Current Research Interests Recent Publications My Latest Book
International Conferences I Recently Attended Useful Links Tribute to Kei Aki

Recent Publications:
  1. Ohnaka, M., 2013, The Physics of Rock Failure and Earthquakes, published by Cambridge University Press, Cambridge CB2 8RU, UK, 279 pages. [Click HERE for more information.]
  2. Ohnaka, M., and A. Kato, 2007, Depth dependence of constitutive law parameters for shear failure of rock at local strong areas on faults in the seismogenic crust, Journal of Geophysical Research, 112, B07201, doi:10.1029/2006JB004260: Reprint (583 kb) [PDF]
  3. Ohnaka, M., 2006, Reply to "Comment on 'Earthquake cycles and physical modeling of the process leading up to a large earthquake'", Earth, Planets and Space, 58, 1529-1531: Reprint (54 kb) [PDF]
  4. Ohnaka, M., 2004, Earthquake cycles and physical modeling of the process leading up to a large earthquake, Earth, Planets and Space, 56, 773-793: Reprint (1224 kb) [PDF]
  5. Ohnaka, M., 2004, A constitutive scaling law for shear rupture that is inherently scale-dependent, and physical scaling of nucleation time to critical point, Pure and Applied Geophysics, 161, 1915-1929.
  6. Kato, A., S. Yoshida, M. Ohnaka, and H. Mochizuki, 2004, The dependence of constitutive properties on temperature and effective normal stress in seismogenic environments, Pure and Applied Geophysics, 161, 1895-1913.
  7. Ohnaka, M., 2004, GEOPHYSICS: Rupture in the Laboratory, Perspectives in Science (19 March 2004 Issue), 303(5665), 1788-1789 (click here for viewing Summary, and here for viewing Full Text): Reprint (79 kb) [PDF].
  8. Ohnaka, M., 2003, A constitutive scaling law and a unified comprehension for frictional slip failure, shear fracture of intact rock, and earthquake rupture, Journal of Geophysical Research, 108(B2), 2080, doi:10.1029/2000JB000123: Reprint (876 kb) [PDF]
  9. Kato, A., M. Ohnaka, S. Yoshida, and H. Mochizuki, 2003, Effect of strain rate on constitutive properties for the shear failure of intact granite in seismogenic environments, Geophysical Research Letters, 30 (21), 2108, doi:10.1029/2003GL018372: Reprint (204 kb) [PDF]
  10. Kato, A., M. Ohnaka, and H. Mochizuki, 2003, Constitutive properties for the shear failure of intact granite in seismogenic environments, Journal of Geophysical Research, 108(B1), 2060, doi:10.1029/2001JB000791: Reprint (798 kb) [PDF]
  11. Ohnaka, M., 2003, The role of water in rock fracture, In: The Role of Water in Earthquake Generation (Editors: J. Kasahara, M. Toriumi, and K. Kawamura), University of Tokyo Press, Tokyo, pp.193-207 (in Japanese) [If you understand Japanese language, click HERE for more info.]
  12. Ohnaka, M., and M. Matsu'ura, 2002, The Physics of Earthquake Generation, published by University of Tokyo Press, Tokyo, 378pp (in Japanese). [If you understand Japanese language, click HERE for more info.]
  13. Odedra, A., M. Ohnaka, H. Mochizuki, and P. Sammonds, 2001, Temperature and pore pressure effects on the shear strength of granite in the brittle-plastic transition regime, Geophysical Research Letters, 28, 3011-3014: Reprint (821 kb) [PDF]
  14. Ohnaka, M., 2000, A physical scaling relation between the size of an earthquake and its nucleation zone size, Pure and Applied Geophysics, 157, 2259-2282: Reprint (200 kb) [PDF]
  15. Kato, A., and M. Ohnaka, 2000, Effect of water on stability or instability of the shear fracture process of rock, Journal of Geography, 109(4), 554-563 (in Japanese).
  16. Ohnaka, M., 2000, A constitutive scaling law that unifies the shear rupture from small scale in the laboratory to large scale in the Earth as an earthquake source, 2nd ACES Workshop, Tokyo and Hakone, 96-101.
  17. Ohnaka, M., and L.-f. Shen, 1999, Scaling of the shear rupture process from nucleation to dynamic propagation: Implications of geometric irregularity of the rupturing surfaces, Journal of Geophysical Research, 104, 817-844: Reprint (946 kb) [PDF]
  18. Ohnaka, M., 1999, The shear rupture nucleation: Horizons broadened by high-resolution laboratory experiments, 1st ACES Workshop Proceedings, GOPRINT, Brisbane, Australia, 117-119.
  19. Ohnaka, M., 1999, Physical scale dependencies, observed scaling relations and simulation, 1st ACES Workshop Proceedings, GOPRINT, Brisbane, Australia, 433-435.
  20. Ohnaka, M., 1999, A unified comprehension for fracture of intact rock, frictional slip failure, and earthquake rupture, and scaling of scale-dependent physical quantities inherent in the rupture, 1st ACES Workshop Proceedings, GOPRINT, Brisbane, Australia, 441-444.
  21. Sammonds, P., and M. Ohnaka, 1998, Evolution of microseismicity during frictional sliding, Geophysical Research Letters, 25, 699-702.
  22. Odedra, A., P. Sammonds, and M. Ohnaka, 1998, Laboratory studies on the dependency of temperature and fluid pressure on fault zone strength, slip displacement and sealing potential, Proceedings of Rock Mechanics In Petroleum Engineering, Society of Petroleum Engineers, 2, 323-329.
  23. Ohnaka, M., M. Akatsu, H. Mochizuki, A. Odedra, F. Tagashira, and Y. Yamamoto, 1997, A constitutive law for the shear failure of rock under lithospheric conditions, Tectonophysics (Special Volume on Earthquake Generation Processes: Environmental Aspects and Physical Modelling), 277, 1-27: Abstract (77 kb) [PDF]
  24. Ohnaka, M., 1996, Nonuniformity of the constitutive law parameters for shear rupture and quasistatic nucleation to dynamic rupture: A physical model of earthquake generation processes, Proceedings of the National Academy of Sciences of the United States of America, 93, 3795-3802: Reprint (307 kb) [PDF]
  25. Ohnaka, M., 1995, A shear failure strength law of rock in the brittle-plastic transition regime, Geophysical Research Letters, 22, 25-28: Reprint (1,466 kb) [PDF]
  26. Ohnaka, M., 1995, Constitutive equations for shear failure of rocks, In: Theory of Earthquake Premonitory and Fracture Processes (Editor: R. Teisseyre), Polish Scientific Publishers PWN, Warszawa, Poland, pp.26-44.
  27. Ohnaka, M., 1995, Earthquake source nucleation model and immediate seismic precursors, In: Theory of Earthquake Premonitory and Fracture Processes (Editor: R. Teisseyre), Polish Scientific Publishers PWN, Warszawa, Poland, pp.45-76.
  28. Ohnaka, M., 1995, Effects of temperature and pressure on shear failure parameters: Failure and friction law of rock in the brittle-plastic transition regime, In: Theory of Earthquake Premonitory and Fracture Processes (Editor: R. Teisseyre), Polish Scientific Publishers PWN, Warszawa, Poland, pp.552-568.



