2006 Fiscal Year Final Research Report Summary
STUDY ON INVERSION OF MICROSEISMS HORIZONTAL-TO-VERTICAL SPECTRAL RATIO FOR DETERMING THE BOUNDARY SHAPE OF A BASIN STRUCTURE
| Project/Area Number |
16560519
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Building structures/materials
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| Research Institution | HIROSHIMA INTERNATIONAL UNIVERSITY |
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Principal Investigator |
UEBAYASHI Hirotoshi HIROSHIMA INTERNATIONAL UNIVERSITY, FACULTY OF INFRASTRUCTURAL TECHNOLOGIES, 社会環境科学部, 助教授 (30300312)
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| Project Period (FY) |
2004 – 2006
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| Keywords | IRREGULAR STRUCTURE / INVERSION / MICROTREMORS / HORIZONTAL-TO-VERTICAL SPECTRAL RATIO / SEDIMENTARY BASIN / NUMERICAL EXPERIMENT / HIERARCHY / VELOCITY INHOMOGENETY / 速度不均質 |
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| Research Abstract |
The inversion of the long-period (1 to 10 seconds) microtremor (microseism) horizontal-to-vertical (H/V) spectral ratios was investigated as a tool for the modeling of the shape of a basin-bedrock interface of basin structures. An inversion procedure applying a genetic algorithm (GA) was formulated on the basis of reproductions of H/V spectra. Using finite element method (FEM), H/V spectra at sediment observation points are derived from transfer functions due to Rayleigh wave incidences from the outsides of the basin region. Numerical experiments of the inversion were performed on 2D virtual basin structure models with spatial variation in medium parameters of the sedimentary layer. The medium parameters are defined as function of depth. To determine the depth distribution of the basin-bedrock interface efficiently with high resolution, the basin region was split into three grid-size (0.6, 0.3 and 0.15 kilometers) hierarchical models and several horizontal submodels. By incorporating these techniques into GA, efficient and accurate optimal solutions could be found. For practical implementation of this technique in the future, two issues need to be investigated: 1) checking the impact of the 3-D basin-bedrock interface numerically, and 2) checking whether a good optimal solution can be obtained in the realistic event containing an observation error.
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