bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spatial distribution of coda Q estimated from local earthquakes in Taiwan area
Authors: Chung Jen-Kuang , Chen Yen-Ling , Shin Tzay-Chyn 
Published: August 2014

AbstractAttenuation of seismic wave energy and its spatial distributions in Taiwan area have been investigated using a large amount of short-period seismograms recorded from the local earthquakes with magnitude ranging from 2.5 to 4.5. The codaQvalues were estimated in the frequency range 1.5∼18 Hz, applying the single backscattering model proposed by Aki and Chouet in 1975. The estimated average frequency dependent codaQvalues within the crust give the relationship,QC= 93f0.75, while varying from 143±33 at 1.5 Hz to 904±164 at 18 Hz central frequencies. However, using the data from deeper earthquakes, the average codaQrelationship is given asQC= 122f0.71in related to the material property of the crust and upper lithosphere, in which the average codaQvalues vary from 180±67 at 1.5 Hz to 1000±144 at 18 Hz. The comparison of different lapse times starting at double the time of the primaryS-wave from the origin time and corresponding to the datasets with different focal depths, reveals that codaQvalues increase with the coda generating volume. As a whole, the regressive relationships of frequency dependent codaQfor Taiwan region approximately agree with those by previous investigators. In addition, the average codaQvalues for three subregions of Taiwan were calculated and correlated with the geology and tectonic features, respectively. The lowestQvalues were obtained in the region consisting of the Coastal Range and the Longitudinal Valley of eastern Taiwan, whilst the highestQfor the region underlain by the Peikang High beneath the western Coastal Plain. Such distinguishable difference has definitely explained that the seismic waves should exhibit lower decay rate in a stable region than within a seismoactive plate boundary.
Slip distribution of the 1973 Nemuro-oki earthquake estimated from the re-examined geodetic data
Authors: Nishimura Takuya 
Published: August 2014

AbstractGeodetic data, including leveling, tide-gauge, triangulation/trilateration, and repeated EDM data, from eastern Hokkaido, Japan, were re-examined to clarify the crustal deformation associated with the 1973 Nemuro-oki earthquake. We inverted the geodetic data to estimate the slip distribution on the interface of the subducting Pacific plate. The estimated coseismic slip, potentially including afterslip, showed a patch of large slip (i.e., an asperity) near the epicenter of the mainshock. The moment magnitude of the Nemuro-oki earthquake was estimated to be 8.0 from the geodetic data, which is comparable to the 2003Mw= 8.0 Tokachi-oki earthquake. The estimated slip distribution suggests a 50 km-long gap in the coseismic slip between the 1973 Nemuro-oki and the 2003 Tokachi-oki earthquakes. The slip area of the 2004Mw= 7.0 Kushiro-oki earthquake, estimated from GPS data, was located at the northwestern edge of the Nemuro-oki earthquake, which implies that the area may have acted as a barrier during the Nemuro-oki earthquake. The postseismic deformation observed by leveling and tide-gauge measurements suggests that the afterslip of the Nemuro-oki earthquake occurred at least in a western and northern (i.e., deeper) extension of the asperity on the plate interface.
On estimation of earthquake magnitude in Earthquake EarlyWarning systems
Authors: Sokolov Vladimir , Wenzel Friedemann , Furumura Takashi 
Published: August 2014

Abstract
Determination of earthquake magnitude from the initial P-wave portion of ground motion is the key problems for Earthquake Early Warning (EEW). We analyzed performance of scaling relations between one of the frequently used early warning parameters, so-called characteristic period τC and moment magnitude M
W in respect of (a) characteristics of datasets accumulated in various regions (earthquake depth, characteristics of network) and (b) variation of initial conditions applying for determination of the parameter τC (length of Pwave window, number of used stations). The used data contain strong-motion records from 110 earthquakes (moment magnitude range 4.4–7.6) occurred in Japan and Taiwan. We show that, although the standard error of regression τC = f (M
W) in general becomes smaller with the increase of the length of P-wave window (PL) and the number (N) of averaged observations (stations), the uncertainty in estimation of MW given observed tC does not decrease further for PL > 3–4 seconds and N > 3–4 stations. The information about earthquake depth also plays an important role in reducing the uncertainty of magnitude estimations. The table of confidence limits for estimations of the moment magnitude MW based on observations of the characteristic period τC is provided.
Magnetohydrodynamic parametric instabilities of parallel propagating incoherent Alfvén waves
Authors: Nariyuki Yasuhiro , Hada Tohru 
Published: August 2014

