著者

鳥海 勲 竹内 吉弘 大場 新太郎 堀家 正則 井上 豊 馬場 研介

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.43, no.3, pp.373-378, 1990-09-24 (Released:2010-03-09)

参考文献数

5

被引用文献数

4 4

---

Seismic wave records at the surface of sedimentary plain are mainly composed of main phase and surface waves. The informations of input wave record in base rock and S wave velocity distribution to base rock are enough to consider the main phase. And moreover the informations about underground structure to bed rock of all sections of plain are necessary to discuss surface wave which travels from surrounding rock range to observation point. For this items of the Osaka plain, there were some crumbs of informations. In 1988, we tried two explosions at a manmade “Hokko” island in Osaka bay. This paper shows the results: five ground structures and a countour map of depth to base rock of the Osaka plain.

著者

関谷 溥

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.29, no.3, pp.299-311, 1976-09-15 (Released:2010-03-11)

参考文献数

7

被引用文献数

4 10

---

The Izuhanto-oki earthquake of May 9, 1974 (M6.9) was preceded by an anomalous seismicity as shown Fig. 1. The duration from the anomalous Seismicity to the mainshock was about 10 years and 4 months. Similar phenomena were also found for 10 events which occurred at shallow depths in Japan.Considering that these data show a linear relation between the magnitude of earthquakes M and duration log T (day), the author calculated the coefficient of logT=bM+a by using the method of least squares as follows: logT=bM+a=0.77M-1.65The relation between the above formula and that of TSUBOKAWA (1969), RIKITAKE (1975) and SCHOLZ et al. (1973), which indicate with a certain accuracy the magnitude and time of an expected earthquake was given by Fig. 7.The author believes that the anomalous seismicity preceding earthquakes is one of the potential parameters which could be employed for earthquake prediction. On the other hand, in some certain fracture zones were found a premonitory change before some events. These phenomena generally are called foreshocks. Anomalous seismicity preceding smaller events cannot clearly be found by data of the Japan Meteorological Agency as shown Fig. 8. It is, however, not certain yet whether such earthquakes were not really preceded by anomalous seismicity.Our study requires further accumulation of examples from the viewpoint of ascertaining the existence of anomalous seismicity preceding earthquakes by observation network for small earthquakes.

著者

竹内 均

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.27, no.1, pp.85-87, 1974-03-30 (Released:2010-03-11)

参考文献数

8

著者

浜田 信生 野坂 大輔 小林 正志 吉川 一光 石垣 祐三 田利 信二朗

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.64, no.4, pp.197-209, 2012-06-25 (Released:2012-08-08)

参考文献数

28

---

Matsushiro earthquake swarm is a most well known and well studied earthquake swarm in the history of seismology. From viewpoints of geophysics, geology and geochemistry, various observations, field surveys and analyses had been made to reveal characteristics of the swarm. On the basis of these studies, several models had been proposed to explain why and how the swarm originated and developed. However, majority of studies had focused on the activity around the climatic stage of the swarm in 1966 and so far, studies on the initial stage of the swarm in mid 1965 had remained few due to lack of sufficient observation data. The exact area where the swarm was born had not been known and the swarm was vaguely believed to originate from the area around Mt. Minakami in former Matsushiro town (now belongs to Nagano city). Considering that the manner of initial development of swarm activity represents an important characteristic of the swarm earthquake, we tried to get more clear view about initial stage of the swarm activity in this study. We re-investigated seismograms obtained by routine observation and studied seismograms of temporal stations for the first time which had not been processed yet. By scanning analogue seismograms, we made a complete data set of S-P times with high precision for each station. Although the data set of S-P times from two stations are not sufficient for conventional hypocenter location, we were able to narrow down a possible source area of the swarm activity under the reasonable assumptions. By considering direction of initial motion of P waves and assuming local velocity model of the upper crust in the region and plausible focal depth of 4.5km of the swarm earthquake, we found that the area of swarm in the very beginning in August, 1965 is located about 4km north-east of the Matsushiro earthquake fault (MEF) in former Wakaho town near its border with former Matsushiro town. Size of the initial swarm area was 3-4km in diameter. While swarm activity in the initial region was gradually decaying in September new swarm activity appeared separately from the initial swarm area around southern and south-west part of the MEF. Activity in the new swarm area had been increasing and it was developed to more intense swarm after October, 1965 when establishment of temporal seismic station network of the Earthquake Research Institute, University of Tokyo enabled detailed hypocenter location. The new swarm area coincides with the area where large amount of ground water moved upward and was released on the ground surface in the climatic stage of the swarm. It was well known that source area of the swarm was split and expanded toward north-east and south-west after March, 1967 in its climatic stage. Present study on the initial development of swarm area suggested that characteristics of the Matsushiro earthquake swarm such as splitting and expansion of its source area toward northeast and southwest were inherent in their early stage of the activity in August and September, 1965.

