11:00 AM - 1:00 PM
[HTT20-P02] Case study of microtremor array measurements for the landslide of colluvial deposit in a mountain area
Keywords:landslide, colluvial deposit, sliding surface, microtremor array, S-wave velocity
This article shows a case study of microtremor array measurements conducted in the landslide of a colluvium in a mountain area. Microtremor array measurements can estimate S-wave velocity structure using more than a seismograph equipment which are set on several arrays. The microtremor, which is low amplitude of natural ground motions, is observed for several tens of minutes at a measurement of an array. In this study, we selected a site with many boring results in a colluvium in mountains to compare with our result of microtremor array measurements.
Figure (a) shows the S-wave velocity structure estimated from microtremor array measurements. At the Point 1, the S-wave velocity (Vs) is 600 m/s or higher around the ground surface, and it is considered that the bedrock is located up to near surface. However, at the Point 2 and the Point 3, the zone with lower Vs of 150 - 300 m/s is spread in the wide range from the surface. These results show that a sedimentary layer was deposited in wider depth range in the near surface at the Point 2 and 3 than the Point 1. Figure (b) is a geological cross section estimated with boring results. The top boundary of the bedrock crosses to the ground surface near the Point 1. Figure (c) shows the photograph of boring cores acquired at the Point 1. You can find that the thicknesses of colluvial deposit at the Point 2 and the Point 3 are wider that the Point 1. It is a same trend with the S-wave velocity structure estimated from the microtremor array measurement. This study shows that the microtremor array measurement in landslides with colluvial deposit in mountain areas becomes a useful and low-cost method to interpolate areas with insufficient geological information between boring points.
Figure (a) shows the S-wave velocity structure estimated from microtremor array measurements. At the Point 1, the S-wave velocity (Vs) is 600 m/s or higher around the ground surface, and it is considered that the bedrock is located up to near surface. However, at the Point 2 and the Point 3, the zone with lower Vs of 150 - 300 m/s is spread in the wide range from the surface. These results show that a sedimentary layer was deposited in wider depth range in the near surface at the Point 2 and 3 than the Point 1. Figure (b) is a geological cross section estimated with boring results. The top boundary of the bedrock crosses to the ground surface near the Point 1. Figure (c) shows the photograph of boring cores acquired at the Point 1. You can find that the thicknesses of colluvial deposit at the Point 2 and the Point 3 are wider that the Point 1. It is a same trend with the S-wave velocity structure estimated from the microtremor array measurement. This study shows that the microtremor array measurement in landslides with colluvial deposit in mountain areas becomes a useful and low-cost method to interpolate areas with insufficient geological information between boring points.