Abstract
Numerical experiments for parametric instabilities of incoherent Alfvén waves in the context of one dimensional Hall-MHD equation sets are studied. The reason why the decay instability of incoherent waves can be explained in terms of that of the coherent wave is understood through analysis on nonlinearly driven finite amplitude density fluctuations. Numerical results suggest the importance of modulational instabilities of left-hand polarized Alfvén waves.
Processing the Bouguer anomaly map of Biga and the surrounding area by the cellular neural network: application to the southwestern Marmara region
Authors: Aydogan Davut 
Published: August 2014

Abstract
An image processing technique called the cellular neural network (CNN) approach is used in this study to locate geological features giving rise to gravity anomalies such as faults or the boundary of two geologic zones. CNN is a stochastic image processing technique based on template optimization using the neighborhood relationships of cells. These cells can be characterized by a functional block diagram that is typical of neural network theory. The functionality of CNN is described in its entirety by a number of small matrices (A, B and I) called the cloning template. CNN can also be considered to be a nonlinear convolution of these matrices. This template describes the strength of the nearest neighbor interconnections in the network. The recurrent perceptron learning algorithm (RPLA) is used in optimization of cloning template. The CNN and standard Canny algorithms were first tested on two sets of synthetic gravity data with the aim of checking the reliability of the proposed approach. The CNN method was compared with classical derivative techniques by applying the cross-correlation method (CC) to the same anomaly map as this latter approach can detect some features that are difficult to identify on the Bouguer anomaly maps. This approach was then applied to the Bouguer anomaly map of Biga and its surrounding area, in Turkey. Structural features in the area between Bandirma, Biga, Yenice and Gonen in the southwest Marmara region are investigated by applying the CNN and CC to the Bouguer anomaly map. Faults identified by these algorithms are generally in accordance with previously mapped surface faults. These examples show that the geologic boundaries can be detected from Bouguer anomaly maps using the cloning template approach. A visual evaluation of the outputs of the CNN and CC approaches is carried out, and the results are compared with each other. This approach provides quantitative solutions based on just a few assumptions, which makes the method more powerful than the classical methods.
Spatial variations in the frequency-magnitude distribution of earthquakes in the southwestern Okinawa Trough
Authors: Lin Jing-Yi , Sibuet Jean-Claude , Lee Chao-Shing , Hsu Shu-Kun , Klingelhoefer Frauke 
Published: August 2014

AbstractThe relations between the frequency of occurrence and the magnitude of earthquakes are established in the southern Okinawa Trough for 2823 relocated earthquakes recorded during a passive ocean bottom seismometer experiment. Three highb-values areas are identified: (1) for an area offshore of the Ilan Plain, south of the andesitic Kueishantao Island from a depth of 50 km to the surface, thereby confirming the subduction component of the island andesites; (2) for a body lying along the 123.3°E meridian at depths ranging from 0 to 50 km that may reflect the high temperature inflow rising up from a slab tear; (3) for a third cylindrical body about 15 km in diameter beneath the Cross Backarc Volcanic Trail, at depths ranging from 0 to 15 km. This anomaly might be related to the presence of a magma chamber at the base of the crust already evidenced by tomographic and geochemical results. The highb-values are generally linked to magmatic and geothermal activities, although most of the seismicity is linked to normal faulting processes in the southern Okinawa Trough.
Compressional and shear wave velocities of serpentinized peridotites up to 200 MPa
Authors: Watanabe Tohru , Kasami Hiroaki , Ohshima Shohei 
Published: August 2014

