Surface wave analysis with beamforming

Tanimoto, Toshiro; Prindle, Kenton

doi:10.1186/bf03352706

Cited by 20 publications

(30 citation statements)

References 16 publications

(14 reference statements)

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“…Concerning the range of observed deviations, they increase from ±8° at 100 s (with one non‐noise outlier at 15° for a Peru event), to ±12° at 25 s with several outliers at up to 20° deviations. The amplitude of the deviations we measure here are in good agreement with deviations measured elsewhere (Alsina et al 1993; Cotte et al 2000; Tanimoto & Prindle 2007) except for the Pacific Ocean array where main arrivals in general deviate less than in our case (Forsyth & Li 2005).…”

Section: Results From the Beamforming Analysissupporting

confidence: 90%

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Upper-mantle structure in southern Norway from beamforming of Rayleigh wave data presenting multipathing

Maupin

2011

Geophysical Journal International

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S U M M A R YA model for the upper mantle SV -wave velocity under southern Norway is obtained by depth inversion of the average phase velocity of the Rayleigh wave fundamental mode in the area. The average dispersion curve is obtained in the period range 22-200 s by beamforming of 190 Rayleigh waves recorded by the MAGNUS network, a temporary regional network of 41 broad-band stations. Resolution of the beamforming procedure is increased by deconvolving the original beams from the array response function using the Lucy-Richardson algorithm. In addition to an average phase velocity, beamforming gives us some information concerning the nature of the incoming wavefield. We detect deviations of the wave propagation direction from the great-circle paths which commonly reach 10 • at a period of 25 s for the teleseismic events. The amplitude of the deviations decreases with increasing period and with decreasing epicentral distance, as expected. The phase velocity measured by beamforming does not show any correlation with the deviation from great circle path, suggesting that deviation does not bias phase velocity measurements. We detect also significant multipathing with characteristics that vary rapidly with frequency. The obtained SV -wave velocity profile clearly shows that southern Norway is underlain by a low-velocity zone in the upper mantle and does not have shield-like characteristics, despite its location in the Baltic shield. These findings support the hypothesis that the high topography of southern Norway is sustained by anomalous upper-mantle material.

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Section: Results From the Beamforming Analysissupporting

confidence: 90%

“…Except for the choice of coordinate system, our beamforming procedure is very similar to the one used by Tanimoto & Prindle (2007) on data from the southern California network.…”

Section: Procedures For Data Analysismentioning

confidence: 99%

Upper-mantle structure in southern Norway from beamforming of Rayleigh wave data presenting multipathing

Maupin

2011

Geophysical Journal International

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“…[11] The surface wave analysis is described by Prindle and Tanimoto [2006] and Tanimoto and Prindle [2007] in which they estimated azimuthal anisotropy in several layers including upper and lower crustal layers (0-15) km and (15-33) km, a mantle lithosphere layer (33-100 km) and an asthenospheric layer (100-150 km). Phase velocities of Rayleigh waves were calculated for various frequency bands after correcting for refraction effects that caused deviation for raypaths from the great circles to the events.…”

Section: Surface Wave Analysismentioning

confidence: 99%

The relationship between upper mantle anisotropic structures beneath California, transpression, and absolute plate motions

et al. 2011

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[1] We calculated SKS splitting parameters for the California Integrated Seismic Network. In southern California, we also estimated splitting in the upper 100 km using azimuthal anisotropy determined from surface waves. The inferred splitting from surface waves in the mantle lithosphere is small (on average < 0.2 s) compared with SKS splitting (1.5 s) and obtains a maximum value (0.5 s) in the transpressive region of the Big Bend, south of, and aligned with, the San Andreas Fault (SAF). In contrast, the SKS splitting is approximately E-W and is relatively uniform spatially either side of the Big Bend of the SAF. These differences suggest that most of the SKS splitting is generated much deeper (down to 300-400 km) than previously thought, probably in the asthenosphere. Fast directions align with absolute plate motions (APM) in northern and southeastern California but not in southwestern California. We interpret the parallelism with APM as indicating the SKS anisotropy is caused by cumulative drag of the asthenosphere by the overlying plates. The discrepancy in southwestern California arises from the diffuse boundary there compared to the north, where relative plate motion has concentrated near the SAF system. In southern California the relative motion originated offshore in the Borderlands and gradually transitioned onshore to the SAF system. This has given rise to smaller displacement across the SAF (160-180 km) compared with central and northern California (400-500 km). Thus, in southwestern California the inherited anisotropy, from prior North American APM, has not yet been overprinted by Pacific APM.Citation: Kosarian, M., P. M. Davis, T. Tanimoto, and R. W. Clayton (2011), The relationship between upper mantle anisotropic structures beneath California, transpression, and absolute plate motions,

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“…This technique was successfully applied by Baumont et al (2002), Bourova et al (2005), Kaviani et al (2007) and more recently by Foster et al (2014a). Tanimoto & Prindle (2007) used a similar approach, but used average corrections for any given azimuth. Beamforming has also been used in lithospheric imaging to obtain the average phase velocities beneath an array of many seismic stations.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2015

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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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Surface wave analysis with beamforming

Cited by 20 publications

References 16 publications

Upper-mantle structure in southern Norway from beamforming of Rayleigh wave data presenting multipathing

Upper-mantle structure in southern Norway from beamforming of Rayleigh wave data presenting multipathing

The relationship between upper mantle anisotropic structures beneath California, transpression, and absolute plate motions

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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