1. General Introduction
1.1. Fluid Distribution Along Megathrust Faults
1.2. Receiver Function Analysis
1.3. Tectonic setting of the Nankai Subduction Zone
1.4. Data
1.4.1. Seismic Stations
1.4.2. Teleseismic Event Records
2. Inverse Water Layer Filter Method
2.1. Introduction
2.2. Definition of Water-Layer Filter
2.3. Synthetic Test
2.3.1. Methodology
2.3.2. Results and Discussion
3. Application of Inverse Water Layer Filter Method
3.1. Introduction
3.2. Inversion Analysis for Water-Layer Filter Parameters 3.2.1. Overview of Inversion Analysis
3.2.2. Prior Estimation of Phase Arrivals
3.2.3. Inversion Scheme
3.2.4. Results and Discussion
3.3. Quantitative Assessment of Inverse Water-Layer Filter
3.4. Application to Receiver Function Estimation
4. Receiver Function Image of the Subducting Philippine Sea Plate
4.1. Introduction
4.2. Methodology
4.2.1. Common-Conversion-Point Stacking
4.3. Results 4.3.1. 3-D Geometry of the Subducting Philippine Sea Plate
4.3.2. Island-arc Moho beneath the Kii Peninsula
4.3.3. Receiver Function Amplitudes Along the Subducting Plate
4.4. Discussion
4.4.1. Forward Modeling of Amplitude Reduction Beneath the Kii Peninsula
4.4.2. Uncertainty of Relative Depth Between Hypocenters and
the Oceanic Moho
4.4.3. Hydrous State of the Subducting Oceanic Crust
4.4.4. Permeability Difference in Source Area of Long-Term Slow Slip Events and Tremors
5. A Fluid-Rich Layer Along the Megathrust Fault Inferred from High-Frequency Receiver Function Inversion Analysis
5.1. Introduction
5.2. High-Frequency Receiver Functions 5.3. Estimation of Sediment Properties by the H-κ Stacking Method
5.3.1. Methodology
5.3.2. Results
5.4. Receiver Function Inversion Analysis
5.4.1. Methodology
5.4.2. Results
5.5. Fluid-Rich Subducting Sediment Layer Along the Plate Interface 6. General Discussion
6.1. Along-Dip Variation in Low-Velocity Zone Thickness
6.2. Comparison to Other Subduction Zones
6.3. New Perspectives by High-Frequency Receiver Function Analysis Using OBS data
7. Conclusion
