The availability of a large amount of TEC data derived from dual frequency GPS measurements observed by GPS reference networks provides a great opportunity for ionosphere studies. In order to obtain better accuracy for the derived TEC, a data smoothing technique is usually employed to take advantage of both code pseudorange and carrier phase GPS measurements. The precision of TEC data therefore is dependent on the smoothing approach. However little work has been done to evaluate the precision of the smoothed TEC data obtained from different smoothing approaches. This investigation examines the properties of two popularly used smoothing approaches and develops the closed-form formulas for estimating the precision of the smoothed TEC data. In addition, a previously proposed approximate formula for estimating TEC precision is also evaluated against its closed-form formula developed in this paper. The TEC precisions derived from the closed-form precision estimation formulas for approaches I and II are analyzed in a numerical test. The results suggest that approach II outperforms approach I and the precision of TEC data smoothed by approach II is higher than approach I. For approach I, a numerical test is also conducted to compare the precision difference between the closed-form and approximate formulas for estimating TEC precision. The comparison indicates that TEC derived from the closed-form formula have better precisions than the approximate formula. Analysis also reminds users that extra cautions should be taken when using the approximate formula in order to avoid the precision divergence phenomenon.

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In recent years an increasing interest in the studies on outlier can be observed, however, for the time being there exists no general definition of outlier. In the present paper we introduced a generic descriptive definition of outlier. We observed that the outlier problems had so far been treated in statistical way without paying proper attention to probabilistic-theoretic backgrounds. In view of this gap, we made an attempt to establish a probabilistic background theory. Within this framework, the large deviations are considered as probabilistic-theoretic model of outlier, and the interrelationship of the laws of large numbers, the central limit theorems and the large deviations are clarified. These considerations are specialized for the case of statistical sample, which is important from the point of view of the assessment of data quality. Some methodological and historical aspects of geodesy, geophysics and astronomy are mentioned, too. We revealed that the data analysis carried out by Kepler in the process of discovery of his famous elliptic law of planetary motion has relevance to the outlier problem. This methodologically interesting fact is a new result in the history of geosciences. We established that the accuracy of Chebyshev inequality increases as the deviation of the random variable involved from its expectation, increases. The possibility of application of Chebyshev inequality to the outlier problem is pointed out.

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We applied a 3-D seismic tomography inversion algorithm to arrival-time data obtained, during 18 years from 1985 to 2002, from local seismic networks and aftershock studies in the Marmara region, in order to better understand the upper crustal structure of the complex tectonic region. We integrated all the available data set into a common data set and relocated the events, using a 1-D velocity model. We then selected 3, 949 earthquakes and obtained 92355 arrival times, in total, consisting of 59, 313 P-wave and 33, 042 S-wave arrival times. In this paper we present detailed crustal structures for V_p, V_s and V_p/V_s ratios from the surface down to 15 km depth with good resolution in terms of the hit count analysis of seismic rays, the checkerboard and restoring resolution tests for the studied region. The results obtained from the inversion suggest that the western part of the North Anatolian Fault Zone shows strong lateral heterogeneity. We concluded that no clear pattern exists between the distribution of microearthquakes and aftershocks and the velocity perturbations presented in this paper. This is probably due to complex tectonic and geological structures. Large coseismic slip associated with the two recent strong earthquakes was found to correspond to higher velocity anomalies, as was often found recently. On the other hand, low velocity values correspond to the sedimentary units or the alluvium regions, as supported by the low resistivity and gravity values. Thus the results presented in this paper are quite consistent with the other data such as gravity, resistivity and magnetic anomalies, indicating that our model is reliable and efficient and it should be useful for further interpretation of tectonic and geological problems in this region. It should be pointed out, however, that the results of S-wave perturbations and V_p/V_s ratio could not be discussed in detail because of insufficient quality of the S-wave data and the reliability of the results is not very high. Nonetheless, the fact that recent large Izmit earthquake and moderate aftershocks that occurred in or around the high velocity zones near the low velocity region suggests that high velocity regions found in the area close to Istanbul in the Marmara Sea and also at the Iznik-Mekece fault are potential sites for strain energy accumulation and release.

