bluuebunny/crossref_metadata_2025 huggingface dataset:
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

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

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

A 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.
Impacts of torus model on studies of geometrical relationships between interplanetary magnetic clouds and their solar origins
Authors: Marubashi Katsuhide , Sung Suk-Kyung , Cho Kyung-Suk , Lepping Ronald P.
Published: August 2014

Our recent analysis of interplanetary magnetic clouds (MCs) showed that the orientations of MC axes determined by a model fitting with curvature of MCs taken into account (referred to as a torus model, hereafter) can be significantly different from those obtained from fittings with a straight cylinder model. Motivated by this finding, we re-examined geometrical relationships between magnetic field structures of MCs and their solar origins. This paper describes the results of the re-examination with special attention paid to two MC events, for which different orientations of MC axes were obtained from a torus model and a cylinder model. For both cases, it is shown that the torus models give the MC geometries of magnetic field structures in good agreement with those of coronal arcade structures which were formed in association with the launch of MCs along the magnetic field inversion lines. Summarizing the analysis results for 12 MCs investigated here, we conclude that: (1) the formation of coronal arcade structure is a good indication of MC formation; (2) MC geometries can be obtained that are consistent with the coronal arcades with respect to the axis orientation and the magnetic field structure including chirality, indicating that no significant direction changes occurred during the propagation of MCs through the interplanetary medium.
Halo coronal mass ejections and geomagnetic storms
Authors: Gopalswamy Nat
Published: August 2014

In this letter, I show that the discrepancies in the geoeffectiveness of halo coronal mass ejections (CMEs) reported in the literature arise due to the varied definitions of halo CMEs used by different authors. In particular, I show that the low geoeffectiveness rate is a direct consequence of including partial halo CMEs. The geoeffectiveness of partial halo CMEs is lower because they are of low speed and likely to make a glancing impact on Earth.
Influence of the foreshock of the Earth’s bow shock on the interplanetary shock propagation during their mutual interaction
Authors: Přech Lubomír , Němeček Zdeněk , Šafránková Jana
Published: August 2014

Interplanetary shocks have been recognized as a very efficient source of geomagnetic disturbances. We present a short study of the propagation of one interplanetary (IP) shock observed by five spacecraft located in the solar wind far upstream of the Earth’s bow shock as well as in its close vicinity. The IP shock normal was highly inclined from the Sun-Earth line and thus the IP shock-bow shock interaction started at the flank. We have found a significant evolution of IP shock parameters during its motion along the bow shock. This modification is discussed and attributed to the presence of strong fluxes of energetic particles in the foreshock.
Seismotectonic implications of the Kyushu-Palau ridge subducting beneath the westernmost Nankai forearc
Authors: Park Jin-Oh , Hori Takane , Kaneda Yoshiyuki
Published: August 2014

The Kyushu-Palau ridge, a remnant arc on the Philippine Sea Plate, subducts beneath the Eurasian Plate along the westernmost part of the Nankai Trough. A seismic reflection profile on strike line images the ∼70-km-wide Kyushu-Palau ridge where it subducts beneath the toe of the forearc accretionary wedge. The geomagnetic anomaly signature, seafloor topographic features, wide-angle refraction data, and on-land geomorphologic evidence enable us to trace the forearc extension of the subducted ridge up to the east Kyushu. The subducted Kyushu-Palau ridge with excess mass may be relatively buoyant, and thus is more likely to resist subduction upon collision with the overriding plate at depth, leading us to speculate that there is locally large tectonic stress at the contact zone between the subducted ridge and base of the overriding plate. The large stress zone is marked by historic thrust-type intermediate-class (magnitude 6 or 7) earthquakes. The flank regions of the subducted buoyant Kyushu-Palau ridge are more likely to tear and result in slab fracturing when the ridge subducts deeper. We propose that the subducted Kyushu-Palau ridge may serve not only as a seismic asperity at depth but also produce the slab fracture as a seismic barrier inhibiting the rupture propagation of the adjacent megathrust earthquakes in the Hyuga segment.
Scale factor mitigating non-compliance of double-frequency altimeter measurements of the ionospheric electron content over the oceans with GPS-TEC maps
Authors: Gulyaeva T. L. , Arikan F. , Delay S. H.
Published: August 2014

