Factors that affect coseismic folds in an overburden layer
- 34 Downloads
Coseismic folds induced by blind thrust faults have been observed in many earthquake zones, and they have received widespread attention from geologists and geophysicists. Numerous studies have been conducted regarding fold kinematics; however, few have studied fold dynamics quantitatively. In this paper, we establish a conceptual model with a thrust fault zone and tectonic stress load to study the factors that affect coseismic folds and their formation mechanisms using the finite element method. The numerical results show that the fault dip angle is a key factor that controls folding. The greater the dip angle is, the steeper the fold slope. The second most important factor is the overburden thickness. The thicker the overburden is, the more gradual the fold. In this case, folds are difficult to identify in field surveys. Therefore, if a fold can be easily identified with the naked eye, the overburden is likely shallow. The least important factors are the mechanical parameters of the overburden. The larger the Young’s modulus of the overburden is, the smaller the displacement of the fold and the fold slope. Strong horizontal compression and vertical extension in the overburden near the fault zone are the main mechanisms that form coseismic folds.
Keywordsground deformation coseismic fold blind thrust fault finite element method
Unable to display preview. Download preview PDF.
We would like to thank the anonymous reviewers for their constructive comments. This research was funded by the National Natural Science Foundation of China (Grant No. 41474080).
- Bray J D (2001). Developing mitigation measures for the hazards associated with earthquake surface fault rupture. Seismic Faultinduced Failures: 55–80Google Scholar
- Chen G H, Xu X W, Zheng R Z, Yu G H, Li F, Li C X, Wen X Z, He Y L, Ye Y Q, Chen X C, Wang Z C (2008). Quantitative analysis of the coseismic surface rupture of the 2008 Wenchuan earthquake, Sichuan, China along the Beichuan-Yingxiu fault. Dizhen Dizhi, 30(3): 723–738 (in Chinese)Google Scholar
- Donald L T, Gerald S (2001). Geodynamics (2nd ed). Cambridge: Cambridge University Press, 78Google Scholar
- Ishiyama T, Sato H, Kato N, Nakayama T, Iwasaki T, Abe S (2011). Structures of active blind thrusts beneath Tokyo Metropolitan area. AGU Fall Meeting 2011, abstract T54B-02Google Scholar
- Lee J C, Chen Y G, Sieh K, Mueller K, Chen W S, Chu H T, Chan Y C, Rubin C, Yeats R (2001). A vertical exposure of the 1999 surface rupture of the Chelungpu Fault at WuFeng, Western Taiwan: structural and paleoseismic implications for an active thrust fault. Bulletin of the Seismological Society of America, 91(5): 914–929CrossRefGoogle Scholar
- Papadimitriou A, Loukidis D, Bouckovalas G, Karamitros D (2007). Zone of excessive ground surface distortion due to dip-slip fault rupture. 4th International Conference on Earthquake Geotechnical Engineering, Paper No. 1583Google Scholar
- Shi C X (1994). Materials Comprehensive Dictionary. Beijing: Chemical Industry Press (in Chinese)Google Scholar