著者

長谷川 昭 海野 徳仁 高木 章雄 鈴木 貞臣 本谷 義信 亀谷 悟 田中 和夫 澤田 義博

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.36, no.2, pp.129-150, 1983-06-25 (Released:2010-03-11)

参考文献数

18

被引用文献数

13 13

---

Precise relocation of earthquakes occurring in Hokkaido and northern Honshu during the period from January, 1979 to October 1981 is made by using 35 stations of the microearthquake observation networks of Tohoku University, of Hokkaido University, of Hirosaki University and of Central Research Institute of Electric Power Industry. Obtained hypocenter distribution shows the double-planed structure of the deep seismic zone in the whole area of Hokkaido and northern Honshu including the junction between the northeastern Japan arc and the Kurile arc. At the junction the deep seismic zone is contorted but is still double-planed at least in the upper 150km depth range. Beneath the southern end of the Kurile arc (central and eastern Hokkaido) the upper seismic plane of the double seismic zone disappears at depths greater than about 120km, whereas the seismicity in the upper seismic plane is still active in this depth range beneath the northeastern Japan arc.Hypocenters on the deep seismic zone beneath Hokkaido, relocated in the present study, are systematically shifted to the SE or SSE direction in comparison with the locations by the Hokkaido University network. This systematic shift of hypocenters is found to be well explained by the existence of the subducted lithosphere with seismic wave velocities higher than the surrounding mantle.

著者

花籠 靖 中西 一郎 森谷 武男 笠原 稔

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.43, no.2, pp.213-225, 1990-06-24 (Released:2010-03-11)

参考文献数

19

---

The rapid determination of seismic moment and source mechanism for near earthquakes is attempted by a moment tensor inversion of long-period seismic waves. The inversion method is based on a normal mode theory. The data for the inversion are recorded at three stations in Hokkaido, Japan. Each station is equipped with a three-components very-broad-band seismograph. Source parameters of six earthquakes (mb_??_5.5) in and around the Japan region (epicentral distances of 200 to 1500km) for the period from January to April 1989 are determind by applying the moment tensor inversion to the long-period waveform data. Changing the components (UD, NS, EW) and record length used in the inversion the stability in the moment tensor solution is examined. A good S/N ratio is required to obtain a stable solution in the inversion of three-components data from a single station. Data length of 4-8min after the earthquake origin time is enough to attain stable source mechanism determination by using the three-stations data.

著者

笹谷 努

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.26, no.1, pp.67-76, 1973

被引用文献数

1

---

A particular type of phase designated as the P₂-phase is found in the P wave train around 9 seconds after the first arrival of the earthquake off east coast of Aomori prefecture of March 29, 1965. In the previous paper, the P₂-phase has been interpreted as the stopping phase from the analysis of the motion direction of this phase. In the present paper, the P₂-phase is re-examined in the wave form of the theoretical displacement of P wave from a fault near the earth's surface, because the unreasonable interpretation for the fault length and the rupture velocity has been given. The examination shows that the P₂-phase concerned does not consist of the stopping phase, but of reflected sP phase, and that the wave form of direct P wave from a fault with a fault length greater than its depth may be disturbed by the reflected waves.<br>The seismic moment and the apparent stress for the present earthquake are estimated to be 3.20&times;10²⁵dyne-cm and 5 bars, respectively.

著者

領木 邦浩

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.52, no.1, pp.51-63, 1999-06-30 (Released:2010-03-11)

参考文献数

63

被引用文献数

2 7

---

The regional gravity anomalies were calculated in Southwestern Japan presuming a three-dimensional density structure. The gravitational effect was calculated by the structural model represented by aggregate bodies of triangular vertical prisms which was generated by compiling the existing vast amount of data on the depths of lower surface of the crust and upper surface of the plate slab in this region. The densities of the Pacific and Philippine Sea plate slabs, upper and lower crusts and asthenosphere were presumed referring to past research. It was shown by the calculation that the gravitational effect of the crust has larger amplitude than that of the plate slabs in this region, while variation of the presumptive density of the plate slab is more effective than that of the crust. Comparison of the regional gravity correction by means of the above method with the ones by the spatial filtering method and the least square method shows that the former derives more accurate local gravity anomaly than the latter. The regional gravity anomaly can be calculated by the above method at an arbitrary point in Southwestern Japan, and then more accurate regional gravity correction can be performed for the analysis of local gravity structure.

