巻号一覧
64 巻 (2011 - 2012)
- 4 号 p. 185-
- 3 号 p. 117-
- 2 号 p. 63-
- 1 号 p. 1-
前身誌
64 巻, 1 号
選択された号の論文の5件中1～5を表示しています
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論説
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─非定常波線分解法の評価─高岸 万紀子, 木下 繁夫2011 年 64 巻 1 号 p. 1-10
発行日: 2011/08/25
公開日: 2011/10/18
ジャーナル フリーA new method to estimate the velocity boundaries of real layered structure from only surface recordings was constructed by decomposing an SH-wave into instantaneous power of wave associated with rays in a homogeneous half space. The estimated results obtained by applying this method to seismograms were represented as a function of lapse-time (t) and depth-time (τ); i.e., travel time from surface toward depth-direction. We conducted the evaluation of the proposed method to the strong motion data recorded at the FCH array. The recordings were obtained using broadband velocity seismometers for the earthquakes that occurred in five source regions, the Eastern Yamanashi, East off Izu peninsula, in and around Tokyo, the Southwestern Ibaraki, and the Central Chiba regions. The estimated results of velocity boundaries obtained by this method were in good agreement with the velocity boundaries previously determined by means of down-hole method. The comparison study with seismic interferometry was also conducted, and yielded concordant results for the estimation of velocity boundaries.抄録全体を表示PDF形式でダウンロード (556K) -
谷口 薫, 渡辺 満久, 鈴木 康弘, 澤 祥2011 年 64 巻 1 号 p. 11-21
発行日: 2011/08/25
公開日: 2011/10/18
ジャーナル フリーThe 150 km long Itoigawa-Shizuoka Tectonic Line Active Fault System (ISTL) in central Japan is one of the most active fault systems in Japan. Paleoseismologcal studies 1980s have revealed that the most recent event and the average recurence interval of the ISTL. The approximately 7 km long portion of the fault system between Matsumoto and Okaya has been regarded as a gap without any active fault trace. The gap namely the “Shiojiri Pass Gap” has long been taken as a segment boundary owing to the geometric discontinuity. Recent geomorphological analyses of the gap have demonstrated a through-going left-lateral slip assocaited with recent earthquakes in this area, based on aerial photograph interpretation and excavation studies. Excavation study on this portion revealed that the latest faulting event occurred between 1,700 cal. B.P. to 1,310 cal. B.P. (255 A.D. -645 A.D.). The timing of the last faulting event at this study area coincides with the timing in the Gofukuji fault and Okaya fault. The active faults extending from the Matsumoto basin as far as the northwestern margin of the Suwa basin display the evidence for its recent reactivation at the same time.抄録全体を表示PDF形式でダウンロード (1055K) -
市橋 正生2011 年 64 巻 1 号 p. 23-32
発行日: 2011/08/25
公開日: 2011/10/18
ジャーナル フリーThe relationship between the days of earthquake in Japan and its vicinity and the Be-7 concentrations in the surface air at Takasaki were statistically analyzed. A day when one or more earthquakes of M 5 or greater occurred in Japan and its vicinity was defined as a “day of earthquake”. Earthquakes which were deemed aftershocks were not included in the analysis. In order to avoid the effect of seasonal variation, the residuals obtained by deducting 31-day moving averages from Be-7 concentrations and those obtained by deducting the ‘21-day’ moving averages of the periods from −15 to +0 days and from +11 to +15 days were analyzed. The ‘21-day’ moving averages were also calculated to avoid the effect of aftershocks. Rank-sum tests of the residuals showed that the Be-7 concentrations decreased from the 31-day and ‘21-day’ moving averages on days of earthquake. A binomial test showed that there were significantly more days of earthquake when the Be-7 concentrations were smaller than the medians of Be-7 concentrations for the 31-day periods (from 15 days before to 15 days after days of earthquake) than those when the Be-7 concentrations exceeded the medians. These suggest that the Be-7 concentrations decrease on days of earthquake. It is noted that the Be-7 concentrations on days of earthquake decreased on days of both precipitation and non-precipitation, respectively.抄録全体を表示PDF形式でダウンロード (1376K) -
平塚 晋也, 佐藤 魂夫, 古川 信雄2011 年 64 巻 1 号 p. 33-45
発行日: 2011/08/25
公開日: 2011/10/18
ジャーナル フリーA swarm activity occurred east off Nicobar Islands about a month after the 2004 Sumatra-Andaman earthquake. We discussed three issues related to the swarm activity, i.e., (1) How can the spatial distribution of strike-slip events and normal fault events be explained? (2) Why was the swarm activity triggered east off Nicobar Islands? (3) What is the mechanism of one month delay of the swarm activity? In order to address these issues, we relocated the hypocenters of the swarm activity using the Modified Joint Hypocenter Determination (MJHD) method and investigated the spatial distribution of fault plane solutions. As a result, we found that the spatial distribution of strike-slip events and normal fault events can be explained by Riedel shears in the region between West Andaman Fault (WAF) and Sumatra Fault System (SFS). We calculated the spatial pattern of the change of the Coulomb Failure Function (ΔCFF) which suggests that the swarm activity was promoted by the coseismic slip and the afterslip of the Sumatra-Andaman earthquake. One month delay of the swarm activity may be explained by the upward migration of fluid due to the change of bulk strain at the lower end of the mainshock fault.抄録全体を表示PDF形式でダウンロード (840K)
総合報告
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三雲 健2011 年 64 巻 1 号 p. 47-62
発行日: 2011/08/25
公開日: 2011/10/18
ジャーナル フリー
電子付録This report reviews various studies on atmospheric pressure waves that have been generated from large earthquakes, tsunamis, and large-scale volcanic eruptions. These waves described here include low-frequency acoustic and gravity waves (0.0008∼0.0166 Hz or its period 1∼20 min) and high to medium frequency (› 0.0166 Hz or its period ‹ 1 min) infrasonic air-waves. The low-frequency acoustic-gravity waves came from coseismic vertical ground deformation associated with two megathrust earthquakes, and sometimes from other large earthquakes and volcanic eruptions, which propagated to more than several thousand kilometers through the lower to part of the upper atmosphere. The waves that reached the upper atmosphere could cause traveling ionospheric disturbances and perturbations of total electron content. The higher frequency infrasounds also have often been observed after large earthquakes and volcanic eruptions, which traveled as air-waves propagating directly from the source, and also as air-waves coupled with traveling seismic Rayleigh waves. Small atmospheric perturbations have also been detected during propagation of tsunami waves caused secondarily by large submarine earthquakes. Theoretical waveform modeling has been made in some of the above cases, incorporating a realistic atmospheric temperature structure. It is expected that more detailed information about the source process of large earthquakes and volcanic eruptions could be extracted through the analysis of the waveforms recorded at a number of stations, including their maximum amplitudes, wave frequencies, duration times, directions of wave approach, and phase and group velocities.抄録全体を表示PDF形式でダウンロード (421K)
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