bluuebunny/crossref_metadata_2025_split huggingface dataset:
Subsidence monitoring within the Athens Basin (Greece) using space radar interferometric techniques
Authors: Parcharidis Is. , Lagios E. , Sakkas V. , Raucoules D. , Feurer D. , Le Mouelic S. , King C. , Carnec C. , Novali F. , Ferretti A. , Capes R. , Cooksley G. 
Published: August 2014

Abstract
The application of conventional SAR Interferometry (InSAR) together with the two techniques of subcentimeter accuracy, the Stacking and the Permanent Scatterers (PS) Interferometry, were used to study the ground deformation in the broader area of Athens for the period 1992 to 2002. Using the Stacking interferometric method, 55 ERS-1&2 SAR scenes, between 1992 and 2002, were acquired producing 264 differential interferograms. Among these only 60 were finally selected as fulfilling certain criteria. The co-seismic deformation associated with the Athens Earthquake (Mw = 5.9, September 7, 1999) was excluded from the analytical procedure in an attempt to present results of only aseismic character. In total ground subsidence results of about 12 mm in the southern suburbs of Athens, but higher value of about 40 mm in the northern ones for the period 1992–2002. Based on the PS technique, a precise average annual deformation rate-map was generated for the period 1992–1999, ending just before the Athens earthquake event. Both circular and elongated-shape areas of subsidence are recognizable especially in the northern part of the Athens Basin (3–4 mm/yr), as well as at its southern part (1–3 mm/yr). In addition, a rate of 2–3 mm/yr is also yielded for some part of the Athens city center. Subsidence rates of 1–2 mm/yr are measured at the western part of the basin over an area of old mining activities, and around the newly built Syntagma Metro Station. The correlation of the observed deformation patterns with respect to the spatial distribution of water pumping, older mining activities, metro line tunneling and other local geological parameters is examined and discussed.
A comparative study of the bottomside profile parameters over Wuhan with IRI-2001 for 1999–2004
Authors: Chen Huajiao , Liu Libo , Wan Weixing , Ning Baiqi , Lei Jiuhou 
Published: August 2014

Abstract
The diurnal, seasonal, and solar activity variations of the bottomside ionospheric profile parameters B0 and B1 are studied using electron density profiles measured over Wuhan (30.4°N, 114.4°E) of China with a DGS- 256 Digisonde during 1999–2004. Comparisons are made with the International Reference Ionosphere model (IRI-2001) using both the standard option (B0-Tab and B1-Tab) and the Gulyaeva’s option (B0-Gul and B1- Gul). The results show that: (1) observed B0 has distinct diurnal and seasonal variations, while observed B1 changes little with season. The value of B0 is larger in summer than that in equinox and winter, especially for daytime. In winter and equinox, B0 also presents morning and afternoon collapses as reported by Lei et al. (2004). (2) B0 increases about 18.6 km from low solar activity (LSA) to high solar activity (HSA). B1 in HSA is smaller than that in LSA before 10:00 LT and with an opposite tendency during the rest time. (3) Observed B0 is in better agreement with B0-Gul than with B0-Tab, though the B0-Gul overestimates during 09:00 to 17:00 LT in equinox and summer. B0-Tab is 12–20 km larger than the observations over Wuhan almost all the time.
Meanwhile, B1-Tab is in good agreement with the observations.
Airglow and other F-layer variations in the Indian sector during the geomagnetic storm of February 5–7, 2000
Authors: Mukherjee G. K. 
Published: August 2014

