bluuebunny/crossref_metadata_2025_split huggingface dataset:
A numerical simulation of ionospheric and atmospheric variations associated with the Sumatra earthquake on December 26, 2004
Authors: Shinagawa H. , Iyemori T. , Saito S. , Maruyama T. 
Published: August 2014

Abstract
In the Sumatra earthquake that occurred on December 26, 2004, significant ionospheric variations were detected immediately after the earthquake in both the TEC (total electron content) data of GPS (Global Positioning System) and the ionosonde data. A magnetic pulsation with a period of about 4 min was also observed in Phimai, Thailand. Recent studies have suggested that these events are associated with acoustic waves excited by a sudden large-scale displacement of the sea surface around the epicenter. In order to study these phenomena quantitatively, a time-dependent two-dimensional nonhydrostatic compressible atmosphere-ionosphere model has been used and compared with relevant data. By modeling in sea surface perturbation, we were able to reproduce an atmospheric oscillation with a period of about 4 min in the upper atmosphere above the epicenter. The electron density variations observed by GPS/TEC and by ionosondes were also reproduced fairly well. We found that the observed TIDs (traveling ionospheric disturbances) with long periods are caused by the ducted thermospheric gravity waves produced in the thermosphere through acoustic pulse from the epicenter. The good overall agreement between the simulation results and observations indicates that numerical simulation with the nonhydrostatic compressible atmosphere-ionosphere model could be a useful tool to investigate the relationship between variations in the upper atmosphere and various sources of disturbances in the lower atmosphere.
Preliminary report on crustal deformation surveys and tsunami measurements caused by the July 17, 2006 South off Java Island Earthquake and Tsunami, Indonesia
Authors: Kato Teruyuki , Ito Takeo , Abidin Hasanuddin Z. , Agustan  
Published: August 2014

Abstract
A large earthquake (Mw=7.7) along a plate boundary occurred in the south of Java Island on July 17, 2006, and caused a significant tsunami. We made GPS observations and tsunami heights measurements during the period from July 24 to August 1, 2006. The earthquake seems to be due to an interplate low angle reverse faulting, though there might be a possibility of high angle faulting within the subducting lithosphere. Crustal deformation distribution due to the earthquake, aided by tsunami heights measurements, might clarify which would be the case. We occupied 29 sites by GPS in the area of southern Java encompassing the area from 107.8 E to 109.50 E. These sites were occupied once before the earthquake. However, we were not able to detect significant coseismic displacements. The obtained displacements, most of which span several years, show ESE direction in ITRF2000 frame. This represents the direction of Sunda block motion. The tsunami heights measured at 11 sites were 6–7 m along the southern coast of Java and indicate that the observed heights are systematically higher than those estimated from numerical simulations that are based on seismic data analysis. This might suggest that fault offsets might have been larger—nearly double—than those estimated using seismic analysis. These results lead us to an idea that the rupture was very slow. If this is the case, the earthquake might have been a “tsunami earthquake” that is similar to the one that occurred on June 2, 1994 in the east of the present earthquake.
Dynamic rupture propagation on a 2D fault with fractal frictional properties
Authors: Ide Satoshi 
Published: August 2014

AbstractWe study dynamic rupture propagation on a 2D fault with a spatially heterogeneous slip-weakening friction law under a homogeneous stress condition. The slip-weakening distanceDcis determined based on fault topography, characterized by the fractal dimension σ and a normalized slip-weakening distanceDc0. Assuming different combination of these parameters, we carry out a large number of dynamic rupture simulations to discuss event size statistics and the scaling relations of macroscopic parameters such as seismic moment, rupture velocity, seismic energy, and radiation efficiency. All stopped events obey an approximately power-law size-number relation. However, statistically self-similar rupture propagation is observed only for selfsimilar fault topography with σ = 1, where the average rupture velocity is controlled byDc0. This suggests that a power-law size-number relation does not simply mean the self-similarity of rupture process. Both upper and lower fractal limits in fault topography disturb the power-law statistics and the lower fractal limit results in excess of events of the characteristic size. The facts that slow ruptures can radiate large seismic energy and that fast ruptures are not always efficient suggest the importance of local acceleration, deceleration, and arrest of rupture. We also show that the spatial regularity of slip-weakening distance is essential to make the above results.
Contribution of heat outputs from high- and low-temperature hydrothermal sources to the neutrally buoyant plume at the TAG hydrothermal mound, Mid-Atlantic Ridge
Authors: Goto Shusaku , Gamo Toshitaka , Chiba Hitoshi , Fujioka Kantaro , Mitsuzawa Kyohiko 
Published: August 2014

