巻号一覧
60 巻 (2007 - 2008)
- 4 号 p. 225-
- 3 号 p. 123-
- 2 号 p. 57-
- 1 号 p. 1-
前身誌
60 巻, 4 号
選択された号の論文の8件中1～8を表示しています
- |<
- <
- 1
- >
- >|
論説
-
神田 克久, 武村 雅之, 髙橋 利昌, 浅野 彰洋, 大内 泰志, 川崎 真治, 宇佐美 龍夫2008 年 60 巻 4 号 p. 225-242
発行日: 2008/03/31
公開日: 2013/08/20
ジャーナル フリーThe major intraslab earthquakes have recurrently occurred in the subducting slab of the Philippine Sea plate in the vicinity of the Bungo Channel and caused great damage. Since the intraslab earthquakes tend to generate more short period seismic waves compared to plate boundary and shallow crustal earthquakes, seismic magnitude of historical earthquakes should be carefully estimated from seismic intensity data. We found that the 1596/9/4, 1749/5/25, 1854/12/26, and 1968/8/6 earthquakes fall under major events in this region. These earthquakes except the 1596 event were identified as intra-slab events. The 1596 event was inferred as a shallow crustal earthquake occurring at a fault in Beppu Bay from the tsunami record and geological survey. At first, the seismic intensity data of the 1596, 1749, and 1854 earthquakes estimated from damage records written in old documents were digitized to analyze their source characteristics. The seismic intensity data were modified using a site correction factor obtained from a difference of observed intensity from estimated intensity with the attenuation relationship of recent earthquakes. The inversion analysis using seismic intensity data was carried out to evaluate short-period wave radiation zones on a given fault plane. It showed that the location of centroid of short-period wave radiation zone was near the corresponding epicenter [Usami (2003)] except the 1749 event. We could also obtain an optimum magnitude MI that gives the minimum estimation error. It was indicated that the 1596 earthquake was inferred as a shallow crustal event (MI=7.2) near the center of Beppu Bay, the 1749 earthquake (MI=6.6) quite resembled the 1968 event in short-period wave radiation zone and magnitude, and the 1854 earthquake (MI=7.0) was the largest event among historical intra-slab earthquakes in this region. Based on the magnitude revaluation, the empirical equation of relationship between magnitude and isoseismal area of IJMA≥5 was modified to estimate magnitude of intra-slab earthquakes in the Bungo Channel adequately.抄録全体を表示PDF形式でダウンロード (5019K) -
功刀 卓, 青井 真, 中村 洋光, 藤原 広行, 森川 信之2008 年 60 巻 4 号 p. 243-252
発行日: 2008/03/31
公開日: 2013/08/20
ジャーナル フリーA new calculation method is proposed for a real-time seismic intensity indicator (Ir), whose concept is similarly to the JMA seismic intensity (IJMA)defined by Japan Meteorological Agency. With the increasing requirements of earthquake early warning (EEW) system, it is much more obvious that IJMA has a real-time delay since the IJMA needs a filtering operation in frequency domain. In order to improve the real-time calculation suitable for the EEW system, a new real-time seismic intensity indicator, Ir (real-time seismic intensity), is defined by using an approximating filter in time domain instead of the original filter in frequency domain. This indicator, Ir,can be calculated as a time series on real-time and its maximum value, Ia (approximate seismic intensity), corresponds to an approximate value of IJMA. The relationships between IJMA and Ia value are examined by means of using a large number of strong motion records. Results show that Ia value estimates IJMA with reasonable accuracy in wide intensity ranges. For a small computing system like a strong-motion seismograph, it is easier to process Ir than processing IJMA. Therefore, Ir is suitable for using in an EEW system based on the concept of JMA seismic intensity.抄録全体を表示PDF形式でダウンロード (1310K) -
—2003年十勝沖地震に対する検討—渡辺 基史, 藤原 広行, 佐藤 俊明, 石井 透, 早川 崇2008 年 60 巻 4 号 p. 253-265
発行日: 2008/03/31
公開日: 2013/08/20
