著者
三井 雄太 柳谷 俊
出版者
北海道大学大学院理学研究院自然史科学部門(地球物理学)
雑誌
北海道大学地球物理学研究報告
巻号頁・発行日
vol.75, pp.109-115, 2012-03-19

We observed clear fractoluminescence in crystalline quartzite, quartz crystal and fused silica at uniaxial compressional loading tests by commercial digital cameras. These fractoluminescence are composed of blue and red colors. In particular, a blue color does not appear in fractures of fused silica but appear in crystalline quartzite and quartz crystal, which implies that the piezoelectric charge and discharge play a key role in the blue-color fractoluminescence via excitation of N2 molecules.
著者
吉澤 和範
出版者
北海道大学大学院理学研究院自然史科学部門(地球物理学)
雑誌
北海道大学地球物理学研究報告 (ISSN:04393503)
巻号頁・発行日
vol.71, pp.39-48, 2008-03-15

Seismic waves generated by a nuclear test carried out by North Korea on October 9, 2006 were observed throughout the Japanese islands. Clear arrivals of Pn waves, which traveled below the Moho discontinuity underneath the Japan Sea, were recorded by the Japanese broad-band seismic network, F-net, deployed by National Research Institute for Earth Science and Disaster Prevention (NIED). We analyzed the waveforms of the nuclear event observed at F-net stations as well as some global seismic stations in East Asia. Apparent path-average velocity of Pn waves and their maximum amplitudes are estimated from vertical component seismograms of the F-net stations. We found conspicuous regional variations of apparent path-average velocity and maximum amplitude. For example, fast apparent velocity and larger amplitude are observed in the paths across the Japan basin in the northern Japan Sea, whereas slow velocity as well as relatively smaller amplitudes are found in the path to stations in Kyushu. Such regional variability of Pn waves is likely to make it difficult to estimate source parameters for this small-scale explosive event in the Korean Peninsula, only using the Japanese seismic network. These results suggest the necessity of a precise three-dimensional seismic model of the Japan Sea to utilize Japanese seismic network data for analysis of regional seismic waves that propagate along a variety of paths in the Japan Sea.
著者
鈴木 建夫 新井田 清信 西田 泰典 大島 弘光 室伏 誠
出版者
北海道大学大学院理学研究院自然史科学部門(地球物理学)
雑誌
北海道大学地球物理学研究報告 (ISSN:04393503)
巻号頁・発行日
vol.70, pp.53-65, 2007-03-15

Many authors have discussed the eruption time sequence and the mechanism of volcanic eruptions by estimating the ejected velocity of the volcanic blocks, with the aid of other factors of eruptive phenomena. Equations of motion for the volcanic blocks have been proposed by considering the factors, such as the air resistance, the influence of the wind, the inclination of the explosion principal axis and so on. However, the equation of motion and its solution has not been considered that the air resistance power was vector quantity for the flight of volcanic blocks. In this paper a new equation of motion for the ejected volcanic blocks is proposed by considering the air resistance power as vector quantity.
著者
鈴木 建夫 新井田 清信 西田 泰典 大島 弘光 室伏 誠
出版者
北海道大学大学院理学研究院自然史科学部門(地球物理学)
雑誌
北海道大学地球物理学研究報告 (ISSN:04393503)
巻号頁・発行日
vol.70, pp.67-83, 2007-03-15

The present authors pointed out, in the last paper, a mistake in the equation of motion for volcanic blocks. Reliable assumption of the air resistance to the blocks is required for accurate estimation of initial velocity of volcanic blocks. However, little attention has been given to the point. This paper organizes the problems about the estimation of the air resistance and proposes a new method of the estimation. Also this paper organizes the effect of factors on the distribution of volcanic blocks. Model calculations revealed the effect of the atmospheric air density cannot be ignored. For the effect of explosion principal axis on the distribution of volcanic blocks, this paper proposes an extended equation which volcanic blocks eject to all the directions around the crater.
著者
武村 雅之
出版者
北海道大学大学院理学研究院自然史科学部門(地球物理学)
雑誌
北海道大学地球物理学研究報告 (ISSN:04393503)
巻号頁・発行日
vol.73, pp.1-22, 2010-03-19

