Seismogenic structure of the 2017 Ms6.9 Milin earthquake in Tibet
Tian Q. JianPublished August 14, 2019, SCEC Contribution #9659, 2019 SCEC Annual Meeting Poster #127
The Ms6.9 Milin earthquake occurred at November 18,2017. The focal mechanism shows that the Milin earthquake is mainly caused by thrust structures. The relocated result shows that the aftershocks concentrate in a narrow stripe along the northeast slope of the Gyala Peri with 36km length and 8km width. The seismic profile perpendicular to the aftershock stripe clearly reveals that a low angle NE-trend thrust plane existing below the aftershock distribution zone. Combined with the known results of the focal mechanism and the GPS co-seismic displacement field, we preliminarily infer that this low angle thrust is the probable seismogenic fault plane. Along both sides of the Jiala-Milin river segment in the upstream of the Yarlung Zangbo gorge, two levels of rock-base terrace with lacustrine deposit and the ridges continually tilt and turn up towards SW on the foot of Namcha Barwa and Gyala Peri The seismogenic fault plane can be considered as the boundary between the Namcha Barwa - Gyala Peri strongly uplifting zone on its hanging wall and the weekly uplifting zone on its footwall where the terraces and the ridges have tilted and deformed We infer that the Gyala Peri has been thrusting and uplifting continually along this low angle thrust plane to accommodate the unevenly squeezing out on both sides of it, and the folding and dragging near the fault on the footwall has caused the tilting and bending of the terrace and the ridges. Based on the regional deformation of the planation surface, we think the strong collision at the NE corner of the India Plate has caused intensive faulted-block movement around the syntaxis. The crust on the northern side of the Jiali fault has obviously thickened, and the main planation plane has also been disassembled accordingly. At the same time, the Paixiang tectonic slice and the Duoxiong-La metaphorical dome have unevenly extruded up from the inside of the IYS gorge, while Namcha Barwa and Gyala Peri have also uplifted accordingly. The Milin earthquake is only one events during this unevenly squeezing-out process, which is caused by a thrusting movement of a secondary fault in the Paixiang tectonic slice.
Key Words
Milin earthquake; River terrace; Planation surface; Tectonic deformation; Seismogenic structure
Citation
Jian, T. Q. (2019, 08). Seismogenic structure of the 2017 Ms6.9 Milin earthquake in Tibet. Poster Presentation at 2019 SCEC Annual Meeting.
Related Projects & Working Groups
Earthquake Geology
