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Hokkaido University Collection of Scholarly and Academic Papers (135.521 recursos)

HUSCAP (Hokkaido University Collection of Scholarly and Academic Papers) contains peer-reviewed journal articles, proceedings, educational resources and any kind of scholarly works of Hokkaido University.

?????????????? = Geophysical bulletin of Hokkaido University

Mostrando recursos 1 - 20 de 677

  1. 中千島で発生した巨大地震

    高橋, 浩晃; 前田, 宜浩; 笠原, 稔
    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...

  2. MT法による黒松内地域の地下構造

    平田, 貴一; 茂木, 透; 山谷, 祐介; 長谷, 英彰; 市原, 寛
    A magnetotelluric (MT) survey was conducted in the Kuromatsunai area to identify resistivity structures and their features. A basin that formed in the Kuromatsunai lowland area during the Miocene contains a thick Miocene to Plio-Pleistocene sediments. On the west side of the lowland is an active fault zone that is experiencing ongoing, east-down displacement. Three magnetic field components and two horizontal electrical field components were observed over 20-40 hours at eleven sites, and magnetotelluric impedances were calculated for a frequency range of 320-0.00034 Hz. The strike direction of dominant resistivity structures was determined using a phase tensor estimation (Caldwell et...

  3. 文禄五年 (1596) 閏七月豊後・伊予地震による伊予国板島城 (現宇和島城) の被害 : 藤堂虎高の遺帖

    中西, 一郎
    A record is found in the historical document of the Toudou family in relation to the 1596 Bungo-Iyo earthquake. The document was written about 180 years after the occurrence of the earthquake. The record shows that the castle Uwajima was damaged by the 1596 earthquake and provides us with an important constraint on the location of the earthquake.

  4. 巨大遠地地震による長周期歪地震波形の解析 : 2004年Sumatra-Andaman地震 (Mw9.0) 及び2005年Nias地震 (Mw8.6)

    上垣, 拓郎; 池上, 裕; 中西, 一郎; 小久保, 一哉; 露木, 貴裕; 中村, 浩二; 原田, 智史
    The long-period strain seismograms from the Sumatra-Andaman earthquake of December 26, 2004 and the Nias earthquake of March 28, 2005 are analyzed by comparing the observed seismograms with synthetic seismograms calculated by normal mode theory. The multiple CMT source (Tsai et al., 2005) and Harvard CMT solution explain the seismograms recorded by both extensometers and volumetric strainmeters from the 2004 and 2005 earthquakes, respectively. The long-period strain seismograms observed in Japan are consistent with about 9 min source duration and 1200 km fault length proposed by Tsai et al. (2005) and Velasco et al. (2006).

  5. 巨大近地地震による長周期体積歪波形の解析 : 2006年及び2007年千島列島地震 (Mw8.3及び8.1) と津波

    上垣, 拓郎; 中西, 一郎; 露木, 貴裕; 原田, 智史
    The Kurile Islands earthquakes of November 15, 2006 and January 13, 2007 are studied by using the volumetric strainmeter array in Tokai-Kanto area, Japan. The first-motion of long-period P waves recorded by the array shows good correlation with the first-arrival of tsunami waves observed on the Pacific side of Japan. The amplitude ratio of the long-period P waves (T > 50 s) between the two earthquakes explains the difference in moment magnitudes. The inconsistency between moment magnitudes and JMA magnitudes of the two earthquakes may have been caused by the difference of phases and period ranges used in the determination...

  6. 雲仙火山周辺域における相対応力場と1990-1995年噴火活動

    河野, 裕希; 松本, 聡; 松島, 健; 植平, 賢司; 清水, 洋; 馬越, 孝道
    We investigated a stress field around the magma chamber beneath Unzen Volcano, Kyushu, Japan, which erupted from 1990 until 1995, by using a stress-tensor inversion method. We used P wave polarity data of seismograms by earthquakes occurred during 1985-1999 for analysis. Our result clearly indicated that there were no changes in stress field during the period except for during 1986-1988. This suggested that the magma intrusion into shallower depths did not affect the stress field in this region. Clear change in stress field was observed during 1986-1988. This might be explained by applying the meshtexture crack model proposed by Hill...

  7. ALOS/PALSARによって観測された,アリューシャン列島・Okmok火山における2008年噴火

    宮城, 洋介
    On July 12 (UTC), 2008, Okmok volcano in the Aleutian Islands began to erupt after a lapse of 11 years. Okmok volcano is located on Umnak Island in the Aleutian volcanic chain, and has erupted from an active vent located in the southwest part of the caldera floor more than 10 times since 19th century. Although there are few habitants around Okmok volcano, ash from the eruption could lead to catastrophic airplane accidents because of the heavy air traffic over the Aleutian Islands. In the 2008 event, ash plumes were emitted up to 15,000m above sea level from the new...