AbstractCompressional and shear wave velocities of serpentinized peridotites were measured at room temperature and high confining pressures of up to 200 MPa. Rock samples were collected from the Hida outer belt, Central Japan, and classified into High-T (containing antigorite) and Low-T (containing lizardite and/or chrysotile) types. Antigorite is stable up to 600∼700°C, while lizardite and chrysotile are stable below 300°C. High-T type samples have distinctly higher velocities than their Low-T type counterparts with the same density. The High-T type with strong foliation shows significant velocity anisotropy, and the azimuthal anisotropy of the compressional wave velocity reaches 30%. These properties can be explained by the crystallographic structure of antigorite. Poisson’s ratio increases with serpentinization in both types. The High-T type shows a lower Poisson’s ratio than the Low-T type with the same density. The High-T type requires a higher degree of serpentinization than the Low-T type to give a certain value of Poisson’s ratio. Observations of high Poisson’s ratio have been interpreted using Low-T type properties. However, High-T type serpentinized peridotite is expected in warm subduction zones. The use of Low-T type properties will lead to a significant underestimation of serpentinization. For good interpretations, it is essential to use the properties of the appropriate type of serpentinized peridotite.
Contributions of the external field to the observatory annual means and a proposal for their corrections
Authors: Verbanac Giuli , Lühr Hermann , Rother Martin , Korte Monika , Mandea Mioara 
Published: August 2014

Abstract
In this study we separate, interpret and explain magnetospheric and ionospheric signals present in the observatory annual means. The data from 46 European geomagnetic observatories collected over 42 years (1960–2001) are used. To characterise the various field components, we use predictions from latest magnetic field models. The core field and its secular variation are described by the CM4 model, and the magnetospheric contributions are successfully removed by parameterising the POMME model with the Dst index. We regard the remaining signal as being caused by ionospheric currents. The annual averages of the Sq variation estimated by the CM4 model are subtracted from the residuals. A remaining variation in anti-phase with the magnetic activity index Ap finally can be removed with a function properly scaled by Ap and Dst. We offer an objective procedure to suppress the external field contributions in the annual means to an uncertainty level of ±2 nT. Except for the ionospheric currents, this could be achieved by applying recent magnetic field models, which shows that the quality of present day models is sufficient to correct observatory data for average external field contributions. Understanding the signal contained in the annual means is a prerequisite for obtaining reliable and physically meaningful results when such data are used in studies of the core field and its secular variation.
VHF radar studies of counter electrojet events during the northern winter solstice period of 1992
Authors: Manju G. , Viswanathan K. S. 
Published: August 2014

Abstract
A sequence of counter electrojet events during the winter solstice period of 1992 are studied along with control quiet day observations at the magnetic equatorial location of Trivandrum (8.5°N, 76.5°E; dip 0.5°N) using VHF (54.95 MHz) coherent backscatter radar observations. Some of the unusual features observed on these days are: (1) an unusual radar signal with reversed Doppler values corresponding to westward electric field, for a brief duration of 5 min at approximately 1330 h, at the higher altitudes 112–117 km on 21 January 1992, as against the usual observation of the signal at lower altitudes below 112 km during CEJ times; (2) type I plasma waves in the late afternoon around 1800 h (after the CEJ event) at altitudes above 101 km (on 21 and 23 January 1992) when the backscattered power is low, indicating the unusual tidal influences on the electric field behavior on certain CEJ days; (3) distortions in the height structure of the vertical polarization electric field, attributed to the modulation of the electrojet altitude structure by action of zonal neutral winds; (4) westward electric field, as seen by the radar, even while the ΔH values are positive.
GPS ionospheric tomography: A comparison with the IRI-2001 model over South Korea
Authors: Jin Shuanggen , Park Jong-Uk 
Published: August 2014

