11:00 AM - 1:00 PM
[HDS12-P05] Modeling of Subsurface Velocity Structures from Seismic Bedrock to Ground Surface, for strong ground motion evaluation, around Byobuyama - Enasan and Sanageyama fault zone
Keywords:underground structure model, strong ground motion, microtrmors, s-wave velocity, gravity
The Byobuyama-enasan fault zone and the Sanageyama fault zone are long active fault zones with a total length of over 100 km from Mt. Ena to the Chita peninsula.
In this fault zone, from the 2020 to the 2022, a basic survey of science and technology was conducted with the aim of improving the accuracy of the long-term evaluation of the Byobutyama-enasan fault zone and Sanageyama fault zone.
As part of the sub-theme 4 "Survey for improving strong ground motion prediction in the vicinity of faults and urban areas" , We are working on constructing a shallow and deep integrated ground structure model for strong ground motion prediction for urban areas.
In this study, based on the shallow and deep integrated underground model(SD model) of the Tokai region constructed by the Strategic Innovation Creation Program (SIP), gravity data analysis, seismic observation, and microtremor were newly implemented by the 2021. Using array observation data, etc., the SD model was upgraded within the range of the pink line in Fig. 1.
In this study, collection of gravity exploration data (26,595 points) and collection of boring data (about 20 holes for deep boring with a drilling length of 100 m to 1000 m, and shallow depth boring with a drilling length of several 10 m to 200 m). Approximately 1000 points), and new seismic observations and microtremor array observations are being carried out. For the gravity exploration data, the data provided by the Tono Research Institute of Earthquake Science(TRIES) and the gravity data edited by the AIST were used. Seismic observation records collect data from K-NET, KiK-net, local governments, the Meteorological Agency, and Nagoya University's seismic stations, and seismographs have been installed at 20 elementary and junior high schools in Aichi and Gifu prefectures (mainly in Aichi and Gifu prefectures. (Fig. 1)). In addition, microtremor array observations were carried out at 40 large array observations with a maximum radius of 400 m and at 843 small arrays with an array radius of about 5 to 10 m (Fig. 2).
The ground is analyzed by joint inversion analysis using the existing ground model of the Tokai region, the seismicbedrock structure set by gravity analysis, the phase velocity of the tremor array, and the R/V spectral ratio of the seismic observation record. The created model(Fig.3) is highly reliable because it is in harmony with the results of the past reflection seismological surveys. In this method, especially by performing gravity analysis, it is possible to obtain information on the distribution shape of the sedimentary basin, which cannot be obtained from the distribution of surface geology, and it is possible to model with high accuracy. This method is considered to be an extremely effective method for constructing a wide-area ground structure model for strong ground motion prediction.
In this fault zone, from the 2020 to the 2022, a basic survey of science and technology was conducted with the aim of improving the accuracy of the long-term evaluation of the Byobutyama-enasan fault zone and Sanageyama fault zone.
As part of the sub-theme 4 "Survey for improving strong ground motion prediction in the vicinity of faults and urban areas" , We are working on constructing a shallow and deep integrated ground structure model for strong ground motion prediction for urban areas.
In this study, based on the shallow and deep integrated underground model(SD model) of the Tokai region constructed by the Strategic Innovation Creation Program (SIP), gravity data analysis, seismic observation, and microtremor were newly implemented by the 2021. Using array observation data, etc., the SD model was upgraded within the range of the pink line in Fig. 1.
In this study, collection of gravity exploration data (26,595 points) and collection of boring data (about 20 holes for deep boring with a drilling length of 100 m to 1000 m, and shallow depth boring with a drilling length of several 10 m to 200 m). Approximately 1000 points), and new seismic observations and microtremor array observations are being carried out. For the gravity exploration data, the data provided by the Tono Research Institute of Earthquake Science(TRIES) and the gravity data edited by the AIST were used. Seismic observation records collect data from K-NET, KiK-net, local governments, the Meteorological Agency, and Nagoya University's seismic stations, and seismographs have been installed at 20 elementary and junior high schools in Aichi and Gifu prefectures (mainly in Aichi and Gifu prefectures. (Fig. 1)). In addition, microtremor array observations were carried out at 40 large array observations with a maximum radius of 400 m and at 843 small arrays with an array radius of about 5 to 10 m (Fig. 2).
The ground is analyzed by joint inversion analysis using the existing ground model of the Tokai region, the seismicbedrock structure set by gravity analysis, the phase velocity of the tremor array, and the R/V spectral ratio of the seismic observation record. The created model(Fig.3) is highly reliable because it is in harmony with the results of the past reflection seismological surveys. In this method, especially by performing gravity analysis, it is possible to obtain information on the distribution shape of the sedimentary basin, which cannot be obtained from the distribution of surface geology, and it is possible to model with high accuracy. This method is considered to be an extremely effective method for constructing a wide-area ground structure model for strong ground motion prediction.