著者

Y. Otsuka T. Ogawa A. Saito T. Tsugawa S. Fukao S. Miyazaki

出版者

The Seismological Society of Japan, Society of Geomagnetism and Earth, Planetary and Space Sciences, The Volcanological Society of Japan , The Geodetic Society of Japan , The Japanese Society for Planetary Sciences

雑誌

Earth, Planets and Space (ISSN:13438832)

巻号頁・発行日

vol.54, no.1, pp.63-70, 2002 (Released:2010-03-09)

参考文献数

24

被引用文献数

237

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The dual frequency radio signals of the Global Positioning System (GPS) allow measurements of the total number of electrons, called total electron content (TEC), along a ray path from GPS satellite to receiver. We have developed a new technique to construct two-dimensional maps of absolute TEC over Japan by using GPS data from more than 1000 GPS receivers. A least squares fitting procedure is used to remove instrumental biases inherent in the GPS satellite and receiver. Two-dimensional maps of absolute vertical TEC are derived with time resolution of 30 seconds and spatial resolution of 0.15° × 0.15° in latitude and longitude. Our method is validated in two ways. First, TECs along ray paths from the GPS satellites are simulated using a model for electron contents based on the IRI-95 model. It is found that TEC from our method is underestimated by less than 3 TECU. Then, estimated vertical GPS TEC is compared with ionospheric TEC that is calculated from simultaneous electron density profile obtained with the MU radar. Diurnal and day-to-day variation of the GPS TEC follows the TEC behavior derived from MU radar observation but the GPS TEC is 2 TECU larger than the MU radar TEC on average. This difference can be attributed to the plasmaspheric electron content along the GPS ray path. This method is also applied to GPS data during a magnetic storm of September 25, 1998. An intense TEC enhancement, probably caused by a northward expansion of the equatorial anomaly, was observed in the southern part of Japan in the evening during the main phase of the storm.

著者

Yoh Nakazawa Toshimi Okada Kazuo Shiokawa

出版者

The Seismological Society of Japan, Society of Geomagnetism and Earth, Planetary and Space Sciences, The Volcanological Society of Japan , The Geodetic Society of Japan , The Japanese Society for Planetary Sciences

雑誌

Earth, Planets and Space (ISSN:13438832)

巻号頁・発行日

vol.56, no.12, pp.e41-e44, 2004 (Released:2010-03-09)

参考文献数

20

被引用文献数

32

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“SEKKI” phenomena often appear in the Japanese historical literatures as distinct red emission in the nocturnal sky. The Japanese word “SEKKI” means the red atmosphere. We compile 16 events of SEKKI for 12-19th centuries in the literatures. In order to understand the SEKKI phenomena, we compared 2 events of SEKKI on February 21, 1204, and September 17, 1770, with the characteristics of low-latitude auroras studied recently by modern scientific methods. We conclude that these historical SEKKI phenomena are probably giant low-latitude auroras.

著者

Takai Nobuo Shigefuji Michiko Rajaure Sudhir Bijukchhen Subeg Ichiyanagi Masayoshi Dhital Megh Raj Sasatani Tsutomu

出版者

Springer

雑誌

Earth, Planets and Space (ISSN:13438832)

巻号頁・発行日

vol.68, no.1, pp.1-8, 2016-01-26

被引用文献数

94 2

---

On 25 April 2015, a large earthquake of Mw 7.8 occurred along the Main Himalayan Thrust fault in central Nepal. It was caused by a collision of the Indian Plate beneath the Eurasian Plate. The epicenter was near the Gorkha region, 80 km northwest of Kathmandu, and the rupture propagated toward east from the epicentral region passing through the sediment-filled Kathmandu Valley. This event resulted in over 8000 fatalities, mostly in Kathmandu and the adjacent districts. We succeeded in observing strong ground motions at our four observation sites (one rock site and three sedimentary sites) in the Kathmandu Valley during this devastating earthquake. While the observed peak ground acceleration values were smaller than the predicted ones that were derived from the use of a ground motion prediction equation, the observed peak ground velocity values were slightly larger than the predicted ones. The ground velocities observed at the rock site (KTP) showed a simple velocity pulse, resulting in monotonic-step displacements associated with the permanent tectonic offset. The vertical ground velocities observed at the sedimentary sites had the same pulse motions that were observed at the rock site. In contrast, the horizontal ground velocities as well as accelerations observed at three sedimentary sites showed long duration with conspicuous long-period oscillations, due to the valley response. The horizontal valley response was characterized by large amplification (about 10) and prolonged oscillations. However, the predominant period and envelope shape of their oscillations differed from site to site, indicating a complicated basin structure. Finally, on the basis of the velocity response spectra, we show that the horizontal long-period oscillations on the sedimentary sites had enough destructive power to damage high-rise buildings with natural periods of 3 to 5 s.