Abstract
A CCD based all-sky imaging system was used to monitor various nightglow emissions (OI 630-nm, OI 557.7- nm, OI 777.4-nm, Na (589.3-nm) and hydroxyl (OH) airglow) at a low latitude station, Kolhapur (16.8°N, 74.2°E, dip lat 10.6°N) in India to study the characteristics of night airglow variations observed during the period of a moderate/weak geomagnetic storm with SSC (Storm Sudden Commencement) commencing at 15:42 UT (21:12 IST (Indian Standard Time = UT + 5.5 hrs)) on February 5, 2000. The images on the night of February 6 show the development of strong ionization anomaly (EIA) with bright intensity regions in OI 630-nm and the signature of rising bubbles with very low intensity. Though the signature of ionospheric plasma bubbles were not observed on the night of February 7, the OI 630-nm images showed the presence of large scale enhanced airglow moving to the southeast direction. The speed was significantly fast (≈300 m/s). There were bright intensity regions also observed in OI 557.7-nm airglow, but no intensity enhancement was seen in other mesospheric emissions (Na (589.3-nm) and hydroxyl (OH) airglow ) during this magnetic disturbance. The ionosonde observations at the nearby station, Visakhapatnam (lat. 17.67°N, long. 83.32°E) also showed enhancement in electron density parameter ((foF2)2) at the station on each night compared to the night of February 4–5 (quiet day) around the same time interval maximizing around 23:00 IST on the night of February 7. The Total Electron Content (TEC) fluctuations obtained from GPS phase delays between two L-band signals (L1 = 1575 MHz and L2 = 1227 MHz) showed no enhancement at night at four mid latitude stations in Japan. However, noontime TEC values were enhanced on February 6 and 7 with maximum intensity occurring on February 7. It is inferred that enhanced storm time effects in the ionosphere were mainly confined to the low latitude region, the effects were subdued in the mid latitude stations.
Magnetic storm effects at equatorial electrojet stations
Authors: Rastogi R. G. 
Published: August 2014

Abstract
It is shown that there are distinctly two different mechanisms for the interaction of solar wind with the earth’s magnetosphere to produce electric field in the ionospheric heights at low and middle latitudes. A persistent or slowly varying southward Interplanetary magnetic field i.e. negative IMF-Bz generates dawn to dusk electric field at polar latitudes and a westward (dusk to dawn) electric field at dayside electrojet region which is anti-Sq in direction. A rapid increase of IMF-Bz (northward turning) imposes a westward (dusk to dawn) electric field at all latitudes of the dayside hemisphere. The process involved is the imposition of -V × Bz electric field at the magnetosphere transmitted instantaneously to the magnetic equator through the polar latitudes. The changes in the H field at ground are largest at stations close to the magnetic equator and the midday longitudes. During magnetic storms, associated with the southward IMF-Bz, there are definite enhancements in the decrease of H field at the dayside equatorial electrojet stations. These changes may be coincident with the development of auroral or magnetospheric ring currents. These enhancements may be observed during the main phase as well as during the recovery phase of the magnetic storm, but the essential condition is that the IMF-Bz has to be steadily significant southward. Sometimes during the storm period abnormally large changes in H field at day side equatorial electrojet regions are observed associated with large sudden changes in IMF-Bz following the second mechanism of solar wind magnetospheric interaction. Thus the equatorial magnetic storm effects are due to combined effects of disturbance ring current, slow and steady IMF-Bz as well as due to sudden large changes in IMF-Bz.
Investigation of the Onikobe geyser, NE Japan, by observing the ground tilt and flow parameters
Authors: Nishimura Takeshi , Ichihara Mie , Ueki Sadato 
Published: August 2014

Abstract
In this study we conducted observations of the Onikobe geyser, NE Japan, by deploying a tiltmeter and an acoustic sensor close to the vent, a flow pressure sensor at the conduit exit, and measuring water temperature at ground level. The data from these instruments are consistent with the model of geysers which involves effusion process of boiling due to depressurization. During the observation period, the geyser generally effused water for about 90 s every 10 mins, although during certain periods these times randomly shortened to about 60 s and 6 mins, respectively. Tilt records show a strong correlation with the short and long effusion times, reflecting water movement in at least two chambers beneath the vent. We are able to empirically predict the duration of effusion from tilt data, although flow pressure does not vary with effusion time.
Long-term seafloor geomagnetic station in the northwest Pacific: A possible candidate for a seafloor geomagnetic observatory
Authors: Toh H. , Hamano Y. , Ichiki M. 
Published: August 2014

