Australia Cretaceous Climate and Tectonics: International Ocean Discovery Program Expedition 369

地震反射法是研究地球埋藏结构的主要工具。这种方法与使用超声成像子宫内胎儿的方法相同，但规模要大得多。在地表产生声脉冲，并记录该脉冲从埋藏的地质变化回送到地表的接收器的时间。通过沿剖面重复实验，可以生成绘制岩层地图的地下图像。然而，这其中存在一个问题。图像被记录为回波返回地表的时间函数，而地质学家需要知道深度。关键是获得一张声速地图，这样时间就可以转换为深度。通过使用多个接收器，可以获得该声速图的估计值，但该信息是不完整的，容易出错和不确定。通过对地震数据的仔细分析，我们已经获得了这些不确定因素的量化估计，这些剖面穿过国际海洋发现方案将在第369航段进行钻探的地点。因此，一旦这些地点被钻探，我们将在地震图像上的某个点获得地面真相，这样我们就可以看到我们的估计有多好，以及预期的地质层是否位于我们预测的深度和时间。然后，我们可以使用井信息来标记每一层，并使用地震数据将这种标记从井中外推出来，并将其与地震图像的人工解释进行比较。我们希望了解的是，在基于地震数据对地下结构进行预测时，我们可以给予何种程度的置信度。这对地球科学具有重大影响，因为地震反射法是碳氢化合物行业用来定位石油和天然气的主要工具，同样，碳封存行业也使用它来掩埋和监测二氧化碳，试图缓解全球变暖。此外，这里开发的理解可用于医疗、建筑和工程行业的各种非破坏性成像方法。

The seismic reflection method is the primary tool for investigating the buried structure of the Earth. The method is the same as used to image a fetus in the womb by ultra-sound, but on a much larger scale. A sound pulse is generated at the surface and the time is recorded for this pulse to be echoed from some buried change in geology back to a receiver at the surface. By repeating the experiment along a profile, an image of the subsurface can be generated that maps the layers of rock. However, there is a problem. The image is recorded as a function of time for the echoes to return to the surface whereas geologists require to know the depths. The key is to obtain a map of the sound-speed so time can be converted to depth. By using multiple receivers it is possible to obtain an estimate of this sound-speed map but the information is incomplete and prone to errors and uncertainty. By careful analysis of the seismic data, we have obtained quantified estimates of these uncertainties for profiles that cross the sites that are to be drilled by the International Ocean Discovery Program during leg 369. So once these sites are drilled we will have ground truth at a point on the seismic image so we can see how good our estimates are and whether the expected geological layers are at the depth and time that we have predicted. We can then use the well information to label the each layer and extrapolate this labeling away from the well using the seismic data and compare this with a manual interpretation of the seismic image. What we hope to learn is what level of confidence can we place in our predictions of the structure of the subsurface based on seismic data. This has major implications in Earth Sciences as the seismic reflection method is the primary tool used by the hydrocarbons industry to locate oil and gas, equally it is used by the carbon sequestration industry to bury and monitor CO2 to try to mitigate global warming. Further, the understanding developed here can be used across a wide-range of non-destructive imaging methods in the medical, construction and engineering industries.