This paper presents results from a study of GPS total electron content (TEC) grid maps and ionospheric electron content (IEC) over the oceans delivered by the TOPEX/Jason satellites during half a solar cycle (July 2001 to December 2008). The IEC data are averaged and binned at latitudes from 60°S to 60°N in steps of 5°±2.5°, at longitudes from 180°W to 180°E in steps of 15°±7.5°, and for 0–23 h UT in steps of 1±0.5 h UT. The ratio of monthly averaged TEC/IEC over the oceans from the observations was compared to the reference model ratio of TECm/IECm obtained using the plasmaspheric model augmented with the International Reference Ionosphere. By definition, TEC should exceed IEC by the plasmaspheric electron content (PEC) contribution at the altitude range from 1336 km (TOPEX orbit) to 20,200 km (GPS orbit). However, as solar activity tends to the minimum, we found that IEC estimates systematically exceed those of GPS TEC. An empirical scale factor was derived in terms of the smoothed sunspot number, and this factor reduced the systematic excess of the TOPEX/Jason-derived IEC over the GPS TEC by a factor of 1.5 towards the solar minimum. This factor was tested with observations made at the solar minimum and revealed that the plasmaspheric electron content to be a residual of the GPS TEC and modified TOPEX/Jason IEC.
Observation of numerous aftershocks of an Mw 1.9 earthquake with an AE network installed in a deep gold mine in South Africa
Authors: Yabe Yasuo , Philipp Joachim , Nakatani Masao , Morema Gilbert , Naoi Makoto , Kawakata Hironori , Igarashi Toshihiro , Dresen Georg , Ogasawara Hiroshi ,   JAGUARS
Published: August 2014

This is the first report from the JAGUARS (JApanese-German Underground Acoustic Emission Research in South Africa) project, the overall aim of which is to observe ultra-small fracturing in a more or less natural environment. We installed a local (∼40-m span) network of eight acoustic emission (AE) sensors, which have the capability to observe up to 200 kHz at a depth of 3.3 km in a South African gold mine. Our specific objective was to monitor a 30-m thick dyke that remains as a dip pillar against active mining ∼90 m above our network. An M
w 1.9 earthquake whose hypocenter was ∼30 m above the network occurred in the dyke. Although the mineowned geophone (4.5 Hz) network detected only five earthquakes in the surrounding 200×200×150-m3 volume within the first 150 h following the main shock, our AE network detected more than 20,000 earthquakes in the same period. More than 13,000 of these formed a distinct planar cluster (∼100×80 m2) on which the main shock hypocenter lay, suggesting that this cluster delineates the main shock rupture plane. Most of the aftershocks were presumably very small, probably as low as M ∼ −4. The aftershock cluster dipped ∼60°. This is consistent with normal faulting under a nearly vertical compression field, as indicated by nearly horizontal breakouts found in a borehole crossing the rupture plane.
Shear-wave anisotropy beneath the Ryukyu arc
Authors: Nakamura Mamoru , Yamamoto Ai
Published: August 2014

We have investigated regional shear-wave splitting beneath the Ryukyu arc in order to clarify the mantle flow beneath the Ryukyu arc and compare it with the extension of the Okinawa Trough. The splitting of regional shear waves (direct S) in the central and southern Ryukyu arc regions was analyzed in terms of fast-polarization direction and delay time using data from 11 short-period stations and two broadband seismic stations. The events occurred at depths ranging between 45 and 217 km, and the magnitude of the events ranged from 2.8 to 5.2. In general, the orientations of fast polarization were found to parallel to the strike of the Ryukyu Trench, with average delay times of 0.25–0.56 s. Specifically, the orientation of fast polarization was parallel to the direction of the extension in the south Ryukyu arc, suggesting that the direction of mantle flow is parallel to the extension in the south Okinawa Trough. However, the orientation of fast polarization was oblique to the direction of extension in the central Ryukyu arc, indicating that the mantle flow beneath the central Ryukyu arc is not parallel to the extension of the central Okinawa Trough. Based on these results, we suggest that the difference between the direction of the mantle flow and that of the lithosphere extension induces extensional strain with a simple shear component, which in turn causes oblique rifting in the central Okinawa Trough.
Analyzing and correcting for contaminating magnetic fields at the Brorfelde geomagnetic observatory due to high voltage DC power lines
Authors: Maule Cathrine Fox , Thejll Peter , Neska Anne , Matzka Jürgen , Pedersen Lars William , Nilsson Anna
Published: August 2014

The magnetic field observations made at the geomagnetic observatory Brorfelde (BFE), Denmark, are subject to disturbances of several nT caused by two single wire high-voltage DC power lines connecting Scandinavia with Central Europe. We have analysed how the magnetic disturbances relate to the currents in the power lines and found a linear relationship. Using linear regression on carefully selected parts of the available data series we have determined the factors of proportionality. Based on the simple relationship between the currents in the power lines and the observed magnetic disturbances, we have derived a method to correct the observatory data for a significant part of the disturbances. In addition we have investigated the influence of the disturbances on the determination of the K-index of the observatory. We found that the K-index based on the original disturbed data compared to the K-indices calculated from corrected data was different in 4% of the 3-hour intervals for the investigated period.
Landwater variation in four major river basins of the Indochina peninsula as revealed by GRACE
Authors: Yamamoto Keiko , Fukuda Yoichi , Nakaegawa Toshiyuki , Nishijima Jun
Published: August 2014

