Studies on Three-Dimensional Seismic Velocity and Attenuation Structures in the Chubu and Kinki Regions, and Their Tectonic Implications

中部近畿地区三维地震速度、衰减结构及其构造意义研究

• 批准号: 60460045
• 负责人: MIKUMO Takeshi
• 金额: $ 3.07万
• 依托单位: Kyoto University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (B)
• 财政年份: 1985
• 资助国家: 日本
• 起止时间: 1985 至 1987
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-60460045/
• 关键词: 3-D Velocity Structure; Seismic Wave Travel-times; Inversion Method; Tectonics; テクトニクス; 中部・近畿地方

(1) 3-D P-wave velocity structure beneath central Japan has been investigated by applying an inversion technique, using 7,500 P-wave arrival times from 120 shallow and intermediate depth earthquakes. The results clealy reveal prominent low-velocity bodies just beneath active colcanoes in central Japan and above the subducting plates.(2) A new method to detect 3-D velocity anisotropy in addition to lateral heterogeneities has been proposed, and applied to P-wave travel time data in central Japan. No significant P-wave anisotropy was detected where shear wave anisotropy has been revealed.(3) Seisomotectionc features of the Hida region, central Honshu, Japan has benn investigated on the basis of seismicity and focal mechanism of earthquakes, with reference to the geological and tectonic setting. The non-uniform seismicity along the Atotsugawa fault, and its sharp variations of deepest seismicity, and the source of the compressive stress working in this region are discussed in detail.(4) 3 … More -D upper crustal structure in the Hida region has been derived by Thurber's inversion method applying to 2,500 P-wave travel time data obtained from a large number of local shocks. It has been found that high-velocity regions exist in the central part particularly along the western part of the Atotsugawa fault, and that low-velocity zones extend over the middle crust beneath active volvanoes in the Hida mountains.(5) 3-D upper crustal structure in the Hokuriku region has been derived from the avove method, using 278 local shocks that occurred around thei region. The results show that there is high-velocity zone trending in the NE-SW direction down to a depth of 3 km.(6) 3-D upper crustal structure in the central to northern Kinki region has been derived by the inversion technique, and compared with seismicity in this region. The largest variations in the velocity structure are found to be within 8 %, but less than 4 % in most part of the region. The deepest seismicity appears to become deeper from the SW to NE direction. Less

(1)利用120次浅、中深度地震的7,500个P波到时资料，应用反演技术研究了日本中部地区的三维P波速度结构。结果清楚地揭示了日本中部活跃火山之下和俯冲板块之上存在明显的低速体。(2)提出了一种新的方法来检测三维速度各向异性，除了横向非均匀性，并应用于P波走时数据在日本中部。没有显着的P波各向异性检测剪切波各向异性已被揭示。(3)根据地震活动性和震源机制，结合地质构造背景，研究了日本本州中部希达地区的地震活动特征。详细讨论了沿Atotsugawa断层沿着的地震活动不均匀性、断层深部地震活动的急剧变化以及作用于该地区的压应力来源。(4) 3 ...更多信息 本文用Thurber反演方法，对从大量地震中获得的2,500个P波走时资料进行了反演，得到了希达地区上地壳三维结构。结果表明，在阿都津川断裂的中部，特别是沿沿着西部存在高速区，而在希达山活动火山之下的中地壳上存在低速区。(5)本文利用北陆地区278个近震资料，用avove方法计算了北陆地区上地壳的三维结构。结果表明，在3 km深处存在NE-SW向的高速带。(6)本文用反演技术求出了近畿中部至北方地区的三维上地壳结构，并与该地区的地震活动作了比较。速度结构的最大变化在8%以内，但该地区大部分地区的变化小于4%。地震活动的深度从西南向东北方向逐渐加深。少

项目成果

Hirahara, K. et al.: "Three-dimensional P-wave velocity structure beneath central Japan -- Low-velocity bodies in the wedge portion of the upper mantle above high-velocity subducting plates" Tectonophysics. (1988)

Hirahara, K. 等人：“日本中部下方的三维纵波速度结构——高速俯冲板块上方上地幔楔形部分的低速体”构造物理学。

Hirahara, K: "Detection of three-dimensional velocity anisotropy" Physics of the Earth & Planetary Interior. 49. (1988)

Hirahara, K：“三维速度各向异性的检测”地球物理

Mikumo, T. et al.: "3-D upper crustal structure in the Hida region, active faults and seismic activity" Tectonophysics. (1988)

Mikumo, T. 等人：“飞弹地区的 3-D 上地壳结构、活动断层和地震活动”构造物理学。

Hirahara, K. et al.: "3-D upper crustal structure in the Hokuriku region" Journal of Physics of the Earth. (1988)

Hirahara, K. 等人：“北陆地区的 3-D 上地壳结构”《地球物理学杂志》。

Mikumo, T. et al.: "Seismotectonics of the Hida region, central Honshu, Japan" Tectonophysics. 147. 95-119 (1988)

Mikumo, T. 等人：“日本本州中部飞騨地区的地震构造”构造物理学。