The relation between fault movement potential and seismic activity of major faults in Northwestern Vietnam

Abstract
In this study, the method of Fault Movement Potential (FMP) proposed by Lee et al. (1997) is used to assess the movement potential of some major faults and its relationship with the seismic activities in Northwestern Vietnam. The fault movement potential is assessed by the magnitude of FMP (from 0 to 1) and calculated based on the relationship between kinematic characteristics of the faults and regional tectonic stress field. The maximum compressive stress axis in Northwestern Vietnam has the nearly horizontal trend (7.4±4.0) and the direction of 170.2±6.7. The calculated results of FMP at 60 geological survey points along major faults in Northwestern Vietnam show that the movement potential of these faults is mainly from medium to high (40/60 points with FMP = 0.6 - 0.9). In particular, the faults in Dien Bien Phu have the highest movement potential (FMP = 0.8 - 0.9). An earthquake catalog that consists of 177 earthquakes with M = 4.0 - 6.8 occurring in the studied area from 1277 to 2016 is used to assess the relationship between seismic activities and fault movement potential. The research results indicate that at the locations on the faults with high movement potential, seismic activities occur frequently. On the segment of Son La fault zone in Tuan Giao, Tua Chua, the movement potential has the highest value (FMP = 0.9), corresponding to the occurrence of Tuan Giao earthquake with M = 6.8 in 1983. On the contrary, weak earthquake or even no earthquake occur at the locations with low movement potential such as the segment of Son La fault in Moc Chau, Yen Chau, the segment of Ma River fault in Lang Chanh and the Than Uyen fault in Than Uyen. With the complete survey dataset on slip surface attitude of faults in contemporary times, FMP is significant for assessing the level of seismic activities on each part of the faults, serving the segmentation of faults, establishment of seismogenic regions, earthquake prediction and seismic hazard assessment. References Andeweg, B., G. de Vicente, S. Cloetingh, J. Giner, and A. Muñoz Martin, 1999. Local stress field and intraplate deformation of Iberia: Variations in spatial and temporal interplay of regional stress sources, Tectonophysics, 305, 153-164. Angelier J. Tarantola A. Valette B. Manoussis S., 1982. Inversion of field data in fault tectonics to obtain the regional stress - I. Single phase fault populations: a new method of computing the stress tensor, Geophys. J. R. astr. Soc., 69, 607-621. Bui Van Duan, 2012. The study on contemporary tectonic characteristics and seismic activities in Muong La - Bac Yen fault zone. Master thesis, Hanoi University of Science, Hanoi (in Vietnamese). Bui Van Duan, Ha Thi Giang, Nguyen Anh Duong, and Pham Dinh Nguyen, 2015. About factors related to the occurrence of earthquakes in the Song Tranh 2 hydropower area in period 2011-2014. Vietnam Journal of Earth Sciences, 37(3), 228-240 (in Vietnamese, abstract English), DOI:10.15625/0866-7187/37/3/7797. Bott M.H.P., 1959. The mechanics of oblique slip faulting, Geol. Mag., 96, 109-117. Findlay R. H. and Phan Trong Trinh, 1997. The structural setting of Song Ma region, Vietnam and the Indochina-South China plate boundary problem. Gondwana Research, 1(1), 11-33. Ha Thi Giang, 2012. Determination of focal mechanisms of some earthquakes in North Vietnam using the broadband seismic data. Master thesis, Hanoi University of Science, Hanoi (in Vietnamese). He S.H., 1989. The Effect of Orientation and Level of Principal Stress on Fault Movement. Crustal Deformation and Earthquake, 9, 44-52. Le Tu Son, 2000. Focal mechanism of Ta Khoa, lai Chau and Muong Luan earthquake in North-West of Vietnam. J. Sciences of the Earth, 22(4), 355-360 (in Vietnamese, abstract English). Le Tu Son, 2004. The Dien Bien earthquake, Ms=5.3 on February 19, 2001. J. Sciences of the Earth, 26(2), 112-121 (in Vietnamese, Abstract English). Lee C.F., Hou J.J. and Ye H., 1997. The Movement Potential of the Major Faults in Hong Kong Area. Episodes, 20, 227-231. Lokajicek T., Spicak, A. and Waniek, L., 1988. Tectonic Stress Orientation and the Seismic Regime of a Single Fault. Tectonophysics, 152, 297-302. Maerten L., P. Gillespie, D.D. Pollard, 2002. Effects of local stress perturbation on secondary fault development. Journal of Structural Geology, 24, 145-153. Mandal P., A. Manglik, R.N. Singh, 1997. Intraplate stress distribution induced by topography and crustal density heterogeneities beneath the Killari, India. Journal of Geophysical Research, 102, 11719-11729. McKenzie D.P., 1969. The relation between fault plane solutions for earthquakes and the directions of the principal stresses, Bull. seism. Soc. Am., 59, 591-601. Moghimi H., Arian M. and Sorbi A., 2015. Fault Movement Potential of Marzanabad Area, North Alborz, Iran. Open Journal of Geology, 5, 126-135. Ngo Van Liem, Phan Trong Trinh, Hoang Quang Vinh, Nguyen Van Huong, Nguyen Cong Quan, Tran Van Phong, Nguyen Phuc Dat, 2016a. Analyze the correlation between the geomorphic indices and recent tectonic active of the Lo River fault zone in southwest of Tam Dao range. Vietnam Journal of Earth Sciences, 38(1) 1-13, DOI:10.15625/0866-7187/38/1/7847. Ngo Van Liem, Nguyen Phuc Dat, Bui Tien Dieu, Vu Van Phai, Phan Trong Trinh, Hoang Quang Vinh, Tran Van Phong, 2016b. Assessment of geomorphic processes and active tectonics in Con Voi mountain range area (Northern Vietnam) using the hypsometric curve analysis method. Vietnam Journal of Earth Sciences, 38(2), 202-216, DOI: 10.15625/0866-7187/38/2/8602 Nguyen Anh Duong, T. Sagiya, F. Kimata, D. T. Tran, Q. H. Vy, C. C. Duong, X. B. Nguyen, and D. X. Nguyen, 2013. Contemporary horizontal crustal movement estimation for northwestern Vietnam inferred from repeated GPS measurements, Earth Planets Space, 65(12), 1399-1410, DOI:10.5047/eps.2013.09.010. Nguyen Anh Duong, Fumiaki Kimata, Tran Dinh...