Stochastic modeling of seismic wave propagation beneath island-arcs and volcanoes

岛弧和火山下面的地壳和上地幔是非常不均匀的。速度层析成像分析揭示了俯冲洋板和地幔楔的精细结构等构造不均匀性。该方法基于P波和S波发作的旅行时间阅读，完全忽略了波形信息。尽管最近通过使用新的密集地震台网的数据已经提高了速度不均匀性的空间分辨率，但是这种分析本质上难以对尺度长度比站间距短得多的短波长不均匀性进行成像。与确定性方法相反，还有一种替代方法，即随机方法。该项目的目标是提出理论模型，解释波通过高度不均匀介质的传播，并制定分析在岛弧和火山中观测到的高频地震图的方法。我们使用分析方法和数值方法的研究波在随机介质中的传播，在那里我们介绍了一个统计处理的波动方程。将与我们的日本研究伙伴东北大学合作，进一步发展现有方法，并将研究默拉皮火山的样本数据集。

The crust and the upper mantle beneath island arcs and volcanoes are known to be very heterogeneous. The structural inhomogeneity including the fine structure of the subducting oceanic slab and the mantle wedge has been revealed from velocity tomography analyses. This method, which is based on the travel time reading of P and S wave onsets, disregards waveform information completely. Even though the spatial resolution of the velocity inhomogeneity has been improved recently by using data of new dense seismic networks, it is inherently difficult for this analysis to image short wavelength heterogeneities with scale length much shorter than the station separation. In contrast to the deterministic approach, there is an alternative, stochastic approach. The objective of this project is to propose theoretical models to explain wave propagation through highly inhomogeneous media and to develop methods for analyzing high frequency seismograms observed in island arcs and volcanoes. We use both analytical methods and numerical methods for the study of wave propagation in randon media, where we introduce a statistical treatment of the wave equation. Existing methods will be further developed in cooperation with our Japanese research partners of Tohoku University, and sample data sets from Merapi volcano will be studied.