We estimated mass variations in four major river basins—the Mekong, Irrawaddy, Salween and Chao Phraya river basins—of the Indochina Peninsula using the newly released GRACE (Gravity Recovery and Climate Experiment) monthly gravity field solutions of UTCSR RL02 (University of Texas at Austin, Center for Space Research Release 02), JPL RL02 (Jet Propulsion Laboratory Release 02) and GFZ RL03 (GeoForschungsZentrum Potsdam Release 03). The estimated variations were compared with that calculated from a numerical model. The results show that there is a good agreement between the GRACE estimations and the model calculation for the Mekong and Irrawaddy basins, while the aggreement for the Salween and Chao Phraya basins is poor, mainly due to the spatial scale of the areas concerned. The comparison over the combined area of the four river basins shows fairly good agreement, although there are small quantitative discrepancies. The amplitudes of the annual signals of the GRACE solutions are 0.9- to 1.4-fold larger than that of the hydrological model, and the phases are delayed about 1 month compared with the model signal. The phase differences are probably due to improper treatments of the groundwater storage process in the hydrological model, suggesting that the GRACE data possibly provide constraints to the model parameters.
Measurement of the duration of high-frequency energy radiation and its application to determination of the magnitudes of large shallow earthquakes
Authors: Hara Tatsuhiko
Published: August 2014

We have developed an algorithm to measure the duration of high-frequency energy radiation by processing the first arriving P-waves and then applied it to analyses of 69 large shallow earthquakes that occurred between 1995 and 2006. We compared our estimates to time differences between centroid and origin times in the Harvard CMT catalog and found that there was a good correlation between them, thereby suggesting that the measured durations are good estimates of source durations. We show that it is possible to determine magnitudes consistent with moment magnitudes in the Harvard CMT catalog using the durations of high-frequency energy radiation and maximum displacement amplitudes of the first arriving P-waves.
Analysis of ionospheric scintillation spectra and TEC in the Chinese low latitude region
Authors: Li Guozhu , Ning Baiqi , Yuan Hong
Published: August 2014

GPS L-band scintillations and total electron content (TEC) were recorded at Sanya (18.33°N, 109.52°E) during the period July 2004–July 2005. Automatic recorded raw digital scintillation data are analyzed to obtain the spectral characteristics of irregularities producing ionospheric scintillations and to estimate the correlation between amplitude scintillation and power spectral density. Concurrent measurements of TEC are used to analyze ROTI, defined as the standard deviation of the rate of change of TEC. The statistical results of S4 indices and power spectral indices indicate that the power spectral indices increase with S4 indices for weak scintillation (0.1 ≤ S4 < 0.3), but for moderate and strong scintillation, spectral indices tend to be saturated. In the analyzed data set, the ratio of ROTI/S4 is found to vary between 0.3 and 6, and the variation in estimated zonal drift velocities during geomagnetic quiet days (K p < 3) shows that the motion of the irregularities is highly variable in the initial phase of irregularity development. After about 22:00 LT, the estimated drift velocities tend to follow the same pattern.
Long-term stability of climate and global glaciations throughout the evolution of the Earth
Authors: Tajika Eiichi
Published: August 2014

Earth’s climate is considered to be stable on the order of > 106years, owing to a negative feedback mechanism in a carbon cycle system. However, any decrease in net input flux of CO2to the atmosphere-ocean system (i.e., volcanic-metamorphic CO2flux minus excess organic carbon burial flux) lowers the surface temperature and would eventually initiate global glaciation. TheFD-FOBdiagram (FD: the total CO2degassing flux,FOB: the organic carbon burial flux) is proposed as a measure of the susceptibility of the Earth to global glaciations. By using this diagram with the carbon fluxes estimated from a carbon cycle model during the Phanerozoic, the net input flux of CO2is found to have been very close to the critical condition for a global glaciation at the Late Paleozoic. During the Proterozoic, a carbon isotope mass balance model with this diagram shows that global glaciations occurred probably due to a decrease in the CO2degassing in addition to an increase in the organic carbon burial. Because the Sun becomes brighter as it evolves, the critical level of atmospheric CO2pressure to cause global glaciation will be lower than the critical CO2pressure for photosynthesis of C4 plants within 500 million years. At this point, the net input flux of CO2will be too large to cause global glaciations. Continuous volcanic-metamorphic activities (i.e., plate tectonics) may be one of the necessary conditions for the Earth and Earth-like planets in extrasolar planetary systems to keep liquid water and life over the timescales of planetary evolution.
Scaling of short-period source spectrum for earthquakes in mid Niigata, Japan
Authors: Izutani Yasuo
Published: August 2014

Strong motion records at K-NET and KiK-net stations for earthquakes which occurred in the mid Niigata area are analyzed to examine the relationship between the amplitude of the short-period source spectrum and the seismic moment. Large earthquakes radiate more short-period seismic energy per unit seismic moment than small ones, which suggests a deviation from the similarity of earthquake source. Appropriate correction for the deviation from the similarity should be made when we synthesize strong ground motion for future large earthquakes by the empirical Green’s function method.
Seismic moments of Taiwan’s earthquakes evaluated from a regional broadband array
Authors: Chen Kou-Cheng , Liang Wen-Tzong , Liu Yu-Hua , Huang Win-Gee , Wang Jeen-Hwa
Published: August 2014

