Hudson Bay Lithospheric Experiment

由于地幔中的对流和刚性板块(岩石圈)在其表面的移动，地球表面不断变化。在整个地球历史上，大陆一直在不断地迁移，融合在一起，然后被撕裂。然而，在大陆的中心是保存完好的屏蔽区。巨大的大陆根位于这些克拉通地区的下方，它们既能抵抗热作用，又能抵抗机械作用。这些树根是如何形成的，它们是由什么组成的，以及它们为什么会保持这么长时间的完好无损，这是有争议的争论焦点。我们提出了一项以北美前寒武纪核心为中心的被动地震实验，北美是地球上最大的前寒武纪克拉通。哈德逊湾位于这个克拉通中心附近，是地球引力场大范围正偏转的地点。尽管是北美最显著的特征之一，但哈德逊湾克拉通内盆地的成因尚不清楚。重力资料和地震图像表明，该地区地幔存在异常，并提出了各种理论来解释这种异常。哈德逊湾的东南岸形成了一个近乎完美的半圆形弧形，被称为纳斯塔波卡弧形。有人提出，这条弧线是一个巨大的陨石撞击坑的标志，但这个想法是推测的。关于这种盆地形成的原因和大陆根的性质的理论可以通过详细的地震学实验来检验。我们将与加拿大和德国的科学家合作，部署为期两年的陆地和海底地震仪，记录遥远的和当地的地震。这些数据将被用来研究下伏地幔的速度结构、地幔和岩石圈变形的性质以及大陆根的形成。我们将检验有关纳斯塔波卡弧线性质的理论。我们还将观察该地区的局部地震活动，这是异常的，并未得到很好的理解。

The surface of the Earth is continually changing due to convection in the mantle and the movement of rigid plates (lithosphere) across its surface. Throughout Earth history the continents have been constantly migrating, being fused together and ripped apart. Nevertheless, at the heart of continents lies shield regions that have remained remarkably intact. Large continental roots lie beneath such cratonic regions and they are resistant to both thermal and mechanical alteration. How these roots are formed, what they are comprised of, and why they remain intact for so long are points of contentious debate. We propose a passive seismic experiment centred on the Preambrian core of North America, the largest Precambrian craton on Earth. Hudson Bay, which lies near the centre of this craton, is the site of the large positive deflection in the Earth's gravitational field. Despite being one of the most striking features of North America, the cause of the Hudson Bay intracratonic basin is not well understood. Gravity data and seismological images show that the mantle is anomalous in this region and various theories have been proposed to explain the anomaly. The southeast shore of Hudson Bay forms a nearly perfect arc of a semicircle and is called the Nastapoka Arc. It has been proposed that this arc is the signature of a huge meteorite impact crator, but this idea is speculative. Theories as to why such basins are formed and the nature of continental roots can be tested with a detailed seismological experiment. In collaboration with scientists in Canada and Germany we will deploy land and ocean-bottom seismometers for a two-year period, recording distant and local earthquakes. These data will be then used to study the velocity structure of the underlying mantle, the nature of mantle and lithospheric deformation and the formation of continental roots. We will test theories of the nature of the Nastapoka Arc. We will also look local seismicity in the region, which is anomalous and not well understood.