Presentation Information
[U09-P04]Study on the Regulatory Zone Width Based on the Position Accuracy of Surface Rupture Appearing in the 2016 Kumamoto Earthquake
*Asaka Konno1 (1.Tokoha University)
Keywords:
Active fault,Surface rupture,Separation distance,RTK-GNSS,The 2016 Kumamoto earthquake
Surface rupture caused by seismic faults deforms structures and causes significant damage. To minimize such damage from fault displacement, some urban areas implement measures such as restricting construction within a certain zone along active faults. However, while regulatory frameworks are progressing, it is difficult to say that the width of these restricted zones is being thoroughly evaluated for adequacy against damage from surface rupture. The distance from existing active fault lines for the 2016 Kumamoto Earthquake faults is quantitatively examined. Applying this to the existing avoidance zone width (25m from active faults), the results showed that current regulations could cover less than 40% of the potential occurrence range of surface rupture (Konno & Toda, 2017). Therefore, this presentation discusses the “accuracy” of the locations of surface rupture that emerged during the 2016 Kumamoto Earthquake.
To do this, we precisely surveyed the locations of these ruptures using a small RTK-GNSS surveying device (LRTK Phone) with centimeter-level positioning accuracy. Furthermore, we calculated the separation distance between these positions and those comprehensively surveyed immediately after the earthquake by the University Joint Surface Rupture Survey Group using mobile GPS devices. The results showed that in urban areas and grasslands, the separation distance between the two sets of positions was typically around 2 meters. However, in forested areas, the separation exceeded 5 meters in some locations. This indicates that it is necessary to recognize that the actual locations of earthquake faults may have errors of several meters, depending on the type of surveying equipment and land use. Furthermore, even if another earthquake occurs in the same location, considering that faults may not reappear in the same place under poorly lithified geological conditions, it is important to set appropriate widths for restricted zones.
To do this, we precisely surveyed the locations of these ruptures using a small RTK-GNSS surveying device (LRTK Phone) with centimeter-level positioning accuracy. Furthermore, we calculated the separation distance between these positions and those comprehensively surveyed immediately after the earthquake by the University Joint Surface Rupture Survey Group using mobile GPS devices. The results showed that in urban areas and grasslands, the separation distance between the two sets of positions was typically around 2 meters. However, in forested areas, the separation exceeded 5 meters in some locations. This indicates that it is necessary to recognize that the actual locations of earthquake faults may have errors of several meters, depending on the type of surveying equipment and land use. Furthermore, even if another earthquake occurs in the same location, considering that faults may not reappear in the same place under poorly lithified geological conditions, it is important to set appropriate widths for restricted zones.