We have taken the seismic moment (M
o) values of 79 earthquakes occurring in the Taiwan region that have been published in the Global centroid-moment tensor (CMT) and regional Broadband Array in Taiwan for Seismology (BATS) catalogues for the period 1996–2005 and compared the values determined from the global and regional networks, respectively. M
oG and M
oB are used to denote the M
o values published in the Global CMT and regional BATS catalogues, respectively. Our results show that M
oB linearly correlates with M
oG and that M
oB is, on average, approximately equal to 0.37M
oG. This difference may be caused by the use of shorter period seismic waves in BATS for estimating M
oB. The moment magnitude evaluated from regional BATS seismograms is about 0.3 less than that estimated from global data.
Electromagnetic full particle simulation of the electric field structure around the moon and the lunar wake
Authors: Kimura Shinya , Nakagawa Tomoko
Published: August 2014

The electric field structure around the moon is studied using a 2-dimensional electromagnetic full particle simulation. By considering absorption of the plasma particles at the surface of the moon, we obtain an intense electric field at the terminator region where the electric field produced by the negatively charged lunar surface and the ambipolar electric field at the wake boundary are in the same direction. The intensity of the electric field is 2.2E
0 (E
0 = m
0
υ

e

ω

p
/q0) at the terminator, corresponding to 3.5 V m−1 in the solar wind. It has a large horizontal component due to the potential difference between the negatively charged, antisolarside surface of the moon and the electrically neutral, solar-side surface, even though the emission of photoelectrons are not taken into consideration in this study. The half width of the electric field structure is of the order of Debye shielding length. The electric field at the downstream wake boundary at x = 6.5R

L
is stillas large as 0.1E
0 ∼ 0.16 V m−1, which is strong enough to cause the pitch angle diffusion of the solar-wind electron beam, as is expected in the generation mechanism of the wake-related whistler wave. The ion acceleration occurs in the close vicinity of the moon and can be explained by the acceleration by the electric field produced by the surface charging of the moon.
Comparison between the KOMPSAT-1 drag derived density and the MSISE model density during strong solar and/or geomagnetic activities
Authors: Park J. , Moon Y.-J. , Kim K.-H. , Cho K.-S. , Kim H.-D. , Kwak Y.-S. , Kim Y.-H. , Park Y.-D. , Yi Y.
Published: August 2014

We have compared the KOrea Multi-Purpose SATellite-1 (KOMPSAT-1) drag derived density with the MSISE model (NRLMSISE-00 and MSISE-90) density during strong solar and/or geomagnetic activities. It is well known that there are two major mechanisms to induce satellite drag caused by atmospheric density enhancement: the heating by solar EUV radiation and joule heating associated with local geomagnetic current enhancements during geomagnetic storms. For this work we select five events dominated by the radiation effect and/or the geomagnetic effect. For these events we compared the satellite drag derived density with the MSISE model density. The major results can be summarized as follows. (1) The density predicted from the MSISE models during radiation dominated periods are comparable to the drag derived density but the MSISE model density during strong geomagnetic storms is significantly underestimated when the MSISE model density is compared to the drag derived density, by about two times for the NRLMSISE-00 model. (2) The ratios of the KOMPSAT-1 (around 685 km) drag derived density to the MSISE model density during a strong geomagnetic storm are abruptly enhanced (up to a factor of about 8 for the MSISE-90 model and about 3 for the NRLMSISE-00 model), which are much larger than previous estimates from low altitude (around 400 km) satellites. (3) There is a possible correlation between daily drag enhancement and daily Dst variation. We note that there is a remarkable difference in daily drag enhancement although solar and geomagnetic activities are quite similar to each other. We suggest that such a difference should be explained by the accumulation of solar radiation effect depending on solar activity cycle.
Ice Box Calorimetry: A useful method for estimating heat discharge rates through steaming ground
Authors: Terada Akihiko , Kagiyama Tsuneomi , Oshima Hiromitsu
Published: August 2014

We developed a new technique, Ice Box Calorimetry, for estimating heat discharge rates through steaming ground. Ice within an aluminum box provides a powerful tool for measuring the total heat transfer from the ground surface, including conductive heat, convective heat, and latent heat within vapor. Using this method, we are able to rapidly measure heat discharge rates without the need for specialized apparatus. Applying Ice Box Calorimetry to the Nishiyama steaming ground at Usu volcano, Japan in September 2006, we identified local variations in heat discharge rates. The total heat discharged from the entire geothermal area in September 2006 is estimated to be 27 MW, which represents just 1% of the rate immediately following an eruption from the volcano in 2000.
Coseismic deformation due to the 2007 Chuetsu-oki earthquake (Mw= 6.8)
Authors: Aoki Yosuke , Furuya Masato , Kato Teruyuki
Published: August 2014

