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Estimation of Far-field Coseismic Deformation Caused by the Recent Giant Earthquakes

In this paper, we estimate coseismic displacements in Vietnam caused by the 2004 Sumatra and the 2011 Tohoku earthquakes using static fault models in a layered spherical earth model. We find that the 2004 Sumatra earthquake caused southwestward movement of about 56 mm in Southern Vietnam and gradually decreasing to the north. | VNU Journal of Science: Mathematics – Physics, Vol. 33, No. 2 (2017) 34-41 Estimation of Far-field Coseismic Deformation Caused by the Recent Giant Earthquakes Nguyen Anh Duong*, Vu Minh Tuan, Bui Van Duan, Vi Van Vung, Nguyen Thuy Linh Institute of Geophysics, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam Received 17 March 2017 Revised 20 April 2017; Accepted 25 May 2017 Abstract: In this paper, we estimate coseismic displacements in Vietnam caused by the 2004 Sumatra and the 2011 Tohoku earthquakes using static fault models in a layered spherical earth model. We find that the 2004 Sumatra earthquake caused southwestward movement of about 56 mm in Southern Vietnam and gradually decreasing to the north. While the 2011 Tohoku earthquake moved the area in the opposite direction, by about 0.9 mm to the east and about 0.4 mm to the north. The difference in amplitude of coseismic displacements is due to the distance from each source fault to the study area and the compact slip region of the 2011 Tohoku earthquake affected to the size of coseismic deformation area. Our results indicate that it is necessary to take into consideration of the coseismic deformation induced by the giant earthquakes on discussion of tectonic deformation in Vietnam. Keywords: Earthquake, coseismic displacement, static fault model, Vietnam. 1. Introduction In the early 21th century, two giant earthquakes occurred: the 26 December 2004 M9.1 Sumatra earthquake [1] and the 11 March 2011 M9.0 Tohoku earthquake [2]. These earthquakes occurred at about 1000 km and 4000 km distance from Vietnam, respectively, if we refer to epicenters. The 2004 Sumatra earthquake ruptured at least 1200 km of the megathrust along the plate boundary between the Indian - Australian plate and the Eurasian plate. Its epicenter located the southernmost end of the source region. Thus, the distance from the study area to the earthquake epicenter is shorter (about 800 km). While, .