著者

Masayuki Kikuchi Misao Nakamura Kazumitsu Yoshikawa

出版者

Society of Geomagnetism and Earth, Planetary and Space Sciences, The Seismological Society of Japan, The Volcanological Society of Japan , The Geodetic Society of Japan , The Japanese Society for Planetary Sciences

雑誌

Earth, Planets and Space (ISSN:13438832)

巻号頁・発行日

vol.55, no.4, pp.159-172, 2003 (Released:2010-03-09)

参考文献数

32

被引用文献数

130

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In the 1940's, several destructive earthquakes occurred in western Japan. Seismograms in this period were usually recorded on smoked paper and the quality was poor compared to modern digital data. But the recent development of image processing technology enabled us to reconstruct feasible waveform data, whereby we investigated source rupture processes of two devastating earthquakes: the Tonankai earthquake (M7.9) of December 7, 1944, and the Mikawa earthquake (M6.8) of January 13, 1945. The results for the Tonankai earthquake show that the source roughly consists of a single asperity with a length scale of 100 km, having no segment structure with a smaller length-scale. Such a feature seems to be reflected to the sea bottom topography above the source region. The main source parameters are as follows: the seismic moment = 1.0 × 1021 Nm (Mw=7.9); the fault area = 140 km × 80 km; (strike, dip, rake) = (225°, 15°, 79°); the maximum and averaged dislocations = 4.4 m and 3.0 m, respectively. The analysis of the seismograms for the Mikawa earthquake shows that the source is a reverse fault with a slight left-lateral component. The pressure axis is directed to ENE-WSW, which is a little rotated from the EW compression axis prevailing in western Japan. This fault can be regarded as the southern extension of the Nobi earthquake fault system. The main source parameters are as follows: the seismic moment = 1.0 × 1019 Nm (Mw=6.6); the fault area = 20 km × 15 km; (strike, dip, rake) = (135°, 30°, 65°); the maximum and averaged dislocations are 2.1 m and 1.1 m, respectively. The slip distribution mainly consists of two asperities: the one near the hypocenter and the other 10-15 km northwest from it. The heavily damaged area is well correlated with the northwestern asperity.

著者

Yoshiko Yamanaka Masayuki Kikuchi

出版者

Society of Geomagnetism and Earth, Planetary and Space Sciences, The Seismological Society of Japan, The Volcanological Society of Japan , The Geodetic Society of Japan , The Japanese Society for Planetary Sciences

雑誌

Earth, Planets and Space (ISSN:13438832)

巻号頁・発行日

vol.55, no.12, pp.e21-e24, 2003 (Released:2010-03-09)

参考文献数

11

被引用文献数

164

---

On September 26, 2003, a large earthquake with a magnitude of 8.0 occurred along the Kuril trench off Tokachi, Hokkaido, Japan. We investigated the source process by using teleseismic P- and SH-wave data. The main source parameters are as follows: the seismic moment 1.0×1021 Nm (Mw = 8.0); (strike, dip, rake) = (230°, 20°, 109°); the depth of initial break point 25 km; source duration 40 sec; and the maximum slip 5.8 m. We estimated the fault area to be 90 × 70 km2, the average slip 2.6 m, and the stress drop 5.0 MPa. This earthquake was an interplate earthquake associated with the subduction of the Pacific plate. The rupture propagated northward from a shallow to a deep region. In this area, a great earthquake (magnitude 8.2) occurred in 1952. We also made limited inversion of nearfield records of the 1952 event and found that the 2003 asperity was also ruptured in 1952. Our result suggests that the 2003 Tokachi-oki earthquake was a recurrent event of the 1952 Tokachi-oki earthquake.

著者

Gehrels Tom

出版者

公益社団法人 日本地震学会、地球電磁気・地球惑星圏学会 、特定非営利活動法人 日本火山学会、日本測地学会、日本惑星科学会

雑誌

Earth, planets and space (ISSN:13438832)

巻号頁・発行日

vol.51, no.11, pp.1155-1161, 1999

参考文献数

52

被引用文献数

3

---

The statistics of Earth-approaching asteroids are first summarized, and an enhanced frequency of objects smaller than 100 meters is noted. Superposed on these random hazards may be a periodic one of new comets due to galactic tides of the Oort Cloud with a period of 26-36 Myr (Rampino, 1998). New asteroids and comets are being found evermore frequently because new telescope-and-detector systems are coming on line. These are intended primarily for the discovery of dangerous objects, but a beginning has been made with the study of statistics of main-belt asteroids. In addition to trans-Neptunian objects, cis-Neptunian “Centaurs” are recognized, which may be a link in the evolution of short-period comets and thereby contribute to the flux of Earth approachers. With the new equipment coming on line, we are beginning to see that the global hazard will be mostly quantified within a few decades. We do see a shortage in astrometric follow up fainter than about the 20th magnitude.