Abstract
For two years, geomagnetic variations have been measured at the seafloor in the northwest Pacific. The seafloor data consist of the geomagnetic vector field measured by a three-component fluxgate magnetometer and the absolute scalar total force measured by an Overhauser (1953) magnetometer with attitude measurements for both orientation and tilt. Using the attitude data, the geomagnetic data at a site in the northwest Pacific (41o06′08″N, 159°57′47″E, -5580 m), hereafter referred to as NWP, were converted into the same reference frame as land and satellite measurements. Short-period variations of the converted vector data were examined by Hamano’s (2002) global time domain analysis method, which showed compatibility of the seafloor geomagnetic observatory data with the existing land observatory network. The smooth and gradual change of the Earth’s main field (i.e., the geomagnetic secular variation) was also found consistent with those predicted by the latest International Geomagnetic Reference Field (IGRF-10; IAGA, 2005) and by Ørsted Satellite (Olsen, 2002) for not only the scalar field but also the vector field. This means that observation of the geomagnetic vector secular variation is now feasible on the seafloor.
Application of GPS in geomagnetic survey
Authors: Gu Zuowen , Zhan Zhijia , Gao Jintian , Yao Tongqi , Han Wei 
Published: August 2014

Abstract
When measuring the geomagnetic declination, the azimuth of the reference mark must be measured. This paper briefly describes the principle of measuring the azimuth by the differential GPS (Global Positioning System), several test observations of GPS and the results. In geomagnetic survey in China during 2002~2003, GPS was used in measuring the azimuth. Field observations by GPS were carried out during the period that satellite signals were better received. The statistical results of the GPS data at 135 stations in China show that the difference of the azimuths between 2 GPS measurements at various stations is 0.0″~5.9″ and the average is 1.6″. The azimuthal accuracy measured by GPS in this paper is 0.1′, and it is much better than the azimuthal accuracy 1.0′ given by Newitt et al. (1996). The observation results show that the azimuths measured by GPS are accurate and reliable; they are not related to the time-space changes. The geomagnetic declinations D at various stations were obtained based on the azimuths measured by GPS, and the standard deviation of the reduced value of D was < 0.4′. Using the reduced values, the 8-order spherical cap harmonic model and the 5-order Taylor polynomial model in China for D were obtained. In geomagnetic survey, GPS is also used in measuring the longitude, the latitude and the elevation at various stations.
Deformation and „deformation quiescence” prior to the Chi-Chi earthquake evidenced by DInSAR and groundwater records during 1995–2002 in Central Taiwan
Authors: Yen Jiun-Yee , Chen Kun-Shan , Chang Chung-Pai , Ng Sin Mei 
Published: August 2014

Abstract
Deformation of Central Taiwan between 1997 and 2002 was investigated using radar interferometry to construct the deformation rate time series before, during, and after the Chi-Chi earthquake. The deformation rate time series was compared to the time series of groundwater level in the monitoring wells of Yuanlin and Tzushan in order to investigate the relation between the geodetic observations and the groundwater levels. The deformation pattern of Central Taiwan generally forms a half-elliptical pattern, with the eastern half of the elliptical shape cut away by the north-south trending Chelungpu fault. Along a selected profile of 10 km near the Chelungpu Fault of Central Taiwan, the differential range change was measured and recalculated into deformation rates. The year-to-year deformation rates near the Chi-Chi earthquake ranged between 1.5 and 3 cm/year in most years except for the years between 1999 and 2000, which showed more than 5 cm/year deformation rates along the profile. Prior to the high deformation rate shown during the coseismic image pair, the deformation rate was low, as shown on the other image pairs. This variation in deformation rate coincides with the recorded trend in the level of groundwater in two monitoring wells in the Yuanlin area. The low deformation rate prior to the Chi-Chi earthquake may—partially—be explained by this lowering in groundwater level.
Integrated gradient interpretation techniques for 2D and 3D gravity data interpretation
Authors: Saibi Hakim , Nishijima Jun , Ehara Sachio , Aboud Essam 
Published: August 2014

AbstractThe Obama geothermal field is located on the western part of Kyushu Island, Japan. This area has importance due to its high geothermal content which attracts sporadic researchers for study. In 2003 and 2004, Obama was covered by gravity surveys to monitor and evaluate the geothermal field. In this paper, the surveyed gravity data will be used in order to delineate and model the subsurface structure of the study area. Gradient methods such as analytic signal and vertical derivatives were applied to the gravity data. The available borehole data and the results of the gradient interpretation techniques were used to model the Obama geothermal field. In general, the obtained results show that the gradient interpretation techniques are useful to obtain geologic information from gravity data.
Simultaneous ground-based and satellite observations of Pc5 geomagnetic pulsations: A case study using multipoint measurements
Authors: Sung S.-K. , Kim K.-H. , Lee D.-H. , Takahashi K. , Cattell C. A. , André M. , Khotyaintsev Y. V. , Balogh A. 
Published: August 2014

