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Fault-related-folding structure and reflection seismic sections. Construction of earth model using balanced cross section; Danso ga kaizaisuru shukyoku kozo no keitai to jishin tansa danmen. 1. Balanced cross section wo mochiita chika model no kochiku  

Energy Technology Data Exchange (ETDEWEB)

Pre-stacking depth migration treatment is studied for the estimation of the fold configuration from seismic survey cross sections. The estimation of a velocity structure is necessary for the execution of such treatment, and the utilization of structural-geological knowledge is required for its interpretation. The concept of balanced cross section in relation to the fault-bend fold constructs a stratum structure model under conditions that the deformation during fold and fault formation is a planar strain, that there is no change in volume due to deformation, and that a fold is a parallel fold. In addition to the above geometric and kinetic approach, there is another fold formation process simulation model using a Newtonian fluid for study from the viewpoint of dynamics. This simulation stands on the presumption that the boundary contains a ramp that had been in presence before fold formation and that an incompressible viscous matter is mounted on the top surface. The viscous matter ...

1997-05-27

2

Shallow seismic reflection prospecting in Hachiro-kata reclaimed land; Hachirogata kantakuchi ni okeru senbu hanshaho jishin tansa  

Energy Technology Data Exchange (ETDEWEB)

Along the Japan Sea coast in Akita Prefecture and in the vicinity, there exist active fault groups, such as the Kitayuri thrust fault group in the south and Noshiro thrust fault group in the north. It is estimated that there is another fault, running from Akita City located between the above-said two thrust fault groups into the Hachiro-kata reclaimed land, roughly connecting the two thrust fault groups. This third fault is supposed to be related to the hypocenter of Tencho Earthquake of 830, but its location and structural configuration are not known, and it is not known whether it is an active fault, either. Investigations are conducted using S- and P-waves. The greatest problem in the use of P-waves is that there exists a layer in which signal attenuation is high and transmission is anomalously slow. This problem is ascribed to the layer pore water rendered unsaturated though slightly by the inclusion of air bubbles, and is explained for the most part by the White model. A survey ...

1997-05-27

3

Near-surface 3D reflections seismic survey; Sanjigen senso hanshaho jishin tansa  

Energy Technology Data Exchange (ETDEWEB)

Faults are being actively investigated across Japan since the Great Hanshin-Awaji Earthquake. Discussed in this report is the application of the 3D near-surface reflection seismic survey in big cities. Data from trenching and drilling is used for the geological interpretation of the surroundings of a fault, and the reflection seismic survey is used to identify the position, etc., of the fault. In this article, when the results obtained from the experimental field are examined, it is found that the conventional 2D imaging reflection survey betrays the limit of its capability when the geological structure is complicated, that the 3D reflection seismic survey, on the contrary, is capable of high-precision imaging and, when augmented by drilling, etc., becomes capable of a more detailed interpretation, and that it also contributes effectively to the improvement of local disaster prevention in big cities. Using as the model the Tachikawa fault that runs near JR Tachikawa Station, embodiment ...

1997-05-27

4

High resolution seismic refraction method with multichannel digital data acquisition system; Digital ta channel sokutei system wo mochiita koseido kussetsuho jishin tansa  

Energy Technology Data Exchange (ETDEWEB)

This paper introduces a multichannel digital data acquisition system and examples of measurements with the system in seismic exploration using the high resolution seismic refraction method. The high resolution seismic refraction system performs analyses nearly automatically by using a computer after initial travel time has been read. Therefore, the system requires high-accuracy travel time data, for which a multichannel digital measuring instrument developed recently for seismic exploration using the refraction method has been used for the measurement. The specification specifies the number of channels at 144 as a maximum, a sampling time of 62.5 {mu}sec to 4 m sec, the maximum number of sampling of 80,000 samples, and gain accuracy of {plus_minus} 1%. The system was used for surveying a tunnel having a maximum soil cover of about 800 m. The traverse line length is about 6 km, the distance between vibration receiving points is 50 m, and the number of vibration receiving points is 194. ...

