巻号一覧
41 巻 (1988)
- 4 号 p. 515-
- 3 号 p. 323-
- 2 号 p. 163-
- 1 号 p. 1-
前身誌
41 巻, 2 号
選択された号の論文の15件中1～15を表示しています
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佐伯 龍男, 梅田 康弘1988 年 41 巻 2 号 p. 163-171
発行日: 1988/06/25
公開日: 2010/03/11
ジャーナル フリーThe high accelerations exceeding the earth's gravity were observed on the small area near the main shock of the 1984 Western Nagano Prefecture Earthquake (M=6.8). Few aftershocks occurred in this small high acceleration spot of main fault. It is inferred that great destruction producing the high accelerations occurred within this small spot. For detecting the evidence of great destruction, we tried to investigate the crack orientation and density by using Shear-wave polarization method.
We have identified that directions of polarization in and out of the high acceleration spot are N40-70°W. These directions are consistent with the axis of maximum compression obtained from earthquake fault mechanisms and geodetic surveys. There are no difference in polarizations between in- and out of the high acceleration spot. It suggests that open-cracks had been made before the main shock. Great destructions of the main shock seems to have little influences on S-wave polarization. The average time-lag between arrival of leading and slower shear-wave is 0.02S. It indicates that present open-cracks are distributed in a shallow depth.抄録全体を表示PDF形式でダウンロード (745K) -
角南 基亮, 河野 芳輝1988 年 41 巻 2 号 p. 173-178
発行日: 1988/06/25
公開日: 2010/03/11
ジャーナル フリーA detailed gravity survey was carried out over the Ochi depression, the sothern part of the Noto peninsula in central Japan. The depression is supposed to have been formed by faulting or flexure of strata. An earthquake (Nanao earthquake M=6.0) occurred around it in 1933.
Terrain corrected Bouguer anomalies are calculated assuming a mean density of 2.67g/cm3. The gravity system is based on IGSN 71. The distribution of gravity anomaly shows remarkably lower gravity anomaly of about 10 mgal within the depression.
The analysis of gravity anomaly by using Talwani's two dimensional method clarifies that subsurface structure under the Ochi depression can be understood as a graben structure, as suggested by geological studies. Using geological evidence and available core sample data, the depth to the per-Tertiary basement is estimated to be more than 800m in southwest region and more than 400m in northeast one.抄録全体を表示PDF形式でダウンロード (830K) -
伊藤 潔, 黒磯 章夫1988 年 41 巻 2 号 p. 179-188
発行日: 1988/06/25
公開日: 2010/03/11
ジャーナル フリーAccuracy of master event location method is studied for the microearthquakes recorded by the telemetered network of the Abuyama Seismological Observatory in northern Kinki district, Japan. The range in which the master event method is effective is examined in order to apply the master event technique using several master events to earthquakes in large area. Moreover the variations of hypocenters are estimated for the variations of the velocity and that of the thickness of the surface layer and the velocity of basement layer.
The master event method is effective for the events of which epicenters are within 20km from a master event, in the case the error of relative location is 0.2km for epicenters and 0.5km for focal depths. The errors of the relative epicenters and focal depths are also small for the possible change of structure parameters. Therefore, the regional change of focal depths can be detected clearly by the master event method using several master events. The precise distribution of hypocenters determined by the use of six master events shows that focal depths of all the earthquakes in this district are located in upper part of the crust shallower than 20km. Moreover the depth-frequency distribution of the earthquakes indicates two peaks at depths of 7-9 and 11-13km with abrupt decrease at 15-20km. Furthermore the depth of the seismic-aseismic boundary changes from place to place, such that the boundary dips from southwest to northeast by about 5km. The focal depths determined by this method is accurate enough to discuss the regional variation of seismic-aseismic boundary and its relation to the brittle-ductile boundary in the crust and to the Conrad discontinuity.抄録全体を表示PDF形式でダウンロード (889K) -
汎用プログラムの開発服部 定育1988 年 41 巻 2 号 p. 189-194
発行日: 1988/06/25
公開日: 2010/03/11
ジャーナル フリーThe purpose of this research is to develop a computer program in which the process of obtaining regional distibutions of maximum earthquake motions are carried out automatically by merely assigning the area. The seismic regional coefficient, which is based on the regional distribution of maximum earthquake motion, is very useful for aseismic design of structures. It is desirable, therefore, that the regional distributions of maximum earthquake motion can be obtained as easily as possible.
