An Inversion of Lg-Wave Attenuation and Site Response in the North China Region

Zhu, Xin‐Yun; Chen, YunTai

doi:10.1785/0120110294

Cited by 4 publications

(2 citation statements)

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“…This contamination of Lg waves by Sn and Pn coda at higher frequencies at large distances has also been reported by Shin and Herrmann [], Shi et al . [], and Zhu and Chen []. Thus, due to the existence of these effects on records used in this study, we measured the RMS of spectral amplitude at eight 3/4 octave passbands between 0.9 and 10.75 Hz.…”

Section: Lg and Sn Propagationmentioning

confidence: 99%

“…Lg is extensively investigated and widely utilized by seismologists for estimating earthquake magnitudes [e.g., Nuttli , ; Herrmann and Nuttli , ; Herrmann and Kijko , ], studying the regional attenuation within the crust [e.g., Hasegawa , ; Campillo et al ., ; Mitchell and Hwang , ; Bowman and Kennett , ; McNamara et al ., ; Benz et al ., ; Ottemöller et al ., ], determining source‐spectrum characteristics [e.g., Street et al ., ; Xie , ; Patton and Taylor , ], seismic energy [e.g., Shi et al ., ], focal depth [e.g., Baker et al ., ], hypocenter [e.g., Matveeva and Husebye , ], crustal velocity gradients [e.g., Bowman and Kennett , ], and site response [e.g., Zhu and Chen , ].…”

Section: Introductionmentioning

confidence: 99%

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Average Q_Lg, Q_Sn, and observation of Lg blockage in the Continental Margin of Nova Scotia

2014

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The term "Lg blockage" refers to the sudden disappearance of the Lg phase along a particular propagation path which is commonly seen at continental-oceanic transition zones. In this paper we present observational evidence of Lg blockage across the continental margin of Nova Scotia in eastern Canada. Regional Lg and Sn spectra from 91 events with epicentral distances between 100 and 1200 km and magnitudes between 2.5 and 4.7 are inverted simultaneously for the source spectrum, site amplification, and average attenuation. The vertical displacement spectra were estimated between 0.9 and 10.75 Hz. The assumptions include a fixed frequency-independent geometric spreading rate for Lg and a frequency-dependent spreading model for the Sn. Estimates for the apparent regional attenuations are Q Lg (f) = 615(±25) f 0.35(±0.04) and Q Sn (f) = 404(±23) f 0.45(±0.03) . Results from this study provide an accurate parameterization of observed amplitude spectra and are valuable for representing wave propagation in the region. Based on the observation of a strong trade-off between Sn and Lg amplitudes which have different attenuation characteristics, we conclude any attenuation study based on measuring amplitude of a package of several different phases, without taking into consideration the propagation characteristics of individual waveforms at the region of study, may bias the estimation of average regional Q.

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Section: Lg and Sn Propagationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Average Q_Lg, Q_Sn, and observation of Lg blockage in the Continental Margin of Nova Scotia

2014

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Two-station Lg wave attenuation tomography in Eastern Asia

Chen,

Xu,

Xie

et al. 2024

Geophysical Journal International

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Summary Utilizing over 31,000 Lg waveforms from 136 crustal earthquakes recorded at 346 regional stations, we conduct detailed tomographic mappings of the Lg Q structure across Eastern Asia in a frequency range from 0.5 to 4.0Hz. By improving the standard two-station (TS) method, we effectively correct non-unity site response ratios using site responses estimated at individual stations. This innovative approach combines the flexible recording geometry of the TS method with the precision of reversed two-station (RTS) and reversed two-event (RTE) methods, producing a comprehensive dataset devoid of source and site effects for Q tomography. To address unsolvable 3D structural effects in the Lg spectral amplitude modeling, we justify these as modeling errors with a Gaussian distribution. This approach supports our SVD-based tomographic method, allowing for effective inversion of attenuation parameters and quantitative assessment of model resolution and errors. Our results reveal a complex relationship between Lg Q and the tectonic characteristics of Eastern Asia. In well-resolved regions, low Qo (1-Hz Q) values correspond to areas with high heat flow, partial melt, thick sediment, and recent tectonic-thermal activities, in contrast to high Qo values in stable, ancient crusts lacking recent tectonic activity. Rift basins are characterized by low Lg Qo, whereas flexural basins generally have high Qo basements. We also note that post-formation factors, such as sedimentation and crustal flow intrusion, significantly impact Qo values. Furthermore, Lg Q shows a complex frequency relationship, though the power-law approximation with positive power η remains useful. The frequency dependence power η is inversely related to Qo: the regions with low Qo typically have high η and vice versa. This study provides reliable attenuation tomographic and relative site response models for Lg waves in Eastern Asia, pertinent for relative geophysical studies.

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Using Lg Waves to Study Attenuation Characteristics of Crustal Media and Station Site Responses before The 2008 Wenchuan M8.0 Earthquake

Zhu

2019

Proceedings of the 2nd International Conference on Information Technologies and Electrical Engineering

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An Inversion of Lg-Wave Attenuation and Site Response in the North China Region

Cited by 4 publications

References 53 publications

Average Q_Lg, Q_Sn, and observation of Lg blockage in the Continental Margin of Nova Scotia

Average Q_Lg, Q_Sn, and observation of Lg blockage in the Continental Margin of Nova Scotia

Two-station Lg wave attenuation tomography in Eastern Asia

Using Lg Waves to Study Attenuation Characteristics of Crustal Media and Station Site Responses before The 2008 Wenchuan M8.0 Earthquake

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An Inversion of Lg-Wave Attenuation and Site Response in the North China Region

Cited by 4 publications

References 53 publications

Average QLg, QSn, and observation of Lg blockage in the Continental Margin of Nova Scotia

Average QLg, QSn, and observation of Lg blockage in the Continental Margin of Nova Scotia

Two-station Lg wave attenuation tomography in Eastern Asia

Using Lg Waves to Study Attenuation Characteristics of Crustal Media and Station Site Responses before The 2008 Wenchuan M8.0 Earthquake

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Product

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Average Q_Lg, Q_Sn, and observation of Lg blockage in the Continental Margin of Nova Scotia

Average Q_Lg, Q_Sn, and observation of Lg blockage in the Continental Margin of Nova Scotia