Abstract
We provide an estimation of the heat output necessary to generate the neutrally buoyant plume above the TAG hydrothermal mound, Mid-Atlantic Ridge, located at 26°N, using a model of plume rise in a density-stratified environment with crossflow. The estimated heat output is 460 ± 40 MW. Previous studies have estimated that the heat outputs from high-temperature hydrothermal discharge and low-temperature diffuse flow at the TAG hydrothermal mound are 90 ± 20 MW and at least 780 MW, respectively. Consequently, the contribution of diffuse flow to make the neutrally buoyant plume is 370 ± 60 MW, which accounts for approximately 80% of the heat output to the neutrally buoyant plume. As this contribution is less than 50% of the total heat output from the diffuse flow, it is likely that more than 50% of the heat output from the diffuse flow dissipates in the ambient current.
Feasibility study on the potential of satellite altimetry for detecting seismic geoid changes due to the 2004 Sumatra-Andaman earthquake
Authors: Hayashi Yutaka , Hirata Kenji , Kuragano Tsurane , Sakurai Toshiyuki , Takayama Hiromi , Hasegawa Yohei , Hamada Nobuo 
Published: August 2014

Abstract
Sea surface height data obtained by satellite altimetry from Jason-1 and TOPEX/Poseidon were analyzed to explore the possibility of a seismic geoid change due to the 2004 Sumatra-Andaman earthquake. This analysis identified a weakly positive geoid change in a region between the trench and outer arc. A subsequent investigation of the characteristics of this coseismic geoid change based on the dislocation theory revealed that a positive peak should indicate the upper edge of the high-slipped area or asperity and that a negative peak is responsible for the lower edge of the earthquake fault. An attempt at modeling the difference in the sea level anomaly failed to explain the observation since a large scatter in the original dataset obstructed its confirmation.
Two-dimensional resistivity structure of the fault associated with the 2000 Western Tottori earthquake
Authors: Yamaguchi Satoru , Murakami Hideki , Iwamoto Hisanori , Takemoto Kazuhiro , Kitada Kazuya , Shiozaki Ichiro , Oshiman Naoto , Katoh Shigehiro 
Published: August 2014

Abstract
Two-dimensional resistivity surveys were carried out along two profiles that were laid across earthquake faults initiated by the 2000 Western Tottori earthquake. One profile was located 7 m from a trenching pit, thereby enabling a direct comparison of resistivity cross-section with the geological cross-section and, subsequently, a precise interpretation of the resistivity structure. Features of the resistivity cross-section were found to correspond fairly well to the geological cross-section. A clear resistivity boundary between the resistive and conductive zones matches the earthquake fault that was found by the trenching survey. Variations in resistivity depend primarily on the development of fractures. Two types of conductive zones were found: (1) a clear and deep-rooted conductor that corresponds to an earthquake fault and (2) an indistinct and spatially localized conductor that corresponds to a fracture attributed by landslides and collapse. A few weak conductive zones that match with discrete earthquake faults characterize our resistivity model. This feature is different from the resistivity cross-sections found at the Nojima and Ogura Faults that appeared at the time of the 1995 Hyogo-ken Nanbu earthquake; these two latter faults are characterized by distinct single conductive zones. Based on geomorphological, geological, and seismological evidence, the earthquake fault of the 2000 Western Tottori earthquake can be classified as an immature fault. In contrast, the Nojima and Ogura Faults have been active for at least the entire Quaternary period. We conclude that the difference in the fault development stages is reflected in their different resistivity structures.
Consistency between the flow at the top of the core and the frozen-flux approximation
Authors: Whaler K. A. , Holme R. 
Published: August 2014