著者

山内 常生 下 道国

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.35, no.3, pp.435-446, 1982-09-25 (Released:2010-03-11)

参考文献数

9

被引用文献数

6 7

---

The concentration of 222Rn in air in the gallery at Mikawa. Crustal Movement Observatory (Toyohashi City, central Japan) has been continuously measured with a flow-type ionization chamber since April, 1977 for the investigation of pre-earthquake anomalies. The observed 222Rn concentration shows remarkable increase after rainfall. It seems that 222Rn rich air is squeezed in the gallery by the contractile force caused by rainfalls from faults with elevated 226Ra content. The variation of 222Rn concentration in the gallery has been calculated from the rainfall data from June, 1977 to December, 1979. Sometimes remarkable disagreements between the observed and calculated values of the 222Rn concentration are seen before and after the occurrence of nearby earthquakes. Such a disagreement might be a precursor of nearby earthquake. The concentration of 222Rn is also influenced by the changes in atomospheric pressure; it increases as the pressure drops and decreases as the pressure rises. Seasonal variations are recognized, too. Continuous observation of 222Rn has also been started in June, 1980 at Kikugawa Crustal Movement Observational Station (Shizuoka Prefecture, central Japan).

著者

松浦 充宏

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.50, no.appendix, pp.213-227, 1998-03-31 (Released:2010-11-17)

参考文献数

42

被引用文献数

1

---

Physical processes of earthquake generation may be divided into three different stages, such as tectonic loading, quasi-static nucleation, and subsequent dynamic rupture propagation. The basic equations governing the earthquake generation process are; the equation of motion in elastodynamics that relates slip motion on a fault surface with deformation of the surrounding elastic media, the fault constitutive law that prescribes the relation between shear stress and fault slip (and/or slip velocity) on the fault surface during earthquake rupture, and the loading function that gives the increase rate of eacternal shear stress induced by relative plate motion. Recent development in physics of earthquake generation enables us to simulate the entire process of earthquake generation by solving these nonlinear coupled equations. For long-term prediction of earthquake occurrence the detection of crustal movements associated with tectonic loading is important. For short-term prediction the detection of precursory phenomena associated with rupture nucleation is important. In either case it is necessary to establish an interactive forecast system based on theoretical simulation and continuous monitoring of earthquake generation processes.

著者

高橋 雪江 石原 吉明 諸田 智克 平松 良浩 古本 宗充

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.57, no.2, pp.233-235, 2004-12-27 (Released:2010-03-11)

参考文献数

5

著者

大久保 泰邦

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.41, no.1, pp.115-123, 1988-03-25 (Released:2010-03-11)

参考文献数

21

---

The aeromagnetic anomalies over the Izu-Oshima Island and its surroundings were interpreted using 3-D magnetic inversion analysis.A magnetic positive anomaly extends from the south of Oshima to the neighboring off-shore area trending northwest by west. Taking the previous rock-magnetic studies into consideration, the magnetic anomaly in the Oshima Island is caused by igneous rocks having high remanent magnetizations. Calculation shows that the observed anomaly can be interpretedwell by the effect of topography over the Oshima Island except for neighboring off-shore area.The thick magnetic layer trending NWW-SEE direction around the Oshima Island was suggested by the iterative inversion. The distribution of the thick magnetic layer coincides with the NW-SE trending dike distribution and the NWW-SEE trending alignment of submarine volcanoes. This indicates that the observed magnetic anomaly is associated with the subsurface volcanisms of the island. According to the comparison between the observed anomalies and the calculated anomalies caused by topographic relief, and the geometry of thick magnetic layer, the high magnetic anomaly around the Oshima Island includes the effect not only of surface volcanics but of a number of high magnetized concealed intrusives underneath.

著者

佐藤 裕

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.46, no.1, pp.49-52, 1993-06-24 (Released:2010-03-11)

参考文献数

10

被引用文献数

3

著者

太田 陽子 小田切 聡子 佐々木 寿 向山 栄

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.58, no.4, pp.385-399, 2006-03-31 (Released:2010-03-11)

