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1.
The lunar cratering rate studied over the past 1.1 Gyr, which is a foundation of the lunar cratering chronology, is a decreasing function of the angular distance from the apex of the orbital motion due to the synchronous rotation of the Moon. We here evaluate an influence of the asymmetrical rate upon the age determination. 相似文献
2.
The long-period Rayleigh waves were investigated for the largest four deep shocks in 1963–1973 to determine the seismic moment by the same technique as used for shallow earthquakes. The results could be used for a quantitative comparison of source parameters between shallow and deep events. Three of the four shocks occurred beneath the South American continent (the Colombia earthquake, 1970; the western Brazil earthquake, 1963; the Peru—Bolivia border earthquake, 1963) and the other beneath the Japan Sea (1973). The focal depths are 653, 576, 593 and 575 km, respectively. The largest value of seismic moment was obtained as 2.1 · 1028 dyncm for the Colombia earthquake. This value is still about forty times smaller than that for the great Alaskan earthquake. A slight inconsistency was found between the first-motion diagram and the Rayleigh wave radiation pattern for the Colombia earthquake and the Peru—Bolivia border earthquake. 相似文献
3.
Yoshihiro Hiramatsu Muneyoshi Furumoto Kin’ya Nishigami Shiro Ohmi 《Physics of the Earth and Planetary Interiors》2002,132(4):269-279
We analyze high sampling waveforms of the initial part of P-wave recorded at the 1800-m-deep borehole seismographs at the Nojima fault from December 1999 to May 2000 to clarify the initial rupture process of microearthquakes. We select 12 events with high S/N, whose magnitudes range from −0.3 to 2.2 and hypocentral distances from 1 to 11 km. We adopt the two different source models by Sato and Hirasawa (1973) and by Sato and Kanamori (1999). The former (model by Sato and Hirasawa (SH model)) generates only a ramp-like onset of velocity pulse. The later (model by Sato and Kanamori (SK model)) is able to generate a weak initial phase that is controlled by a trigger factor and the length of pre-existing crack. We perform the waveform inversion to estimate the optimum source parameters of each model. Waveforms of 5 of the 12 events are clearly reproduced by both SH model and SK model with a large trigger factor and a small length of pre-existing crack. The others are explained by not SH model but only SK model with a small trigger factor and a large length of the pre-existing crack, indicating that the weak initial phase is a nucleation phase and reflects the source process. These seven events satisfy roughly a relation that a large event has a large length of the pre-existing crack; the final crack length is proportional to the length of the pre-existing crack. 相似文献
4.
Seismic evaluation of earthquake resistance and retrofitting measures for two story masonry houses 总被引：1，自引：0，他引：1
Navaratnarajah Sathiparan Kotaro Sakurai Muneyoshi Numada Kimiro Meguro 《Bulletin of Earthquake Engineering》2014,12(4):1805-1826
This paper discusses on the shaking table test results of two 1:4 scale model of two-story masonry structure typically used in constructing low-rise residential buildings. This test is performed to provide a better understanding of the seismic behavior of the PP-band (polypropylene band) mesh retrofitted adobe masonry house. The test structure is subjected to a series of different levels of harmonic motion that applied along the longitudinal direction. The results of the shaking table tests on building models show that the PP-band retrofitting technique can enhance the safety of masonry buildings, even during severe ground motion. 相似文献
5.
Muneyoshi Furumoto 《Physics of the Earth and Planetary Interiors》1977,15(1):1-12
The deep Colombia earthquake of July 31, 1970, showed a very high multiple-shock activity. The hypocentres of the seven events forming the multiple shock were determined by a relative location method. They cluster on a plane which coincides fairly well with the westerly-dipping nodal plane and show a southwards and upwards migration with time. The hypocentre distribution suggests that the earthquake occurred in the form of shear faulting. The primary P waveforms are computed from the long-period P-wave signals by eliminating the responses of the instrument, crust and mantle. The fault process is inferred from the spacio-temporal relation of the seven events and from the primary P waveforms: the rupture initiated in the lower part of the source region and spread out southwards and upwards. The whole process was almost finished when the intense multiple-shock activity terminated (about 50 s). The mechanism change of this earthquake can be described mainly by the change of the orientation of the fault plane rather than by slip vector change. The strike of the fault plane rotated clockwise about 10° during the events which occurred in the lower part of the source region. The further rotation of about 10° occurred at the subsequent stage. The rupture spread out with a jerk over a curved surface. The difference between the rupture processes in shallow and deep large earthquakes is discussed. 相似文献
6.