著者

Ceja Maria Rodríguez Goguitchaichvili Avto Calvo-Rathert Manuel Morales-Contreras Juan Alva-Valdivia Luis Elguera José Rosas Fucugauchi Jaime Urrutia Granados Hugo Delgado

出版者

公益社団法人 日本地震学会、地球電磁気・地球惑星圏学会 、特定非営利活動法人 日本火山学会、日本測地学会、日本惑星科学会

雑誌

Earth, Planets and Space (ISSN:13438832)

巻号頁・発行日

vol.58, no.10, pp.1349-1358, 2006

被引用文献数

11

---

This paper presents new paleomagnetic results from 24 independent cooling units in Tequila area (western Trans-Mexican Volcanic Belt). These units were recently dated by means of state-of-the-art <SUP>40</SUP>Ar-<SUP>39</SUP>Ar method (Lewis-Kenedy <I>et al</I>., 2005) and span from 1130 to 150 ka. The characteristic paleodirections are successfully isolated for 20 cooling units. The mean paleodirection, discarding intermediate polarity sites, is <I>I</I> = 29.6&deg;, <I>D</I> = 359.2&deg;, <I>k</I> = 26, &alpha;<SUB>95</SUB> = 7.1&deg;, <I>n</I> = 17, which corresponds to the mean paleomagnetic pole position <I>P</I><SUB>lat</SUB> = 85.8&deg;, <I>P</I><SUB>long</SUB> = 84.3&deg;, <I>K</I> = 27.5, <I>A</I><SUB>95</SUB> = 6.9&deg;. These directions are practically undistinguishable from the expected Plestocene paleodirections, as derived from reference poles for the North American polar wander curve and in agreement with previously reported directions from western Trans-Mexican Volcanic Belt. This suggests that no major tectonic deformation occurred in studied area since early-middle Plestocene to present. The paleosecular variation is estimated trough the study of the scatter of virtual geomagnetic poles giving <I>S<SUB>F</SUB></I> = 15.4 with <I>S<SUB>U</SUB></I> = 19.9 and <I>S<SUB>L</SUB></I> = 12.5 (upper and lower limits respectively). These values are consistent with those predicted by the latitude-dependent variation model of McFadden et al. (1991) for the last 5 Myr. The interesting feature of the paleomagnetic record obtained here is the occurrence of an intermediate polarity at 671&plusmn;13 ka which may correspond the worldwide observed Delta excursion at about 680-690 ka. This gives the volcanic evidence of this event. Two independent lava flows dated as 362&plusmn;13 and 354&plusmn;5 ka respectively, yield transitional paleodirections as well, probably corresponding to the Levantine excursion.

著者

Kimura Hiroshi Fukagawa Misato Tamura Motohide KOBAYASHI Hiroshi YAMAMOTO Tetsuo ISHII Miki SUTO Hiroshi

出版者

Terra Scientific Pub. Co.

雑誌

Earth, planets and space (ISSN:13438832)

巻号頁・発行日

vol.62, no.1, pp.111-116, 2010-01-01

参考文献数

37

---

We report near-infrared imaging observations of the β Pic dust disk, from which we infer the orbital architecture of planetesimal belts that remain near mean motion resonances (MMRs) with a planet at 62 AU. Our results reveal that one of the previously identified planetesimal belts lies in the 2/3 MMR with the planet, similar to the resonant relation between Plutinos and Neptune. We suggest that all the previously reported planetesimal belts are located near the 2/3 MMRs of four planets whose spatial arrangements make a similar figure of Jupiter, Saturn, Uranus, and Neptune. This implies that the Solar System is a prototype of planetary systems around main-sequence stars in terms of planets' configuration, as expected from planet formation theories.

出版者

The Seismological Society of Japan, Society of Geomagnetism and Earth, Planetary and Space Sciences, The Volcanological Society of Japan , The Geodetic Society of Japan , The Japanese Society for Planetary Sciences

雑誌

Earth, Planets and Space (ISSN:18805981)

巻号頁・発行日

vol.55, no.5, pp.271-275, 2003 (Released:2010-03-09)

被引用文献数

39

著者

K. Legat B. Hofmann-Wellenhof

出版者

The Seismological Society of Japan, Society of Geomagnetism and Earth, Planetary and Space Sciences, The Volcanological Society of Japan , The Geodetic Society of Japan , The Japanese Society for Planetary Sciences

雑誌

Earth, Planets and Space (ISSN:13438832)

巻号頁・発行日

vol.52, no.10, pp.771-776, 2000 (Released:2010-03-09)

