EGU2020-18365
https://doi.org/10.5194/egusphere-egu2020-18365
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Complex seismic activity and local stress perturbation of the Pyeongnam basin, northern Korean Peninsula

Tae-Seob Kang1 and Heekyoung Lee2
Tae-Seob Kang and Heekyoung Lee
  • 1Pukyong National University, Department of Earth and Environmental Sciences, Busan, Korea, Republic of (tskang@pknu.ac.kr)
  • 2Pohang City Hall

The western region of the Pyeongnam Basin has relatively higher e​arthquake activity than the rest of the Korean Peninsula. We analyzed 48 earthquakes in the area, with a magnitude (ML) of 2.0 or more, from January 2009 to June 2019. The hypocentral parameters were re-determined using an iterative algorithm that repeats the calculation until the residual error between the observed and calculated arrival time of a seismic phase at each station is minimized. Using the hypocenters and the optimal 1-D velocity model derived from this process, the focal mechanisms were determined using the first-motion polarities of body waves. Many earthquakes are associated with left-lateral strike-slip faults, with a strike in the NW-SE direction and a normal faulting component. A stress inversion was performed using data of the pressure and tensional axes from the focal mechanisms. The maximum principal stress in the study area acts in the NW-SE direction with high angles of plunge and differs from the maximum horizontal principal stress in the rest of the Korean Peninsula. This stress perturbation is caused by the detachment of a small local stress from the regional stress field due to the presence of weak faults with low shear strength that develop in the sedimentation environment of the Pyeongnam Basin.

How to cite: Kang, T.-S. and Lee, H.: Complex seismic activity and local stress perturbation of the Pyeongnam basin, northern Korean Peninsula, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18365, https://doi.org/10.5194/egusphere-egu2020-18365, 2020