  8. 1988年雌阿寒岳の噴火活動に伴う地震活動の特性

    高木, 朗充
    Meakandake volcano is located southwest on the Akan caldera rim, the eastern part of Hokkaido. Four small eruptions occurred at Meakandake from January to February, 1988. Seismic activity was higher for one year including this eruption stage. Research Center for Earthquake Prediction of Hokkaido University (RCEP) installed temporal seismic array on the northwest flank of the volcanic edifice twenty days before the first eruption in order to clarify characteristics of seismicity associated with volcanic activity. Daily number of earthquakes became suddenly decreased, three days before the first eruption. And hypocenters were estimated to be very shallow by seismic amplitude ratios....

  9. ボアホール地震観測網により観測された札幌周辺の微小地震

    吉田, 邦一; 笠原, 稔; 笹谷, 努
    On May, 1997, Sapporo municipality installed three borehole seismometers in Sapporo city to observe microearthquakes in and in its vicinity of Sapporo. Ueyama company has also installed strong-motion and high-gain seismometers at three borehole stations in and around Sapporo since 1999. We have collected seismic record from these borehole stations as well as other highgain seismic stations operated by various organizations and have determined hypocenters of 128 microearthquakes (M=0.2-2.8) occurring beneath Sapporo urban area from May, 1997 to January, 2004. Hypocentral distribution shows clusters of earthquakes near the central part and the eastern--southeastern part of Sapporo. A focal mechanism for...

  10. 高密度臨時地震観測による2004年斜里岳群発地震活動

    一柳, 昌義; 高橋, 浩晃; 山口, 照寛; 高田, 真秀; 岡山, 宗夫; 笠原, 稔; 岡崎, 紀俊
    From April 27, 2004, Mt. Syari-dake earthquake swarm occurred in the eastern part of Hokkaido, Japan. The activity began at 4:19 on April 27, 2004. We installed nine temporary seismic stations around the seismic active area immediately after its occurrence and had continued the observation for about seven months. We determined 2228 hypocenters of earthquakes. It is found that the seismic active area is clearly distributed on the plane having southwest-northeast strike with dip angle of about 80 degrees. This plane well agrees with one of the nodal planes of the focal mechanisms of several earthquakes determined by P-wave first...

  11. 孔井式歪計によって観測された福島県沖の地震に伴った余効変動

    三品, 正明; 立花, 憲司; 三浦, 哲
    Borehole strainmeters installed in the coastal area of Miyagi and Fukushima prefectures recorded the remarkable postseismic strain change following earthquake off Fukushima Prefecture on July 19, 2008 (M 6.9). Using exponential function, we simulated the postseismic strain change and obtained time constant and amplitude of the postseismic change. Time constant was 57 h. The amplitude ratio to the amplitude of the co-seismic change was 0.9 (KNK: Kinkazan), 1.1 (EN3: Enoshima) and 1.6 (MH2: Mihodo), respectively. This means almost the same amount of slip as the main shock occurred on the fault plane after the shock. We also analyzed data at...

  12. 地震に先行するVHF帯散乱波の観測的研究(II)

    森谷, 武男; 茂木, 透; 高田, 真秀; 山本, 勲
    A new observation system established in Hokkaido, northern Japan to confirm a suspected relationship between anomalous radio-wave propagation and impending earthquakes has been documenting anomalous VHF-band radiowave propagation beyond the line of sight prior to earthquakes since December, 2002. During such events, radio waves transmitted from an FM radio station were scattered, such that they could be received by an observation station beyond the transmitting station's line of sight. A linear relationship was established between the logarithm of the total duration time of the anomalous transmissions (Te) and the magnitude (M) or maximum seismic intensity (I) of the impending earthquake...

  13. クリギング法を用いた歪場の推定の試み

    小林, 知勝
    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...

  14. 2008年5月中国四川省の地震に伴う歪地震動と地下水位変化

    浅井, 康広; 石井, 紘; 青木, 治三
    The dynamic strain variations and co-seismic groundwater level changes associated with May 2008 Sichuan, China Earthquake (Mw7.9) were observed at TGR350 and SZB (97FT-01, SN-1 and SN-3) at Tono area, Gifu Prefecture, Central Japan. We investigated the relationship between the hydroseismogram and the dynamic strain variations observed at each observatory. The following results were obtained: As for the TGR350, the observed co-seismic groundwater level change was caused by dynamic strain variation with peak-to-peak amplitude of order of 10^[-6] strain. As for the SZB (97FT-01, SN-1 and SN-3), the observed co-seismic groundwater level changes in SN-1 and SN-3 were also caused...

