当前位置: X-MOL 学术Geophys. J. Int. › 论文详情
Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)
Crustal structure of the Azores Archipelago from Rayleigh wave ellipticity data
Geophysical Journal International ( IF 2.8 ) Pub Date : 2020-02-14 , DOI: 10.1093/gji/ggaa076
Ana M G Ferreira 1, 2 , Augustin Marignier 2, 3 , Januka Attanayake 4 , Michael Frietsch 2 , Andrea Berbellini 5
Affiliation  

Determining the crustal structure of ocean island volcanoes is important to understand the formation and tectonic evolution of the oceanic lithosphere and tectonic swells in marine settings, and to assess seismic hazard in the islands. The Azores Archipelago is located near a triple junction system and is possibly under the influence of a mantle plume, being at the locus of a wide range of geodynamic processes. However, its crustal structure is still poorly constrained and debated due to the limited seismic coverage of the region and the peculiar linear geometry of the islands. To address these limitations, in this study we invert teleseismic Rayleigh wave ellipticity measurements for 1-D shear wave speed (VS) crustal models of the Azores Archipelago. Moreover, we test the reliability of these new models by using them in independent moment tensor inversions of local seismic data and demonstrate that our models improve the waveform fit compared to previous models. We find that data from the westernmost seismic stations used in this study require a shallower Moho depth (∼10 km) than data from stations in the eastern part of the archipelago (∼13–16 km). This apparent increase in the Moho depth with increasing distance from the mid-Atlantic ridge (MAR) is expected. However, the rate at which Moho deepens away from the MAR is greater than that predicted from a half-space cooling model, suggesting that local tectonic perturbations have modified crustal structure. The 1-D VS models obtained beneath the westernmost seismic stations also show higher wave speeds than for the easternmost stations, which correlates well with the ages of the islands except Santa Maria Island. We interpret the relatively low VS profile found beneath Santa Maria Island as resulting from underplating, which agrees with previous geological studies of the island. Compared to a recent receiver function study of the region, the shallow structure (top ∼2 km) in our models shows lower shear wave speed, which may have important implications for future hazard studies of the region. More generally, the new seismic crustal models we present in this study will be useful to better understand the tectonics, seismicity, moment tensors and strong ground motions in the region.

中文翻译:

从瑞利波椭圆度数据看亚速尔群岛的地壳结构

确定海洋岛火山的地壳结构对于了解海洋岩石圈的形成和构造演化以及海洋环境中的构造膨胀,以及评估岛屿的地震危险性非常重要。亚速尔群岛位于三重连接系统附近,可能受到地幔柱的影响,处于各种地球动力学过程的所在地。然而,由于该地区有限的地震覆盖范围和岛屿独特的线性几何形状,其地壳结构仍然缺乏约束和争论。为了解决这些限制,在本研究中,我们对亚速尔群岛一维横波速度 (VS) 地壳模型的远震瑞利波椭圆度测量值进行了反演。而且,我们通过在局部地震数据的独立矩张量反演中使用这些新模型来测试它们的可靠性,并证明与以前的模型相比,我们的模型改进了波形拟合。我们发现,本研究中使用的最西部地震台站的数据需要比群岛东部台站的数据(约 13-16 公里)更浅的莫霍面深度(约 10 公里)。预计莫霍面深度会随着距大西洋中脊 (MAR) 距离的增加而明显增加。然而,莫霍面远离 MAR 的速度比半空间冷却模型预测的要大,这表明局部构造扰动改变了地壳结构。在最西边地震台站下方获得的一维 VS 模型也显示出比最东台站更高的波速,这与除圣玛丽亚岛以外的岛屿的年龄相关。我们将在圣玛丽亚岛下方发现的相对较低的 VS 剖面解释为底板,这与先前对该岛的地质研究一致。与最近对该地区的接收函数研究相比,我们模型中的浅层结构(顶部~2 公里)显示出较低的剪切波速度,这可能对该地区未来的灾害研究具有重要意义。更一般地说,我们在本研究中提出的新地震地壳模型将有助于更好地了解该地区的构造、地震活动、矩张量和强地面运动。这与先前对该岛的地质研究一致。与最近对该地区的接收函数研究相比,我们模型中的浅层结构(顶部~2 公里)显示出较低的剪切波速度,这可能对该地区未来的灾害研究具有重要意义。更一般地说,我们在本研究中提出的新地震地壳模型将有助于更好地了解该地区的构造、地震活动、矩张量和强地面运动。这与先前对该岛的地质研究一致。与最近对该地区的接收函数研究相比,我们模型中的浅层结构(顶部~2 公里)显示出较低的剪切波速度,这可能对该地区未来的灾害研究具有重要意义。更一般地说,我们在本研究中提出的新地震地壳模型将有助于更好地了解该地区的构造、地震活动、矩张量和强地面运动。
更新日期:2020-02-14
down
wechat
bug