EGU2020-2257
https://doi.org/10.5194/egusphere-egu2020-2257
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

What if a larger earthquake would occur at the causative fault of the Gyeongju earthquake with ML 5.8 on September 11, 2016 in South Korea?

Hoseon Choi
Hoseon Choi
  • Korea Institute of Nuclear Safety, Department of Nuclear Safety Research, Daejeon, Korea, Republic of (hoseon@kins.re.kr)

A seismic source can be a capable tectonic source or a seismogenic source. A capable tectonic source is a tectonic structure that can generate both vibratory ground motion and tectonic surface deformation at or near the earth's surface in the present seismotectonic regime. On the other hand, A seismogenic source generates vibratory ground motion but is assumed to not cause surface displacement, covering wide range of seismotectonic conditions, from a well-defined tectonic structure to simply a large region of diffuse seismicity.

The ML 5.8 Gyeongju earthquake on September 11, 2016 in South Korea is the largest instrumental one since 1978 that occurred in buried fault not exposed to the surface area. So to speak, there is no evidence of surface faulting till now. On the other hand, the geometry of the causative fault of the Gyeongju earthquake was revealed in detail from the distribution of foreshocks and aftershocks. Therefore, the causative fault of the Gyeongju earthquake can be treated as a seismogenic source corresponding to a well-defined tectonic structure as mentioned above.

What level of ground motions would occur at the site of interest if a larger earthquake would occur at the causative fault of the Gyeongju earthquake? To make a rough estimate of that question, we carried out a simple study of modeling the causative fault with the data available, and simulating strong ground motions with the stochastic and empirical Green’s function techniques. The magnitude of the maximum earthquake potential on the causative fault is in the range of 6.0 to 7.0 and increased by 0.5. We do not claim the possibility of such a large earthquake in the region, but have a goal to evaluate the seismic safety evaluation of the site of interest from such an earthquake potential. This type of study may help us elucidate the seismic hazard in a low seismicity area such as South Korea and review the seismic safety of the site of interest.

How to cite: Choi, H.: What if a larger earthquake would occur at the causative fault of the Gyeongju earthquake with ML 5.8 on September 11, 2016 in South Korea?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2257, https://doi.org/10.5194/egusphere-egu2020-2257, 2020

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Presentation version 1 – uploaded on 04 May 2020
  • CC1: Comment on EGU2020-2257, Christoph Grützner, 08 May 2020

    Thanks for the interesting poster!
    I have a question that relates a bit to the case from Australia in the same session:
    Was there any evidence for this being a fault beforehand? Did you see it in geophysical data or in isolated outcrops or so? Is it an old, reactivated structure?

    Thanks!

    • AC1: Reply to CC1, Hoseon Choi, 08 May 2020
      Thanks for the comment.
      In the area where the earthquake occurred, a lot of quaternary faults are identified on the surface.
      In the past 2000 years, there have been also many historical earthquakes with moderate and larger magnitude in the area.
      However, in the case of 2016 Gyeongju earthquake, there is little connection with the faults identified on the surface.
      The strike and dip of the causative fault are very different from those of the faults at the surface.
      Currently, seismological and geophysical investigations are in progress to image the causative fault of the Gyeongju earthquake.
      Therefore, we have not seen existing geophysical data or isolated outcrops of the fault, and we are pursuing research to see whether the caustive fault is an old and revitalized structure or not.
      Have a nice day.
      • CC2: Reply to AC1, Christoph Grützner, 08 May 2020

        Great, thanks for the detailed explanations!