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Over the past two decades, there has been controversy regarding what the constitutive law for real earthquake ruptures ought to be, and how it should be formulated. For the physics of earthquakes to be a complete, quantitative science in the true sense, it is essential to resolve this controversy. However, it is not possible to preliminarily deploy a series of high-resolution instruments for measuring local shear stresses (or strains) and local slip displacements along the fault on which a pending earthquake is expected to occur at a crustal depth. Hence, the resolution of seismological data observed in the field is not high enough to strictly formulate the constitutive law and to fully elucidate the physical nature of a scale-dependent earthquake rupture generation process from its nucleation to the subsequent dynamic propagation on a heterogeneous fault. In order to resolve the controversy, therefore, it is critically important to strictly formulate the constitutive law, based on positive facts elucidated by high-resolution laboratory experiments on shear rupture properly devised for the purpose intended, from comprehensive viewpoints, by correctly recognizing the fact that real faults embedded in the Earth's crust are inherently heterogeneous, and that the earthquake rupture process at shallow crustal depths is not a simple process of frictional slip failure on a uniformly precut weak fault, but a more complex process, including the fracture of initially intact rock at some local strong areas on a heterogeneous fault.
Rupture phenomena, including earthquakes, are inherently scale-dependent. Indeed, some of the physical quantities inherent in shear rupture exhibit scale-dependence. Therefore, to quantitatively account, in a unified and consistent manner, for scale-dependent physical quantities inherent in the rupture over a broad scale range, the governing law must be formulated in such a way that the scaling property inherent in the rupture breakdown is incorporated into the law.
Thus, it is essential to formulate the governing law as a unifying constitutive law which governs not only frictional slip failure on precut interface areas on a fault but also the shear fracture of intact rock on some local strong areas on the fault, and into which the scaling property inherent in shear-rupture breakdown is incorporated.
With these in mind, this book was written deductively in a consistent manner, based on positive facts elucidated in high-resolution laboratory experiments properly devised for the purpose intended. In laboratory experiments, the experimental method can be properly devised for the purpose intended, and high temporal and spatial resolution measurements can be made at a series of locations along a preexisting fault on which a shear rupture occurs. Thus, high-resolution laboratory experiments on shear rupture on an inhomogeneous fault are best suited for fully elucidating the physical nature of a scale-dependent shear rupture generation process from its nucleation to the subsequent dynamic rupture, and for revealing the constitutive law for the shear rupture. I have devoted myself to conducting such leading-edge research through high-resolution laboratory experiments properly devised for the purpose intended, and contributed to the elucidation of the physical nature of the scale-dependent shear rupture generation process and to the derivation of underlying physical laws, such as a unifying constitutive law and a constitutive scaling law, and a physical model of shear rupture nucleation, to achieve a deeper understanding of the physical process from earthquake nucleation to its dynamic propagation in terms of the underlying physical laws. This deductive approach based on the results of high-resolution laboratory experiments is the prominent feature of this book.
This book is designed for researchers and professional practitioners in earthquake seismology and rock failure physics, and also in adjacent fields such as geology and earthquake engineering. It is also a helpful reference for graduate students in earthquake physics, rock physics, and earthquake seismology.
Contents
Preface;
1 Introduction; 2 Fundamentals of rock failure physics; 3 Laboratory-derived constitutive relations for shear failure; 4 Constitutive laws
for earthquake ruptures; 5 Earthquake generation processes; 6 Physical scale-dependence; 7 Large earthquake generation cycles and accompanying seismic
activity; List of illustration credits; References; Index.
If you would like to get more detailed information about this book, please click here (Cambridge University Press catalogue).
Rock & Earthquake Physics Lab aims to unravel in terms of the underlying physics and seismogenic fault
structure/heterogeneity how and where an earthquake rupture nucleates and develops spontaneously at
accelerating speeds into the regime of dynamic propagation at a steady high-speed close to elastic wave velocities,
and thereby to build a comprehensive and integrated model of the process leading up to a large earthquake in
real, seismogenic environments.
To this end, focus is currently directed on:
By Miti Ohnaka
It is a great pleasure and privilege for me to express my heartfelt congratulations to Kei Aki on this glorious occasion. When I was
an undergraduate student at the University of Tokyo, I was told by a professor of seismology in his lecture that there was a young
but internationally recognized seismologist whose name was Keiiti Aki at the Earthquake Research Institute (ERI). This was the first time
I heard his name. When I became a graduate student at the Department of Geophysics to study rock magnetism under the supervision
of Takeshi Nagata, however, he had moved from ERI to MIT to take the professorship of seismology offered.
My first chance to meet him came in 1977 when I visited W. F. Brace at MIT on my way back to Tokyo from London. At that time,
my research interests had changed to the field of rock physics to unravel the earthquake generation process in terms of the underlying
physics as a research associate of ERI. Professor Brace invited me to have a lunch at a nearby restaurant, and we took an elevator,
where we came across Kei Aki. He joined us for lunch. Perhaps, he would not remember this, but I still clearly remember the encounter.
Since then, I have had a chance to see him at many international meetings held in various countries; however, it was not until 1999
that we finally had the opportunity to talk closely and exchange ideas on matters of mutual interest. In early 1999, the inaugural workshop
on APEC Cooperation for Earthquake Simulation (ACES), organized by Peter Mora, was held in Brisbane and Noosa, Australia. As a convener
of the session dealing with scaling physics of earthquakes, I earnestly invited Kei Aki to participate in the meeting, since I have been most
impressed by his physics-oriented approach, and inspired by his work on scale-dependence in earthquake seismology. Through this
inaugural meeting and the second ACES meeting held in Tokyo and Hakone, Japan, 2000, I had a fortunate and joyous time to talk with
him personally.
Kei Aki has striven to make earthquake seismology a quantitative science. For earthquake seismology to be a quantitative science, it is
critically important to recognize the physical scale dependencies. For instance, he was the first to note that the earthquake rupture energy
is scale-dependent, more than two decades ago, when most scientists believed the observed shear rupture energy to be material constant.
I know there has been strong criticism of his idea. Any radical new scientific idea takes time to become accepted. Now, his idea's support
is growing, and it is obvious that the earthquake rupture energy estimated by seismological means is the apparent rupture energy, so that
it cannot be material constant, and can be scale-dependent. Without recognizing the physical scale-dependence, it would not be possible
to understand earthquakes of vast different scales quantitatively in a unified and consistent manner. I admire him for his profound physical
intuition and sense.