The Great Hanshin-Awaji Earthquake Disaster in 1995 killed more than 6000 people. At that moment, the Seismological Society of Japan and the Japanese government examined themselves and fully recognized that communications beneficial for disaster prevention were not sufficiently exchanged and valuable knowledge obtained from earthquake research were not efficiently applied to the general public and disaster prevention organizations. The Seismological Society of Japan established new committees in charge of publicity and education in 1996 to provide opportunities of the communication between seismologists and general public. The Japanese government also established the Headquarters for Earthquake Research Promotion as a direct system of accountability for government policies regarding earthquakes. Since 1880, the year of the establishment of the first Seismological Society in the world, the Japanese seismological community has experienced 4 big changes such as the Great Nobi Earthquake Disaster in 1891, the Great Kanto Earthquake Disaster in 1923, the Second World War, and this earthquake disaster. These histories are reviewed from the point of view of social activities in Japanese seismology. Finally, we will discuss achievement for the sake of the mitigation of earthquake disaster on the lessons learned from the history.
著者
高橋 浩晃 前田 宜浩 笠原 稔
出版者
北海道大学大学院理学研究院自然史科学部門(地球物理学)
雑誌
北海道大学地球物理学研究報告 (ISSN:04393503)
巻号頁・発行日
vol.72, pp.399-410, 2009-03-15

We investigate the characteristics of great earthquakes occurring in the central Kuril Islands on 1915, 1918, 2006 and 2007. Comparisons of seismic intensity distributions, tsunami data and waveforms of above four events were made. Though magnitudes of these earthquakes were almost the same, only the 1915 event did not generate observable tsunami. This fact may be due to deep focal depth of this earthquake. Similarities of seismic intensity distributions between the 1915, 1971 and 2008 deep-focus earthquakes also imply that the 1915 event was the deep-focus event in the northeastern Okhotsk Sea. Waveform properties of the 1915 and 2008 events supports above hypothesis. We conclude, therefore, that the 1915 earthquake was not the event in the central Kuril Island but in the Okhotsk Sea with deep depth. Large tsunami and widespread felt area of the 1918 earthquake show that this event was a typical shallow-dipping thrust event on plate boundary as indicated by previous studies.
著者
小山 順二 都筑 基博 蓬田 清
出版者
北海道大学大学院理学研究院自然史科学部門(地球物理学)
雑誌
北海道大学地球物理学研究報告 (ISSN:04393503)
巻号頁・発行日
vol.75, pp.161-174, 2012-03-19

Since the 2011 Tohoku-oki megathrust earthquake, Japan, it has been recognized that there is a variety of megathrust earthquakes occurring in the world not just only the Chilean type megathrust earthquake. In the variation, one end member is the 1960 Chile earthquake and the other is the 2004 Sumatra-Andaman earthquake, while the former is characterized by subduction zone of a young plate forming the Cordilleran orogeny, the latter is by an obliquely subducting plate along a continental margin with active back-arc activity. We study in detail megathrust earthquakes along such oblique subduction zones, considering characteristics of earthquake activities, focal mechanisms, rupture patterns, geometry of subduction zones, types of overriding plates and back-arc activities. Discussions are further made on one of the oblique subduction zones near Japan Islands, the Sagami Trough, in order to derive some information and the possibility of future large earthquakes there from the seismological data at hand. We found that there is a variety of large earthquakes in the oblique subduction zones in the world. Since we have no hand to suspect the future activity of a particular subduction zone, comparative studies on seismic activities in different oblique subduction zones are inevitable.
著者
吉澤 和範
出版者
北海道大学大学院理学研究院自然史科学部門(地球物理学)
雑誌
北海道大学地球物理学研究報告 (ISSN:04393503)
巻号頁・発行日
no.71, pp.39-48, 2008-03