The outline of analysis is as follows: (1) The largest values of maximum earthquake motion on the base rock and on the ground at one site are calculated for all unit periods by using seismic data and attenuation models. (2) The expectation of the maximum earthquake motion for certain return periods are obtained from the frequency distribution of the values and the method of extreme value fitting. (3) The processes mentioned above are repeated for every site in the area concerned. (4) All the expected values of maximum earthquake motions are plotted on the map for certain return periods. (5) The contour lines are drawn on the basis of the plotted values, that is, the regional distributions of maximum earthquake motion are obtained for the area. All the processes can be carried out so long as the latitude and longitude which identify the area are given as input data.
Fundamental seismic information such as magnitude frequency distribution and epicentral distribution is also obtained as output.抄録全体を表示PDF形式でダウンロード (683K) -
堆積盆地上での地震動の解析と数値計算干場 充之, 堀家 正則, 出射 隆文, 岩田 知孝1988 年 41 巻 2 号 p. 195-202
発行日: 1988/06/25
公開日: 2010/03/11
ジャーナル フリーEffects of surface geology on seismic motions are investigated using observed seismograms by an array across the Kyoto basin extending from the rock outcrop near the eastern margin to the center. By a comparison with low-pass-filtered seismograms in the basin sites, the spatial wave-form variation and elongation of duration of the S-wave portion (from the onset of S-wave to a later part where amplitudes decrease to a specified low level) are found. The phase and group velocities of the wavelets in the S-wave portion suggest that these characteristics of the seismic motion in the Kyoto basin are primarily caused by the excitation of surface waves at the eastern margin of the basin.
To reproduce the recorded seismograms in the Kyoto basin, the extended Aki and Larner method is used. Though insufficient in amplitude, the simulated seismic waves exhibit the spatial wave-form variation and the elongation of duration time due to surface waves generated at the eastern margin of the basin.抄録全体を表示PDF形式でダウンロード (822K) -
六甲諏訪山実験坑黒石 裕樹, 小笠原 宏, 竹内 智一, 田中 豊, 水田 義明1988 年 41 巻 2 号 p. 203-213
発行日: 1988/06/25
公開日: 2010/03/11
ジャーナル フリーCrustal stress measurements were carried out monthly by a hydraulic fracturing method at the Rokko-Suwayama test site in Hyogo Prefecture. To determine a three-dimensional stress state, the measurements were made in three boreholes with lengths of about 15m and independent directions. The purpose of the measurements was to obtain basic data (1) to ascertain the reproducibility of a determined stress state and (2) to examine the applicability of the method to detecting a change in a stress state with time. To this end, exactly the same fractures were reopened in each measurement. During reopening them, the secondary-breakdown and the stable-flow pressures were measured. In order to attenuate pulsations of about 2-3 MPa in hydraulic pressure, an accumulator was engaged in the measurements. The accumulator consequently reduced the error of the measurements to about one-tenth compared with that of the previous ones. The stresses thus obtained were discussed in detail. It was ascertained that the method presently improved can detect a change with time of about 0.5 MPa (10%) and a change of 10° in a direction of principal axis.抄録全体を表示PDF形式でダウンロード (1299K) -
羽鳥 徳太郎1988 年 41 巻 2 号 p. 215-221
発行日: 1988/06/25
公開日: 2010/03/11
ジャーナル フリーThree Nankaido earthquakes which occurred near the Nankai Trough in 1707 (Hoei 4), 1854 (Ansei 1) and 1946 (Showa 21) hit the West Japan and the Wakayama, Tokushima and Kochi coasts, facing the Pacific Ocean, have suffered severe damage from large tsunamis. Inundation heights along these coasts were surveyed by the author (HATORI, 1978, 1980, 1981). In this paper, we investigate the tsunami behaviors in the Seto Inland Sea and Bungo Channel on the basis of newly collected documents. The obtained results are as follows:
1) Inundation heights (above M. S. L.) of the 1946 tsunami at the coasts facing the Bungo Channel were 1-3 meters, and heights at the south region of channel were large. The inundation heights of the 1707 Hoei and 1854 Ansei tsunamis have reached 3-4 meters.
2) According to the refraction diagram of the 1946 tsunami, the wave-fronts propagated into the Seto Inland Sea through the Kii and Bungo Channels meet the central part about 3 hours after the earthquake occerrence. The inundation heights about 1 meter were uniformly distributed.