Abstract
The flow just below the core-mantle boundary is constrained by the radial component of the induction equation. In the Alfvén frozen-flux limit, thought to be applicable to the outer core on the decade timescale of interest in geomagnetism, this gives a single equation involving the known radial magnetic field and its secular variation in two unknown flow components, leading to a severe problem of non-uniqueness. Despite this, we have two specific pieces of flow information which can be deduced directly from the frozen-flux induction equation: the component of flow perpendicular to null-flux curves, contours on which the radial magnetic field vanishes, and the amount of horizontal convergence and divergence at local extrema (maxima, minima and saddle points) of the radial magnetic field. To produce global velocity maps, we make additional assumptions about the nature of the flow and invert the radial induction equation for flow coefficients. However, it is not clear a priori that the flows thus generated are consistent with what we know about them along null-flux curves and at local extrema. This paper examines that issue. We look at typical differences between the null-flux curve perpendicular flow component, and convergence and divergence values at extrema, deduced directly from the induction equation and those from the inversions, investigate the effect of forcing the inversions to produce the correct null-flux curve and extremal values, and characterise the uncertainties on the various quantities contributing. Although the differences between the flow values from the induction equation directly and obtained by inversion seem large, and imposing the direct flow information as side constraints during inversion alters the flows significantly, we also show that these differences are within the likely uncertainties. Thus, we conclude that flows obtained through inversion do not contravene the specific flow information obtained directly from the radial induction equation in the frozen-flux limit. This result should reassure the community that frozen-flux flow inversion is a consistent process, even if including the extremal-value and null-flux conditions as additional information on flow inversion is unlikely to be useful. Solving for a time-dependent core-mantle boundary field model and flow simultaneously may be a good way to produce a temporally-varying field model consistent with the frozen-flux constraint; the ability to fit the data with such a model could be used to establish the timescale over which the frozen-flux assumption is valid.
Stochastic finite-fault modeling of ground motions from the June 27, 1998 Adana-Ceyhan earthquake
Authors: Yalcinkaya Esref 
Published: August 2014

AbstractIn this study, acceleration time histories of the June 27, 1998 Adana-Ceyhan (Turkey) earthquake, are simulated using a stochastic modeling technique for finite faults proposed by Beresnev and Atkinson (1997). The fault length, width and the depth to the top of the fault for the earthquake are assumed 30 km, 21 km and 15 km, respectively, based on the aftershock distribution. Simulations are made for two common site classes: soil and rock. Their response characteristics are obtained from the site-specific amplification functions estimated for the weak motion seismograms at stations located in the region using spectral ratio methods. The results show that the overall agreement between simulated and observed waveforms and spectra is quite satisfying. However, significant discrepancies exist at certain stations, implying that site amplification functions play an important role in the simulation process. The effects of nonlinearity and basin edge generated surface waves do not clearly dominate on the results. The peak horizontal acceleration contours estimated using the calibrated model are consistent with the observed intensity values and the other evidences of strong ground motions.
Numerical simulation of resonant scattering of energetic electrons in the outer radiation belt
Authors: Katoh Yuto , Ono Takayuki , Iizima Masahide 
Published: August 2014

Abstract
Resonant diffusion processes of high energy electrons are studied numerically by using an original simulation scheme where cold electrons are treated as a fluid and hot electrons are treated as particles including fully relativistic effects. The present simulation scheme enables us to investigate the resonant scattering process in the inner magnetosphere, which has been difficult to study by using the PIC code. We investigated the variation of the distribution of electrons through the resonant diffusion process by comparing the present numerical experiment and the quasi-linear theory under the same condition of the interaction between whistler-mode waves and high energy electrons. The difference between their results suggests the importance of the verification of the theory under the realistic plasma condition corresponding to the observed parameters in the outer radiation belt.
Detection of phase disturbances of free core nutation of the Earth and their concurrence with geomagnetic jerks
Authors: Shirai Toshimichi , Fukushima Toshio , Malkin Zinovy 
Published: August 2014

