Passive Imaging of the Lithosphere Asthensphere Boundary (PiLAB)

近50年来，板块构造一直是地球科学的一个基本原则，但一些基本问题仍然存在，比如板块的底部在哪里，是什么使板块“像板块”？更好地理解从刚性岩石圈板块到下面较弱的地幔的转变对板块构造、自然灾害和气候变化的驱动力具有重要意义。有许多替代方法用于估计构造板块底部的深度和性质，但迄今为止尚未达成共识。例如，已知温度对岩石的力学行为有强烈的影响，如果这是控制板块定义的唯一过程，那么我们将期望在海洋中脊附近看到一个薄板块，在古老的海底下面看到一个非常厚的板块。然而，许多地球物理研究观察到，在所有海底时代，板块厚度几乎都是恒定的。这使得科学家们提出了其他的机制，比如地幔脱水来加强地幔，形成一个刚性板块。同样，对非常强烈的异常现象的观察也使其他人认为，可能存在熔融以削弱板块下的地幔。然而，这些观测中有许多只来自一个海洋，即太平洋，来自不同地区和尺度的间接、远程观测，对地球性质的敏感度也不同。尽管结果很有希望，但研究之间的比较是具有挑战性的，阻碍了对构造板块的全面了解。我们将系统地描绘一个海洋板块的整个长度，从它在大西洋中脊的诞生到它在非洲边缘最古老的形成。这是一项大规模的重点工作，具有从米到公里的多尺度分辨率和灵敏度，使用地震和电磁方法。这种规模、重点和跨学科的方法将最终确定使钢板坚固的过程和特性，并定义它。该项目将通过一个大型的、重点突出的国际合作来完成，涉及欧盟合作伙伴（350万欧元）和工业界（640万欧元），两者都已获得资助。

Plate tectonics has been a fundamental tenet of Earth Science for nearly 50 years, but fundamental questions remain, such as where is the base of the plate and what makes a plate, "plate-like?" A better understanding of the transition from the rigid lithospheric plate to the weaker mantle beneath has important implications for the driving forces of plate tectonics, natural hazards, and climate change.There are many proxies used to estimate the depth and nature of the base of tectonic plates, but to date no consensus has been reached. For example, temperature is known to have a strong effect on the mechanical behaviour of rocks, and if this were the sole process governing the definition of the plate, then we would expect to see a thin plate near a mid ocean ridge and a very thick plate beneath old seafloor. However numerous geophysical studies observe what are interpreted as nearly constant thickness plate at all seafloor ages. This has led scientists to propose other mechanisms, such as dehydration of the mantle to strengthen the mantle to form a rigid plate. Similarly, observations of very strong anomalies have led others to suggest that melt might exist to weaken the mantle beneath the plates. However many of these observations come from only one ocean, the Pacific, from indirect, remote observations, at different areas and scales, and with different sensitivities to earth properties. Although results have been promising, comparisons among studies are challenging, hindering a complete understanding of the tectonic plate.We will systematically image the entire length of an oceanic plate, from its birth at the Mid Atlantic Ridge to its oldest formation on the African margin. This is a large-scale focused effort with multiple scales of resolution and sensitivity, from a metre to kilometre scale using seismic and electromagnetic methods. This scale, focus, and interdisciplinary approach will finally determine the processes and properties that make a plate strong and define it. The project will be accomplished through a large, focused international collaboration that involves EU partners (3.5 M euro) and industry (6.4M euro), both already funded.