3) The inundation heights of the 1707 Hoei and 1854 Ansei tsunamis in the western to central parts of the Seto Inland Sea were about 1.5 meters, but those in the eastern part were 2-3 meters. This behavior seems to be caused by the differences of tsunami heights between both channls and the propagated distances. For each Nankaido tsunami, the inundation heights along the coasts facing the Kii Channel were 1-2 meters larger than those of the Bungo Channel.
Althogh tsunami heights in the Seto Inland Sea were small compared with those of the Pacific side, many salt fields along the coast were damaged both by earthquakes and tsunamis. Further more, velocity of the tidal current was locally fast, and many sailors were shipwrecked in straits of the Inland Sea. In future, it is indispensable to take precautions against the effect of tidal currents.抄録全体を表示PDF形式でダウンロード (709K) -
翠川 三郎, 福岡 知久1988 年 41 巻 2 号 p. 223-233
発行日: 1988/06/25
公開日: 2010/03/11
ジャーナル フリーTo clarify physical meanings of seismic intensity scale and to make seismic intensity data more applicable in seismological and earthquake engineering studies, the correlation of Japan Meteorological Agency (J. M. A.) intensity scale with physical parameters of earthquake motion has been investigated. The total number of ground motion data used is 226 sets. These data cover the J. M. A. intensity of O to V. Results from the analysis of these data are as follows: (1) The correlation of intensity with horizontal motion is higher than that with the vertical in high intensity range, but is almost same as that with the vertical in low intensity range; (2) At low intensity range, high frequency motion with frequency of around 5Hz shows higher correlation with intensity, but the lower frequency motion with frequency of around 2Hz shows higher correlation in high intensity range; (3) At high intensity range, the contribution of duration time to intensity could be recognized; (4) The above-mentioned results are come from the difference in the objects to define the intensity at each intensity level; and (5) From low to high intensity range, peak ground acceleration shows relatively high correlation with intensity, but in high intensity range which has more significance in earthquake engineering problems, peak ground velocity or total power of ground acceleration shows higher correlation.抄録全体を表示PDF形式でダウンロード (1173K) -
―浅発地震の断層不均質性と短周期波動のドップラー効果―小山 順二, 鄭 斯華1988 年 41 巻 2 号 p. 235-245
発行日: 1988/06/25
公開日: 2010/03/11
ジャーナル フリーIsoseismals of seismic intensity distribution are shown not only by the size of earthquakes but also by the faulting mode and the rupture velocity of fault propagations. Unilateral faulting forms an egg-shaped isoseismal, meanwhile bilateral faulting forms an elliptical one. It is also shown that the ratio of major and minor axes of the isoseismals is sensitive to the variation of rupture velocities. Rupture velocities, faulting modes, fault trends of the 1964 Niigata and the 1983 Japan Sea earthquakes in Japan and the 1975 Haicheng and the 1976 Tangshan earthquakes in China have been determined from the seismic intensity maps by matching the theoretical isoseismals to those observed. Rupture velocities thus estimated are mostly 70 to 90% of shear wave velocity. They are a little larger than those obtained from long-period seismic waves. This difference would be considered as follows: Short-waves which determine the seismic intensity are strongly dependent on the rupture of small-scale fault heterogeneities and on the jerky-onsets and abrupt terminations of local rupture propagations. On the other hand, the rupture velocities from the long-waves represent the average rupture propagation along the whole length of the fault. Faulting-modes and fault trends estimated from the seismic intensity maps match with the independent results of the earthquake faultings. This suggests that the present method would be applicable to infer the faulting mode, rupture velocity, and rupture direction of some historical earthquakes.抄録全体を表示PDF形式でダウンロード (1352K) -
赤尾 嘉彦, 渡部 丹1988 年 41 巻 2 号 p. 247-257
発行日: 1988/06/25
公開日: 2010/03/11