Abstract
We detected phase disturbances of the Free Core Nutation (FCN) of the Earth directly from the analysis of the Very Long Baseline Interferometer (VLBI) observation of the Earth rotation for the period 1984–2003 by applying the Weighted Wavelet Z-Transform (WWZ) method and the Short-time Periodogram with the Gabor function (SPG) method. During the period, the FCN had two significant phase disturbances in 1992 and 1998. These epochs coincide with the reported occurrence of geomagnetic jerks.
Source process of the 1923 Kanto earthquake inferred from historical geodetic, teleseismic, and strong motion data
Authors: Kobayashi Reiji , Koketsu Kazuki 
Published: August 2014

AbstractThe historical geodetic and teleseismic data are jointly inverted for the rupture process of the 1923 Kanto earthquake together with the strong motion data recently discovered. The resultant slip distribution shows two asperities (areas of large slips) on the fault plane with a total seismic moment of 1.1 ⊙ 1021 Nm (Mw8.0). The asperity in the shallow central portion of the fault is larger with maximum slip of approximately 10 m than the one in the hypocentral region. The recovered slip functions indicate that the initial slip was abrupt in the hypocentral asperity, though it was gradual in the larger asperity. The major discrepancies between the observations and synthetics are attributed to volcanic activities and the 3-D structure of the Kanto Basin. We compare the slip and aftershock distributions and also discuss the relation of the asperities to silent earthquakes.
Tsunami due to the 2004 September 5th off the Kii peninsula earthquake, Japan, recorded by a new GPS buoy
Authors: Kato Teruyuki , Terada Yukihiro , Ito Keiji , Hattori Ryuji , Abe Takenori , Miyake Toshihide , Koshimura Shun’ichi , Nagai Toshihiko 
Published: August 2014

Abstract
A tsunami due to the 2004 M7.4 September 5th earthquake off of the Kii peninsula, Japan, was recorded at the GPS buoy newly designed and established in April 2004, about 13 km off of the Muroto Promontory, southwestern Japan. The tsunami arrived at the buoy about 8 minutes before its arrival to the nearest tide gauge station at the tip of the Muroto Promontory. The predicted tsunami record based on preliminary source model shows excellent agreement (rms 2.7 cm) with the observed GPS record. This demonstrates that GPS buoy observations can be used not only for a tsunami warning system, but also for precise determination of the tsunami source.
The 2004 sequence of triggered earthquakes off the Kii peninsula, Japan
Authors: Park Sun-Cheon , Mori Jim 
Published: August 2014

AbstractWe examine the spatial and temporal relationships of the sequence of strong earthquakes that occurred off the Kii Peninsula, Japan, on 5 September 2004. The first event (Mj 7.1) occurred at 10:07:08 (UTC) on a northward dipping plane within the subducting Philippine Sea plate. From 10:16 to 14:47 the seismicity shows a group of earthquakes (Mj 3.2 to 4.8) 35 km to the east which are regarded as foreshocks to the second large earthquake. At 14:57:17, a Mw 6.1 strike-slip event occurred on a northwest trending plane. Some 14 seconds later, a large (Mj 7.4) thrust earthquake started 4.2 km southeast of the initial epicenter of the second earthquake. This largest earthquake is thought to have occurred on a southward dipping plane with the strike in an east-southeastly direction. Using the geometry of faults determined in this study, calculations of the Coulomb failure function show that simple static stress changes do not provide a good explanation for the triggering of the subsequent earthquakes.
The September 5, 2004 off the Kii Peninsula earthquakes as a composition of bending and collision
Authors: Seno Tetsuzo 
Published: August 2014

