Seismicity of the 2016 ML 5.8 Gyeongju earthquake and aftershocks in South Korea

Lee, Jimin; Ryoo, Y.; Park, Sun Cheon; Ham, Young Mo; Park, Jong Soo; Kim, Myeong Su; Park, Sang Mi; Cho, Hyen Geom; Lee, Keun Soo; Kim, In Sun; Kim, Hye Su; Bae, Sunhee

doi:10.1007/s12303-017-0071-z

Cited by 11 publications

(6 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This value for stress drop is the global average for crustal earthquakes [Allmann and Shearer, 2009]. Song and Lee [2018] estimated the stress drop of the Pohang mainshock in the region near the hypocenter to be in the range from 2 to 4 MPa. focal mechanisms calculated using the PX-2 seismicity plane and preferred ("Pref.")…”

Section: Data and Resourcesmentioning

confidence: 99%

“…Situated on the eastern margin of the Eurasian tectonic plate, the Pohang area and Korea in general exhibit low levels of seismicity in comparison with neighboring Japan and China. However, damaging earthquakes have happened in historical and modern times including the ML 5.8 (MW 5.4) Gyeongju event in 2016 (Kim et al, 2018b;Kim et al, 2016;Lee et al, 2018). An alternative view is that the 2017 Pohang earthquake was triggered by the hydraulic stimulations that had taken place at the Pohang EGS site nearby over the previous two years.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Triggering of the Pohang, Korea, Earthquake (Mw 5.5) by Enhanced Geothermal System Stimulation

Ellsworth

Giardini

Townend

et al. 2019

Seismological Research Letters

117

116

View full text Add to dashboard Cite

On the afternoon of 15 November 2017, the coastal city of Pohang, Korea, was rocked by a magnitude 5.5 earthquake (Mw, U.S. Geological Survey). Questions soon arose about the possible involvement in the earthquake of the Republic of Korea’s first enhanced geothermal system (EGS) project because the epicenter of the earthquake was located near the project’s drill site. The Pohang EGS project was intended to create an artificial geothermal reservoir within low‐permeability crystalline basement by hydraulically stimulating the rock to form a connected network of fractures between two wells, PX‐1 and PX‐2, at a depth of ∼4 km. Forensic examination of the tectonic stress conditions, local geology, well drilling data, the five high‐pressure well stimulations undertaken to create the EGS reservoir, and the seismicity induced by injection produced definitive evidence that earthquakes induced by high‐pressure injection into the PX‐2 well activated a previously unmapped fault that triggered the Mw 5.5 earthquake. Important lessons of a general nature can be learned from the Pohang experience and can serve to increase the safety of future EGS projects in Korea and elsewhere.

show abstract

Section: Data and Resourcesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Triggering of the Pohang, Korea, Earthquake (Mw 5.5) by Enhanced Geothermal System Stimulation

Ellsworth

Giardini

Townend

et al. 2019

Seismological Research Letters

117

116

View full text Add to dashboard Cite

show abstract

Section: Data and Resourcesmentioning

confidence: 99%

Triggering of the Pohang, Korea, Earthquake (Mw 5.5) by enhanced geothermal system stimulation

Ellsworth¹,

Giardini²,

Townend³

et al. 2021

Preprint

View full text Add to dashboard Cite

© 2019 Seismological Society of America. All rights reserved. On the afternoon of 15 November 2017, the coastal city of Pohang, Korea, was rocked by a magnitude 5.5 earthquake (Mw, U.S. Geological Survey). Questions soon arose about the possible involvement in the earthquake of the Republic of Korea's first enhanced geothermal system (EGS) project because the epicenter of the earthquake was located near the project's drill site. The Pohang EGS project was intended to create an artificial geothermal reservoir within low-permeability crystalline basement by hydraulically stimulating the rock to form a connected network of fractures between two wells, PX-1 and PX-2, at a depth of ∼4 km. Forensic examination of the tectonic stress conditions, local geology, well drilling data, the five high-pressure well stimulations undertaken to create the EGS reservoir, and the seismicity induced by injection produced definitive evidence that earthquakes induced by high-pressure injection into the PX-2 well activated a previously unmapped fault that triggered the Mw 5.5 earthquake. Important lessons of a general nature can be learned from the Pohang experience and can serve to increase the safety of future EGS projects in Korea and elsewhere.

