3:45 PM - 4:00 PM
[SSS09-12] Microtremor observation around the anticline structures in the Tainan region, Taiwan
Keywords:microtremor, horizontal-to-vertical spectral ratio, directional dependence, Tainan, anticline
This study focuses on conducting microtremor observations in the Tainan region, Taiwan and try to investigate about the relation between the characteristics of the observed microtremor and the lateral heterogeneity, especially the inclination of the bedrock or other high impedance layer of the subsurface structure formed by the complex geological setting of south-western Taiwan. The two target areas are 1) crossing the Napalin Anticline which is formed by the Napalin backthrust due to the Tainan Detachment and 2) between Tainan Anticline (Tainan Tableland) and Dawan Lowland which is assumed to be formed by the Houchiali Fault.
We observed microtremor at 26 stations along Zhongxing Road and route South 168 continuing to the south-east from the central part of Xinhua district of Tainan City (Line 1 denoted by blue symbols in the figure). The station interval was designed to be about 500 m to make the total survey length about 12.5 km. The strata of the west side of the Napalin Anticline is estimated to gradually incline downward toward the west and for the east side of Napalin Anticline it is estimated to have a steeper slope because of the Shihtzuchi Syncline (Le Béon et al., 2019). We assumed to that we would be able to catch directional dependence features in the microtremor horizontal-to-vertical spectral ratios (MHVRs) due to the inclination of the layers, however there were not clear evidence of directional dependence seen in the preliminary anaysis. We will further investigate about the directional dependence in the MHVRs.
On the other hand, we observed microtremor along three survey lines in the eastern part of Tainan City. The survey lines were design to be distributed in the area between the Tainan Tableland and Dawan Lowland. One survey line runs north-south (Line 2 denoted by green symbols in the figure) and two survey lines run east-west (Lines 3 and 4 denoted by purple and yellow symbols in the figure, respectively). Line 2 is mostly in the middle of the Dawan Lowland. Lines 3 and 4 continue from the Tainan Tableland in the west crossing the transition zone and continuing into the Dawan Lowland in the east. The station interval for these survey lines were 1 km and the total number of stations for the three survey lines is 24, eg. eight stations per survey line. The data obtained by these observations will be analyzed in detail to study about the relation between the characteristics of MHVRs and the local subsurface structure.
Acknowledgements
This study was partially supported by an internal fund of DPRI, Kyoto University for the collaboration between NCKU and DPRI. The observations were conducted with the strong support by the researcher, staff and students of NCKU, Ying-Chi Chen, Min-Zuo Weng, Zi-Chang Yang, John Emmanuel Fungo and a student of Kyoto University, Thinzar Yadanar.
We observed microtremor at 26 stations along Zhongxing Road and route South 168 continuing to the south-east from the central part of Xinhua district of Tainan City (Line 1 denoted by blue symbols in the figure). The station interval was designed to be about 500 m to make the total survey length about 12.5 km. The strata of the west side of the Napalin Anticline is estimated to gradually incline downward toward the west and for the east side of Napalin Anticline it is estimated to have a steeper slope because of the Shihtzuchi Syncline (Le Béon et al., 2019). We assumed to that we would be able to catch directional dependence features in the microtremor horizontal-to-vertical spectral ratios (MHVRs) due to the inclination of the layers, however there were not clear evidence of directional dependence seen in the preliminary anaysis. We will further investigate about the directional dependence in the MHVRs.
On the other hand, we observed microtremor along three survey lines in the eastern part of Tainan City. The survey lines were design to be distributed in the area between the Tainan Tableland and Dawan Lowland. One survey line runs north-south (Line 2 denoted by green symbols in the figure) and two survey lines run east-west (Lines 3 and 4 denoted by purple and yellow symbols in the figure, respectively). Line 2 is mostly in the middle of the Dawan Lowland. Lines 3 and 4 continue from the Tainan Tableland in the west crossing the transition zone and continuing into the Dawan Lowland in the east. The station interval for these survey lines were 1 km and the total number of stations for the three survey lines is 24, eg. eight stations per survey line. The data obtained by these observations will be analyzed in detail to study about the relation between the characteristics of MHVRs and the local subsurface structure.
Acknowledgements
This study was partially supported by an internal fund of DPRI, Kyoto University for the collaboration between NCKU and DPRI. The observations were conducted with the strong support by the researcher, staff and students of NCKU, Ying-Chi Chen, Min-Zuo Weng, Zi-Chang Yang, John Emmanuel Fungo and a student of Kyoto University, Thinzar Yadanar.