcano, Mexico. High temperature susceptibility measurements have yielded Curie points (T
C) mostly between 430 and 550°C, two samples additionally containing a magnetic phase with T
C of 300-320°C, and one sample—with 140-170°C. Hysteresis measurements at room temperature have revealed invariably the presence of a low-coercivity mineral with coercive force ranging from 10 to 20 mT. This suggests that NRM of Popocatepetl rocks is carried by an intermediate titanomagnetite of composition between approximately TM04 and TM20. Thermal demagnetization of SIRM given at 2 K displays no evidence for the Verwey transition, further showing that samples are essentially magnetite free. At the same time, an inflection between 30-50 K reported previously for intermediate titanomagnetites (Moskowitz et al., EPSL, 157, 141-149, 1998) is seen in all studied Popocatepetl samples except one. As well, below 50 K the coercive force increases sharply with decreasing temperature reaching up to 100 mT at 10 K. On the other hand, examining the behavior of low-field susceptibility at cryogenic temperatures shows that susceptibility signal is dominated by intermediate titanomagnetites only in a part of our samples. In four out of 12 samples, however, susceptibility signal appears to be due to a hemoilmenite phase containing about 20 mole% of hematite. Caution is thus advised when interpreting low-temperature susceptibility data in terms of magnetic mineralogy.
Paleomagnetic behavior of volcanic rocks from Isla Socorro, Mexico
Authors: Sbarbori Elise , Tauxe Lisa , Goguitchaichvili Avto , Urrutia-Fucugauchi Jaime , Bohrson Wendy A. 
Published: August 2014

Abstract
The direction and magnitude of the geomagnetic field vary both spatially and temporally and undergo significant departures from that of a geocentric axial dipole. In order to properly characterize persistent behaviors, time-averaged field models must be based on the highest quality data. Here we present full-vector paleomagnetic data for volcanic units exposed in the southeast quadrant of the island of Socorro, Mexico. We carried out a joint expedition between the Scripps Institution of Oceanography and the Universidad Nacional Autónoma México to Isla Socorro in January of 2005 during which we collected oriented paleomagnetic samples from 21 sites, representing as many as 10 different volcanic units (the oldest of which is ~540 ka). We subjected over 100 specimens to the most up-to-date paleointensity methods, and included the standard reliability checks. In an earlier study, Bohrson et al. (1996) proposed a series of widespread eruptive events, based on similarities of argon/argon dates. Paleointensity from specimens that conform to the strictest acceptance criteria are available from both the (unoriented) original sample collection and our fully oriented (but as yet undated) new collection. Correlation between the two collections is however problematic. The time-averaged direction from Socorro is consistent with that expected from a geocentric axial dipole, and the time-averaged intensity is 30.0±7.1 μT, equivalent to a virtual axial dipole moment (VADM) of 67.6±16.0 ZAm2.
Analyzing the variation of embedding dimension of solar and geomagnetic activity indices during geomagnetic storm time
Authors: Mirmomeni M. , Lucas C. 
Published: August 2014

Abstract
Cyclic solar activity as one of the natural chaotic phenomena has significant effects on Earth, climate, and satellites. Rapid changes in the near-Earth space environment can affect the performance and reliability of both spacecraft and ground-based systems. This can imply major problems due to communication and satellite operational anomalies. Therefore, it is meaningful to analyze solar activity and geomagnetic indices to elicit the behavior of sun as the origin of most of these chaotic phenomena. One of the most important tools for analyzing the chaotic trends is the “Embedding Dimension” (ED). In this paper, the variation of ED for solar activity indices especially during storm time for two well-known storms is considered. The first storm is the super-storm on 13 March 1989, which shuts down the power supply system in Québec, Canada and the second one is the storm caused by Coronal Mass Ejection on 11 January 1997 which causes the failure of Telstar 401 satellite. The method of this paper is based on the fact that the reconstructed dynamics of an attractor should be a smooth map, i.e. with no self intersection in the reconstructed attractor. It is shown that the Embedding Dimension (and other chaotic characteristics) of some solar and geomagnetic activity indices during these storms varies rapidly.
Gravity and magnetic constraints on the crustal structure and evolution of the Horeki seamount in the Izu-Ogasawara (Bonin) arc
Authors: Fujiwara Toshiya , Kido Yukari , Tamura Yoshihiko , Ishizuka Osamu 
Published: August 2014