Global Positioning System (GPS) and Synthetic Aperture Radar Interferometry (InSAR) detected substantial ground deformation due to the 2007 Chuetsu-oki earthquake (Mw= 6.8); GPS observation detected a horizontal deformation of up to about 170 mm and subsidence of up to 30 mm, and InSAR detected up to 290 mm of line-of-sight changes. A fault model is proposed to fit the ground deformation field as well as the aftershock distribution. Our model shows that a northwest-dipping fault to the north and a southeast-dipping fault to the south, consistent with the aftershock distribution, fits well with the observed data. However, our model also suggests that the modeled faults are likely to extend to shallower depths, where aftershocks are terminated. Combining our model with the subsurface structure suggests that the earthquake rupture initiated at depth and propagated into shallower depths that are not capable of nucleating an earthquake because of the presence of unconsolidated sediments.
Existence of low-velocity zones under the source areas of the 2004 Chuetsu and 2007 Chuetsu-oki earthquakes inferred from travel-time tomography
Authors: Nakajima Junichi , Hasegawa Akira
Published: August 2014

Travel-time tomography reveals the presence of highly heterogeneous seismic velocity structures around the source areas of the 2004 Chuetsu and 2007 Chuetsu-oki earthquakes. A prominent low-velocity zone present below the Moho under the source areas of the two events is probably formed by fluids being conveyed through a small-scale upwelling in the mantle wedge. A low-velocity zone distributed in the lower crust below each source area is attributable to fluids supplied from the uppermost mantle to the source area. Since this region with these two source areas is exceptional in that the low-velocity zone is distributed in the uppermost mantle but no Quaternary volcanoes are formed at the surface, a relatively large amount of fluids may be stored below the source areas. These localized fluids may have reduced the strength in the lower crust as well as in the fault zones in the upper crust and, consequently, have promoted a brittle failure in the seismogenic layer. Relocated hypocenters of aftershocks of the two events become several kilometers shallower than the original locations determined by the Japan Meteorological Agency, suggesting the importance of using the three-dimensional velocity model in locating the hypocenter.
Coseismic displacement due to the 2008 Iwate-Miyagi Nairiku earthquake detected by ALOS/PALSAR: preliminary results
Authors: Takada Youichiro , Kobayashi Tomokazu , Furuya Masato , Murakami Makoto
Published: August 2014

Applying interferometric SAR (InSAR) analysis to the 2008 Iwate-Miyagi Nairiku earthquake, we detected notable ground displacements of several tens of centimeters to about 1.2 m that extend further south of the epicentral area. We explained the InSAR data by constructing a fault model consisting of four WNW dipping and one ESE dipping reverse faults. The residuals between observed and modeled deformation are less than 6 cm in most of the area, which is comparable to the errors caused by atmospheric effect. To fill the lack of InSAR data in the hypocentral area, we applied a pixel matching technique to the intensity images, which shows a shortening in range offsets by as much as ∼2 m along a narrow zone stretching along the eastern foot of Mt. Kurikoma, indicating a localized uplift. We also found remarkable contrasts in the range offsets around the low coherence area equivalent to a very large displacement gradient to the WNW of the hypocentral area as well as ESE. We conclude that the main faulting occurred on the WNW dipping reverse faults, but that the overall geometry of the fault system is quite complex including at least one conjugate faulting, as also supported by the hypocentral distribution of aftershocks.
The spread F Experiment (SpreadFEx): Program overview and first results
Authors: Fritts D. C. , Abdu M. A. , Batista B. R. , Batista I. S. , Batista P. P. , Buriti R. , Clemesha B. R. , Dautermann T. , de Paula E. , Fechine B. J. , Fejer B. , Gobbi D. , Haase J. , Kamalabadi F. , Laughman B. , Lima L. M. , Liu H. -L. , Medeiros A. , Pautet P. -D. , Riggin D. M. , Sabbas F. São , Sobral J. H. A. , Stamus P. , Takahashi H. , Taylor M. J. , Vadas S. L. , Wrasse C. M.
Published: August 2014

We performed an extensive experimental campaign (the spread F Experiment, or SpreadFEx) from September to November 2005 to attempt to define the role of neutral atmosphere dynamics, specifically wave motions propagating upward from the lower atmosphere, in seeding equatorial spread F and plasma bubbles extending to higher altitudes. Campaign measurements focused on the Brazilian sector and included ground-based optical, radar, digisonde, and GPS measurements at a number of fixed and temporary sites. Related data on convection and plasma bubble structures were also collected by GOES 12 and the GUVI instrument aboard the TIMED satellite. Initial results of our analyses of SpreadFEx and related data indicate 1) extensive gravity wave (GW) activity apparently linked to deep convection predominantly to the west of our measurement sites, 2) the presence of small-scale GWactivity confined to lower altitudes, 3) larger-scaleGWactivity apparently penetrating to much higher altitudes suggested by electron density and TEC fluctuations in the E and F regions, 4) substantial GW amplitudes implied by digisonde electron densities, and 5) apparent direct links of these perturbations in the lower F region to spread F and plasma bubbles extending to much higher altitudes. Related efforts with correlative data are defining 6) the occurrence and locations of deep convection, 7) the spatial and temporal evolutions of plasma bubbles, the 8) 2D (height-resolved) structures of plasma bubbles, and 9) the expected propagation of GWs and tides from the lower atmosphere into the thermosphere and ionosphere.
Radar observations of the diurnal tide in the tropical mesosphere-lower thermosphere region: Longitudinal variabilities
Authors: Gurubaran S. , Rajaram R. , Nakamura T. , Tsuda T. , Riggin D. , Vincent R. A.
Published: August 2014

