Global observation of off-great-circle propagation of Long-Period surface waves

Laske, G.

doi:10.1111/j.1365-246x.1995.tb06673.x

Cited by 105 publications

(77 citation statements)

References 30 publications

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“…For example, before we include polarization data in the modelling process, we correct for possible errors in the instrument calibration which lead to an apparent rotation of the horizontal components. These rotation angles are approximately {5 0 and z1X8 0 at stations PPT and KIP (Laske 1995). Whilst {5 0 at PPT has been con¢rmed by the operators as true misrotation of the horizontal components, the observation at KIP is as yet unexplained.…”

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confidence: 96%

Surface-wave polarization data and global anisotropic structure

Laske

Masters

1998

Geophys. J. Int.

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S U M M A RYIn the past few years, seismic tomography has begun to provide detailed images of seismic velocity in the Earth's interior which, for the ¢rst time, give direct observational constraints on the mechanisms of heat and mass transfer. The study of surface waves has led to quite detailed maps of upper-mantle structure, and the current global models agree reasonably well down to wavelengths of approximately 2000 km. Usually, the models contain only elastic isotropic structure, which provides an excellent ¢t to the data in most cases. For example, the variance reduction for minor and major arc phase data in the frequency range 7^15 mHz is typically 65^92 per cent and the data are ¢t to within 1^2 standard deviations. The ¢t to great-circle phase data, which are not subject to bias from unknown source or instrument e¡ects, is even better. However, there is clear evidence for seismic anisotropy in various places on the globe. This study demonstrates how much (or little) the ¢t to the data is improved by including anisotropy in the modelling process. It also illuminates some of the trade-o¡s between isotropic and anisotropic structure and gives an estimate of how much bias is introduced by neglecting anisotropy. Finally, we show that the addition of polarization data has the potential for improving recovery of anisotropic structure by diminishing the trade-o¡s between isotropic and anisotropic e¡ects.

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confidence: 96%

Surface-wave polarization data and global anisotropic structure

Laske

Masters

1998

Geophys. J. Int.

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“…, 합성파형과 관측파형의 상관성을 분석하는 방법 (Ekstrom and Busby, 2008) (Laske, 1995). 두 개의 지진계에 기록된 배경잡음 의 교차상관으로부터 두 관측소 사이를 전파하는 레일리 파를 추출할 수 있다는 사실은 이미 수 많은 연구에서 증명 되었다 (e.g., Shapiro, 2004;Bensen et al, 2007;Lin et al, 2008;Kang and Shin, 2006 (Fig.…”

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Determining the Orientations of Broadband Stations in South Korea using Ambient Noise Cross-correlation

Lee

Rhie²

2015

Geophysics and Geophysical Exploration

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Orientation corrections for Korean seismic stations were calculated by using ambient noise cross-correlation. This method uses Rayleigh waves extracted from ambient noise cross-correlation instead of teleseismic waveforms from earthquakes, which have been generally used for previous studies. The theoretical background of the method is that the phase of radial-vertical cross-correlation function should be the same as that of 90 o phase-shifted vertical-vertical crosscorrelation function. The results calculated from stacked cross-correlograms from Jan. 2007 to Sep. 2008 are comparable to the previous results obtained from teleseismic waveforms. In addition, overall the standard deviations of orientation corrections are less than 5 o . The temporal variation in orientation corrections calculated for every 30 days shows no significant change and also standard deviations of them are mostly less than 5 o . This means that the orientations of stations used in this study have been kept constant during the period. The sensitivity test for stacking period of the ambient noise cross-correlation method shows that continuous ambient noise record of at least about 30 days is required for estimating reliable orientation corrections.

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“…Vidale 1986;Lerner-Lam & Park 1989;Laske 1995;Laske & Masters 1996;Yoshizawa et al 1999;Larson & Ekström 2002;Zhang et al 2003;Ferreira & Woodhouse 2007) gained interest because they could be used to identify station misalignment (e.g. Laske 1995;Laske & Masters 1996;Ekström & Busby 2008) and used as additional input to ray-based inversions (e.g. Laske 1995; Laske & Masters 1996;Laske & Masters 1998;Yoshizawa et al 1999).…”

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Arrival angle anomalies of Rayleigh waves observed at a broadband array: a systematic study based on earthquake data, full waveform simulations and noise correlations

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S U M M A R YDeviation of seismic surface waves from the great-circle between source and receiver is illustrated by the anomalies in the arrival angle, that is the difference between the observed backazimuth of the incident waves and the great-circle. Such arrival angle anomalies have been known for decades, but observations remain scattered. We present a systematic study of arrival angle anomalies of fundamental mode Rayleigh waves (20-100 s period interval) from 289 earthquakes and recorded by a broadband network LAPNET, located in northern Finland. These observations are compared with those of full waveform synthetic seismograms for the same events, calculated in a 3-D Earth and also compared with those of seismograms obtained by ambient noise correlation. The arrival angle anomalies for individual events are complex, and have significant variations with period. On average, the mean absolute deviation decreases from ∼9 • at 20 s period to ∼3 • at 100 s period. The synthetic seismograms show the same evolution, albeit with somewhat smaller deviations. While the arrival angle anomalies are fairly well simulated at long periods, the deviations at short periods are very poorly modelled, demonstrating the importance of the continuous improvement of global crustal models. At 20-30 s period, both event data and numerical simulations have strong multipathing, and relative amplitude changes between different waves will induced differences in deviations between very closely located events. The source mechanism has only limited influence on the deviations, demonstrating that they are directly linked to propagation effects, including near-field effects in the source area. This observation is confirmed by the comparison with seismic noise correlation records, that is where the surface waves correspond to those emitted by a point source at the surface, as the two types of observations are remarkably similar in the cases where earthquakes are located close to seismic stations. This agreement additionally confirms that the noise correlations capture the complex surface wave propagation.

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Global observation of off-great-circle propagation of Long-Period surface waves

Cited by 105 publications

References 30 publications

Surface-wave polarization data and global anisotropic structure

Surface-wave polarization data and global anisotropic structure

Determining the Orientations of Broadband Stations in South Korea using Ambient Noise Cross-correlation

Arrival angle anomalies of Rayleigh waves observed at a broadband array: a systematic study based on earthquake data, full waveform simulations and noise correlations

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