| We re-analyze and re-interpret the very shallow S-wave land seismic reflection survey data across the Naruto-South fault, Median Tectonic Line active fault system in Naruto city, Tokushima prefecture acquired in 1998. By re-analysis and re-interpretation, more detailed interpretation of active fault properties, including fault position and displacement amount, are obtained.A reflection survey is the one of important method to search underground discontinuous structures. Particularly in the disaster prevention area, reflection surveys are widely utilized to search faults. Identifying a position and properties of concealed the active fault for considering fault activities were important to urban disaster planning. But a quality of analysis in several decades ago were low, due to poor computer performance. In this study, we change various analysis factors with a currently compute progress to secure high resolution.The survey line, we re-analyzed and re-interpreted, was deployed across the Naruto-south fault, the part of Median Tectonic Line active fault system. The S-wave survey line was 100m long with 0.5m sensor separation. The portable vibrator was utilized as seismic source with a 1.0m spacing.As the result of re-analysis, we obtained more detailed active fault structure less than 50m depth. In this study, we can identify the position of the about 70 degree dip fault , lied from 10m to 50m depth, with more resolution. Also, we achieved to show the continuous structure, not cut off by the active fault, more clearly than conventional. In this study, we show that more detailed active fault structure are obtained by re-analysis and re-interpret old data to give useful information for urban disaster planning. |