1997-05-27

5

Visualization of strong around motion calculated from the numerical simulation of Hyogo-ken Nanbu earthquake; Suchi simulation de miru Hyogoken nanbu jishin no kyoshindo  

Energy Technology Data Exchange (ETDEWEB)

Hyogo-ken Nanbu earthquake with a focus in the Akashi straits has given huge earthquake damages in and around Awaji Island and Kobe City in 1995. It is clear that the basement structure, which is steeply deepened at Kobe City from Rokko Mountains towards the coast, and the focus under this related closely to the local generation of strong ground motion. Generation process of the strong ground motion was discussed using 2D and 3D numerical simulation methods. The 3D pseudospectral method was used for the calculation. Space of 51.2km{times}25.6km{times}25.6km was selected for the calculation. This space was discretized with the lattice interval of 200m. Consequently, it was found that the basement structure with a steeply deepened basement, soft and weak geological structure thickly deposited on the basement, and earthquake faults running under the boundary of base rock and sediments related greatly to the generation of strong ground motion. Numerical simulation can be expected to ...

1996-10-01

6

Seismic response of pile-supported structure considering nonlinearity of superstructure and pile, and liquefaction of surrounding ground; Shuhen jiban no ekijoka oyobi kui no hisenkeisei wo koryoshita kui shiji tatemono no jishin oto kaiseki  

Energy Technology Data Exchange (ETDEWEB)

Recent earthquake disasters have revealed the importance of countermeasures against soil Liquefaction in seismic design. In particular, the 1995 Hyogoken Nanbu earthquake caused several types of severe damages to pile foundations. This paper describes an analysis method for soil liquefaction using simple parameters such as SPT-N values and seismic response analyses for the pile-supported structure to consider soil-structure interaction effects and soil non-linearity using a modified Penzien model. It is important to find a way to determine the region of surrounding soil whose behavior is identical to that of piles. This paper adopts the thin layer element method to systematically determine the volume of the surrounding soil. The responses of pile-supported structure are similar, whether soil liquefaction and nonlinearity of pile are considered or not. However, the bending moment of pile become large as to soil liquefaction, and small as to nonlinearity of pile. (author)

2000-01-10

7

Data processing for the mise-a-la-masse survey; Ryuden den`iho tansa no data shori  

Energy Technology Data Exchange (ETDEWEB)

Data processing method was studied for mise-a-la-masse survey. Mise-a-la-masse method using wells as current sources measures resultant ground surface potential difference, and detects underground local resistivity anomaly. To extract resistivity anomaly largely different from surroundings, the anomaly is extracted as difference between the estimated value of regular resistivity structure (background) and potential difference or apparent resistivity. The following three approximations were attempted to estimate the background: the theoretical equation assuming isotropic homogeneous resistivity structure, that assuming horizontal multi-layered structure and the exponential function of distance from linear electrode for apparent resistivity, and these were compared with each other by numerical model experiment. The data processing method which determines the resistivity structure of the background and the residual of apparent resistivity distribution by inversion analysis using the above ...

1996-10-01

8

Borehole geophysics for delineating the geological structure in the Sakonishi prospect, the Hida area, Japan; Hida chiiki Sako nishi chiku ni okeru boring ko riyo butsuri tansa ni yoru chishitsu kozo kaiseki  

Energy Technology Data Exchange (ETDEWEB)

In order to discuss effectiveness of physical exploration in the Sakonishi prospect in the Hida area, physical exploration was carried out by utilizing bored wells. This area contains the Kamioka mine, one of the major base metal mines in Japan, where electrical exploration has been attempted several times in the past. No effective results have been obtained, however, because specific resistance contrast between mine beds and base rocks is too small, and the topography is too steep making site workability inferior. As part of the investigations on geological structures over wide areas, electrical logging (specific resistance and natural potential) was performed in fiscal 1995 and 1996 by utilizing the boreholes. Induced polarization logging was also conducted on the same boreholes. A traverse line on the ground with a length of 600 m and boreholes were used to execute specific resistance tomography. Clear extraction was possible on a fault structure which is thought related with ...

1997-05-27