Random Seismic Waves and Laboratory Ultrasonics

这个项目支持最近一位博士对美国的长期访问，他是在随机超声波和地震波的新“介观”理论背景下进行实验的唯一（世界范围内的）专家。这些理论最初是在伊利诺斯州的超声波实验室中发展起来的，它们对地球科学特别重要，因为它们暗示了地震信号处理的新方法，通过这种方法可以提取有关地壳结构的新信息。这位研究人员在伊利诺斯州的出现将促进漫射场超声研究人员和地震学家之间的交流，并将加速美国在这种波上的实验和理论努力。研究人员将构建地球和地壳的比例模型，并对其进行超声波实验，以验证这些理论。也许与直觉相反，随机波场（例如在环境地震噪声中发现的或在地震后的长环形地震尾波中发现的）包含了它们传播的介质中许多有用的信息。原则上，它们包含了通常在地震学和勘探地球物理学中使用炸药和“重击器”或无法控制地使用地震直接波而获得的所有信息，这些信息通常花费巨大且不方便。这个项目将阐明这种在地球上获取信息的有前途的新方法的局限性和潜力

This project supports an extended visit to the U.S. by a recent PhD who is the sole (world-wide) expert at experiments with random ultrasonic and seismic waves in the context of new "mesoscopic" theories for such waves. These theories, first developed in the ultrasonics lab at Illinois, are particularly important for earth sciences in that they imply new methods for seismic signal processing with which new information on the structure of the earth's crust could be extracted. This researcher's presence at Illinois will facilitate cross fertilization between diffuse field ultrasonics researchers and seismologists and it will accelerate the US experimental and theoretical effort on such waves.Researchers will construct scale models of the earth and the earth's crust and conduct ultrasonic experiments on them in order to test these theories. Contrary to intuition perhaps, random wave fields (such as are found in ambient seismic noise or in the long ringing seismic coda that follows earthquakes) contain much useful information on the medium in which they propagate. In principle they contain all information which is normally obtained at great expense and inconvenience in seismology and exploration geophysics by use of explosives and "thumpers," or with no control by use of direct waves from earthquakes. This project will elucidate the limits and potential of this promising new approach for obtaining information on the earth.--