Deformation patterns and potential active movements of the Fansipan mountain range, northern Vietnam
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ORIGINAL PAPER
Deformation patterns and potential active movements of the Fansipan mountain range, northern Vietnam Thi‑Hue Dinh1,2 · Yu‑Chang Chan1,2 · Chung‑Pai Chang3 · Chih‑Tung Chen4 · Yi‑Chun Hsu4 Received: 24 December 2019 / Accepted: 3 September 2020 © Geologische Vereinigung e.V. (GV) 2020
Abstract Located in northern Vietnam, the Fansipan mountain range is the highest topography in the Indochina area. Until recently, there has been limited research regarding the tectonic deformation of the Fansipan mountain range and whether there are notable surface ruptures or active faults in the area. This study provides the first insight into the deformation patterns and potential active movements of the Fansipan mountain range, and may improve our understanding of the overall tectonic activities in northern Vietnam. Our observations from ASTER 30-m DEM show a symmetrical mountain form in the north and an asymmetrical form in the south. The analysis of river profiles indicates similar patterns on both sides in the north and different patterns in the south with short and steep rivers on the SW side and long and gentle rivers on the NE side. The results of the normalized steepness index (ksn) also show higher values on the SW side of the south part than the values from the other sides. These results suggest a spatial variation in rock uplift patterns of the Fansipan mountain range. Notably, the mountain front of the SW side of the southern Fansipan mountain range is associated with the Phong Tho-Nam Pia normal fault, suggesting that the normal faulting activity likely played an important role in tectonic uplift of this high mountain range. Our investigation of the stress field using fault kinematics indicates that the Fansipan mountain range and its surrounding areas are undergoing an inhomogeneous mixture of strike-slip and normal faulting. It is proposed that the strike-slip and normal motions alternated because of a permutation of σ1/σ2 under the same extensional stress regime of approximately NE–SW σ3. This kinematic pattern may effectively control the recent tectonic movements in northern Vietnam. Keywords Fansipan mountain range · River profile · Normalized steepness index (ksn) · Stress field analysis · Active normal faulting · Stress permutation
Introduction As a consequence of the collision between the India and Eurasian plates, many strike-slip faults and deformation structures developed in central and eastern Asia (Molnar and Tapponnier 1975; Tapponnier et al. 1982). Located * Yu‑Chang Chan [email protected] 1
Taiwan International Graduate Program (TIGP) ‑ Earth System Science Program, Academia Sinica and National Central University, Taipei, Taiwan
2
Institute of Earth Sciences, Academia Sinica, No. 128, Sec. 2, Academia Road, Taipei, Taiwan
3
Center for Space and Remote Sensing Research, National Central University, Zhongli, Taiwan
4
Department of Earth Sciences, National Central University, Zhongli, Taiwan
in the southern part of the collisional deformation zone, northern V
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