Japan Geoscience Union Meeting 2016

Presentation information


Symbol S (Solid Earth Sciences) » S-SS Seismology

[S-SS31] Active faults and paleoseismology

Mon. May 23, 2016 5:15 PM - 6:30 PM Poster Hall (International Exhibition Hall HALL6)

Convener:*Mamoru Koarai(Earth Science course, College of Science, Ibaraki University), Hisao Kondo(Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology), Ken-ichi Yasue(Japan Atomic Energy Agency), Hideaki Goto(Graduate school of letters, Hiroshima University)

5:15 PM - 6:30 PM

[SSS31-P22] Co-seismic conjugate Riedel faulting associated with the 2014 Mw 6.9 Yutian earthquake on the Altyn Tagh Fault, Tibetan Plateau

*Aiming Lin1, Haibing Li2, Zhiming Sun3 (1.Department of Geophysics, Graduate School of Science, Kyoto University, 2.Institute of Geology, Chinese Academy of Geological Sciences, 3.Institute of Geomechanics, Chinese Academy of Geological Sciences)

Keywords:Altyn Tagh fault, 2014 Mw 6.9 Yutian earthquake, Co-seismic conjugate faulting, Tibet Plateau

The Altyn Tagh Fault is located at the northwestern edge of the Tibetan Plateau, and is the largest active strike-slip fault in Asia with a total length of ~2000 km. The fault accommodates sinistral motion between the Tibetan Plateau and the Tarim Basin within the India–Eurasia collision zone. Although the Altyn Tagh Fault plays a key role in accommodating India–Eurasia convergence, little is known about its nature as a seismogenic strike-slip fault due to a lack of instrumentally recorded large earthquakes on the fault. The 12 February 2014 Mw 6.9 Yutian earthquake, which occurred in the Yutian region of the Tibetan Plateau, provides an opportunity to study the seismotectonic nature of the Altyn Tagh strike-slip fault system.
Field investigations reveal that the 2014 Mw 6.9 Yutian earthquake on the left-lateral strike-slip Altyn Tagh fault system, Tibetan Plateau, produced a ~25-km-long surface rupture zone that contains conjugate Riedel shear faults (Li et al., 2016). The co-seismic surface ruptures occurred mainly along two parallel ENE-trending active left-lateral strike-slip faults. Rupture also occurred in a conjugate, WNW-trending zone along an active right-lateral strike-slip fault. The ENE-trending ruptures are concentrated in a zone of <500 m wide and ~25 km long, and are characterized by Riedel shear structures including distinct shear faults (Y) with a maximum sinistral displacement of ~1 m, right-stepping en echelon cracks, and mole tracks. In contrast, the WNW-trending ruptures occur within a zone of up to 1.5 km wide and ~4 km long in the jog area between the two parallel ENE-trending faults, and this zone is characterized by discontinuous shear faults with dextral displacements of <0.5 m, left-stepping en echelon cracks, and mole tracks, all oriented oblique to the ENE-trending rupture zones at an angle of 30°–40°. The lengths and displacements of the co-seismic surface ruptures measured in the field are comparable with those obtained from the empirical relationships between magnitude and co-seismic surface rupture length and displacement. Our findings demonstrate that the co-seismic conjugate Riedel faulting was controlled mainly by pre-existing active faults of the Altyn Tagh fault system, reflecting the present-day tectonic stress field associated with the ongoing penetration of the Indian Plate into the Eurasian Plate.

Li, L., Pan, J., Lin, A. (*corresponding author), other 8, 2016. Co-seismic surface ruptures associated with the 2014 Mw 6.9 Yutian earthquake on the Altyn Tagh Fault, Tibetan Plateau. Bulletin of Seismological Society of America, in press.