  15. 上杵臼ひずみ高精度記録からの鋸歯状成分の除去について

    雨宮, 晋一郎; 高波, 鐵夫; 北川, 源四郎
    Recently, high precision high frequency A/D converter system was installed for the strainmeters in Urakawa Seismological Observatory, Kami-Kineusu, Urakawa, Hokkaido, Japan. The record could be used as seismogram with very wide frequency-band as well as measuring geodetic deformation. However, a peculiar saw-shape wave was found in the record and it prevents from extracting the component of seismic waves. In this paper, we develop a statistical model for decomposing the observed strainmeter time series into two components: one is the low-frequency component that consists of the effect of air pressure and earth tide, and the other is the saw-shape component, which...

  16. 2007年サハリン西方沖の地震 (Mw 6.2) の震源特性

    前田, 宜浩; 笠原, 稔
    On August 2, 2007, a shallow crustal earthquake occurred at west off Sakhalin Island, far eastern Russia. Moment magnitude (MW) of this earthquake determined by Global CMT is 6.2. This earthquake generated severe damage to habitants and buildings at Nevelsk city near the epicenter. Visible large uplift was reported along the coast, and tsunami was observed even though its small magnitude. Teleseismic broadband waveforms from IRIS show long-duration P-wave pulse; the duration is comparable to that of MW 6.8 event. Teleseismic data also show later phases at some stations. Seismic source model is estimated using teleseismic data by applying the...

  17. 北海道北部地域の重力測定(その2)

    本多, 亮; 笠原, 稔; 茂木, 透
    Although there are a plenty amount of gravity data over the northern part of Hokkaido (Dohoku region), most of them are not published yet. We have been performing gravity measurement in this region since 2007. Additionally, new data is added by new measurement during 2008. These new data clearly demonstrate the improvement of the gravity anomaly distribution over the Japan-sea side area of Dohoku region. Recurrent thrust type faultings which are dominant in this region generate positive Bouguer gravity anomalies over the hanging wall side, and horizontal gravity gradients above fault lines. Bouguer gravity anomaly map clearly indicates that the...

  18. 連続および繰返しGPS観測による2006年雌阿寒岳小噴火に伴う地殻変動

    岡崎, 紀俊; 高橋, 浩晃; 笠原, 稔; 志賀, 透
    Continuous and temporary dense GPS network in Meakandake volcano, eastern Hokkaido, operated by Geological Survey of Hokkaido, Japan Meteorological Agency and Hokkaido University, detected co-eruptive crustal deformation due to the 2006 small phreatic eruption. Although no deformation was observed at stations in foot of volcano edifice, large horizontal displacements with ̃5cm were observed at stations in the northern part of Ponmachineshiri summit crater. We estimated crustal deformation models from ten stations data and obtained following findings; (1) stations in the northern part of summit crater indicate relative large horizontal displacement to northward, (2) displacements at stations in the southern part...

  19. 日本列島における深部低周波地震の発生状況

    高橋, 浩晃; 宮村, 淳一
    We investigate the activity of deep low-frequency earthquakes (DLE) in Japanese Islands by JMA hypocenter catalogue during 1997 to 2008. It is confirmed that DLE cluster is distributed in every region. This implies that DLE phenomenon is common in Japanese subduction zone. Many active DLE clusters are identified in and around the quaternary volcanoes in whole area. There are also many non-volcanic clusters in Hokkaido and Tohoku regions, but very few in Kanto, Koushinetsu, Chubu, Hokuriku and Kyushu regions. High activity of non-volcanic clusters is observed in Kinki region. No clear correlation between DLE number and volcano activity index during...

  20. Goto (1997) の粘性計算法の再評価

    後藤, 章夫
    Viscosity evaluation model by Goto (1997) has been re-examined using 608 viscosity data for 37 samples from literature. The model gives viscosity (η) of multicomponent silicate melts using Williams -- Landel -- Ferry (WLF) equation: logη = logηTg + A(T-Tg)/(B+T-Tg) {ηTg: viscosity at glass transition temperature; A, B: adjustable constants; T: temperature; Tg: glass transition temperature} Although used samples were only seven to formulate compositional dependency/independency of four parameters in WLF equation, by measuring viscosity and glass transition temperature, this model has successfully evaluated the viscosity from literature in wide range of temperature and chemical composition. Compared to other well-accepted...

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