Seismic waves generated by a nuclear test carried out by North Korea on October 9, 2006 were observed throughout the Japanese islands. Clear arrivals of Pn waves, which traveled below the Moho discontinuity underneath the Japan Sea, were recorded by the Japanese broad-band seismic network, F-net, deployed by National Research Institute for Earth Science and Disaster Prevention (NIED). We analyzed the waveforms of the nuclear event observed at F-net stations as well as some global seismic stations in East Asia. Apparent path-average velocity of Pn waves and their maximum amplitudes are estimated from vertical component seismograms of the F-net stations. We found conspicuous regional variations of apparent path-average velocity and maximum amplitude. For example, fast apparent velocity and larger amplitude are observed in the paths across the Japan basin in the northern Japan Sea, whereas slow velocity as well as relatively smaller amplitudes are found in the path to stations in Kyushu. Such regional variability of Pn waves is likely to make it difficult to estimate source parameters for this small-scale explosive event in the Korean Peninsula, only using the Japanese seismic network. These results suggest the necessity of a precise three-dimensional seismic model of the Japan Sea to utilize Japanese seismic network data for analysis of regional seismic waves that propagate along a variety of paths in the Japan Sea.
著者
三輪田 吾郎 高井 伸雄 清水 学 笹谷 努 前田 宜浩 山本 明夫
出版者
北海道大学大学院理学研究院自然史科学部門(地球物理学)
雑誌
北海道大学地球物理学研究報告 (ISSN:04393503)
巻号頁・発行日
no.73, pp.195-205, 2010-03

Nonlinear site response was observed at TKCH 07 in Toyokoro and HKD 109 in Urakawa during the mainshock(Mj 8.0)and the largest aftershock(Mj 7.1)of the 2003 Tokachi-oki Earthqua ke. At TKCH 07, peak ground acceleration(PGA)was smaller than PGA at the other strong motion station in Toyokoro. At HKD 109, the accelerogram shows a characteristic spiky waveform. Due to this spiky wave, large PGA was observed compared to the other stations in Urakawa, although PGA at HKD 109 was smaller than PGA at JMA Urakawa station during the main shock and smaller aftershocks.
著者
植竹 富一
出版者
北海道大学大学院理学研究院自然史科学部門(地球物理学)
雑誌
北海道大学地球物理学研究報告 (ISSN:04393503)
巻号頁・発行日
no.73, pp.49-55, 2010-03

A deep(H=374 km)earthquake of Mj=6.7 occurred in Kyoto-Oki region on July 16, 2007. Broad-band velocity ground motions during this event were observed at many thermal power stations in the Tokyo bay area. Waveforms observed at the stations of the east side of the Tokyo bay show longer duration than those at the west side of the bay. The apparent frequencies of later arrivals are lower than those of S-wave parts. Velocity waveforms observed in the mountain area and in the bedrock of the basin have short duration and no significant later arrivals. This suggests that the later arrivals were excited by the Kanto basin.
著者
前田 宜浩 高井 伸雄 笹谷 努
出版者
北海道大学大学院理学研究院自然史科学部門(地球物理学)
雑誌
北海道大学地球物理学研究報告 (ISSN:04393503)
巻号頁・発行日
no.73, pp.217-227, 2010-03
被引用文献数
1

The largest aftershock(Mw 7.3)of the 2003 Tokachi-oki earthquake(Mw 8.3)generates larger peak ground acceleration(PGA)values than the main shock in the western side of the epicenters despite their magnitude difference. We study the features of strong ground motions from the largest aftershock in detail using PGA values. Spatial distribution maps of PGA ratio between the largest aftershock and adjacent earthquake shows obvious azimuth dependency compared with the other earthquake pairs occurring around Japan. Attenuation relationship of the largest aftershock shows a large azimuth-dependent scattering at distances from 200 to 300 km compared with three smaller earthquakes occurring around the largest aftershock. Because this large scattering appears only in the largest aftershock, we conclude that the azimuth dependency is a peculiar feature of the largest aftershock. Fourier spectral ratios between the largest aftershock and adjacent earthquake at several stations show azimuth dependency at higher frequencies than 1 Hz, which is consistent with the azimuth dependency of PGA values. The azimuth dependency in high-frequency range cannot be explained simply by the source and path effects, and therefore, we make a hypothesis that the azimuth dependency is an apparent one generated by two earthquakes occurring simultaneously at different regions. Synthetic PGA distributions generated by two simultaneous events calculated by the empirical attenuation relationship are in agreement with the observed PGA distribution of the largest aftershock.
著者
諸井 孝文 武村 雅之
出版者
北海道大学大学院理学研究院自然史科学部門(地球物理学)
雑誌
北海道大学地球物理学研究報告 (ISSN:04393503)
巻号頁・発行日
vol.73, pp.101-116, 2010-03-19

