A Study of the Regional Variation of Low-Frequency around the Korean Peninsula

Chung, Tae Woong; Noh, Myung-Hyun; Kim, Junk Kyong; Park, Yun Kyong; Yoo, Hyung Joun; Lees, Jonathan M.

doi:10.1785/0120070066

Cited by 16 publications

(8 citation statements)

References 17 publications

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“…However, in a narrow band, such a model may still be a useful and convenient approximation. Several authors have indicated that the measurement of η is generally unstable and poorly constrained [e.g., Xie et al , 2006; Chung et al , 2007]. Our Q Lg model is calculated without a power‐law assumption and, thus, can be used to examine the behavior of η .…”

Section: Resultsmentioning

confidence: 99%

“…Using the M L amplitude catalog, Pei et al [2006] obtained a laterally varying 1 Hz Q model within the crust of northern China. Chung et al [2007] studied the 1 Hz Q Lg around the Korean Peninsula including part of Northeast China and the Sea of Japan. Ford et al [2009] compared the Q Lg images in the Yellow Sea and North Korea region obtained using different methods.…”

Section: Introductionmentioning

confidence: 99%

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Seismic Lg‐wave Q tomography in and around Northeast China

Zhao¹,

Xie²,

Wang³

et al. 2010

J. Geophys. Res.

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[1] We investigate regional variations in the Lg-wave quality factor (Q) in Northeast China and its vicinity with a tomographic method. Digital seismic data recorded at 20 broadband stations from 125 regional events are used to extract Lg-wave spectra. Tomographic inversions are independently conducted at 58 discrete frequencies distributed log evenly between 0.05 and 10.0 Hz. We simultaneously invert for the Lg-wave Q distribution and source spectra at individual frequencies without using any a priori assumption about the frequency dependence of the Q model and source function. The best spatial resolution is approximately 1°× 1°in well-covered areas for frequencies between 0.4 and 2.0 Hz. The Lg Q shows significant regional variations and an apparent relationship with regional geology. We use a statistical method to investigate the regional variations of Lg Q and their frequency dependence. The average Q 0 (1 Hz Lg Q) in the entire investigated region is 414. Sedimentary basins are usually characterized by lower average Q 0 values (from 155 to 391), while volcanic mountain areas have relatively high average Q 0 values (from 630 to 675). Lg Q generally increases with increasing frequency. However, the frequency dependence has complex nonlinear features on a double-logarithmic scale, indicating that the commonly adopted power-law relationship may be oversimplified in a broad frequency band. The frequency dependence varies in different geological areas, with larger variations seen at lower frequencies.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Seismic Lg‐wave Q tomography in and around Northeast China

Zhao¹,

Xie²,

Wang³

et al. 2010

J. Geophys. Res.

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“…The seismic Q factor has been widely investigated to measure the attenuation characteristics of the medium by using different parts of seismogram such as P waves ( Q P ), S waves ( Q S ), coda waves ( Q C ) and Lg waves ( Q Lg ) (Yoshimoto et al 1993; Chung & Lee 2003; Kim et al 2004; Chung et al . 2005, 2007; Sharma et al 2008; Ma’hood & Hamzehloo 2009).…”

Section: Introductionmentioning

confidence: 99%

Frequency-dependent attenuation of P and S waves in northeast India

Padhy¹,

Subhadra²

2010

Geophysical Journal International

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S U M M A R YWe have analysed 202 seismograms recorded at 10 seismic stations in the northeast (NE) India region to infer the frequency-dependent attenuation characteristics of both P and S waves, in the frequency range from 1.5 to 24 Hz and in the distance range from 30 to 100 km. We used extended coda-normalization method to determine the attenuation of P wave (Q −1 P ) and S wave (Q −1 S ). The results show that both P and S waves undergo a strong attenuation along ray paths. The values of Q −1 P and Q −1 S , corresponding to spectral amplitude decays, show strong frequency dependence and are expressed as Q −1 P = (0.035 ± 0.014) f −(0.96±0.01) and Q −1 S = (0.014 ± 0.006) f −(0.94±0.03) , respectively, in 1.5-24 Hz. The ratio Q −1 P /Q −1 S is found to be larger than unity for the whole frequency range. The high frequency dependence of both P-and S waves indicate the highest attenuation among the world at lower frequencies.

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“…In this context it can be mentioned that no earthquakes larger than M 6 were observed in terrestrial S. Korea after 1905 Kim et al, 2004). The low seismicity of S. Korea correlates with low attenuation of P and S waves Kim et al, 2004), and Lg waves Chung et al, 2005Chung et al, , 2007, showing a few regional variations. These studies, however, seem to reflect the values of the deep parts of the crust obtained from long hypocentral distances reaching 160 km for P and S waves, and longer than 150 km for Lg waves.…”

Section: Previous Studies For S Koreamentioning

confidence: 82%

Separation of Intrinsic and Scattering Attenuation Using Single Event Source in South Korea

Rachman¹,

Chung²,

Yoshimoto³

et al. 2015

Bulletin of the Seismological Society of America

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Simultaneous use of numerous events in the multiple lapse time window analysis (MLTWA) method is the most effective way to obtain Q −1 i and Q −1 S values. Such simultaneous use of numerous events normally shows a large observational scatter, which may be caused by different radiation pattern and focal depth of each earthquake, and regional alteration of the local structure. To avoid these scattering factors, the current study attempted to use single event source as the input data in MLTWA for South Korea. The direct simulation Monte Carlo (DSMC) method was used to simulate the observations, which showed realistic results when the number of recorded stations was eight or more. The obtained values of seismic albedo (B 0 ) were less than 0.5, which were in accordance with the same in the previous results. Three envelopes constructed by combination of three regional values of Q −1 Lg at 1 Hz produced regional variations, of which the ones at high frequencies of Q −1 i and at low frequencies of Q −1 S were remarkable. This result, showing the local variation indicated an advantage of the study using single source event over the previous studies in South Korea that involved extensively distributed data. Because DSMC was known to be applicable to 3D structure due to its simple algorithm, the current study also tried to correct radiation pattern of the observations by inserting focal mechanism algorithm to the code of the DSMC method. Such insertion, however, generated extremely low values of Q −1 S because the geometrically shrunk receiver could not capture most of the scattered particles. This receiver problem is most likely to be a major obstacle of the 3D study of DSMC. In addition, the significant depth effect of Q −1 was identified for the prior MLTWA studies resulting from different measurement range and focal depth.

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A Study of the Regional Variation of Low-Frequency around the Korean Peninsula

Cited by 16 publications

References 17 publications

Seismic Lg‐wave Q tomography in and around Northeast China

Seismic Lg‐wave Q tomography in and around Northeast China

Frequency-dependent attenuation of P and S waves in northeast India

Separation of Intrinsic and Scattering Attenuation Using Single Event Source in South Korea

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