Significant attention is being paid in recent times by several observational and modeling studies to quantify the spatial and temporal variabilities of diurnal tide in the mesosphere and lower thermosphere (MLT) region. These variabilities are ascribed to spatial and temporal variations in the tidal forcing or interactions between the propagating tides and background wind, planetary waves or gravity waves. The present work makes use of simultaneous ground-based radar wind observations of different durations from five equatorial/low latitude sites in the Indian, Indonesian and Pacific sectors: Tirunelveli (8.7°N, 77.8°E), Jakarta (6.4°S, 106.7°E), Pontianak (0.03°N, 109°E), Kauai (22°N, 160°W) and Christmas Island (2°N, 157°W). This study delineates the longitudinal differences in the tidal characteristics in (i) interannual time scales over Tirunelveli and Kauai during 1993–2002, (ii) seasonal time scales over Christmas Island, Jakarta and Tirunelveli for the years 1993–1997 and (iii) shorter than seasonal time scales over Christmas Island, Pontianak and Tirunelveli during 1996–1997. An important observational feature noticed in this work is the differing behavior of the long-term tidal fields over Tirunelveli and Kauai. The monthly tidal amplitudes over Tirunelveli reveal a strong QBO signature whereas a similar, strong QBO signal could not be traced in the long-term observations from Kauai.
Validity on radar observation of middle- and upper-atmosphere dynamics
Authors: Kato Susumu
Published: August 2014

Doppler radar observations have made a large contribution towards improving our understanding of middle- and upper-atmosphere dynamics. This radar echo is mainly due to radiowave scattering by atmospheric turbulence, which occurs almost universally throughout the atmosphere as a result of gravity wave (GW) breaking. In the strictness sense, the radar pulse is back-scattered by radio refractive index (RRI) perturbations caused by turbulence whose size along the radar beam is half of the radar wavelength. Understanding of the validity of the MST (mesosphere, stratosphere and troposphere)-radar observation requires a precise knowledge of how RRI perturbations are formed and behave. A basic property of the RRI of the atmosphere is that it has a static vertical gradient in terms of distribution and the turbulence velocity is divergence-free. The RRI depends on three atmospheric properties—humidity, air density and electron density. These three elements each have a static vertical gradient along which turbulence transports each element, hereby perturbing the density distribution of each element; that is to say, it produces the RRI irregularity for scattering the radar pulse. Since the turbulence motion and winds are divergence-free, PRI perturbation co-moves with the total air flow, i.e. turbulence motion plus winds. This can be true even in the mesosphere where the perturbation is controlled electromagnetically. Co-movement of turbulence with local winds has been shown from a comparison of observations with radars and radiosondes. In addition to tracking turbulence as wind-tracers, MST-radar observations provide important data in the study of atmosphere turbulence dynamics.
Co-seismic and post-seismic pore-fluid pressure changes in the Philippine Sea plate and Nankai decollement in response to a seismogenic strain event off Kii Peninsula, Japan
Authors: Davis Earl , Becker Keir , Wang Kelin , Kinoshita Masa
Published: August 2014

New pressure data from a pair of Ocean Drilling Program (ODP) hydrologic borehole observatories at ODP Sites 1173 and 808, located off Japan in the subducting Philippine Sea plate and in the nearby Nankai accretionary prism, respectively, show clear signals associated with an earthquake swarm off the Kii Peninsula that began on September 5, 2004, roughly 220 km away from the observatory sites. At Site 1173, formation pressures rose by 1.0–1.5 kPa at the time of the largest earthquake (Mw= 7.5), then continued to rise to a total anomaly of 4 kPa during the following 200–300 days. These transients are inferred to reflect co-seismic and slow continuing volumetric contraction of the plate by amounts of roughly 0.2 × 10−6and 0.5 × 10−6, respectively. The sign of the estimated strain is consistent with that predicted with a seismic-moment-constrained elastic half-space dislocation model, but the amplitude is much larger, by roughly a factor of 6 at the time of the main earthquake, and by nearly a factor of 20 when the total pressure-estimated strain at the end of the post-seismic period is compared to that estimated from the total cumulative seismic moment including aftershocks. The simplest inference that can be drawn is that a large component of aseismic slip occurred in the epicentral area. At Site 808, pressure at the deepest monitoring zone just above the subduction decollement fell at the time of the largest earthquakes. This may reflect shear-induced dilatation which would be consistent with strain-or velocity-hardening behaviour along this seaward-most part of the subduction thrust interface.
Improved geoid model determination for Japan from GRACE and a regional gravity field model
Authors: Kuroishi Yuki
Published: August 2014