show abstract

“…Hereafter, for convenience, we refer to the three events of M L 5.1, M L 5.8 and M L 4.5 as E1, E2 (the main shock) and E3, respectively. From the distribution of the hypocentres and inverted moment tensors of the three events, it has been demonstrated that these earthquakes occurred on a deep-seated fault system at a depth range of 10-18 km (Kim et al 2016a;Hong et al 2017;Son et al 2017;Kim et al 2017a,b;Lee et al 2018). In particular, Son et al (2017) delineated two distinct parallel dextral faults striking to the NNE-SSW direction from relocated aftershocks, and Uchide & Song (2018) observed that the inverted finite fault slips of E1 and E2 propagated towards SSW and NNE directions, respectively.…”

Section: Introductionmentioning

confidence: 98%

“…In particular, Son et al (2017) delineated two distinct parallel dextral faults striking to the NNE-SSW direction from relocated aftershocks, and Uchide & Song (2018) observed that the inverted finite fault slips of E1 and E2 propagated towards SSW and NNE directions, respectively. A possible correlation between the Yangsan Fault and the Gyeongju earthquakes has been raised because the epicentres are located close to the fault, with 30 km of dextral displacement (Kyung 2003;Kim et al 2017b,c;Lee et al 2018). However, it is difficult to prove whether the deep-seated fault system extends to the surface because the focal depths exceed 10 km, and no surface deformation due to E2 has been reported (Park et al 2018).…”

Section: Introductionmentioning

confidence: 99%

The 2016 Gyeongju earthquake sequence revisited: aftershock interactions within a complex fault system

Woo

Rhie

Kim

et al. 2019

Geophysical Journal International

View full text Add to dashboard Cite

, a moderate earthquake (M L 5.8) occurred in Gyeongju, South Korea, located hundreds of kilometres away from the nearest plate boundaries. The earthquake, the largest instrumentally recorded event in South Korea, occurred in a sequence of thousands of earthquakes, including a M L 5.1 event 50 min before the main quake and a M L 4.5 event a week later. As a case study, we analyse the source parameters of the 2016 Gyeongju earthquake sequence: precise relocations, fault structures, focal mechanisms, stress tensor analysis and Coulomb stress changes. To determine high-resolution hypocentres and focal mechanisms, we employ our temporary seismic network for aftershock monitoring as well as regional permanent seismic networks. The spatio-temporal distribution of events and inverted moment tensors indicate that the M L 5.1 event and the M L 5.8 event occurred on two parallel dextral faults striking NNE-SSW at a depth of 11-16 km, and the M L 4.5 event occurred on their conjugate fault with sinistral displacements. Seismicity on the fault for the M L 5.1 event abruptly decreased as soon as the M L 5.8 event occurred. This is not solely explained by the Coulomb stress change and requires more complex processes to explain it. The tectonic stress field obtained from inverted focal mechanisms suggests that the heterogeneity between the intermediate and minimum principal stresses exists along the NNE-SSW and vertical directions. The Coulomb stress changes imparted from the M L 5.1 event and the M L 5.8 event are matched with the off-fault seismicity, including that from the M L 4.5 event. Multifaceted observations, such as Coulomb stress interactions between parallel or conjugate faults and the heterogeneity of the tectonic stress field in the aftershock area, may reflect the reactivation processes of a complex fault system. This study offers a distinctive case study to understand the general characteristics of intraplate earthquakes in multifault systems.

show abstract

Seismicity of the 2016 ML 5.8 Gyeongju earthquake and aftershocks in South Korea

Cited by 11 publications

References 13 publications

Triggering of the Pohang, Korea, Earthquake (Mw 5.5) by Enhanced Geothermal System Stimulation

Triggering of the Pohang, Korea, Earthquake (Mw 5.5) by Enhanced Geothermal System Stimulation

Triggering of the Pohang, Korea, Earthquake (Mw 5.5) by enhanced geothermal system stimulation

The 2016 Gyeongju earthquake sequence revisited: aftershock interactions within a complex fault system

Contact Info

Product

Resources

About