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The crustal structure beneath southwest Japan is investigated through waveform modellings of four local crustal earthquakes by using the generalized ray theory. High-quality seismograms recorded by the Hi-net seismic network are used. The focal mechanism solutions of the events used are estimated by using the first P-wave polarity data. Twenty-nine paths are used to characterize the crustal waveguide in SW Japan. Optimal 1-D velocity models for different paths are derived individually by waveform modelling. Synthetic tests are conducted to study the effects of different model parameters and to confirm the focal mechanism solutions. Modelling the waveforms individually is proven applicable for the heterogeneous regions. The resulted synthetics match the observed seismograms well. Considerable variations of the Conrad and Moho depths are found in the study area. The Conrad depth ranges from 14.8 to 19.7 km, and the Moho depth ranges from 28.4 to 33.4 km. Considerable variations in the crustal structure are found for the eastern portion of the study area where Biwa Lake lies. The effects of Biwa Lake on different paths are examined in detail.

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The 2000 Tottori-ken Seibu earthquake (M_W6.6) occurred in Tottori prefecture, western Japan on October 6, 2000. We conducted aftershock observation and analyzed S-wave anisotropy using the aftershocks M_JMA2.0 to 3.5 observed at two stations near the aftershock region. The fast S-waves are polarized to almost E-W direction, which corresponds to the P-axis direction of the mainshock. The delay time of the split S-waves ranges between 20 and 100 ms. The crack density inside and outside the aftershock area is estimated from the delay time. The distribution of crack density shows a strong spatial variation and depends on the ratio of the path length inside the aftershock region against the whole path length. Assuming a uniform distribution of anisotropy inside and outside the aftershock region, the crack densities inside and outside are 0.017 and 0.007, respectively. It thus seems probable that in the aftershock region the distribution of cracks is intensive and cracks are opened due to the presence of fluids in seismogenic layers. This considerable spatial variation of anisotropy between inside and outside the aftershock region suggests that the aftershock region may have different mechanical properties from the surrounding area.

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The acoustic basement map of the East China Sea, established by the Shanghai Offshore Petroleum Bureau with all available industry seismic data, shows the existence of a 30-km-wide, 10-km-deep basin, that we named the Ho Basin. The Ho Basin belongs to a series of elongated deep basins extending over 600 km east of the Taiwan-Sinzi Ridge and flanked to the East by a ridge named the Longwan Ridge in its northern part. This new system of basin and ridge was probably formed during middle Miocene, sometimes in between rifting episodes occurring in the Taipei Basin and Okinawa Trough. It complements the already defined system of five belts of backarc basins and associated arc volcanic ridges in the East China Sea, which are progressively younger from the Mainland China shoreline (late Cretaceous/early Tertiary) to the Okinawa Trough (Present). In order to determine the crustal thickness beneath the East China Sea continental shelf, we used a power spectrum method to calculate the depth of the top (Zt) and the centroid (Zo) of the magnetic basement by fitting a straight line through the high- and low-wave number portions of the power spectrum, respectively. Then, the depth of the base (Zb) is estimated from Zt and Zo. After optimizing the size of the data squares, we demonstrate that, except for basins more than 10 km deep, Zt corresponds to the basement depths and Zb, the depth of the Curie point, to the Moho depth. As wide-angle reflection and refraction data are scarce in the East China Sea, this method provides a way to characterize the crustal thickness of the East China Sea and to compute the theoretical heat flow values.