A highly improved gravimetric geoid model for Japan, JGEOID2008, is developed on a 1×1.5 arc-minute grid by combining a GRACE (the Gravity Recovery And Climate Experiment)-based global geopotential model, GGM02C, surface (land and ship-borne) gravity measurements, and an altimetry-derived marine gravity model, KMS2002. In the combination, a semidiscrete two-dimensional wavelet analysis/reconstruction method is employed, selecting the spatial wavelength signals of the highest quality out of the respective data sets. Intercomparison with GPS/leveling geoid undulations shows substantial improvement of JGEOID2008 over the previous model, JGEOID2004, and reveals that the systematic errors at long wavelengths contained in JGEOID2004 have been effectively removed. Deviations of JGEOID2008 from the mean sea surface height at tidal stations on isolated islands were comparable to the differences in the sea surface dynamic heights (SSDH) in the Japan Sea, the Nansei Islands and the Izu Island chain from that in Tokyo Bay. The deviations show good agreement with SSDH features estimated from oceanographic observation, indicating that JGEOID2008 has an accuracy within 10 cm. The geoid model is strongly expected to serve as a reference in ocean dynamics studies.
Implementation of a non-oscillatory and conservative scheme into magnetohydrodynamic equations
Authors: Tanaka Shin , Umeda Takayuki , Matsumoto Yosuke , Miyoshi Takahiro , Ogino Tatsuki
Published: August 2014

We present a magnetohydrodynamic (MHD) simulation technique with a new non-oscillatory and conservative interpolation scheme. Several high-resolution and stable numerical schemes have recently been proposed for solving the MHD equations. To apply the CIP scheme to the hydrodynamic equations, we need to add a certain diffusion term to suppress numerical oscillations at discontinuities. Although the TVD schemes can automatically avoid numerical oscillations, they are not appropriate for profiles with a local maximum or minimum, such as waves. To deal with the above problems, we implement a new non-oscillatory and conservative interpolation scheme in MHD simulations. Several numerical tests are carried out in order to compare our scheme with other recent high-resolution schemes. The numerical tests suggest that the present scheme can follow long-term evolution of both Alfvén waves and compressive shocks. The present scheme has been used for a numerical modeling of Alfvén waves in the solar wind, in which sinusoidal Alfvén waves decay into compressive sound waves that steepen into shocks.
Dependence of waveform of near-field coseismic ionospheric disturbances on focal mechanisms
Authors: Astafyeva Elvira , Heki Kosuke
Published: August 2014

Using Total Electron Content (TEC) measurements with Global Positioning System we studied ionospheric responses to three large earthquakes that occurred in the Kuril Arc on 04 October 1994, 15 November 2006, and 13 January 2007. These earthquakes have different focal mechanisms, i.e. high-angle reverse, low-angle reverse, and normal faulting, respectively. TEC responses to the 2006 and 2007 events initiated with positive and negative changes, respectively. On the other hand, the initial TEC changes in the 1994 earthquake showed both positive and negative polarities depending on the azimuth around the focal area. Such a variety may reflect differences in coseismic vertical crustal displacements, which are dominated by uplift and subsidence in the 2006 and 2007 events, respectively, but included both in the 1994 event.
Global deformation from the great 2004 Sumatra-Andaman Earthquake observed by GPS: Implications for rupture process and global reference frame
Authors: Kreemer Corné , Blewitt Geoffrey , Hammond William C. , Plag Hans-Peter
Published: August 2014

Static coseismic offsets > 1 mm are observed up to 7800 km away from the great Sumatra-Andaman earthquake of 26 Dec. 2004 using global GPS network data. We investigate the rupture process based on far-field continuous GPS data. To reduce error in the coseismic offset estimates due to post-seismic deformation in the days following the main shock, we simultaneously fit a model of co- and postseismic offsets for nearby stations SAMP (500 km) and NTUS (900 km). The 3-month cumulative postseismic displacement for station SAMP amounts to 20% of the coseismic displacement, and can be well modeled by velocity-strengthening afterslip. We find that coseismic slip on the northern rupture segment is ∼3 m, which is consistent with seismic estimates. Our best estimate of the moment magnitude isMw= 9.13 if we take into account the expected increase of the shear modulus with depth (for uniform μ = 30 GPa, the moment-magnitude would only be 8.97). Our geodetic results, and thus our inferred rupture model, are different from a similar study using far-field data of Banerjeeet al.(2005). These differences highlight the challenge in earthquake studies on a global scale in terms of the sensitivity of far-field offset estimates to the analysis strategy and reference frame treatment. Our predicted coseismic offsets from this event are at least 1 mm across almost the entire globe. This warrants a reconsideration of how to maintain the global terrestrial reference frame affected by earthquakes ofMw> 9.0.
Ionospheric perturbations observed by the GPS following the December 26th, 2004 Sumatra-Andaman earthquake
Authors: DasGupta Ashish , Das Aditi , Hui Debrup , Bandyopadhyay Kalyan Kumar , Sivaraman M. R.
Published: August 2014