Abstract
Data on the crustal structure, bulk composition, and eruption ages of an arc seamount were obtained in an investigation aimed at studying the spatial and temporal variations in the magma composition of an intra-oceanic arc. We conducted gravity and magnetic surveys of the Horeki seamount and evaluated the density and magnetization structure using inversion and forward modeling. The seamount is located on the back-arc side of the Izu-Ogasawara arc. This seamount has an elliptical shape, a flat summit, and satellite ridges and cones on its northern and southern flanks. The flanks are consistent with a higher density anomaly, with an estimated mean density corresponding to dense basaltic rocks. A low-density anomaly is distributed in the seamount top, indicating that the top likely consists of porous basalts or differentiated rocks. The prominent circular low Bouguer gravity anomaly, which appeared in the northern part of the flat-topped summit, indicates that a light-density material fills the summit. The main body of seamount is normally magnetized. Combined with the age of the rocks, the volcanism constructing the main body may be most robust in the Gauss chron. The deeper part of seamount may consist of intrusive rocks, with induced magnetization over remanence. The eastern part of the northern ridges is reversely magnetized, while the western part is normally magnetized. These features and the ages of the sampled rocks suggest that these ridges were constructed in the Matuyama and Brunhes chrons, respectively. The southern part of the seamount flanks shows weak normal magnetization, probably caused by the small cones with different polarities of remanent magnetization.
A two-step scenario for both solar flares and magnetospheric substorms: Short duration energy storage
Authors: Tsurutani Bruce T. , Shibata Kazunari , Akasofu Syun-Ichi , Oka Mitsuo 
Published: August 2014

Abstract
The basic observations for magnetic storms and substorms at Earth and for flares at the Sun are reviewed for background. We present a common scenario of double magnetic reconnection for both substorms and flares based on previous interplanetary observations and substorm-triggering results. Central to the scenario is that the first magnetic reconnection phase is the source of energy loading for possible substorms and flares. The energy placed in the magnetotail or magnetosphere/at the sun lasts for only a short duration of time however. The energy gets dissipates away rapidly (in some less dramatic form). This scenario predicts that if the initial reconnection process is sufficiently intense and rapid, concomitant substorms and flares occur soon thereafter. If the energy input is less rapid, there may be lengthy delays for the onset of substorms and flares. If external influences (shocks, etc.) occur during the latter energy buildup, the “trigger” will cause a sudden release of this energy. The model also explains reconnection without subsequent substorms and flares. The model addresses the question why strong triggering events are sometimes ineffective.
Flares and the chromosphere
Authors: Hudson Hugh S. , Fletcher Lyndsay 
Published: August 2014

Abstract
The chromosphere (the link between the photosphere and the corona) plays a crucial role in flare and CME development. In analogies between flares and magnetic substorms, it is normally identified with the ionosphere, but we argue that the correspondence is not exact. Much of the important physics of this interesting region remains to be explored. We discuss chromospheric flares in the context of recent observations of white-light flares and hard X-rays as observed by TRACE and RHESSI, respectively. We interpret key features of these observations as results of the stepwise changes a flare produces in the photospheric magnetic field.
The interplanetary magnetic decrease automatic detection (IMDAD) code
Authors: Guarnieri F. L. , Tsurutani B. T. , Echer E. 
Published: August 2014

AbstractA new code, called the interplanetary magnetic decrease (MD) automatic detection (IMDAD) code, has been developed to enable researchers in the field to rapidly identify MD events for further analyses. The criterion used for MD selection isBmin<XB0, whereXis a variable value andB0is the ambient magnetic field magnitude. The code can be applied to data sets from different instruments/missions located in different space plasma environments in the heliosphere. The code has been tested during slow solar wind, fast solar wind and CIR intervals at ∼5 AU (from November 28 to December 03, 1992). For this test, we used a sliding window with a width of 300 seconds applied to 1-second high-resolution magnetic field data. The events identified by the code have been confirmed by hand analyses. The routine was able to identify 57 of the 118 MDs identified by hand (∼50%). The selection criteria for IMDAD and hand-analyses MDs were not exactly the same, accounting for the different rates of occurrence. What is particularly encouraging is that IMDAD did not falsely identify any events. The discrepancies between the two methods are discussed in the text. This code will be made available to the general public.