参考文献数

15

被引用文献数

1

---

Satellite-based navigation rapidly evolved into an efficient tool extensively used in a wide variety of civilian applications covering numerous modes of transportation, communication, administration, geodesy, agriculture, and many others. The current systems globally available are the US Global Positioning System (GPS) and the conceptually very similar Russian Global Navigation Satellite System (GLONASS). Considering the worldwide applications, GPS clearly predominates over GLONASS. However, GPS and GLONASS are mainly under military control of single nations and, also critical, do not fulfill certain performance requirements of the civil users, especially in terms of safety-critical applications. Thus, augmentations to the current systems and even completely new systems are under investigation. These are usually summarized under the abbreviation Global Navigation Satellite Systems (GNSSs). The various types of GNSS are described where emphasis is put on the future US and European contributions to the second-generation GNSS, i.e., the modernized GPS and the definition of the new European Galileo system. These two systems may be characterized as “compatible competitors”-thus, one might ask for whom the bell tolls.

著者

Matsushima Takeshi Takagi Akimichi

出版者

The Seismological Society of Japan, Society of Geomagnetism and Earth, Planetary and Space Sciences, The Volcanological Society of Japan , The Geodetic Society of Japan , The Japanese Society for Planetary Sciences

雑誌

Earth, Planets and Space (ISSN:13438832)

巻号頁・発行日

vol.52, no.11, pp.1015-1018, 2000

被引用文献数

11

---

Following 198 years of dormancy, an eruption started at Mt. Fugen, the main peak of Unzen volcano, in Kyushu, Japan, in November 1990. A dacite lava dome began to grow in May 1991. We installed the surveying points of GPS in 1992 around the lava dome in order to observe the ground deformation that accompanied the growth of the lava dome. In the winters of 1993 and 1994, we observed swift ground deformations that radiated from the vent of the volcano. It was presumed that rising magma accumulated and expanded the volcano body. After the lava effusion stopped in 1995, we also installed surveying points on the lava dome. EDM mirrors were permanently fixed to the large rocks with bolts. A GPS survey was carried out 2 or 3 times each year to estimate the 3-dimensional displacement. The result of the EDM survey showed that the baselines from the flank of the volcano were shortening 5 mm per day, and the result of the GPS survey showed that the displacement vector of the dome was parallel to the direction of the steepest slope of the old volcano body. This indicates that the inside of the lava dome is still very hot, and that deformation of the dome is viscous.

著者

Yuichiro Tanioka Kenji Satake

出版者

The Seismological Society of Japan, Society of Geomagnetism and Earth, Planetary and Space Sciences, The Volcanological Society of Japan , The Geodetic Society of Japan , The Japanese Society for Planetary Sciences

雑誌

Earth, Planets and Space (ISSN:13438832)

巻号頁・発行日

vol.53, no.4, pp.235-241, 2001 (Released:2010-03-09)

参考文献数

18

被引用文献数

73

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Coseismic slip distribution on the fault plane of the 1946 Nankai earthquake (Mw 8.3) was estimated from inversion of tsunami waveforms. The following three improvements from the previous study (Satake, 1993) were made. (1) Larger number of smaller subfaults is used; (2) the subfaults fit better to the slab geometry; and (3) more detailed bathymetry data are used. The inversion result shows that the agreement between observed and synthetic waveforms is greatly improved from the previous study. In the western half of the source region off Shikoku, a large slip of about 6 m occurred near the down-dip end of the locked zone. The slip on the up-dip or shallow part was very small, indicating a weak seismic coupling in that region. In the eastern half of the source region off Kii peninsula, a large slip of about 3 m extended over the entire locked zone. Large slips on the splay faults in the upper plate estimated from geodetic data (Sagiya and Thatcher, 1999) were not required to explain the tsunami waveforms, suggesting that the large slips were aseismic. Two slip distributions on the down-dip end of the plate interface, one from geodetic data and the other from tsunami waveforms, agree well except for slip beneath Cape Muroto in Shikoku. This suggests that aseismic slip also occurred on the plate interface beneath Cape Muroto.

著者

Fujiwara Hitoshi Miyoshi Yasunobu

出版者

Terra Scientific Pub. Co.

雑誌

Earth, planets and space (ISSN:13438832)

巻号頁・発行日

vol.61, no.4, pp.463-470, 2009-04-01

被引用文献数

1

著者

Miyoshi Yasunobu Fujiwara Hitoshi

出版者

Terra Scientific Pub. Co.

雑誌

Earth, planets and space (ISSN:13438832)

巻号頁・発行日

vol.61, no.4, pp.471-478, 2009-04-01

被引用文献数

1

著者

Fujiwara Hitoshi Nozawa Satonori Maeda Sawako OGAWA Yasunobu MIYOSHI Yasunobu JIN Hidekatsu SHINAGAWA Hiroyuki TERADA Kaori

出版者

Terra Scientific Pub. Co

雑誌

Earth, planets and space (ISSN:13438832)

巻号頁・発行日

vol.64, no.6, pp.459-465, 2012-06-01