The 2017 Mw 5.5 Pohang Earthquake, South Korea, and Poroelastic Stress Changes Associated With Fluid Injection

H. Lim, K. Deng, Y. H. Kim, J. H. Ree, T. R.A. Song, K. H. Kim

Research output: Contribution to journalArticlepeer-review

24 Citations (Scopus)

Abstract

The 2017 Mw 5.5 Pohang earthquake in South Korea, the first reported and largest magnitude-induced earthquake, occurred near the enhanced geothermal power plant in Pohang on 15 November 2017. We compute the spatiotemporal changes in poroelastic stresses perturbed by injected fluid under various conditions to better understand the occurrences of the Pohang earthquake and the small-magnitude earthquakes preceding it. Space-time variation of the earthquakes that occurred before the Pohang earthquake correlates significantly with fluid injection history between January 2016 and September 2017. We attribute the timing in earthquake occurrence to slow fluid diffusion, making hydraulic diffusivity of bedrock the critical model parameter for representing this slow process. In this context, the delay between the injection and the Pohang earthquake requires diffusivity estimates within a range of 1 × 10−4–5 × 10−4 m2/s for damaged granodiorite at 4–5 km, corresponding to the depth range between the well and the focal depth. According to these estimates, the pore pressure and thus the Coulomb failure stress changes are further enhanced by each injection with minimum stress dissipation. We find fluid injection can result in a change of the Coulomb stress of up to 0.4–1.1 bar, exceeding those associated with the 2016 Mw 5.5 Gyeongju earthquake by 2 orders of magnitude.

Original languageEnglish
Article numbere2019JB019134
JournalJournal of Geophysical Research: Solid Earth
Volume125
Issue number6
DOIs
Publication statusPublished - 2020 Jun 1

Bibliographical note

Funding Information:
H. Lim and Y. Kim would like to acknowledge the Creative‐Pioneering Researchers Program of Seoul National University (SNU SRnD 3345‐20160014). H. Lim, Y. Kim, J.‐H. Ree, and K.‐H. Kim acknowledge the Nuclear Safety Research Program of the Korea Foundation of Nuclear Safety (KoFONS) that were granted financial resources by the Nuclear Safety and Security Commission (NSSC), Republic of Korea (1705010). T.‐R. A. Song acknowledges the support by the Natural Environment Research Council, UK (NE/P001378/1). The software for linear poroelasticity calculation is from https://www.gfz-potsdam.de/en/section/physics-of-earthquakes-and-volcanoes/data-products-services/downloads-software/ (Wang & Kümpel, 2003 ; last accessed on 21 June 2017). The authors would like to thank the universities and research institutes that supplied the seismic data used in this study: the Korea Institute of Geoscience and Mineral Resources, Korea Meteorological Administration (KMA), Korea Hydro & Nuclear Power Co., Ltd., Seoul National University (SNU), Pukyong National University, and Pusan National University. The waveform data and earthquake catalog from the KMA are accessible online at http://necis.kma.go.kr (last accessed on 9 April and 2 May 2018, respectively). The authors are grateful for the help of E. Kim (SNU) and J. Kim (SNU) in determining the arrival times of the aftershocks. Finally, the authors thank Editor Y. Ben‐Zion, Associate Editor, and the reviewers for their comments, which greatly improved this article.

Funding Information:
H. Lim and Y. Kim would like to acknowledge the Creative-Pioneering Researchers Program of Seoul National University (SNU SRnD 3345-20160014). H. Lim, Y. Kim, J.-H. Ree, and K.-H. Kim acknowledge the Nuclear Safety Research Program of the Korea Foundation of Nuclear Safety (KoFONS) that were granted financial resources by the Nuclear Safety and Security Commission (NSSC), Republic of Korea (1705010). T.-R. A. Song acknowledges the support by the Natural Environment Research Council, UK (NE/P001378/1). The software for linear poroelasticity calculation is from https://www.gfz-potsdam.de/en/section/physics-of-earthquakes-and-volcanoes/data-products-services/downloads-software/ (Wang & K?mpel,?2003; last accessed on 21 June 2017). The authors would like to thank the universities and research institutes that supplied the seismic data used in this study: the Korea Institute of Geoscience and Mineral Resources, Korea Meteorological Administration (KMA), Korea Hydro & Nuclear Power Co., Ltd., Seoul National University (SNU), Pukyong National University, and Pusan National University. The waveform data and earthquake catalog from the KMA are accessible online at http://necis.kma.go.kr (last accessed on 9 April and 2 May 2018, respectively). The authors are grateful for the help of E. Kim (SNU) and J. Kim (SNU) in determining the arrival times of the aftershocks. Finally, the authors thank Editor Y. Ben-Zion, Associate Editor, and the reviewers for their comments, which greatly improved this article.

Publisher Copyright:
©2020. American Geophysical Union. All Rights Reserved.

Keywords

  • 2017 Pohang earthquake, South Korea
  • Coulomb stress change
  • enhanced geothermal system
  • induced earthquake
  • pore pressure
  • poroelastic modeling

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

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