The purpose of our study is to evaluate the applicability of the seismic interferometry to P coda waves between first arrivals of P-wave and S-wave of local earthquakes in order to extract reflection signals and obtain reflection profiles. Our continuous observation with the dense seismometer array was carried out for about four months from December 2010 to April 2011 at Narita area in Chiba, Japan. At first of the data analysis, seismic event data of local earthquakes satisfying some conditions were extracted from the continuous record based on the unified earthquake catalog of Japan Meteorological Agency, then 437 seismic records were selected after the quality check with manual pick of P and S wave first arrivals. Second, the virtual reflection seismic data were generated from the P coda waves by applying the two types of interferometry, the correlation type and the deconvolution type. Finally, PP reflection profiles were obtained by following the conventional data processing for the pseudo reflection seismic data. In our results, the virtual source records with clear reflection from basin bottom could be generated. Then, the high-resolution PP reflection profiles were obtained along 1 km array with dense receiver deployment, and deep reflections were recognized on the section of the 5 km array with sparse receiver deployment. The deconvolution type interferometry was better than correlation type to apply to natural earthquakes because of ability to eliminate the effect of different source mechanism. We can conclude that the seismic interferometric is useful for subsurface imaging of sedimentary layers and basin structures from the P coda waves of local earthquakes.

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 The stepped-frequency continuous wave (SFCW) ground penetrating radar (GPR) combined with wideband bow tie antennas and a handheld vector network analyzer (VNA) is successfully demonstrated and compared with three types of commercial pulse GPRs for the detection and identification of the buried targets at depths of 20 cm, 80 cm and 2.5 m. It has the performance of the better signal to clutter ratio than all of the tested commercial pulse GPRs for the metal pipe at a depth of 20 cm and also the better range and azimuth resolutions than the pulse GPR having a center frequency of 250 MHz. We conclude that the proposed SFCW GPR has a great potential to meet the conflicting needs of deeper penetration and high resolution.

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 Kitsunezaki (2015) proposed a theoretical model on gravity change due to thermal expansion source. Some basic problems could not be discussed sufficiently there. In this paper, we systematically supplement them in two issues. The first issue is gravity change due to a minute expansion source in a semi-infinite elastic solid. The second issue is gravity change due to a minute thermal expansion source in a semi-infinite permeable water-saturated porous medium. At first, outline of analysis process of the first issue is illustrated to make clear its basic concept, following Hagiwara (1977). This provides a base to solve the second issue. An incorrect expression in the former paper is also revised in the discussion of the second issue.

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 We have explored S-wave velocity structures of Kazo lowland in central part of the Kanto plain through microtremor survey method. Dimensions of the exploration area are east-west about 20km by north-south about 15km. Spatial autocorrelation (SPAC) technique has been employed to estimate Rayleigh wave phase velocities. The S-wave velocity structures have been estimated through inversion analyses of observed phase velocities with genetic algorisms (GA). According to some previous knowledge, it has been predicted that the maximum depth of the basement surface reach to about three kilometers. We have therefore deployed three types of circular arrays whose radii are 600m, 300m and 100m on each observation site. Creating initial structure models for the GA inversions, we have employed velocity structure models that had been created for the earthquake disaster prevention plan.
 The result shows that many of estimated basement depth are analogous to the gravity contour of the Kazo lowland which had been examined by GSJ, AIST. However, as estimated basement depth of several sites didn't accord with the gravity contour, it suggests that the further consideration for making precise velocity models will need.

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 With the spread of small unmanned aerial vehicle (UAV) equipped with a digital camera (UAS: unmanned aerial system), it has been facilitated to acquire multi-view aerial images. Whereas, the technique of Structure-from-Motion Multi-View Stereo photogrammetry (SfM-MVS) has also been developed to enable the creation of three-dimensional models of targets including landforms and objects on the land surface from a large number of stereo-pair images. The combined use of these UAS and SfM, i.e., the photogrammetry of low-altitude aerial images, has enhanced topographical measurements of landforms and ground objects in a variety of fields. In this paper, we outline the overviews of UAS as a platform and SfM as measurement technique, and then introduce some examples of applied topographic measurements by SfM based on the aerial imaging with UAS. Thus, the low price and easy operation of UAS-SfM technique have allowed rapid acquisition of high-definition three-dimensional data of landforms and ground objects based on the aerial measurement, as well as the change detection of such objects, for any researchers and practitioners. Therefore the method has a large potential to be effectively used as the basic data acquisition and analysis for geophysical surveys. In addition, it is desirable to perform such high-definition topographic measurements with careful examination of optimized resolution and reasonable accuracy by the scale and the purpose of the phenomenon of interest.

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[in Japanese]

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[in Japanese]

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