High resolution imaging in the inhomogeneous crust with cosmic-ray muon radiography: The density structure below the volcanic crater floor of Mt. Asama, Japan
High resolution imaging in the inhomogeneous crust with cosmic-ray muon radiography: The density structure below the volcanic crater floor of Mt. Asama, Japan
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DOI：
10.1016/j.epsl.2007.09.001
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发表时间：
2007-11-15
影响因子：
5.3
通讯作者：
Niwa, Kimio
中科院分区：
文献类型：
--
作者：
Tanaka, Hiroyuki K. M.;Nakano, Toshiyuki;Niwa, Kimio
我们开发了一种新的射线成像方法来探测地壳的不均匀结构。例如，我们在山上进行了测量。并研究了在能量范围可达几TeV的宇宙射线µ子的方位向各向同性通量的可行性。这项技术的原理是，通过测量穿过固体的不同近水平路径上的介子吸收，可以推断出物体内部的密度分布。一台面积为4000Cr-2的月球探测器被安装在距离山顶陨石坑约1公里的1米深的仪器库中。浅间弥生。通过3D图像处理分析了探测器乳胶层内的Muon轨迹，以确定穿过顶端陨石坑区域的不同射线路径的能量吸收水平。定量探测器的典型角分辨率为10毫弧度(Mrad)，相当于在1公里处的空间分辨率为10米。这些测量将是研究地壳浅层结构的理想之选，这些地点由于其强烈的结构不均质性和潜在的难以进入而无法很好地分辨，因此无法通过传统的电磁或地震技术来确定其结构。本方法还可以通过从两个或多个不同的点进行测量来提供地下表面的三维图像。在这项工作中，我们对山口底部几百米以下的地方进行了射线成像。日本浅草，并探测到与上次喷发期间形成的熔岩丘的位置和形状相对应的密集区域(Urabe，B.，Watanabe，N.，Murakami，M.，根据机载合成孔径雷达测量得出的浅草火山顶端火山口在2004年喷发期间的地形变化，地理勘测所公报，第53页，第1-6页(2006年))。就在熔岩丘的正下方，我们发现了一个低密度区域，这表明了一种由排水回流引起的多孔管道(Urabe，B.，Watanabe，N.，Murakami，M.，根据机载合成孔径雷达(SAR)测量得出的2004年喷发期间阿萨马火山顶端火山口的地形变化，地理调查研究所公告，第53页，1-6页(2006)。密度对比度的分辨精度为1-3%。这种方法提供的浅层密度结构的分辨率远远高于常规地球物理测量的可能。(C)2007 Elsevier B.V.保留所有权利。
We have developed a novel radiographic imaging method to survey the inhomogeneous structure of the crust. As an example, we performed measurements at Mt. Asama volcano, and studied the feasibility of using an azimuthally isotropic flux of cosmic-ray muons in the energy range up to a few TeV. The principle of the technique is that by measuring muon absorption along different nearly horizontal paths through a solid body, one can deduce the density distribution in the interior of the object. A moon detector with an area of 4000 Cr-2 was installed in a 1-m deep instrument vault located about 1 km from the summit crater of Mt. Asama. Muon tracks within emulsion layers in the detector were analyzed by 3d image processing to determine the level of energy absorption along different ray paths through the summit crater region. A typical angular resolution of the ration detector of 10 milliradians (mrad) corresponds to a spatial resolution of 10 m at a distance of 1 km. The measurements would be ideal for studying the shallow structure of the crust at sites which cannot be well resolved because of their strong structural heterogeneity and potential difficulty to be accessed, and which therefore cannot have their structure determined by conventional electromagnetic or seismic techniques. The present method can also provide three dimensional images of the subsurface by making measurements from two or more different points. In this work, we have radiographically imaged a few hundred meters below the crater floor of Mt. Asama, Japan, and have detected a dense region, which corresponds to the position and shape of a lava mound created during the last eruption (Urabe, B., Watanabe, N., Murakami, M., Topographic change of the summit crater of Asama Volcano during the 2004 eruption derived from Airborne Synthetic Aperture Radar (SAR) measurements, Bulletin of Geographical Survey Institute, 53, 1-6 (2006).). Right below the lava mound we found a low density region that suggests a drain-back-induced porous conduit (Urabe, B., Watanabe, N., Murakami, M., Topographic change of the summit crater of Asama Volcano during the 2004 eruption derived from Airborne Synthetic Aperture Radar (SAR) measurements, Bulletin of Geographical Survey Institute, 53, 1-6 (2006).). The density contrast was resolved with a precision of 1-3%. This method provides a resolution of the shallow density structure that is significantly higher than is possible with conventional geophysical measurements. (c) 2007 Elsevier B.V. All rights reserved.