Random Seismic Waves and Laboratory Ultrasonics

该项目支持最近的一位博士对美国的长期访问，他是在这种波的新“介观”理论背景下进行随机超声波和地震波实验的唯一（世界范围内）专家。 这些理论首先在伊利诺斯州的超声波实验室发展起来，对地球科学特别重要，因为它们意味着地震信号处理的新方法，可以提取有关地壳结构的新信息。 这位研究人员在伊利诺伊州的存在将促进扩散场超声学研究人员和地震学家之间的交叉施肥，并将加速美国在这种波方面的实验和理论工作。研究人员将建造地球和地壳的比例模型，并在其上进行超声实验，以测试这些理论。 也许与直觉相反，随机波场（例如在周围的地震噪音中或在地震后的长振铃地震尾波中发现的）包含关于它们传播的介质的许多有用信息。 原则上，它们包含了地震学和勘探地球物理学中通常通过使用炸药和“thumpers”，或者通过使用地震直接波而不受控制，以巨大的成本和不便获得的所有信息。 该项目将阐明这种有前途的获取地球信息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.--