Using the Total Electron Content (TEC) data recorded by the GPS receiver network, installed under the GPS and Geo Augmented Navigation (GAGAN) program, ionospheric electron content on the day of the great Sumatra-Andaman earthquake of December 26, 2004 was examined. A significant perturbation of 1.5 to 2 TEC units over a smooth variation of TEC in the morning hours was observed within 45 minutes of the quake at stations situated near the east coast of the Indian subcontinent. The disturbance was found to propagate northwestward with its origin situated about 2° northeast of the quake epicenter. Possible coupling mechanism of the crustal movement and the ionosphere are discussed.
Rupture process of the 2004 great Sumatra-Andaman earthquake estimated from tsunami waveforms
Authors: Tanioka Yuichiro , Yudhicara  , Kususose Tomohiro , Kathiroli S. , Nishimura Yuichi , Iwasaki Sin-Iti , Satake Kenji
Published: August 2014

Rupture process of the 2004 Sumatra-Andaman earthquake is estimated using tsunami waveforms observed at tide gauges and the coseismic vertical deformation observed along the coast. The average rupture speed of the 2004 Sumatra-Andaman earthquake is estimated to be 1.7 km/s from tsunami waveform analysis. The rupture extends about 1200 km toward north-northwest along the Andaman trough. The largest slip of 23 m is estimated on the plate interface off the northwest coast in the Aceh province in Sumatra. Another large slip of 21 m is also estimated on the plate interface beneath the north of Simeulue Island in Indonesia. The other large slip of 10–15 m is estimated on the plate interface near Little Andaman and Car Nicobar Inlands. The total seismic moment is calculated to be 7.2 × 1022 Nm (Mw 9.2) which is similar to the other studies using seismic waves (Park et al., 2005; Ammon et al., 2005).
The 2004 Indian tsunami in Thailand: Surveyed runup heights and tide gauge records
Authors: Tsuji Yoshinobu , Namegaya Yuichi , Matsumoto Hiroyuki , Iwasaki Sin-Iti , Kanbua Wattana , Sriwichai Mongkonkorn , Meesuk Vorawit
Published: August 2014

Tsunami accompanied with the Sumatra earthquake of 26 December 2004 affected many countries around the Indian Ocean. Thailand located approximately 500 km east of its source, was also severely suffered from the tsunami. From 24 February through 4 March 2005, we surveyed the damaged areas in Thailand from south of Phuket Island up to the border of Myanmar including four islands. The whole coastal area facing the Andaman Sea could be covered. We measured 37 points in total, the tsunami heights are less than 10 m, except at a few locations. We found that the largest tsunami height reached up to 19.6 m at Ban Thung Dap of Phra Thong Island. During our survey, we also collected five paper copies of analog tide gauge records. In addition that we could detect two other tide gauge records from the web-site. Therefore, totally seven tide gauge records were obtained in Thailand. All of the recorded tsunami waveforms indicate that sea level initially withdrew with duration in 30 to 60 min, followed by the rising-up. This phenomenon corresponds to the eyewitnesses’ accounts of the survivors who experienced the tsunami.
Factors associated with severe deep neck space infections: Targeting multiple fronts
Authors: Barber Brittany R , Dziegielewski Peter T , Biron Vincent L , Ma Andrew , Seikaly Hadi
Published: August 2014

Objectives

To determine factors predictive of a severe deep neck space infection (DNSI), defined as those requiring surgery and/or postoperative intensive care unit (ICU) admission. To specifically examine dental practices and socioeconomic factors that may contribute to the development of a DNSI.

Study design

Retrospective review.

Methods

This study was conducted at 2 tertiary care academic referral centers from January 2007 to September 2011. The study was composed of 2 arms: a prospective questionnaire and data collection to identify modifiable risk factors such as dental practices and socioeconomic considerations for a DNSI, and a retrospective review of deep neck space infections to identify commonly associated risk factors predictive of a severe DNSI, requiring surgery and/or postoperative ICU admission.

Results

233 patients were reviewed retrospectively and 25 patients prospectively. Patients with a low level of education (p = 0.03), those living greater than 1 hour from a tertiary care center (p = 0.002), those that have tonsils (p = 0.03), and those with Streptococcus infections (p = 0.03) have an increase risk of developing a severe DNSI. Patients that were smokers (p = 0.02) or had diabetes (p = 0.02), and those that presented with airway compromise (p = 0.03) were more likely to have a prolonged hospital stay.

Conclusions

Factors predictive of severe DNSIs are Streptococcus infections, the presence of tonsils, education level, and geographic location.