基于核爆炸地震资料的中朝克拉通东北部神秘的地壳和上地幔结构

IF 2.1 3区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS
Xiaoqing Zhang , Hans Thybo , Irina M. Artemieva , Tao Xu , Zhiming Bai
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引用次数: 0

摘要

我们沿着中韩克拉通东北部约2500公里长的地震剖面解释了地壳和上地幔结构。以朝鲜核爆炸为震源,获得了信噪比较高的地震资料。地震剖面显示了几个阶段,包括莫霍反射(PmP)及其表面多次反射(PmPPmP。观测要求薄地壳(30km)具有非常低的平均地壳速度(约6.15km/s)和莫霍面异常强烈的速度对比,这可以用具有强烈水平各向异性的薄莫霍过渡带(<;5km厚)来解释。我们推测,这种各向异性是由分层滴落过程中较低的地壳流动引起的。具有正速度对比度的~75km深度的岩石圈内不连续(ILD)可能是由尖晶石到石榴石的相变引起的。在800–1300 km的偏移范围内观察到延迟的首次到达,随后是长达4 s的散射相的长波序列,这是通过中岩石圈不连续性(MLD)下方120至190 km深度的低速带(LVZ)中的连续随机速度波动来建模的。该LVZ的平均速度约为8.05km/s,远低于IASP91标准模型。这种LVZ很可能是由部分熔融或接近固相线的岩石引起的,这解释了低速和非均质结构。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Enigmatic crustal and upper mantle structure in the NE Sino-Korean Craton based on nuclear explosion seismic data

We interpret the crustal and upper mantle structure along ∼2500 km long seismic profiles in the northeastern part of the Sino-Korean Craton (SKC). The seismic data with high signal-to-noise ratio were acquired with a nuclear explosion in North Korea as source. Seismic sections show several phases including Moho reflections (PmP) and their surface multiple (PmPPmP), upper mantle refractions (P), primary reflections (PxP, PL, P410), exceptionally strong multiple reflections from the Moho (PmPPxP), and upper mantle scattering phases, which we model by ray-tracing and synthetic seismograms for a 1-D fine-scale velocity model. The observations require a thin crust (30 km) with a very low average crustal velocity (ca. 6.15 km/s) and exceptionally strong velocity contrast at the Moho discontinuity, which can be explained by a thin Moho transition zone (< 5 km thick) with strong horizontal anisotropy. We speculate that this anisotropy was induced by lower crustal flow during delamination dripping. An intra-lithospheric discontinuity (ILD) at ∼75 km depth with positive velocity contrast is probably caused by the phase transformation from spinel to garnet. Delayed first arrivals followed by a long wave train of scattered phases of up to 4 s duration are observed in the 800–1300 km offset range, which are modelled by continuous stochastic velocity fluctuations in a low-velocity zone (LVZ) below the Mid-Lithospheric Discontinuity (MLD) between 120 and 190 km depth. The average velocity of this LVZ is about 8.05 km/s, which is much lower than the IASP91 standard model. This LVZ is most likely caused by rocks which are either partially molten or close to the solidus, which explains both low velocity and the heterogeneous structure.

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来源期刊
Journal of Geodynamics
Journal of Geodynamics 地学-地球化学与地球物理
CiteScore
4.60
自引率
0.00%
发文量
21
审稿时长
6-12 weeks
期刊介绍: The Journal of Geodynamics is an international and interdisciplinary forum for the publication of results and discussions of solid earth research in geodetic, geophysical, geological and geochemical geodynamics, with special emphasis on the large scale processes involved.
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