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The Physics of Rock Failure and Earthquakes
The Physics of Rock Failure and Earthquakes
by Mitiyasu Ohnaka
Publisher: Cambridge University Press (April, 2013)
ISBN: 9781107030060

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).



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Current Research Interests:

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:

  1. Establishing the unifying constitutive law that governs both frictional slip failure and the shear fracture of intact rock, on the basis of laboratory data,
  2. Establishing the constitutive scaling law that makes it possible to scale scale-dependent physical quantities inherent in the shear rupture over a broad range from laboratory-scale to field-scale, and
  3. Physical modeling of the process leading up to a large earthquake, with the eventual goal of establishing a rational methodology of forecasting large earthquakes.



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International Conferences I attended recently:
  • KITP Conference: From the Atomic to the Tectonic: Friction, Fracture and Earthquake Physics, organized by James Dieterich, Michael Falk, and Mark Robbins, held in 2005 at the Kavli Institute for Theoretical Physics, University of California at Santa Barbara, California, USA (invited as a visiting scholar of the Kavli Institute for Theoretical Physics to participate in the Conference)
  • 4th ACES (APEC Cooperation for Earthquake Simulation) Workshop, held on July 9-14, 2004, in Beijing, China (Session convener)
  • Workshop on Numerical Modeling of Earthquake Source Dynamics, held on September 1-3, 2003, at Smolenice Castle near Bratislave, Slovak Republic (Invited speaker)
  • 23rd General Assembly of the International Union of Geodesy and Geophysics, held on June 30-July 11, 2003, in Sapporo, Japan (IASPEI symposium convener and Invited speaker)
  • 22nd Course of the International School of Geophysics, held on August 1-8, 2002, in Erice, Sicily, Italy (Key note speaker)
  • 3rd ACES (APEC Cooperation for Earthquake Simulation) Workshop, held on May 5-10, 2002, in Maui, Hawaii, USA (Invited speaker)
  • 2nd ACES (APEC Cooperation for Earthquake Simulation) Workshop, held on October 15-20, 2000, in Tokyo and Hakone, Japan (Session convener and speaker)
  • Western Pacific Geophysical Meeting, American Geophysical Union, held on June 27-30, 2000, in Tokyo, Japan (Invited speaker)
  • 17th Course of the International School of Geopohysics, held on June 17-23, 2000, in Erice, Sicily, Italy (Invited speaker)
  • 22nd General Assembly of the International Union of Geodesy and Geophysics, held on July 16-August 1, 1999, in Birmingham, UK (IASPEI Simposium convener and speaker)
  • 14th General Assembly of the European Geophysical Society, held on April 19-23, 1999, in The Hague, Netherlands (Session invited speaker)
  • ACES (APEC Cooperation for Earthquake Simulation) Inaugural Workshop, held on January 31-February 5, 1999, in Brisbane and Noosa, Queensland, Australia (Session convener and speaker)



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Useful Links:



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Tribute to Professor Keiiti Aki

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.

(November 29, 2004)



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