Ground vulnerability derived from the horizontal‐to‐vertical spectral ratio: Comparison with the damage distribution caused by the 2017 ML 5.4 Pohang earthquake, Korea

Kang, Su Young; Kim, Kwanghee; Choi, Mikyung; Park, Sun-Cheon

doi:10.1002/nsg.12150

Cited by 3 publications

(4 citation statements)

References 40 publications

(42 reference statements)

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“…The ground vulnerability index (K g ), estimated by the amplification factor and fundamental frequency of the HVSR curve, was further proposed by Nakamura (1996Nakamura ( , 1997Nakamura ( , 2019 to evaluate the risk of soil liquefaction. Recent studies have used K g to identify sites that are susceptible to strong ground shaking by assessing the correlations between K g and the distributions of structural damage, liquefaction, and ground amplification effects (or site effects) in regions that have experienced strong ground shaking (e.g., Huang and Tseng 2002;Hardesty et al, 2010;Singh et al, 2017;Farid and Mase 2020;Kang et al, 2021). We also validate the use of HVSR in assessing liquefaction potential based on the case study of the 2017 Pohang earthquake.…”

Section: Introductionmentioning

confidence: 73%

“…HVSR has been successfully employed in a wide range of geological and environmental settings (e.g. Liu et al, 2014;Picotti et al, 2017;Singh et al, 2017;Mase et al, 2020;Singh et al, 2020;Kang et al, 2021;Mase and Sugianto Refrizon, 2021). The advantages of this technique in real-world applications include its low-cost implementation, non-invasive data collection approach, flexible and straightforward instrumentation requirements, relatively short data collection and processing times, and the generation of results that are easily interpreted.…”

Section: Methods and Data Processingmentioning

confidence: 99%

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Soil liquefaction potential assessment using ambient noise: A case study in Pohang, Korea

Kang

Kim²,

Gihm³

et al. 2022

Front. Earth Sci.

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An MW 5.5 earthquake occurred in Pohang, Korea, on 15 November 2017 and caused large damage. In and around the epicentral area the earthquake also remained numerous sand boils, which is a surface representation of soil liquefaction at shallow depth during the earthquake. Soil liquefaction is one of the most dangerous consequences of an earthquake. Here we show that the spatial distribution of the ground vulnerability index (Kg), which we estimate via ambient noise analysis, correlates very well with the distribution of sand boils. Our Kg model based on the dense microtremor surveys at differing geological conditions and urbanizations indicates that only 28.4% of the study area is vulnerable to ground shaking (Kg > 20), with 91.1% of the observed sand boils occurring in these vulnerable areas. We also observed that Kg values estimated in the study correlate well with both VS30 values and geologic units in the study area. This case report confirmed that the Kg can be an affordable supplement to traditional, but expensive and time-consuming, geotechnical/geophysical techniques for the initial screening and regional evaluations. Such a Kg map can assist stakeholders in earthquake-prone regions in identifying areas more susceptible to liquefaction and bring a recommendation to consider seismic hazard mitigation.

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Section: Introductionmentioning

confidence: 73%

Section: Methods and Data Processingmentioning

confidence: 99%

Soil liquefaction potential assessment using ambient noise: A case study in Pohang, Korea

Kang

Kim²,

Gihm³

et al. 2022

Front. Earth Sci.

Self Cite

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“…The fragility index has been shown to positively correlate to damage and liquefaction potential in several settings, including Japan, California, and India (Nakamura, 1997;Nakamura et al, 2014;Singh et al, 2017;Nakamura et al, 2014 analysed the correlation between fragility index and liquefaction in Tokyo following the 2011 Mw9.1 Tohoku earthquake and suggested that a fragility index above 12 corresponds to areas with high liquefaction risk. Other studies suggest fragility index values above 10 ( Huang and Tseng, 2002) or 20 (Singh et al, 2017;Kang et al, 2021) are indicative of sites with high liquefaction potential. All our sites with a measurable HVSR peak have a fragility index exceeding 10, with several sites exceeding 100, which may represent a high risk of severe shaking and liquefaction in an earthquake.…”

Section: Site Resonance Frequenciesmentioning

confidence: 98%

Characterization and spatiotemporal variations of ambient seismic noise in eastern Bangladesh

Bin Abdul Rahman,

Lythgoe,

Muktadir

et al. 2024

Front. Earth Sci.

