The Ministry of Land, Infrastructure, and Transport has been adopted “knowledge” and “imagination and applied force” as the bidding evaluation criteria for bidding scoring. Based on these criteria, we will consider the history the exploration geophysics and we try to predict the future technological development. Technical ingenuity and innovation at the core of “imagination and applied force” can be recognized to be stylized, popularization, obsolescence through the field applications. In addition, hints of innovation are obtained through historical study. The science is becoming fragmented individually, however, the technology involved in the Earth system must be necessary considering the whole human life and activities in the Earth. Attaches great importance to this not only “knowledge” expansion, it should strive to create customers of a wide range of fields that require technology innovations. Consider as an example the expansion and progress of Geological Survey of Japan, and the creation of civil engineering exploration geophysics by Dr. Toru Watanabe, the history of (elastic wave exploration in particular) exploration geophysical methods in Japan is investigated with the comparison to the world. As a result, the history of ideas and the spread of civil engineering exploration geophysics of technology have been revealed as the oriented practice with purpose, the import of foreign technology, and the technical progresses have achieved Dr. Watanabe. Some differences in deep and shallow exploration targets but, for comparison, studying the history of exploration geophysics in resource development the technology revolution occurs at 30 year each. (1) In the early years of the 1930s, technology development field-oriented (2) In the 1960s, innovation in processing and recording technology by the development of digital equipment. And by improving the quality of that artifact information, “seismic stratigraphy” has been developed for the interpretation and evaluation of the data. (3) In the 1990s, the three-dimensional seismic survey including visualization techniques by improving electronic devices had realized. Also the realization of geological formation properties such as representation by inversion processing was achieved. On the other hand, in civil engineering exploration geophysics, technical development during this period was great, however, it is a loss to the realization of the excess demand items to technical provider and the difficulty of new customer acquisitions. The expected 2020 innovation of the next, in that realization, technological development that reflects (1) directly the purpose of the analysis and evaluation of artifacts, (2) positive attitude to innovation of technology themselves, and (3) the overcoming “travel time” and “body waves” and breaking down the narrow frame of exploration geophysics are required.
In the North America, enormous natural gas and light crude oil production became possible by dissolving or cracking the petroleum source rock, shale, which was said not to become the resources until the 20th century. The influence of “the shale gas revolution” that caused a dramatic change for world energy policy, industry, the issue of security is commented.
The Society of Exploration Geophysicists Japan (SEGJ) was established in 1948. SEGJ has reached its 65th anniversary in this year. Research and development as for exploration geophysics have been performed to support various social needs until now. We can now handle enormous data by adopting advanced electronics and computer technology. As a result, three-dimensional and four-dimensional explorations have been enabled. The Japanese energy policy is standing at a turning point since the East Japan Earthquake disasters. On the other hand, our expectation increases for new mineral and energy resources such as methane hydrate and rare earth elements. However, the uneasiness to security by the deterioration is actualized such as the ceiling collapse accident in the Sasago Tunnel when we turn interest to social infrastructural facilities. Natural disasters diversify from deep-seated slope failures, landslides to abnormal weather events in recent years. Furthermore it is concerned about the Nankai Trough mega earthquake or the directly Tokyo area earthquake. We performed the panel discussion by four researchers or engineers to study about how we can contribute using exploration geophysics in such complicated situation surrounding Japan. We discussed the prospects in the future of SEGJ which reaches the 75th anniversary ten years later. The topics were offered from the four panelists on the viewing points of innovation, social needs, personnel training and sustainable society. Active discussion was accomplished from the audience. We discussed about the following suggestions ; social needs are opportunities of the innovation ; clear explanation about the applicability of the geophysical exploration is necessary on the viewpoint of the users ; we must find engineers from overall natural science widely without limiting to geoscience ; it is important to visualize subsurface using the continuous monitoring.
Zero offset VSP measurements were carried out at the Nagaoka CO2 injection site, Japan. Waveforms were observed in two wells (OB-2 and OB-4) where CO2 breakthrough had been observed by time-lapse logging. Basic data processing including spherical divergence correction, up and down wavefield separation, wave-shaping deconvolution and corridor stacking was carried out for observed seismograms. The processed seismograms were in good agreement with the synthetic seismograms calculated from an acoustic impedance model based on logging data. By giving 28msec time delay to the 3D seismic survey data at the well location, good agreements were recognized inmany reflections between the VSP seismograms and the seismic images of the 3D surface seismic survey. By assuming the time shift above, the 3D structure of the CO2 reservoir was estimated over the survey area, with spatial variations of the formation distribution and thickness. The VSP survey is thus useful for better understanding the CO2 reservoir, by linking two complementary imaging results: well log data that gives high resolution but spot-localized images, and 3D surface seismic observation data that gives wide-ranged but crude images. The difference between the amplitudes of the synthetic seismograms from logging data before and after CO2 injection was clearly changed at the depth of CO2 trapped depth. These results indicate that if the VSP data had been acquired before CO2 injection, a comparison with baseline and repeated VSP survey would have been able to suggest its applicability to estimate the CO2 plume extent.
Previous studies of artificial bedrock with self-repair ability in coastal area have indicated the important of building coastal levees at low cost with minimal environment load. The goal is to form the extreme artificial bedrock using natural materials (e.g., microbes, sand, shell, pieces of coral, and seaweed etc.) in a short time that can tolerate climate conditions. Most studies have focused on beachrocks in tropical and subtropical coral reef coastal areas, but little research has been done on the subsurface structure. Therefore, we performed both a DC electrical survey and a surface wave survey along the same lines to elucidate the subsurface structure of beachrocks in the coastal area of Okinawa Prefecture, Japan. In addition, we measured the physical properties of the beachrock sample collected from the survey lines by laboratory tests. As the results, both the resistivity and the shear wave velocity of the beachrock were higher than those of the underlying unconsolidated sand layer. Furthermore, the beachrock is up to approximately 1 m thick, increasing toward the coastline.
In order to investigate existence of buried objects and shallow subsurface structure, archaeological prospecting using Ground Penetrating Radar (GPR) was conducted at Antokudai ruins in Nakagawa town, Fukuoka prefecture, Japan. The total survey area is approximately 2,800m2 and GPR surveys using Noggin Smart Cart System were carried out at Area-A, Area-B and Area-C. The result of GPR survey at Area-A that obvious anomalies were observed is described in this paper. A large anomalous zone where is 0.2m higher than surrounded area can be detected at 0.2m depth by depth slice maps of shallower depth. This anomalous zone is considered as an ancient compartment of dwelling site. There are two anomalous groups that are composed of equal-spaced (5.5m) anomalies at 0.9m depth. The diameters of small anomalies are almost same and approximately 1.0m. There are also three groups of anomalies inside the large anomalous zone. The each size of inside anomalies is almost same as anomalies of surrounding anomalous groups. These small anomalies are considered pillar marks or cornerstones for ancient buildings. From an archaeological point of view, there was a large construction at the northern part of Area-A.
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