ジャーナル フリーThe procedure for source modeling according to a characterized source model has been proposed and established in prevenient researches on the estimation of strong ground motions from scenario earthquakes along active faults. In recent researches, such procedure is also applied to the strong ground motion prediction for some great subduction earthquakes. In these cases, it seems that short-period motions are underestimated while long-period ground motions explain the observed records well. We examine the effects of complexity of fault rupture process on strong ground motions in period range form 5 to 10 s by handling source parameters of the 2003 Tokachi-Oki earthquake. For that purpose, we referred to the source model obtained by inversion analysis of near-field strong motion records in the antecedent research. First, we have made several simplified models from original source model. In the models, we gradually simplified the source parameters, such as slip amount, rupture time, rake angle, and the form of slip velocity time function of fault elements. Contribution of each source parameter to the waveform complexity has been evaluated by comparing spectral levels of synthetic waveforms from different source models in three frequency ranges and by comparing synthetic waveforms themselves. As a result, the complexity of rupture propagation is most important to correctly simulate ground motions in the period of several seconds for M 8 earthquake. We have also examined relation between the rupture propagation complexity and the slip distribution. The result shows that acceleration of rupture propagation is seen in the areas where either slip or spatial gradient of slip is large.抄録全体を表示PDF形式でダウンロード (10133K) -
松村 正三, 里村 幹夫, 内海 さや香2008 年 60 巻 4 号 p. 267-277
発行日: 2008/03/31
公開日: 2013/08/20
ジャーナル フリーIt is meaningful to presume the location of asperities for the anticipated Tokai earthquake in view of risk assessment and also for earthquake prediction. These asperities were first specified based on the seismic activity change, and verified in comparison with the result derived from GPS measurements. In central Shizuoka Prefecture, the seismicity change progressed almost simultaneously with the slow-slip beneath Lake Hamana from 2000 to 2005 and resulted in a separation of the activity into quiescence and activation. This change was considered to be caused by a quasi-static slip on the locked plate boundary, triggered by the slow-slip, and the activated zones were assigned to be asperities due to stress concentration there. We thus extracted several zones as candidates of the major asperities. On the other hand, the Japanese University Consortium developed a dense GPS network in the western and central parts of Shizuoka Prefecture in order to know the crustal deformation in detail. Analyzing the data together with those from GEONET by the Geographical Survey Institute during two years since 2004, we got the detailed distribution of the areal strain associated with the slow-slip. The results show a patch-like pattern between the contracted areas and the dilated ones with a wavelength of about 20 km. We estimated areal strain by using a dislocation model arranged for the candidates of the asperities obtained from the seismicity change, and compared it with that from the GPS measurements. The result gave a good correspondence between them. This fact suggests that the presumed asperity model is reliable and valuable in the study on hazard mitigation against the anticipated Tokai earthquake.抄録全体を表示PDF形式でダウンロード (28804K)
寄書
-
高山 博之, 前田 憲二, 弘瀬 冬樹2008 年 60 巻 4 号 p. 279-284
発行日: 2008/03/31
公開日: 2013/08/20
ジャーナル フリーPDF形式でダウンロード (3939K) -
関谷 博, 後藤 和彦, 八木原 寛, 宮町 宏樹, 角田 寿喜2008 年 60 巻 4 号 p. 285-289
発行日: 2008/03/31
公開日: 2013/08/20
ジャーナル フリーPDF形式でダウンロード (990K) -
河内 一男2008 年 60 巻 4 号 p. 291-295
発行日: 2008/03/31
公開日: 2013/08/20
ジャーナル フリーPDF形式でダウンロード (874K)
訂正
-
弘瀬 冬樹, 中島 淳一, 長谷川 昭2008 年 60 巻 4 号 p. 297-300
発行日: 2008/03/31
公開日: 2013/08/20
ジャーナル フリーPDF形式でダウンロード (6757K)
- |<
- <
- 1
- >
- >|