Fault zone evolution during Cenozoic tectonic inversion in SE Korea

Choi, Jin‐Hyuck; Yang, Seok-Jun; Han, S.; Kim, Young‐Seog

doi:10.1016/j.jseaes.2014.11.009

Cited by 21 publications

(17 citation statements)

References 35 publications

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“…The risk maps represented by the intensity values in a 10% exceedance probability demonstrated that (1) all industrial parks, in particular UPC, belong to the highest risk area; (2) the peak time of seismic risk is around ten years, as shown in Figure 11c. Regarding the confidences of modelled parameters employed for the risk assessment, it is worth noting that the recent active fault studies [31,79] around Ulsan reconstructed the migrating structure similar to this study. Thus, the PSHA outcomes in this study can be used for future safety planning as well as the establishment of new industrial regulations.…”

Section: Risk Assessmentssupporting

confidence: 69%

Seismic Surface Deformation Risks in Industrial Hubs: A Case Study from Ulsan, Korea, Using DInSAR Time Series Analysis

et al. 2019

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The unprecedentedly strong 2016 Gyeongju and 2017 Pohang earthquakes on the Korean Peninsula aroused public concern regarding seismic hazards previously considered improbable. In this study, we investigated the effects of recent seismic activity close to the epicenters of both earthquakes in the heavy industrial complex of Ulsan. This was performed using Sentinel-1 InSAR time series data combined with on-site GPS observations and background GIS data. The interpretations revealed ongoing topographic deformation of a fault line and surrounding geological units of up to 15 mm/year. Postseismic migrations through the fault line, coupled with the two earthquakes, were not significant enough to pose an immediate threat to the industrial facilities or the residential area. However, according to InSAR time series analyses and geophysical modelling, strain from the independent migration trend of a fault line and eventual/temporal topographic changes caused by potential seismic friction could threaten precisely aligned industrial facilities, especially chemical pipelines. Therefore, we conducted probabilistic seismic hazard and stress change analyses over surrounding areas of industrial facilities employing modelled fault parameters based on InSAR observations. These demonstrate the potential of precise geodetic survey techniques for constant monitoring and risk assessment of heavy industrial complexes against seismic hazards by ongoing fault activities.

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Section: Risk Assessmentssupporting

confidence: 69%

Seismic Surface Deformation Risks in Industrial Hubs: A Case Study from Ulsan, Korea, Using DInSAR Time Series Analysis

et al. 2019

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“…The southeastern Korean Peninsula (SeKP) is above the Gyeongsang Basin which was formed in the Cretaceous period. The Gyeongsang Basin is an area related to the Cretaceous intrusive and Tertiary volcanic activities 14 . During the early Cretaceous period, the Gyeongsang Basin formed a number of pull-apart basins and strike-slip faults in association with the subduction of the Izanagi plate, which resulted in the accumulation of lacustrine siliciclastic sediments 15,16 .…”

Section: Introductionmentioning

confidence: 99%

Mantle degassing along strike-slip faults in the Southeastern Korean Peninsula

Lee

Kim

Kagoshima

et al. 2019

Sci Rep

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On September 12, 2016, a ML 5.8 earthquake hit Gyeongju in the southeastern part of the Korean Peninsula (SeKP), although the area is known to be far from the boundary of the active plate. A number of strike-slip faults are observed in heavily populated city areas (e.g., Busan, Ulsan, Pohang, and Gyeongju). However, dissolved gases related to the active faults have rarely been studied despite many groundwater wells and hot springs in the area. Here we report new results of gas compositions and isotope values of helium and carbon dioxide (CO2) in fault-related fluids in the region. Based on gas geochemistry, the majority of gas samples are abundant in CO2 (up to 99.91 vol.%). Measured 3He/4He ratios range from 0.07 to 5.66 Ra, showing that the mantle contribution is up to 71%. The range of carbon isotope compositions (δ13C) of CO2 is from −8.25 to −24.92‰, showing mantle-derived CO2 is observed coherently where high 3He/4He ratios appear. The weakening of faults seems to be related to enhanced pressures of fluids containing mantle-derived helium and CO2 despite the ductile lower crust underneath the region. Thus, we suggest that the SeKP strike-slip faults penetrate into the mantle through ductile shearing.

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“…Yehya et al 33 showed that high-permeability fault damage zones facilitate diffusion of elevated fluid pressures from injection to greater distances and deeper locations. Fault zones at regional scale can be more complex with multiple basic fault architectures such as those in southeastern Korea 34 . Sutherland et al 35 inferred the existence of an alteration zone imbedded between the low permeability core and high permeability damage zones and that hydrologic processes in this zone affect fault strength and seismic properties.…”

Section: Resultsmentioning

confidence: 99%

Causal mechanism of injection-induced earthquakes through the Mw 5.5 Pohang earthquake case study

Yeo

Brown

et al. 2020

Nat Commun

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Causal mechanisms for fluid injection-induced earthquakes remain a challenge to identify. Past studies largely established spatiotemporal correlations. Here, we propose a multiprocess causal mechanism for injection-induced earthquakes through a case study of the 2017 M w 5.5 induced earthquake near Pohang Enhanced Geothermal System, Korea, where detailed hydraulic stimulation and on-site seismicity monitoring data provide an unprecedented opportunity. Pore pressure modeling reveals that pore pressure changes initiate seismicity on critically stressed faults and Coulomb static stress transfer modeling reveals that earthquake interactions promote continued seismicity, leading to larger events. On the basis of these results, we propose the following causal mechanism for induced seismicity: pore pressure increase and earthquake interactions lead to fault weakening and ultimately triggering larger earthquakes later in the process. We suggest that it is prudent that pore pressure change, initial seismicity locations, and Coulomb static stress transfer from seismicity earlier in the sequence are assessed in real-time.

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Fault zone evolution during Cenozoic tectonic inversion in SE Korea

Cited by 21 publications

References 35 publications

Seismic Surface Deformation Risks in Industrial Hubs: A Case Study from Ulsan, Korea, Using DInSAR Time Series Analysis

Seismic Surface Deformation Risks in Industrial Hubs: A Case Study from Ulsan, Korea, Using DInSAR Time Series Analysis

Mantle degassing along strike-slip faults in the Southeastern Korean Peninsula

Causal mechanism of injection-induced earthquakes through the Mw 5.5 Pohang earthquake case study

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