Abstract
The International Reference Ionosphere model 2001 (IRI-2001) is one of the most comprehensive empirical models of the ionosphere and has been widely used to estimate the electron density profiles in the altitude ranging from about 60 to 2000 km and the total electron content (TEC) at any given location, time and date, which reflect smooth-average global ionospheric behaviors. However, whether it provides normal actual estimations in the ionosphere over some regions should be tested with real observation data. In this paper, the three-dimensional ionospheric electron density profiles over South Korea in 2003 are obtained using the ionospheric tomography reconstruction technique with the permanent Korean GPS Network (KGN) data, and its validity is further verified by another independent ionosonde data. The GPS ionospheric reconstruction results are used to compare then results obtained with the IRI-2001 model in South Korea in terms of NmF2 and TEC. The monthly averaged diurnal values of these key parameters in January, April, July and October 2003 are considered to represent the winter, spring, summer and autumn seasons, respectively. Compared with the GPS reconstruction results, averaged monthly NmF2 medians from the IRI-2001 are overestimated in daytime and underestimated in nighttime for all seasons, but the deviation magnitudes in autumn and winter are smaller than in spring and summer. In addition, averaged monthly TEC medians from the IRI-2001 are overestimated in daytime in winter, but almost always underestimated in other seasons.
Collisional disruption of weakly sintered porous targets at low-impact velocities
Authors: Setoh Masato , Nakamura Akiko M. , Hirata Naru , Hiraoka Kensuke , Arakawa Masahiko 
Published: August 2014

Abstract
Porous structure is common in the asteroids and satellites of the outer planets. In order to study the relationship between the structure of small bodies and their thermal and collisional evolution, we performed impact disruption experiments on porous sintered targets using a light-gas gun at velocities ranging from 10 to 100 m/s. The sintered glass bead targets were prepared to have roughly the same porosity but with different compressive strengths, ranging over an order of magnitude, by controlling sintering duration and temperature. The results of the impact experiments show that the targets of higher compressive strength have higher impact strengths. However, compared to previous results on impact disruption of porous sintered targets with a collisional velocity of approximately 6 km/s, the values of impact strength in this study were found to be lower by an order of magnitude.
Stress due to the interseismic back slip and its relation with the focal mechanisms of earthquakes occurring in the Kuril and northeastern Japan arcs
Authors: Takeuchi M. , Sato T. , Shinbo T. 
Published: August 2014

AbstractAssuming a uniform and inhomogeneous distribution of back slip, based on a realistic configuration of the plate boundary that was newly determined from the distribution of earthquakes, we have investigated if the stress due to the interseismic back slip can explain the focal mechanisms of earthquakes occurring in the Kuril and northeastern Japan arcs. The inhomogeneous back-slip model was taken from the distribution of slip deficit estimated from GPS data collected in recent years. We examined the change in the Coulomb Failure Function (ΔCFF) for several target faults to evaluate the fitness of the models to the observed focal mechanisms. The results of ΔCFF are clearly different in the two back-slip models near the down-dip end of the locked zone. Despite this difference, the models can generally explain the earthquake focal mechanisms in the overriding plate as well as those on the megathrust plate boundary. However, they cannot explain the focal mechanisms of intermediate-depth earthquakes in the double-planed deep seismic zone. Neither can they fully explain the focal mechanisms with the pressure axis parallel to the trench that are observed at the junction of the Kuril and northeastern Japan arcs. Other tectonic processes, such as the transcurrent movement of the forearc sliver along the Kuril arc, may be involved in producing the stress anomaly.
Relocation of large intermediate-depth earthquakes in the Vrancea region, Romania, since 1934 and a seismic gap
Authors: Hurukawa Nobuo , Popa Mihaela , Radulian Mircea 
Published: August 2014

