Vol.9 No.2 2016

Research paper : Development of rock deformation techniques under high-pressure and high-temperature conditions (Koji MASUDA)−110−Synthesiology - English edition Vol.9 No.2 (2016) fault history and tsunami deposits, as well as research on quickly detecting abnormalities through continuous monitoring of crustal changes, can be easily understood by the general public, perhaps largely because of frequent media exposure. Therefore, although you already address this issue in Paragraph 2 of the Introduction, I think the readers’ understanding will increase if you include a diagram showing the various research (technological) components of earthquake research and the role of each component in earthquake forecasting; in particular, the diagram should show where refinement of the forecast model through high-temperature and high-pressure rock deformation experiments fits in the overall research scheme, and how they can contribute to better earthquake forecasts.Answer (Koji Masuda)I added Fig. 1, which summarizes the current flow of the earthquake forecast research, based on information in existing textbooks. I also added my own thoughts on the position of various research components and of rock experiments in particular in this research flow.3 Research scenarioComment (Chikao Kurimoto)I think that a diagram that organizes the working hypothesis and the development and integration of the component technologies into the research scenario leading to the proposal of the new concept would deepen the readers’ understanding.Answer (Koji Masuda)I combined photographs of actual rock samples and the experimental apparatus to show the research scenario in Fig. 3. I arranged the photographs to enhance the readers’ understanding of how the whole research effort contributes to earthquake forecasts.4 History of research and overseas technological advancesQuestion (Toshimi Shimizu)You give us an explanation of the history of the rock deformation experimental devices, but what is the current situation overseas? If the same rock samples were used, can you tell us what the advantages would be if analyses were performed with the devices developed by other countries? Shale gas, which is an unconventional source of natural gas that is in the news right now, can be collected from shale strata, but are the oil companies still interested in and working on rock experiments? Related to this, please tell us about international collaborations or frameworks, if any exist, and about any work on the international standardization of rock deformation experiments.Answer (Koji Masuda)There aren’t many different features or advantages of the devices developed by other countries that should be particularly described with respect to their basic performance and capabilities. Nor is there any particular organization that promotes international collaboration. This is in contrast to worldwide collaboration with regard to the observation of earthquakes and tsunamis.As I wrote in the history section of this paper, the people of Shell Technology Center in Houston, USA, carried out research and developed a device for rock experiments during the early stages of shale gas research. Rock experiments are being actively conducted at oil companies currently. However, the shale gas that these companies are interested in developing is found at a much shallower depth than that at which many earthquakes we are interested in occur, and technologically speaking, devices developed specifically for earthquake research are better able to reproduce the necessary high-temperature and high-pressure conditions.5 Mechanism of earthquake occurrence and rock deformationComment (Toshimi Shimizu)I understand that an earthquake is a fracture phenomenon that occurs when a force applied to the buried bedrock surpasses the fracture strength of the rock. On the other hand, earthquakes are often discussed at macro-scale in terms of the release of stress between the plates with thicknesses of tens of kilometers that cover the surface of the earth. For general readers, discussions of the causes of earthquakes involve everything from nanometer- to micrometer-scale rock fractures to macro-scale stress release by tectonic plates, and this scale gap gives rise to confusion. In this research, since the objective is the reproduction of fault movement occurring deep underground and the clarification of fault movement processes, I suggest you prepare a diagram that enhances the readers’ understanding of the spatial scale, for example, by combining Figs. 2 and 5 into a single diagram and adding a scale, such as kilometers, meters, micrometers, nanometers, and so on, to each diagram, as well as adding explanatory text for technical terms such as friction, slip, fracture, water molecule, mineral crystals, and others.Answer (Koji Masuda)The objective of Fig. 2 is to show the essential reason why a rock experiment is conducted in the first place. Here, it is not merely a downscaling of fault movement, and spatial scale is not the issue. With this figure, I wanted to emphasize that rock experiments are performed to determine the essence of this natural phenomenon and to extract and verify the factors involved. I modified the diagram and caption to make this point easier to understand. On the other hand, Fig. 5 is a diagram that shows how, by shifting the spatial scale, an investigation of fault movement becomes an investigation of micro-mechanisms. I modified the diagram and its explanation to clarify and improve the readers’ understanding of the spatial scale argument.6 Proposal of a new conceptComment (Chikao Kurimoto)You mention a contribution to the refinement of simulations of earthquake occurrences and the transmission of accurate information to society. In view of the latest related research trends, can you describe the present position and contribution of this research, as well as its prospective contribution, to such simulations?Answer (Koji Masuda)In this study, we demonstrated an important mechanism that explains earthquake occurrence processes that cannot be directly observed at a normal timescale. I stated in Chapter 5 that, in the future, these processes must be incorporated into a numerical model, and the necessary parameter values and their dependence on environmental characteristics such as temperature and pressure must be clarified.7 Materials testing deviceQuestion (Toshimi Shimizu)In tests of materials such as plastics, ceramics, metals, wood, and concrete, diverse forces in addition to compression are applied, such as tension, bending, and torsion, and mechanical characteristics such as strength, elasticity, and hardness are measured up until fracture occurs. In contrast, for rocks in a deep underground environment, it is necessary to consider a non-hydrostatic pressure system in which various types of pressure are applied from various directions, and I imagine that various types of controls are necessary to apply such pressure. Therefore, can


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