Datasets of structural damage and regional damage due to past earthquakes are not only useful to know the actual state of each event but also effective for strong ground motion predictions and damage mitigations of future earthquakes. In this paper, several considerations are illustrated concerning strong ground motion research and data processing analysis. Especially, the activity to make research results contribute to society is discussed based on three examples of earthquake damage data analysis. The examples shown here describe that the well known notion in general, what is called common knowledge, does not necessarily have high reliability, and that the lack of confirmation of the data accuracy misleads the conclusion of research results beyond common sense. From these examples, the importance of an empirical research policy as well as a reasonable research policy is discussed. And it is pointed out that the information exchange among the researchers in various fields will be very effective for the development of the strong ground motion research.
著者
武村 雅之
出版者
北海道大学大学院理学研究院自然史科学部門(地球物理学)
雑誌
北海道大学地球物理学研究報告 (ISSN:04393503)
巻号頁・発行日
no.73, pp.1-22, 2010-03

The Great Hanshin-Awaji Earthquake Disaster in 1995 killed more than 6000 people. At that moment, the Seismological Society of Japan and the Japanese government examined themselves and fully recognized that communications beneficial for disaster prevention were not sufficiently exchanged and valuable knowledge obtained from earthquake research were not efficiently applied to the general public and disaster prevention organizations. The Seismological Society of Japan established new committees in charge of publicity and education in 1996 to provide opportunities of the communication between seismologists and general public. The Japanese government also established the Headquarters for Earthquake Research Promotion as a direct system of accountability for government policies regarding earthquakes. Since 1880, the year of the establishment of the first Seismological Society in the world, the Japanese seismological community has experienced 4 big changes such as the Great Nobi Earthquake Disaster in 1891, the Great Kanto Earthquake Disaster in 1923, the Second World War, and this earthquake disaster. These histories are reviewed from the point of view of social activities in Japanese seismology. Finally, we will discuss achievement for the sake of the mitigation of earthquake disaster on the lessons learned from the history.
著者
小林 知勝
出版者
北海道大学大学院理学研究院自然史科学部門(地球物理学)
雑誌
北海道大学地球物理学研究報告 (ISSN:04393503)
巻号頁・発行日
vol.72, pp.257-268, 2009-03-15

A feasibility test of a kriging method is conducted for estimate of a strain field. In this test the kriging method is applied to man-made data and actual ground displacement data observed in Taiwan. It is investigated how well the method can reproduce the given strain field and extract the complex strain field of Taiwan. To clarify the merits/demerits of this method, we compare the results of the kriging to those inferred from other analysis methods; one is a conventional method in which a strain is directly calculated using a triangulation network and the other is a method incorporating a spatial smoothing procedure. The results demonstrate that the kriging method enables us to provide a largescale strain field spatially smoothly, and further to simultaneously extract a localized deformation. Additionally it is noteworthy that this method is robust for anomalous data, i.e., weights of anomalies are suppressed automatically. On the other hand, the standard triangulation method cannot stably extract a large-scale strain field and at a certain case artificial strain errors are produced. This method is very sensitive to anomalous data and/or even to small fluctuations (errors) of data. The method incorporating a spatial smoothing procedure that has been developed and applied in many recent studies can robustly evaluate strain components that are spatially dominant in the analyzed domain, but miss out a small-scale deformation due to the smoothing.