著者

村上 ひとみ 鏡味 洋史

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.44, no.4, pp.271-281, 1991

被引用文献数

1

---

Seismic intensity is an important parameter measuring earthquake shaking severity, especially in regions where few strong motion instruments are in operation. This study aims to apply high-precision questionnaire intensity method widely used in Japan to other earthquake countries.<br>Based on the Modified Mercalli (MM) Intensity Scale, an intensity questionnaire form was prepared and survey was conducted for two California earthquakes and the 1988 Nepal-India border earthquake. First, intensity coefficients are assigned to each item category based on the definition of the scale. For each questionnaire, &ldquo;average&rdquo; item intensity is calculated by taking average of intensity coefficients as marked, and also &ldquo;maximum&rdquo; item intensity by taking maximum intensity coefficient among responses.<br>In California, intensities of the USGS isoseismal maps are found larger than the &ldquo;average&rdquo; item intensities and is comparable to the &ldquo;maximum&rdquo; item intensities, presumably because the USGS guideline of intensity assessment is to choose the maximum damage phenomena.<br>In order to solve this discrepancy, we introduced fuzzy set theory and expressed intensity coefficients as distribution of likelihood belonging to continuous intensity level. Accumulating membership functions corresponding to selected item categories, the maximum value of distribution suggests the most probable intensity.<br>New method for questionnaire intensity evaluation is examined for previous data. Questionnaire intensities reasonably correlate with intensities locally reported by the USGS and Nepalese agency. Simple adjustment based on age of buildings is found satisfactory for the case of California but not so for the Nepal-India region.

著者

功刀 卓

出版者

公益社団法人 日本地震学会

雑誌

地震. 2輯 (ISSN:00371114)

巻号頁・発行日

vol.53, no.1, pp.89-93, 2000-07-25

参考文献数

13

被引用文献数

2 6

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

瀬野 徹三

出版者

公益社団法人 日本地震学会

雑誌

地震. 2輯 (ISSN:00371114)

巻号頁・発行日

vol.46, no.4, pp.461-477, 1994-03-01

参考文献数

63

被引用文献数

2 1

---

Tectonics of the Taiwan region is reviewed. Relative plate motions so far obtained are described and rated. The most reliable solution gives 7.4cm/yr Philippine Sea-Eurasian motion in the N50&deg;W direction in central Taiwan. Plate boundary geometries and modes of plate consumption in the region are discussed on the basis of geophysical, geological and geomorphological data. The major thrust zones at the Western Foothills and the Longitudinal Valley constitute mechanical plate boundaries, but a considerable fraction of the relative plate motion is also consumed by the strike-slip faulting off the southeast coast of Taiwan.<br>The cause for the occurrence of the strike-slip faulting off the southeast coast of Taiwan is discussed based on the various models so far proposed. The bending of the Philippine Sea plate due to the subduction at the Ryukyu Trench and the collision in the Longitudinal Valley are similar to the tectonics of the Izu Peninsula region in Japan, and are the most likely cause for the strike-slip faulting.<br>The reconstruction of the motion and plate boundaries in the vicinity of Taiwan for the past 4-6m. y. is reviewed. The Philippine Sea-Eurasian motion for the past 4 Ma is similar to the present one. The motion prior to 4 Ma may be more northward than present due to the absence of subduction at the Philippine Trench. The Luzon arc started to collide with the continental margin of S. E. China around 4 Ma.

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

吉山 良一

出版者

公益社団法人 日本地震学会

雑誌

地震 第1輯 (ISSN:00371114)

巻号頁・発行日

vol.9, no.6, pp.250-260, 1937-06-15 (Released:2010-03-09)

参考文献数

4

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

弘瀬 冬樹 中島 淳一 長谷川 昭

出版者

日本地震学会

雑誌

地震. 2輯 (ISSN:00371114)

巻号頁・発行日

vol.60, no.3, pp.123-138, 2008-02-15

参考文献数

46

被引用文献数

6

著者

今村 明恒

出版者

公益社団法人 日本地震学会

雑誌

地震 第1輯 (ISSN:00371114)

巻号頁・発行日

vol.11, no.8, pp.372-384, 1939-08-25 (Released:2010-03-09)

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.