Time Variation of Earthquake Volume and Energy-Density with Special Reference to Tohnankai and Mikawa Earthquake Akira IKAMi and Kumizi IIDA Department of Earth Sciences, Nagoya University (Received January 8, 1971) The time variation of earthquake volume was investigated from the spatial distribution of aftershocks of both Tohnankai earthquake (1944) and Mikawa earthquake (1945). As these two great earthquakes occurred during the period of the World War II, there were not sufficient data which were published, but the available data concerning the aftershock activity were obtained by virtue of Nagoya Meteorological Observatory. Owing to these collected data the magnitude of all aftershocks were calculated by using the duration of preliminary tremors and the duration of oscillations. Thus the time variations of both released seismic wave-energy and energy-density were obtained. It was found that the released wave-energy density varied from 1 x 104 erg/cm3 at the time soon after the main shock to 4 x 103 erg/cm3 at the time after one year passed in the case of Tohnankai earthquake and from 6 x 103 erg/cm3 to 1 x 103 erg/cm3 in the case of Mikawa earthquake.
Fig. 1. Distribution of epicenters for main shock and aftershocks of the Tohnankai earthquake. Fig. 2. Distribution of epicenters for main shock and aftershocks of the Mikawa earthquake.
IogFN=-0.87Mf5.5 Io9EN=-0.64M+4,61 Fig. 3, Frequency distribution of magnitude for aftershocks of the Tohnankai earthquake. Fig. 4. Frequency distribution of magnitude for aftershocks of the Mikawa earthquake.
Fig. 5. Frequency distribution of maximum amplitude for aftershocks of the Mikawa earthquake. Fig: 6. Daily number of aftershocks of the Tohnankai earthquake. Fig. 7. Daily number of aftershocks of the Mikawa earthquake.
Fig. 8. Cumulative number of aftershocks of the Tohnankai earthquake. Fig. 9. Cumulative number of aftershocks of the Mikawa earthquake. Fig. 10. Cumulative sum of aftershock area of the Tohnankai earthquake. Fig. 11. Cumulative sum of aftershock area of the Mikawa earthquake.
Fig. 12. Cumulative sum of aftershock volume of the Tohnankai earthquake. Fig. 13. Cumulative sum of aftershock volume of the Mikawa earthquake. Fig. 14. Relation between magnitude of each aftershock M and the (F-P) time of the Tohnankai earthquake. F-P Fig. 15. Relation between magnitude of each aftershock M and the (F-P) time of the Mikawa earthquake.
Fig. 16. Cumulative sum of released energy of the Tohnankai earthquake. Fig. 17. Cumulative sum of released energy of the Mikawa earthquake.
Fig. 18. Energy area density as a function of time of the Tohnankai earthquake. DAYS AFTER MAIN SHOCK Fig. 19. Energy area density as a function of time of the Mikawa earthquake. Fig. 20. Energy volume density as a function of time of the Tohnankai earthquake. Fig. 21. Energy volume density as a function of time of the Mikawa earthquake.
IIDA, K., 1963, A Relation of Earthquake Energy to Tsunami Energy and the Estimate of the Vertical Displacement in a Tsunami Source, J. Earth Sciences, Nagoya Univ., 11, No. 1, 49-67. IIDA, K., 1965, Earthquake Magnitude, Earthquake Fault and Source Dimensions, J. Earth Sciences, Nagoya Univ., 13, No. 2, 115-132. IIDA, K., 1969, Magnitude of Micro Earthquakes and Their Occurrence Frequency, Proc. Second United State-Japan Conference on Research Related to Earthquake Prediction Problem, 98. 99. KISSLINGER, C., 1968, Energy Density and the Development of the Source Region of the
Matsushiro Earthquake Swarm, Bull. Earthq. Res. Inst., 46, 1207-1223. MINAKAMI, T and S. UCHIBORI, 1946, Aftershocks' Distribution of the Tohnankai Earthquake, Bull. Earthq. Res. Inst., 24, 19-30. PAGE, R., 1968, Aftershocks and Micro Aftershocks of the Great Alaska Earthquake of 1964, Bull. Seism. Soc. Amer., 58, 1131-1168. TsuBoI, C., 1956, Earthquake Energy, Earthquake Volume, Aftershock Area and Strength of the Earth's Crust, J. Phys. Earth, 4, 6-23.