AbstractWe relocatedM6 or larger intermediate-depth earthquakes in Vrancea, Romania that have occurred since 1934. To determine their absolute hypocenters accurately, we combined them with recent (from January 1996 to November 2003) smaller earthquakes recorded by the Romanian local network and then relocated all of them simultaneously using a modified joint hypocenter determination method. Using the data on recent small earthquakes we first obtained an estimate of the dimensions of the active seismic region of intermediate-depth earthquakes: length, 85 km; along a NE-SW direction; width, 20 km; depth 60-160 km. We then determined that the 1940 (M7.7), 1977 (M7.5) and 1990 (M6.9) major earthquakes were located near the NE edge of the seismic region, while the 1986 (M7.2) was located inside the seismic region. The focal depths of the 1940, 1977, 1986 and 1990 major earthquakes were calculated to be 124, 98, 135 and 84 km, respectively and their source areas to range from 60 to 140 km in depth. The only unbroken area is at a depth of 140–160 km, which we current consider to be a seismic gap. Based on the regularity of past large earthquakes, we propose that the nextM7 intermediate-depth earthquake can be expected to occur in Vrancea at a depth interval of 140–160 km sometime early in this century.
Coseismic and postseismic deformation related to the 2007 Chuetsu-oki, Niigata Earthquake
Authors: Ohta Yusaku , Miura Satoshi , Iinuma Takeshi , Tachibana Kenji , Matsushima Takeshi , Takahashi Hiroaki , Sagiya Takeshi , Ito Takeo , Miyazaki Shin’ichi , Doke Ryosuke , Takeuchi Akira , Miyao Kayo , Hirao Akihiko , Maeda Takahiro , Yamaguchi Teruhiro , Takada Masamitsu , Iwakuni Makiko , Ochi Tadafumi , Meilano Irwan , Hasegawa Akira 
Published: August 2014

AbstractAn intermediate-strength earthquake of magnitudeMj6.8 occurred on July 16, 2007, centered beneath the Japan Sea a few kilometers offshore of Niigata Prefecture in central Japan. We constructed a dense GPS network to investigate postseismic deformation after this event, choosing our GPS sites carefully so as to complement the nationwide GPS GEONET array. Coseismic displacements caused by the mainshock detected at some GEONET sites were used to estimate coseismic fault parameters. The results indicate that the geodetic data can be explained by a combination of two rectangular faults dipping northwest and southeast. Minor but definite postseismic deformation was detected largely in the southern part of the dense network. The time series of site coordinates can be characterized by a logarithmic decay function, and the estimated time constant seems to be almost similar in range to that of the 2004 Mid-Niigata Prefecture Earthquake. We also found a possible site instability at 960566 (Izumo-zaki, GEONET) caused by a small, local landslide associated with the mainshock and therefore concluded that the data obtained at this site should not be used for coseismic or postseismic analysis.
Determination of dip direction for the 2007 Chuetsu-oki earthquake from relocation of aftershocks using arrival times determined by cross-correlation
Authors: Mori Jim 
Published: August 2014

Abstract
Waveform correlations were used to redetermine P arrival times at 31 stations for a selected set of 321 aftershocks of the 2007 Chuetsu-oki earthquake. These data were used with several different relocation techniques, 1-D velocity structure, 3-D velocity structure using SIMULPS12, 1-D velocity structure using hypoDD, and 3-D velocity structure using tomoDD. The results from all of these methods show a consistent southeast dipping trend for the entire aftershock sequence. The same pattern is also seen for the time period before the largest aftershock. These results indicate that the mainshock fault dips to the southeast.
Seismic scaling relation of the 2007 Off Mid Niigata, Japan, earthquake (Mw 6.6) sequence in comparison with two other earthquake (Mw 6.6) sequences
Authors: Tajima Reiko , Tajima Fumiko 
Published: August 2014

AbstractThe relationship of seismic moment (M0) to corner frequency (fc) of the 2007 Off Mid Niigata prefecture (Chuetsu-oki) earthquake sequence is examined in comparison with that of two other earthquake sequences. TheM0-f0relation of this sequence (3.4 ≤Mw≤ 6.6) isM0∝fc−3.87, which deviates fromM0∝fc−3. The relatively large deviation fromfc−3may reflect the influence of fluids identified in tomographic studies around the source region of the tectonic strain concentration. Moreover, the lowerfcs of the small events (3.4 ≤Mw≤ 3.8) in this sequence are similar to those of off-main-fault events in the 2004 Mid Niigata prefecture earthquake sequence. The characteristics in the scaling relation may be interpreted in the context of the event locations, which are either on- or off-main faults, and may have implications for the seismogenic conditions. Key words: The 2007 Off Mid Niigata earthquake, seismic scaling, seismogenic conditions.