参考文献数

19

---

A flight of late Holocene marine terrace fringes the central area of Puget Sound, and records uplift over an extensive area above the Seattle fault zone. The E-W trending blind thrust fault zone is a source of major seismic hazards in the Seattle metropolitan area. Gravity and seismic reflection surveys indicate a south- dipping fault plane, but its exact location and timing of past activities were unknown. LiDAR topographic mapping of the Puget lowland revealed several fault scarps on the glacial landscape hidden under the dense forest. We observed the fault, offset on the Holocene marine terrace surface and measured the former shoreline height at 97 locations using LiDAR DEM to map terrace deformation patterns and their relation to the faults. Studied areas include 1) Alki Point, 2) the southern part of Bainbridge Island, and 3) the southeastern Kitsap Peninsula near Port Orchard and southwestern Bainbridge Island. The height of the former shorelines marked by the Holocene terrace changes from ca. 10.7 to 7.3m a. s. l in the west to 12.2 to 10.1m in the east of the Toe Jam Hill fault, and 10.6 to 7.8m in the west to 9.7 to 7.9m in the east of the Waterman Point fault. These changes indicate differential uplift of the terrace surfaces across the faults. There are two newly identified faults in this study. One is the Point Glover fault that is marked by a scarp in the LiDAR map and associated 2m offset of the terrace surface. The other is the South Beach Point fault inferred by the northward tilt of the terrace surface. Because these faults strike E-W, parallel to the main Seattle Fault on its south side, and have south-facing scarps and north-dipping fault planes, they are probably back-thrsuts to the main Seattle Fault. The width of the backthrust zone is at least 4km. The age of the terraces approximately coincides with the most recent faulting event on the surface fault (at least for Toe Jam Hill Fault, ca. 1000yr BP), thus the differential uplift probably occurred simultaneously with fault movement. Although the surface backthrust scarps are less than a few kilometers long and vertical offset is 2-3m, the total amount of uplift reaches about 12m. Subtracting the effect of the vertical displacement and the amount of northward tilting, the uplift of several meters still remains on the Seattle fault zone of over about 4km wide. This broad zone of uplift is not due to the slip on the subsidiary backthrusts, but probably due to the blind thrust of the main Seattle fault. We infer that at least some of the coastal deformation is caused by broad surface upwarping above the Seattle fault and that the upwarping occurred at ca. 1000yrs BP, associated with ruptures on at least three of the backthrusts. The uplift and faulting may represent the largest earthquake in the Puget Sound area during the late Holocene.

著者

勝間田 明男

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.53, no.1, pp.83-88, 2000-07-25 (Released:2010-03-11)

参考文献数

20

著者

石橋 克彦

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.28, no.3, pp.347-364, 1975-10-10 (Released:2010-03-11)

参考文献数

31

被引用文献数

1

---

For the purpose of precise relocation of earthquakes which had occurred in Japan around the first quarter of this century, a computer program was written which calculates hypocenter parameters by the method of least squares using S-P times at more than three stations and employing an arbitrary multi-layered crustal structure.As examples of relocation, about five semi-destructive earthquakes in the Kanto district: the Ryugasaki earthquake of 1921, the Yatabe earthquake of 1922, the Mitsukaido earthquake of 1923, the Uraga Channel earthquake of 1922 and the Haneda earthquake of 1926, all near-field S-P time data were carefully examined and hypocenters were redetermined. The epicenters and the focal depths obtained are expected to be uncertain by less than ±10km except the Uraga Channel earthquake. The former three, which has been suspected to be precursory activities of the Great Kanto earthquake of 1923, were ascertained to have their origins in the upper mantle beneath the SW part of the Ibaraki Prefecture where is even now a remarkable swarm area.

著者

堀内 茂木 山本 明 松沢 暢 河野 俊夫 長谷川 昭 高木 章雄 伊神 輝 山田 守 青木 治三

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.38, no.4, pp.529-539, 1985-12-25 (Released:2010-03-11)

参考文献数

11

被引用文献数

1

---

A real-time system of automatic detection and location of seismic events has been developed by using a personal computer. Since speed of computation by a personal computer is low, a simple digital band-pass filter has been developed for the real-time system. The band-pass filter needs only several times of addition and subtraction to get an output. Event dection is based on a ratio of short to long term average of outputs of the filter whose cutoff frequencies are set to decrease amplitude of long period noise owing to microtremor and amplitude of short period noise owing to culture. Arrival times of the P and S waves are determined by applying Akaike Information Criterion (AIC) to outputs of the band-pass filter with narrow band whose central frequency is set to be a value of predominant frequency of the seismic signal.A temporary seismic observation with 8 stations for the aftershocks of the 1984 Western Nagano Prefecture Earthquake has been made by the use of radio and telephone telemetries. The real-time system of the automatic location of the seismic events was tested to demonstrate that hypocenter distribution obtained by the real-time system is nearly consistent with that determined from arrival time data which were read manually. It is shown that hypocenters of 60% among triggered events can be determined by this real-time system.

