Shallow Volcano‐Tectonic Structures on the Island of Hawai'i Imaged by Multimode Rayleigh Wave Ambient Noise Tomography
Shallow Volcano‐Tectonic Structures on the Island of Hawai'i Imaged by Multimode Rayleigh Wave Ambient Noise Tomography
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DOI：
10.1029/2022jb026244
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发表时间：
2023-04
期刊：
影响因子：
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通讯作者：
XiaoZhuo Wei;Yang Shen;J. Morgan
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文献类型：
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作者：
XiaoZhuo Wei;Yang Shen;J. Morgan
盾状火山的地震层析成像可用于更好地了解其结构、形成和演化。以前在夏威夷岛的层析成像研究使用地震和活动源的体波，在地壳浅层的分辨率有限。在这项研究中，我们获得了经验绿色函数（EGFs）和经验绿色张量（EGTs）的互相关和叠加多年的地震环境噪声记录在岛上。EGFs/EGT包含基模和第一高阶模瑞利波。用一种新的算法分离了不同的模式，并测量了它们的群速度。使用群到达时间，我们反演了二维群速度图，这是第一次提供夏威夷岛的完整覆盖。从群速度图中，我们反演了三维剪切波速度模型，该模型显示了强烈的横向变化，并对岛上火山的结构和生长产生了新的见解：克基拉岛的东裂谷带在所有深度都有明显的高速，而莫纳罗亚山目前的裂谷带的特点是只有在地表以下1公里以上的深度才有中高速，这可能是由于它们的历史相对较短且欠发达。火山的侧翼，有些被断层带切断，在一定深度范围内显示出低速，通常被解释为由喷出岩石组成，这些岩石可能会被断层进一步破碎。
Seismic tomography of shield volcanoes can be used to better understand its structure, formation, and evolution. Previous tomographic studies on the Island of Hawai'i used body waves from earthquakes and active sources and had limited resolution in the shallow crust. In this study, we obtained the empirical Green Functions (EGFs) and empirical Green Tensors (EGTs) from cross‐correlating and stacking of multiyear seismic ambient noise recorded on the island. The EGFs/EGTs contained fundamental mode and first higher mode Rayleigh waves. The different modes were separated with a new algorithm and their group velocities were measured. Using the group arrival times, we inverted for two‐dimensional group velocity maps, which provide, for the first time, a full coverage of the Island of Hawai'i. From the group velocity maps, we inverted for a three‐dimensional shear wave velocity model, which shows strong lateral variations and yields new insights into the structure and growth of the volcanoes on the island: Kı̄lauea's East Rift Zone has prominent high velocities at all depths, whereas the current rift zones of Mauna Loa are characterized by intermediate to high velocities only at depths greater than 1 km below ground surface, which may be attributed to their relatively short history and less developed state. The flanks of the volcanoes, some cut by fault zones, displayed low velocities at over a range of depths, generally interpreted as consisting of extrusive rocks, which could be further shattered by faulting.