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This study analyses the ambient noise field recorded by the seismic network, TREMBLE, in Bangladesh, operational since late 2016. Horizontal-vertical spectral ratios confirm the placement of stations on sediment, many situated on thick sedimentary columns, consistent with local geology. Noise across the broadband spectrum is systematically examined. A high amplitude local microseism (0.4–0.8 Hz) is recorded, originating near the coast and modulated by local tides. The secondary microseism (0.15–0.35 Hz) correlates strongly with wave height in the Bay of Bengal and varies with seasons, with greater power and higher horizontal amplitude in the monsoon season when the wave height is highest. The microseism increases in amplitude and decreases in frequency as a tropical depression moves inland. The primary microseism (∼0.07–0.08 Hz) exhibits no seasonal changes in power but display strong horizontal energy which changes with seasons. Low frequency (0.02–0.04 Hz) noise on the horizontal components has a 24-h periodicity, due to instrument tilt caused by atmospheric pressure changes. A station located next to the major Karnaphuli River shows elevated energy at ∼5 Hz correlated to periods of high rainfall. Anthropogenic noise (∼4–14 Hz) is station-dependent, demonstrating changing patterns in human activity, such as during Ramadan, national holidays and the COVID pandemic. Our work holds implications for seismic deployments, earthquake, and imaging studies, while providing insights into the interaction between the atmosphere, ocean, and solid Earth.

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“…In various studies, Kg represents the impact of seismic wave propagation in terms of damage to building structures, liquefaction, and local site effects [33][34][35][36][37]. The K g values in the Opak River area range from 0.01 to 20.25 (Fig.…”

Section: Seismic Vulnerability Index (Kg) In the Opak Rivermentioning

confidence: 99%

Microzonation of Seismic Parameters in Geological Formation Units Along the Opak River Using Microtremor Measurements

Budi Wibowo

2023

GEOMATE

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The 2006 Yogyakarta earthquake, with a magnitude of Mw 6.3, caused significant damage primarily on the west side of the Opak River. The Opak River area encompasses formations that exhibit distinct responses to seismic wave propagation. Formations consisting of unconsolidated and young sedimentary materials tend to experience wave amplification during seismic events. This study aims to investigate the seismic wave characteristics within each formation unit using microtremor measurements. The seismic wave parameters analyzed include dominant frequency, amplification factor, shear wave velocity, weathered layer thickness, seismic vulnerability index, and lithology based on N-SPT data. The study utilized 190 microtremor data sets and 7 N-SPT data sets. The microtremor data was processed using the Horizontal to Vertical Spectral Ratio Nakamura method, while the shear wave velocity data was processed using the Imai and Tonouchi approach. The findings revealed higher amplification factors in areas dominated by unconsolidated sedimentary materials and young formations. Quaternary formations are dominated by unconsolidated sedimentary material composed of sand, silt, clay, and breccia. Formations with a tertiary age are composed of more complex lithologies such as breccia-tuff, dacite tuff, andesitic tuff, volcanic breccias, lavas, siltstone, sandstone, and conglomerate. These conditions make Quaternary formations have seismic parameter characteristics such as lower dominant frequency, higher amplification factor, thicker sediment layer thickness, and higher seismic vulnerability index compared to Tertiary formations. Quaternary formations correlate with damage to buildings after the Yogyakarta earthquake, with an average shear wave velocity character of 279-293.67 m/s, and are in a zone with a vulnerability index >20. Tertiary formations demonstrated higher seismic resistance compared to Quaternary formations, indicating their relative stability.

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Ground vulnerability derived from the horizontal‐to‐vertical spectral ratio: Comparison with the damage distribution caused by the 2017 M_L 5.4 Pohang earthquake, Korea

Cited by 3 publications

References 40 publications

Soil liquefaction potential assessment using ambient noise: A case study in Pohang, Korea

Soil liquefaction potential assessment using ambient noise: A case study in Pohang, Korea

Characterization and spatiotemporal variations of ambient seismic noise in eastern Bangladesh

Microzonation of Seismic Parameters in Geological Formation Units Along the Opak River Using Microtremor Measurements

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