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，他是随机超声波和地震波实验的唯一(世界范围内)专家，在这种波的新“介观”理论的背景下。这些理论最先由伊利诺伊州的超声波实验室开发，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，利用这些方法可以提取关于地壳结构的新信息。这位研究人员在伊利诺伊州的存在将促进扩散场超声波研究人员和地震学家之间的交叉受精，并将加快美国对这种波的实验和理论工作。研究人员将建立地球和地壳的比例尺模型，并在其上进行超声波实验，以验证这些理论。也许与直觉相反的是，随机波场(例如，在周围的地震噪声中或在地震后的长响地震尾波中发现的)包含了许多关于它们在其中传播的介质的有用信息。原则上，它们包含了在地震学和勘探地球物理中通常花费巨大和不便的所有信息，这些信息是通过使用炸药和“推进器”获得的，或者是无法利用地震直达波控制的。这个项目将阐明这一很有前途的新方法在获取地球信息方面的局限性和潜力。

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.--