ジャーナル フリーupture propagation process of multiple events is identified from short-period strong motion seismograms. The North Palm Springs earthquake (ML=5.9), which occurred in southern California on July 8, 1986, provided many strong motion records in the near field. CDMG's digital records from the five close stations (Δ=10-42km) are used for inversion analysis of multiple events. Short-period records obtained in the near field are thought to be more informative for understanding the local rupture mechanism than long-period worldwide records. However, waveforms of short-period records are usually very complicated to identify rupture mechanism. In addition, near-field records tend to include many kinds of seismic waves (i. e., direct P-, S-, reflected, or surface waves) at the same moment, while in the far-field records most of these waves would be separately observed. These facts make it difficult to discern distinct phases from strong motion records. Therefore, we employ non-stationary spectra (multi filter) to identify feeble distinct phases. Then sveral phases are successfully distinguished from other noiselike signals on the specta. Especially, two distinct phases, which have consicuous peaks and similar predominant frequencies among the records, appear in the all spectra of transverse components of the five stations. We regard them as S-wave arrivals that have directly propagated from two sub-sources. Source locations and trigger times of these sub-events are inversely calculated from the arrival times. Numerical results show that these events occurred immediately after initial rupture of the mainshock, and they were located close to the fault plane and within several kilometers from the initial hypocenter. Considering a fault dimension of 16km×12km which was inferred from aftershock distribution, it can be concluded that the major ruptures causing short-period motions concentrated near the initial hypocenter and did not extend throughout the fault plane.抄録全体を表示PDF形式でダウンロード (1164K) -
多田 堯, 橋本 学1988 年 41 巻 2 号 p. 259-262
発行日: 1988/06/25
公開日: 2010/03/11
ジャーナル フリーA fault of the 1918 Omachi earthquake (M=6.5) have been estimated based on the vertical crustal movement associated with the earthquake. The 1918 Omachi earthquake was the largest earthquake which had ever occurred near the northern part of the Itoigawa-Shizuoka Tectonic Line (ISTL). The estimated fault is a high dip angle reverse fault with left lateral strike slip component. The fault plane strikes to the N-S and dips to the east. The fault model suggests a possibility that the Chikuma Mountains (Northeastern Japan) thrust against the Matsumoto Basin (Southwestern Japan).抄録全体を表示PDF形式でダウンロード (376K) -
岩崎 貴哉1988 年 41 巻 2 号 p. 263-266
発行日: 1988/06/25
公開日: 2010/03/11
ジャーナル フリーPDF形式でダウンロード (394K) -
鈴木 敬一, 木下 肇1988 年 41 巻 2 号 p. 267-269
発行日: 1988/06/25
公開日: 2010/03/11
ジャーナル フリーPDF形式でダウンロード (314K) -
本多 了1988 年 41 巻 2 号 p. 271-282
発行日: 1988/06/25
公開日: 2010/03/11
ジャーナル フリーI review the recent topics of the mantle convection, especially with regard to the scales of mantle flows. The studies of 3-D velocity structure of the earth's mantle, geoid, gravity and isotope geochemistry provide a new perspective of the flow in the mantle. Several workers show a clear correlation between the distribution of hotspots and the geoid anomalies obtained by subtracting the contribution of the subducted slabs. Assuming a spherically symmetric viscous earth, several researchers could constrain the form of mantle flow and viscosity structure in the earth by correlating the calculated geoid with the observed one. Seismological studies suggest the existence of aseismic slab beneath 650km discontinuity. If this is a case, the aseismic slab may be explained by several ways on the basis of convection theories, that is, whole mantle convection, layered convection with thermal coupling and the penetrative convection. 3-D velocity structure obtained by several workers show the correlation between the geoid and lower mantle heterogeneity at low degrees (l=2-3) and this correlation was explained by the flow models. Possible seismological indicators of mantle layering are proposed. Seismic anisotropy found by the studies of the long period surface wave correlates with some mantle flow model and may suggest the flow direction or stress field in the real earth. The topography of core-mantle boundary revealed by recent seismological and geodetic studies may constrain the viscosity and thermal properties of mantle near CMB. The heterogeneity in the CMB may be closely related to the dynamics near CMB, for example, entrainment of dense material by the convection and the double diffusive convection. Isotope geochemistry shows that there are many geochemical source regions which have various sizes and age distrbution. Convective mixing was investigated and two opposite views have been presented. In one view, the convection is strong enough to homogenize the geochemical heterogeneities within a geologically short time; in another, both small and large scale heterogeneities persist for 1-2 b. y. The studies mentioned above are combined into the flow models by several workers.抄録全体を表示PDF形式でダウンロード (3000K) -
田中 貞二, 横田 治彦, 岩田 孝行1988 年 41 巻 2 号 p. 283-285
発行日: 1988/06/25
公開日: 2010/03/11
ジャーナル フリーPDF形式でダウンロード (281K)
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