Abstract
The 2004 off the Kii Peninsula earthquakes ruptured the subducting Philippine Sea plate near the axis of the Nankai Trough. A series of major events (the fore- and mainshocks with Mw>7) showed very peculiar rupture characteristics. The depth extent of the foreshock is around 12–23 km below the sea surface; in contrast, that of the mainshock is around 7–17 km, shallower and closer to the upper surface of the plate than the foreshock. The focal mechanism of the foreshock is almost pure reverse faulting, with a P-axis directing roughly N-S, that is rotated clockwise by 20–25° from the trough normal. In contrast, the mainshock involved a significant component of strike-slip faulting, with a similar P-axis. The OBS survey revealed a double layer of the aftershock activity and the upper NW trending layer contains aftershocks with strike-slip focal mechanisms. These features indicate that the compressional and tensional stress domains due to bending are significantly modified by tectonic stress disturbance and produced the fore- and mainshock ruptures deviated from simple reverse and normal faulting. I show that a supposed N-S compressional stress, which might be produced by the collision south of the Izu Peninsula, can rotate the principal stress axes and change the stress type, which are consistent with the P-axes of these events and the strike-slip component for the mainshock. The complex rupture mode of the mainshock might have been produced by superposition of the depth-dependent tensional bending stress in the upper half of the lithosphere and the collisional stress. This collisional stress should be comparable to the bending stresses in magnitude, which is much larger than the stress perturbation caused by nearby interplate locking.
Slow slip in the focal region of the anticipated Tokai earthquake following the seismo-volcanic event in the northern Izu Islands in 2000
Authors: Kobayashi Akio , Yoshida Akio , Yamamoto Takeyasu , Takayama Hiromi 
Published: August 2014

Abstract
Transient crustal deformation occurred in the regions of Kanto and Tokai during the seismo-volcanic event in the northern Izu Islands in 2000. In our investigation of the observed deformation, we constructed an optimum-source model of the event between Miyake and Kozu Islands. We then made an inversion analysis of the differences between the observed displacement field and the calculated displacement field from the optimum model, assuming that the differences were caused by the changes in the interplate coupling beneath the Tokai region. From the inversion analysis of data for each of three-month periods, May to August, June to September, and July to October, we found decreased interplate coupling in the early stages of the 2000 event. In the first stage, either a slow slip or a temporary suspension of the plate subduction occurred in the focal region of the anticipated Tokai earthquake. The area then extended to the west and, finally, a slow slip exceeded the secular convergence velocity on the plate interface near Lake Hamana in the fall of 2000. We believe this ongoing slow slip began in August or early September 2000.
Ground motion and rupture process of the 2004 Mid Niigata Prefecture earthquake obtained from strong motion data of K-NET and KiK-net
Authors: Honda R. , Aoi S. , Morikawa N. , Sekiguchi H. , Kunugi T. , Fujiwara H. 
Published: August 2014

Abstract
The 2004 Mid Niigata Prefecture earthquake (37.289°N, 138.870°E, 13.1 km, MJMA 6.8; JMA), also known as the 2004 Niigata Prefecture Chuetsu earthquake, was a thrust type earthquake that occurred on October 23, 2004 at 17:56 (JST). Strong ground motions of PGA 800-1700 cm/s2 and PGV 60-130 cm/s were observed at stations located immediately above the source region. We deduced the rupture process of this earthquake with a multi-time-window linear waveform inversion procedure. We used near-fault strong ground motion data observed at nine K-NET and KiK-net stations within 50 km from the epicenter. In order to obtain appropriate Green’s functions for the waveform inversion, we constructed two velocity structure models for stations on the hanging wall and one structure model for stations on the footwall. The estimated total slip distribution contains three asperities: (a) around the hypocenter, (b) in the upper-middle section of the fault plane, and (c) southwest of the hypocenter. The maximum slip is 3.8 m at the hypocenter and the total seismic moment is 1.2 × 1019 Nm, which corresponds to Mw=6.7. The moment rate functions in asperities (a) and (c) have a short rise time, while those in asperity (b) have a longer rise time.