Kazuo Konagai Muneyoshi Numada Athanasios Zafeirakos Jörgen Johansson Amir Sadr Toshihiko Katagiri 《Landslides》2005,2(2):159-163
A large number of landslides induced by the 2004 Mid Niigata Prefecture earthquake resulted in the closure of 233 segments of national and prefectural routes in Higashiyama mountain district, and 61 localities were completely isolated. Since railway and road facilities follow closely the motion of soils, damage to these facilities has to be discussed in terms of soil deformations that they experienced. The example of Kizawa tunnel shows that even relatively small soil deformations can be large enough to cause serious cracking of tunnel lining. 相似文献
7.
We investigate the initial rupture process of microearthquakes to reveal relationships between nucleation region sizes and eventual earthquake sizes. In order to obtain high quality waveform data, we installed a trigger recording system with a sampling frequency of 10 kHz at the base of a deep borehole at the Nojima Fault, Japan. We analyze waveform data of 31 events around the borehole, with seismic moment ranging from 4.2 × 109 Nm to 7.1 × 1011 Nm. We use both a circular crack model with an accelerating rupture velocity (SK model) [Sato, T., Kanamori, H., 1999. Beginning of earthquakes modeled with the Griffith's fracture criterion, Bull. Seism. Soc. Am., 89, 80-93.], which generates a slow initial phase of velocity pulse, and a circular crack model with a constant rupture velocity (SH model) [Sato, T, Hirasawa, T., 1973. Body wave spectra from propagating shear cracks, J. Phys. Earth, 21, 415-431.], which generates a ramp-like velocity pulse. Source parameters of these two models are estimated by waveform inversion of the first half cycle of the observed velocity pulse applying both a grid search and a non-linear least squares method. 14 of 31 events are never reproduced by the SH model with a constant Q operator. But SK model with a constant Q operator provides a size of the pre-existing crack, corresponding to the size of the nucleation regions, and a size of the eventual crack. We recognize that (i) the eventual seismic moment is approximately scaled as the cube of the size of pre-existing cracks, (ii) the eventual seismic moment is scaled as the cube of the size of eventual cracks, and (iii) the size of eventual cracks is roughly proportional to the size of pre-existing cracks. We, thus, conclude that the size of eventual earthquakes is controlled by the size of the nucleation regions. 相似文献
8.
Experimental investigation on the seismic performance of PP-band strengthening stone masonry houses 总被引：1，自引：0，他引：1
Navaratnarajah Sathiparan Kotaro Sakurai Muneyoshi Numada Kimiro Meguro 《Bulletin of Earthquake Engineering》2013,11(6):2177-2196
The collapse of stone masonry is one of the greatest causes of death in major earthquake events around the world. This paper investigates a recently developed retrofitting technology specifically aimed at preventing or prolonging the collapse of stone masonry buildings under strong earthquakes. This technology uses common polypropylene packaging straps to form a mesh, which is then used to prevent or prolong collapse. This paper examines the findings from static and dynamic testing of the proposed retrofit. It is shown that the proposed technique effectively prevents brittle masonry collapse and the loss of debris. 相似文献
9.
Abstract Using topography and observed gravity anomalies, we have estimated the effective elastic thickness as a measure of strength of Japanese island arc lithosphere. The thickness is found to range from about 3 km to >20 km. The thickness seems to be controlled primarily by the thermal state of the lithosphere. The higher the heat flow, the thinner is the elastic plate. However, several areas show significant deviations. The smaller effective elastic thickness in the northern Ryukyu arc than that inferred from heat flow may be attributed to the stress regime. In Japan, extensional tectonics are going on only in the Ryukyu arc region. Shallow subducting slab under the south-western Japan frontal arc probably increases the effective thickness by several kilometers. The determined effective elastic thickness suggests that when we consider vertical movements in the volcanic arc, we should take account of topographic and subsurface loading over a few hundred kilometers. However, if the dip of the slab is shallow, the flexural responses of the underlying slab, not only that of the island arc lithosphere, should be taken into account for the compensation, as is the case of the south-western Japan frontal arc. 相似文献
10.