Spatiotemporal Distribution of Events during the First Three Months of the 2016 Gyeongju, Korea, Earthquake Sequence

Son, Miwon; Cho, Chang Soo; Shin, Jehyun; Rhee, H. M.; Sheen, Dong‐Hoon

doi:10.1785/0120170107

Cited by 36 publications

(18 citation statements)

References 26 publications

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“…The accurate estimation of stress drop from fault slip models is usually difficult because the spatial derivative of the slip is sensitive to small fluctuations in the slip distributions. In this case, the average stress drop values from our models for the main shock and the largest foreshock were consistent with those derived from spectral analysis (Son et al, ). Moreover, the rupture area extent in our model is also comparable to that from Son et al ().…”

Section: Discussionsupporting

confidence: 90%

“…In this case, the average stress drop values from our models for the main shock and the largest foreshock were consistent with those derived from spectral analysis (Son et al, ). Moreover, the rupture area extent in our model is also comparable to that from Son et al ().…”

Section: Discussionsupporting

confidence: 90%

“…If this hypothesis is correct, the pull‐apart stress between two faults would produce normal faulting earthquakes. However, such normal faulting events have not been found thus far (Son et al, ).…”

Section: Discussionmentioning

confidence: 94%

“…Many areas of South Korea felt the shaking caused by these two consecutive events ( M L 5.1 and M L 5.8), but there were no casualties partially due to the events occurring at a depth of approximately 15 km. Both events were strike slip (29° and 26°), slightly dipping to the east with dip angles of 73° and 68°, respectively (Son et al, ).…”

Section: Introductionmentioning

confidence: 99%

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Fault Rupture Model of the 2016 Gyeongju, South Korea, Earthquake and Its Implication for the Underground Fault System

Uchide

Song

2018

Geophysical Research Letters

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The 2016 Gyeongju earthquake (ML 5.8) was the largest instrumentally recorded inland event in South Korea. It occurred in the southeast of the Korean Peninsula and was preceded by a large ML 5.1 foreshock. The aftershock seismicity data indicate that these earthquakes occurred on two closely collocated parallel faults that are oblique to the surface trace of the Yangsan fault. We investigate the rupture properties of these earthquakes using finite‐fault slip inversion analyses. The obtained models indicate that the ruptures propagated NNE‐ward and SSW‐ward for the main shock and the large foreshock, respectively. This indicates that these earthquakes occurred on right‐step faults and were initiated around a fault jog. The stress drops were up to 62 and 43 MPa for the main shock and the largest foreshock, respectively. These high stress drops imply high strength excess, which may be overcome by the stress concentration around the fault jog.

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Section: Discussionsupporting

confidence: 90%

Section: Discussionsupporting

confidence: 90%

Section: Discussionmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

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Fault Rupture Model of the 2016 Gyeongju, South Korea, Earthquake and Its Implication for the Underground Fault System

Uchide

Song

2018

Geophysical Research Letters

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“…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: 99%

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

Woo

Rhie

Kim

et al. 2019

Geophysical Journal International

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, 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.

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Correction factors for GMMs considering site and topographic effects in South Korea

Park

Lee

Kim

2021

Bull Earthquake Eng

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Spatiotemporal Distribution of Events during the First Three Months of the 2016 Gyeongju, Korea, Earthquake Sequence

Cited by 36 publications

References 26 publications

Fault Rupture Model of the 2016 Gyeongju, South Korea, Earthquake and Its Implication for the Underground Fault System

Fault Rupture Model of the 2016 Gyeongju, South Korea, Earthquake and Its Implication for the Underground Fault System

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

Correction factors for GMMs considering site and topographic effects in South Korea

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