Abstract
Pc5 pulsations with a latitude-independent frequency of ∼2.8 mHz (period ∼6 min) were observed with ground-based magnetometers in the morning sector (0700–1000 local time) from 0730 to 0810 UT, April 29, 2001. The pulsations exhibited an amplitude peak and a ∼180° phase change at ∼67° geomagnetic latitude. A vortex structure of the equivalent ionospheric current system was also observed centered at the geomagnetic latitude between 67° and 71°. During the Pc5 event, the Polar spacecraft was located near the morningside magnetic equator and crossed magnetic field lines conjugate to the ground stations at which the pulsations were strong. Polar observed ∼2.8 mHz pulsations in the radial electric field and compressional magnetic field components. Since toroidal mode Alfvén waves in the magnetosphere are characterized by an electric field perturbation in the radial direction, the simultaneous presence of pulsations in both components indicates that a field line resonance (FLR) was driven by compressional pulsations. The ground H component at the station conjugate to Polar and the radial electric field perturbation at Polar oscillated with a great similarity without a phase delay. From an analysis of the ground-satellite data, we suggest that the ground perturbations are associated with toroidal mode Alfvén waves rather than compressional mode propagating across magnetic field lines. In addition, we discuss the source of the compressional perturbations observed at Polar using solar wind and geosynchronous data.
Seafloor displacement at Kumano-nada caused by the 2004 off Kii Peninsula earthquakes, detected through repeated GPS/Acoustic surveys
Authors: Kido Motoyuki , Fujimoto Hiromi , Miura Satoshi , Osada Yukihito , Tsuka Kentaro , Tabei Takao 
Published: August 2014

AbstractIn 2004, we started monitoring crustal deformation at Kumano-nada in the Nankai trough using the GPS/Acoustic technique. We observed a large southward seafloor displacement of ∼30 cm associated with the off Kii Peninsula earthquake, which occurred in September 2004, between our two survey campaigns in August and November 2004. The observed seafloor displacement is larger than that predicted from a slip model derived solely from GPS measurements on land. This may indicate the earthquake fault is slightly shallower and extends move to the NW than previously estimated.
EISCAT observational results during the DELTA campaign
Authors: Nozawa S. , Ogawa Y. , Brekke A. , Tsuda T. , Hall C. M. , Miyaoka H. , Kurihara J. , Abe T. , Fujii R. 
Published: August 2014

Abstract
This paper aims at describing the ionospheric conditions during the DELTA (Dynamics and Energetics of the Lower Thermosphere in Aurora) campaign period based on EISCAT radar observations conducted at Tromsø (69.6°N, 19.2°E). We conducted EISCAT UHF radar observations on December 5 and from December 8 to December 13, 2004 with a beam-scanning mode for a total of 74 hours. Except for December 8 during a 2 hr interval operation, we operated the EISCAT UHF radar for 12 hour intervals everyday to make it possible to derive semidiurnal tidal amplitudes and phases in the lower thermosphere. Observed electron densities and derived electric fields by the EISCAT UHF radar indicate that magnetospheric activity was high during the period from December 5 to 13 except for the night of December 13. Derived semidiurnal amplitudes during December 9–12, 2004 exhibited a day to day variation at and below 110 km, while the corresponding phase was relatively stable over the four days except for the zonal component on December 12. Neutral and electron temperatures measured by the DELTA rocket were compared with neutral/ion and electron temperatures from the EISCAT UHF radar observations. Comparison of neutral/ion temperatures show some agreement, while poor agreements were found for the electron temperature. Possible causes of the discrepancy are discussed.
A new model for the fault beneath the sedimentary basin in the 1891 Nobi earthquake
Authors: Nakano Masaru , Miyakoshi Jun’ichi , Yamaoka Koshun 
Published: August 2014