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A synoptic survey of Sudden Phase Anomalies (SPAs) observed in the phase variation measurements of 16 kHz VLF transmissions from Rugby (England) made at Visakhapatnam (India) has been carried out. These Sudden Ionospheric Disturbances caused during solar flares are examined in relation to flare time enhancements of X-ray radiation fluxes. It is found that nearly 81% of SPAs recorded have accompanying X-ray enhancements and in 80% of the cases Hα flares and microwave bursts also occur concurrently. Using SPA magnitudes and flare time X-ray flux values, the threshold level of X-ray flux to induce an SPA has been estimated as 1.5×10^-3 ergs/cm²/s. In majority of the events, the change in reflection height during the flare is observed to be less than 4 kms. Other SPA characteristics like onset times, growth and relaxation times etc. have also been studied. These results are consistent with those obtained for other propagation paths.

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Two kinds of sharply concentrated excess flux of cosmic rays from heliomagnetospheric nose and tail directions (right ascension α - 18 hours and -6 hours) are found by the analysis of sidereal daily variation of neutron intensity (median energy E_m - 20 GeV) on the ground. These fluxes do not show any response to the polarity reversal of solar magnetic field at the north pole and is contradictory to the simulation of the solar modulation of galactic anisotropy, which produces sidereal variation at the Earth greater in the negative polarity state than in the positive state. This indicates that they are not of the galactic origin and would be produced on the heliomagnetospheric nose and tail boundaries where it is considered that the interaction between the galactic and solar magnetic fields could produce the cosmic-ray acceleration. The acceleration mechanism producing the polarity-independent sidereal variation against solar modulation will be discussed.

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The Mid-Niigata earthquakes (mainshock: JMA M6.8, the largest aftershock: JMA M6.4) occurred on 23 October 2004 in the Shinano River fold and thrust zone, western margin of Northeast Japan. Two major Quaternary reverse fault systems, fault related to Higashiyama-Tamguiyama fold in western side and Muikamachi fault in eastern side, had already been mapped in aftershock area from the geological structure and tectonic morphostructure. These active fault and fold strike almost north-northeast-south-southwest. We investigated destructions of man-made structures and surface deformation using the releveling data by Geography Survey Institute. In turn, we examined about the origin of observed surface destructions from the compare with aftershock distribution. Our leveling and G.S.I leveling results indicate the deformation concordant with the Higashiyama-Tamugiyama fold and the offset along the a part of the northern half of Muikamachi fault. The vertical displacements are estimated to be ca. 70 cm and less than 20 cm, respectively. The surface destructions were identified almost only along the Suwatoge flexure (correlated to the eastern limb of the Higashiyama-Tamugiyama fold), Tagawa anticline, Obiro fault and Muikamachi fault. The shortening amounts were estimated to be ca. 16 cm at the Suwatoge flexure, less than 2 cm at the Tagawa anticline and ca. 8 cm at the Muikamachi fault from the compressional destruction of man-made structure. The maximum vertical displacement and shortening was appeared at the bottom of Suwatoge flexure. The Suwatoge flexure is located onto the shallower extension of the row of aftershocks which was correlated to main shock earthquake. The Muikamachi fault is located near the shallower extension of the source fault of the largest aftershock. The stress regime inferred from the character of the observed surface destructions is concordant with the trend of geological structure and focal mechanism solutions. The small compressional destructions of man-made structures are byproducts created by buried faulting and folding. Thus, the Higashiyama-Tamugiyama folding structure grew in association with the buried faulting in the 2004 earthquake. Key words: Tectonic surface destruction, active fold, buried fault, aftershock distribution.

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The observation of ULF/ELF electromagnetic emissions at Nakatsugawa, Gifu, has indicated that ULF emissions in the frequency below 0.1 Hz take place about two-three weeks before the 2004 Mid Niigata Prefecture earthquakes. The most important support to this is based on the goniometric direction finding for those ULF emissions in the period of October 2-6, which indicates their azimuth being very close to the epicenters of the earthquake. So, these ULF emissions on October 2-6 are likely to be associated with the 2004 Mid Niigata Prefecture earthquake.

