Vol.6 No.3 2014
Research paper : Marine geological mapping project in the Okinawa area (K. ARAI et al.)−165−Synthesiology - English edition Vol.6 No.3 (2013) more surveys will be conducted in the Okinawa region in the future.Answer (Kohsaku Arai)The survey around Okinawa region has produced new geoscientific findings. Based on the situation with surrounding countries of Japan in recent years, I believe it is necessary to organize the basic geological information quickly. I hope to improve the efficiency of the organization while maintaining the quality of the AIST survey.2 Flow from collection to use of basic land information dataComment (Shigeko Togashi)For the “flow from collection to use of basic geological information data” and Fig. 4, I think you should add detailed information as a Synthesiology paper. Particularly, to the people outside the field, it is necessary to carefully explain the process by which the collected data become sedimentological or geological maps. For example, please add the explanation about the necessity of employing the latest knowledge of sedimentology, structural geology, geophysics, geochemistry, mineralogy, seismology, and others, to conduct interpretations of the sedimentation unique to the region, geological structure, or mineral deposition process. Please state clearly that sedimentological or geological maps are compiled by clarifying the geological phenomena of the target region by “synthesizing” the various “elemental technologies” based on a scientific scenario. Also, in Fig. 4, please indicate the process for integrating the disciplines you deem most important among the aforementioned “ologies” that are the keywords. For the “development of the submarine mineral resources,” please clarify what was the objective, how the method was selected, and what you found out. Please show the flow of what is necessary to be known in the future, what selection of methods must be made to achieve this, and what are the issues involved.Answer (Kohsaku Arai)I have added details of the flow of geological information from collection to use in marine geological maps. During survey cruises, many researchers are involved in the collection of data and samples, and a variety of academic specialties are required to analyze and interpret these data. Samples do not stay within AIST, but are distributed to the specialists in various universities and other institutions. The marine geological map series is the grand culmination of such efforts.3 “Uniform data”Comment (Shigeko Togashi)You use the expression “uniform data,” and since this is an important keyword of this paper, please elaborate on this point. When you say uniform, do you mean, for example, “the data is collected spatially in a systematic and comprehensive manner, the selection and collection methods of the data are done in some standardized way, or a certain level of quality is maintained”?Answer (Kohsaku Arai)I have added an explanation of this in section 2.4 Survey method of fault activity in the the seabedComment (Masahiro Seto)You mention that there are faults that intersect the island arc in the Ryukyu Arc and the upper part of its fore-arc slope. You also indicate the importance of the detailed survey of the fault activity. I think the methods for the survey and assessment of the submarine fault activities must be different from the methods on land. Is there technology and methodology established for surveying the submarine faults? If so, what are they?Answer (Kohsaku Arai)Many of the earth’s plate boundaries are in oceanic areas, along with associated faults that cause major earthquakes. Activity on these submarine faults may also cause tsunamis. AIST studies that assess these active faults consider them from this perspective. First, the distribution and form of active submarine faults are investigated using the seismic reflective profiler. However, estimating the activity and activity history of these faults may be more important than describing their distribution. Previous research investigating faults activity includes studies in which cores were collected on both sides of the active fault, allowing the history of fault activity to be inferred through comparative changes in sediment layer thicknesses. The activity history of submarine faults can also be derived from the frequency of seismic-related sediment structure (turbidites) occurring in columnar core samples. It is important to use the method appropriate for the individual regions for these surveys, and necessary to accumulate case studies on active submarine faults.5 Restriction caused by geological structures in locations of mineral depositsComment (Masahiro Seto)In general, which structure or phenomenon do you mean when you say, “the geological structure restricts the potential mineral deposition”?Answer (Kohsaku Arai)Potential hydrothermal activity is concentrated in the island arc volcano and the back-arc basin. In the back-arc basin, hydrothermal activity accompanies underground magmatic activity due to the formation of the back-arc rift zone in response to the tensile stress field. It is thought that the locations of structures that are continuous to considerable depths underground (e.g., faults) have high potential for mineral deposits.6 Characteristics of the marine geological survey of the Okinawa region and future developmentComment (Masahiro Seto)For the marine geological survey of the Okinawa region that started in 2008, what are the future plans for organizing and publishing the geological maps, and by when will they be done? Also, in organizing the geological maps, I think the originality of the researchers in charge is expressed. What differences in characteristics can we expect for the Okinawa region survey compared to the conventional marine geological survey?Answer (Kohsaku Arai)The survey is planned to continue until FY 2019. For the production of the geological maps, we are starting from the regions around Okinawa-jima and Kume-jima islands, where the surveys have already been completed. We hope to publish the maps as they are completed. The primary difference between this region and the other surveys conducted to date is the variation in geological structure, as described in this report. One particularly interesting characteristic that distinguishes this region from the four main islands is the lack of major rivers. Instead of land-derived siliciclastic material, this region is dominated by high bioclastic productivity and carbonate particles derived from coral reefs.