AbstractWe have investigated the geometry and detailed location of the Gifu-Ichinomiya (GI) fault, a buried fault considered to have ruptured during the 1891 Nobi earthquake. Based on an inversion of coseismic vertical displacements obtained by leveling surveys, we obtain an inclined fault plane showing a reverse fault-type mechanism, rather than the vertical fault plane assumed in previous models. The fault dips 60? to the east and its slip during the earthquake is estimated to have been 1.48 m along the fault dip. The fault is located 5 km east of the location assumed in the previous models. Recent earthquakes have been scattered along the new fault location, not the previously estimated one. Focal mechanisms of the earthquakes that have occurred around the fault are dominated by a reverse fault component, which is consistent with the focal mechanism of the GI fault obtained by the inversion of coseismic displacements. The seismic intensity distribution calculated using the new fault geometry and location explains well the distribution of observed damage caused by the 1891 Nobi earthquake.
Two parallel trench-normal fault planes within the Pacific slab associated with the 1994 and 2000 Kurile earthquakes as revealed by simultaneous relocation of their main shocks and aftershocks
Authors: Harada Tomoya , Ishibashi Katsuhiko 
Published: August 2014

Abstract
The 1994 Hokkaido-Toho-Oki (M
w 8.3) and the 2000 Nemuro-Hanto-Oki (M
w 6.8) earthquakes have been regarded as great/large intraslab events within the subducted Pacific plate along the southern Kurile trench. Determining which nodal planes of their mechanism solutions are actual fault planes and whether or not the 2000 event occurred on the southwestern extension of the 1994 fault plane have been problematic. In order to clarify these points, we examine the relative location of their main-shock and aftershock distributions accurately by simultaneous relocation of their hypocenters using the Modified Joint Hypocenter Determination (MJHD) method. The result clearly shows that the two earthquakes occurred on trench-normal shallow-dipping fault planes within the Pacific slab, apart from and parallel to each other. Therefore, the 2000 earthquake was not a rupture on the deeper extension of the 1994 fault plane, but one on another fault plane. A large intraslab earthquake (M
w 7.8; depth, about 100 km) occurred to the northwest of the 1994 event in 1978, and two trench-normal fracture zones exist outside the trench to the southeast of the 1994 and 2000 events. Therefore, these three intraslab great/large earthquakes are considered to have been ruptures along pre-existing trench-normal weak zones within the subducted Pacific plate.
Substorm time scales from polar cap convection measurements
Authors: Jayachandran P. T. , MacDougall J. W. 
Published: August 2014

Abstract
A recent study by Jayachandran et al. (Geophys. Res. Lett., 30, 2064, 2003) reported repeated and detectable changes in the polar cap convection associated with substorms. We report here our use of ionospheric convection measurements to determine the time scales of growth, expansion, and recovery/reconfiguration associated with the substorms. The average time scales, determined from polar cap convection, associated with growth, expansion, and recovery are 31.6, 22.4, and 38.8 min, respectively. A comparison of the growth and expansion time scales determined from the convection measurements with those determined from the geosynchronous satellite measurements revealed interesting differences. The growth time scale determined from the ionospheric convection measurement is smaller than that of the time scale determined from geosynchronous measurements, whereas the expansion time scale determined using the ionospheric convection is much larger than that of the time scale determined using the geosynchronous measurements. The implications of the results in the Magnetosphere-Ionosphere (M-I) coupling are discussed.
Surface wave propagation in a fluid saturated incompressible porous half-space lying under two layers of different liquids
Authors: Kumar Rajneesh , Hundal B. S. 
Published: August 2014

Abstract
A study of surface wave propagation in a fluid saturated incompressible porous half-space lying under a double-layer consisting of non-homogeneous and homogeneous liquids is presented. The frequency equation connecting the phase velocity with wave number is derived. Special cases as: (i) Rayleigh type surface waves in an incompressible poro-elastic half-space lying under a uniform layer of a homogeneous liquid, (ii) Rayleigh type surface waves in an incompressible poro-elastic half-space lying under a uniform layer of a non-homogeneous liquid and (iii) Rayleigh type surface waves propagating along the free surface of a fluid saturated incompressible porous elastic half-space, are investigated. Numerical results with graphical presentations of the variations of phase velocity with wave number for different cases are also included.