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Following the Mid Niigata prefecture Earthquake (M_JMA 6.8) in 2004, 4 large aftershocks (M_JMA 6.3, 6.0, 6.5, 6.1) occurred: three within 40 minutes and one after 4 days. We examine the possibility for the triggering of this sequence of large aftershocks by static stress changes. For the close spatial triggering, it is important to have information about the fault geometries, slip distribution, and focal mechanisms. We determine the fault plane orientations from the aftershock distributions. Slip distributions of the mainshock and the largest aftershock are obtained by seismic waveform inversions of local strong-motion records. Mechanisms for the events are taken from MT solutions. The temporal variations of Coulomb failure function changes (ΔCFF) are calculated on the fault planes of the aftershocks before their rupture. Positive ΔCFF values (0.06-0.3 MPa) are obtained around the hypocenters on the fault planes, indicating the possibility that static triggering from the main event and following aftershocks can explain the occurrence of subsequent aftershocks.

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The 2004 off the Kii peninsula earthquakes (M_w 7.5 for the main shock) occurred within the subducting Philippine Sea (PHS) plate near its boundary, the Nankai trough, southwest Japan. The rupture mode of the foreshock-main shock-aftershock sequence was complicated, a combination of ENE-WSW striking (almost trough parallel) reverse faulting beneath the trough and NW-SE trending (almost trough normal) strike-slip faulting mostly on the landward side of the former. In this paper, we discuss the tectonic meaning of this NW-SE running strike-slip fault. We examined hypocenter distribution and focal mechanisms of slab earthquakes from October 1997 through September 2004 and confirmed a NW-SE striking tear of the PHS slab beneath the middle part of the Kii Peninsula pointed out by Miyoshi and Ishibashi (2004). According to the Earthquake Research Committee (2004) there is a NW-SE trending structural discontinuity in the PHS crust to the southeast of the main shock epicenter. Putting all features together, we interpret that there is a NW-SE striking fracture within the PHS plate continuously from the Nankai trough region to the slab beneath the Kii Peninsula, and that a partial rupture of this fracture occurred during the off the Kii peninsula earthquakes together with trough-parallel reverse faulting. It should be noted that two disastrous M 7-class slab earthquakes seem to have occurred along this tear beneath the peninsula in 1899 and 1952.

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The gravity inversion for the lunar crustal thickness needs three parameters: the crustal density, mantle density, and the reference radius of the crust-mantle boundary. The assumption of crust and mantle densities is found to significantly affect on the resultant crustal thickness variations. Moreover, the recent seismic analyses suggest the possibility of thinner crustal thickness around the Apollo 12 site than that proposed in the Apollo-era, on which the previous gravity inversions relied upon. Therefore the validity of the assumption used in previous gravity-inversion studies must be re-examined in detail. By using a simple three-layered mass model of the Moon including a uniform crust, mantle, and core, we determine possible combinations of the three parameters, satisfying the mass and moment of inertia constraints. The results show that the set of the parameters used in Neumann et al. (1996) can be consistent with mass and moment of inertia constraints, while those in Wieczorek and Phillips (1998) does not satisfy the constraints.

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High-resolution gravity anomalies on the surface of the Moon are determined from Lunar Prospector tracking data residuals. By means of a benchmark test the recovery method is validated with respect to the orbit determination and gravity field recovery strategy. Tracking data for the entire extended mission of Lunar Prospector, during which the satellite flew at an average altitude of 30 km above the lunar surface, have been completely and independently processed and orbits have been determined. Using tracking data residuals from these precise orbits, adjustments to the a priori gravity field model have been created for Mare Serenitatis. The results for Mare Serenitatis with the local recovery are comparable to global recovery results, yet faster and more efficient with a possibility to increase the resolution.

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The depth of the magma chamber is shown to be an important factor governing the initial type, scale, and collapse of a caldera. The collapse of the magma chamber is approximated by the contraction of a sphere in an elastic medium, and the distribution of plastic and/or rupturing area on the surface is calculated using the Coulomb failure criterion under the assumption of an elastic-perfectly plastic material. It is found that the necessary contraction for the formation of a caldera is described by fifth-power polynomial expression of the depth of the magma chamber, and that the radius and geometry of the caldera are dependent on the depth of the magma chamber.

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