著者

植平 賢司 深畑 幸俊 飯高 隆 溝上 恵

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.47, no.3, pp.347-350, 1994-10-14 (Released:2010-03-11)

参考文献数

4

著者

諸井 孝文 武村 雅之

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.52, no.1, pp.11-24, 1999-06-30 (Released:2010-03-11)

参考文献数

37

被引用文献数

1 7

---

The distribution of seismic intensity I=VII (very disastrous) for the 1995 Hyogoken-Nanbu earthquake was reported by the Japan Meteorological Agency (JMA). It was the first announcement since the seismic intensity in JMA scale had been revised in 1949 to include the highest class of I=VII. Originally the seismic intensity of I=VII was defined as “strong ground motion with collapse more than 30% of wooden houses”, which was based on destructive damage at the 1948 Fukui earthquake. During the last half century, aseismic design of wooden houses has progressed especially due to the popularization of the standard building code published in 1950. Recent cities like Kobe include various kinds of buildings in seismic performance from modern earthquake-resisting structures to old and vulnerable residences. Therefore the seismic intensity of I=VII should be recognized as “with collapse more than 30% of less aseismic wooden houses such as those built before 1950”. From these points, it must be confirmed whether the increase of the seismic performance of buildings was taken into account in the reported distribution of I=VII. First we review the term of “collapse of houses”. Then relationship between the collapse rate of houses and the overturning acceleration of tombstones is investigated and analyzed using damage data obtained from the 1995 Hyogoken-Nanbu earthquake. The analysis result and its comparison to the relationships for past earthquakes show that the average of the seismic performance has increased by 40-60% from 1948 to 1995, and that the collapse rate of 10% at the Hyogoken-Nanbu earthquake corresponds to that of 30% at the Fukui earthquake for the same overturning acceleration. Comparing the reported distribution of I=VII to the area with collapse more than 10%, historical continuity of the seismic intensity in JMA scale is discussed.

著者

入倉 孝次郎 釜江 克宏

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.52, no.1, pp.129-150, 1999-06-30 (Released:2010-03-11)

参考文献数

33

被引用文献数

9

---

We simulate strong ground motions during the 1948 Fukui earthquake with the JMA magnitude 7.1 based on a heterogeneous source model and the hybrid simulation technique. So far there are no existing source models available for simulating strong ground motions from the 1948 Fukui earthquake. Most of the source models have been assumed to have uniform slip distribution on rectangular fault plane. Such models could generate ground motions only available longer than several seconds, underestimating shorter period motions (<1sec) of engineering interest. The objective of this paper is to construct a heterogeneous source model for simulating strong ground motions in a broad period band during the 1948 Fukui earthquake. We assume two source models to examine: Model 1 is a reverse fault model determined from the analysis of geodetic data by YOSHIOKA (1974) and Model 2 is a normal fault model from strong motion displacement data by KIKUCHI et al. (1999). Heterogeneous slip distribution on fault plane is estimated based on the self-similar scaling relationships of seismic moment versus asperity areas and slips by Somerville et al. (1999). Then we obtained the standardized source model consisting of two asperities to have the average characteristics of asperities for the seismic moment of the Fukui earthquake. Relative locations and rupture times of the asperities on the fault plane are determined following the source model by KIKUCHI et al. (1999). The maximum asperity corresponding to the second event in their model has an area of 12×12km2 and slip of 1.7m and is located under the most heavily damaged area along the buried fault, known as the Fukui earthquake fault. The smaller asperity corresponding to the first event is located north of the maximum asperity. Rupture was initiated at the northern edge of the smaller asperity, propagated toward south, then broke to start the maximum asperity 7 seconds after the initial rupture. Large ground motions from both models, Model 1 and 2, are spread over the Fukui basin, although peak velocity distributions are rather different between the two models. Areas over 30% collapse ratio during the Fukui earthquake correspond to those with peak velocity over 60cm/s for Model 1 and over 80cm/s for Model 2. The level of the peak velocity in the areas with more than 30% collapse ratio are estimated to be over 80cm/s connected with both results by MOROI et al. (1998) and MIYAKOSHI and HAYASHI (1998). Pseudo velocity response spectra in the center of the Fukui basin for Model 2 have almost the same level of the observed ones at Takatori (TKT) and the simulated ones at Fukuike (FKI) within the damage belt during the 1995 Hyogo-ken Nanbu earthquake. We conclude that the damage distribution during the Fukui earthquake is well explained by strong ground motions simulated for Model 2 combined with the normal fault model by KIKUCHI et al.. (1999) and a standardized heterogeneous source model developed by SOMERVILLE et al. (1999).