Muography. Группа авторов
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8 and 9). Part III explores the potential of muography to be applied to other geophysical and environmental applications, such as water management, resilient cities, climate action, and affordable or sustainable energy. Experts with practical experience describe how to apply muography to the exploration of underground water and karstic cave systems (Chapters 10 and 11), detection of underground cavities (Chapters 11 and 12), monitoring of glaciers and carbon capture storage sites (Chapters 13 and 14), as well as for applications in mineral exploration, mine geology, and geotechnical and mining engineering (Chapters 15 and 16). Part IV turns to recent technological developments for next‐generation muography, including compact muographic observation systems that are based on scintillators (Chapter 17), gaseous detectors (Chapters 18, 19, and 20), and nuclear emulsions (Chapter 21), which will provide optimal imaging resolution, operational reliability, and efficiency in the challenging natural environment of field operations.
This work aims to extend and deepen the knowledge of geophysicists, geologists, mining and mineral exploration professionals, volcanologists, and engineers about the applicability of muography. It will help them to assess how this technique can complement conventional geophysical observations and explore which scientific questions can be addressed by muography experiments. This monograph can also serve as an introduction to muography for those new to using this technique and aid the cooperation between developers and users, which is a prerequisite to making muography a standardized technique. This cooperation will be critical for using muography in a broad range of applications.
The editors would like to thank all the contributing authors, many of them leaders in the field, for their valuable chapters. Guest editors Constantin Athanassas, Tadahiro Kin, David Mahon, and several anonymous reviewers were greatly appreciated for their constructive reviews that improved the quality of the chapters. We also thank the American Geophysical Union and John Wiley & Sons, Inc. for providing the opportunity and continuous support for the publication of this book.
László Oláh The University of Tokyo, Japan and International Virtual Muography Institute, Global
Hiroyuki K. M. Tanaka The University of Tokyo, Japan and International Virtual Muography Institute, Global
Dezső Varga Wigner Research Centre for Physics, Hungary and International Virtual Muography Institute, Global
1 Principles of Muography and Pioneering Works
Hiroyuki K. M. Tanaka
Earthquake Research Institute, and International Muography Research Organization (MUOGRAPHIX), The University of Tokyo, Tokyo, Japan; and International Virtual Muography Institute, Global
ABSTRACT
Visualization of the subsurface flow of geofluids with meter‐scale resolution is one of the essential components of current and future geophysical observation technologies. The principles and a critical account of key results on pioneering works in muography are presented. These are compared with other geophysical and geochemical experiments and observations for the study of volcanic dynamics, tectonics, and underground water behavior, which can help us to understand and possibly predict future volcanic eruption and underground water‐associated disasters.
1.1 INTRODUCTION
Many geodynamical activities on Earth are driven by movements of geofluids, i.e., any subsurface fluid, such as magmatic fluid, groundwater, petroleum, etc., that passes through subsurface porous media. In many cases in geophysical studies, it is important to identify such geofluid motions as well as the properties of these porous media, which serve as the pathways of these fluids. Muography, the technique of using high‐energy (relativistic) muons as a radiographic probe, can be used to image the internal structure of hectometric to kilometric‐scale objects. The term muography means “muon rendering” in ancient Greek. While photography utilizes photons (the word for “light” in ancient Greek), muography utilizes the characteristics of relativistic muons. Muography can be explained by using the analogy of medical imaging. One example is medical radiography, in which X‐ray transmission through the human body clarifies the shape and state of internal organs based on differences in thickness or density; for example, bones are easily differentiated from skin tissue. The muon, also indicated by the Greek letter μ, is a charged lepton, which is free from strong force interaction but sensitive to electromagnetic force. Therefore, high‐energy muons can be easily detected, but they have a stronger penetration power than X‐rays. Muons can therefore be used to create similar shadows inside objects with much larger proportions than the human body.
These high‐energy muons are produced continuously via the interactions of galactic cosmic‐ray (GCR) particles with the upper atmosphere of the Earth. Muography is perhaps the only technology that harnesses energy originated from outside of the solar system. Muography is a technique that doesn’t require active energy sources to transmit probing signals, and thus it is power‐efficient and almost maintenance free. Therefore, it is a cost‐effective technique, in particular for the purpose of long‐time‐range monitoring.
Since GCRs also arrive at other planets, comets, and asteroids, in principle, muography can be conducted on these celestial objects. Under the conditions of the extraterrestrial environments, muons are generated either in the atmosphere or within the planet itself, depending on the existence and thickness of the atmosphere. As a consequence, the resultant energy spectra vary among stellar bodies and thus, the size of the objects that can be imaged also depends on the type of stellar body to be studied. The purpose of this chapter is to provide a clear understanding of the advantages, disadvantages, and characteristic properties of muography. The layout of this chapter is as follows. In Section 1.2, we review the principles of muography. The general features of the muographic probe including the energy spectra on the Earth, Mars, and asteroids (Section 1.2.1), geomagnetic effect (Section 1.2.2), altitude effect (Section 1.2.3), time‐dependent variations (Section 1.2.4), the general concept of muography including energy‐range relationship in terms of muon flux reduction after passing through matter (Section 1.2.5), scattering by the target volume (Section 1.2.6), measurement background (Section 1.2.7), required measurement times (Section 1.2.8), muographically averaged thickness (Section 1.2.9), and limitations