Improving C1 and C3 empirical Green’s functions from ambient seismic noise in NW Iran using RMS ratio stacking method

Safarkhani, Mahsa; Shirzad, Taghi

doi:10.1007/s10950-019-09834-1

Cited by 8 publications

(3 citation statements)

References 60 publications

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“…The final selection criterion, before signal preparation, was the waveform signal-to-noise ratio, which should be greater than 4 (SNR event ≥ 4). In this study, the SNR value is the ratio of the peak of the signal envelope (from the P arrival to the time corresponding to velocity 2.0 km/s) to the root-mean-square of the noise window (1.3 to 1.6 km/s), filtered in period range of 4 to 26 s 23 .…”

Section: Dataset and Data Selectionmentioning

confidence: 99%

Crustal Structure of the Collision-Subduction Zone in South of Iran Using Virtual Seismometers

Shirzad

Riahi

Assumpção

2019

Sci Rep

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Improving the resolution of seismic tomography by adding virtual seismometers is an ambitious aim in regions with poor instrumental coverage. In this study, inter-event empirical Green’s functions (EGFs) were retrieved using cross-correlation of the vertical component of 630 earthquakes with M ≥ 4 which occurred around the collision-subduction transition zone in south Iran. To extract reliable inter-event EGFs and obtain stable tomographic results, we used about 1300 event pairs with good signal-to-noise ratio, each pair well aligned to a seismic station. Our results show that the retrieved inter-event EGFs agree well with those obtained from earthquakes in similar paths. The inverted velocity model presents two main layers including upper crust (up to ~16 km) and middle crust (deeper than ~18 km) in both sides of the Minab-Zendan-Palami transition zone. The upper crust contains two main layers: sedimentary and basement layers with thicknesses ~6 and ~10 km, respectively. Moreover, the main faults cause lateral variations in these main layers. The difference between the average velocities of the middle crust, between the collision and subduction zones, is about 0.5 km/s, delimited by faults. Also, an area with a 30 km width along these faults can be defined as the collision-subduction transition zone.

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Section: Dataset and Data Selectionmentioning

confidence: 99%

Crustal Structure of the Collision-Subduction Zone in South of Iran Using Virtual Seismometers

Shirzad

Riahi

Assumpção

2019

Sci Rep

Self Cite

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“…Numerous ambient seismic noise studies have assumed uniform distribution of noise sources or energies in different azimuths as a main condition in determining accurate EGF between the stations (e.g., Snieder, 2004;Wapenaar, 2004). Recent studies regarding noise source distribution (e.g., ambient seismic noise directionality by Stutzmann et al, 2009; RMS stacking by Shirzad and Shomali, 2013; RMS-S stacking by 2021; RMS-SS by Xie et al, 2020) overcome the problem via separating stationary sources. We applied the WRMS (weighted root-mean-square; Shirzad et al, 2020 and2022) stacking for these signals.…”

Section: Introductionmentioning

confidence: 99%

Shear wave velocities in the upper crust of the Quadrilátero Ferrífero, Minas Gerais: Rayleigh-wave tomography

et al. 2022

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We applied a combination of ambient seismic noise and classical earthquake-receiver techniques to characterize the shallow crustal shear-wave velocities in the Quadrilátero Ferrífero (QF), Minas Gerais state, SE Brazil, to a depth of about 4 km. Ambient seismic noise was recorded by up to 26 stations. To improve the signal of the extracted empirical Green's function (EGF), we correlated short time windows of 10 min with 70% overlapping before stacking. To test the accuracy of the retrieved EGF signals, we compared the results obtained from ambient seismic noise correlation with results from an earthquake occurred near FABR station. After measuring dispersion using frequency-time analysis (FTAN), we applied strict quality criteria (e.g., eliminating paths with residuals larger than two standard deviations, or lengths smaller than 3 wavelengths). The Fast Marching Surface wave Tomography (FMST) method was used to obtain group velocity maps. Then, the local dispersion curves were inverted to obtain a 3D Vs model. The resulting 3D model shows low velocity anomalies in the middle of the QF, compared with high velocities in the Archean part of the São Francisco Craton to the west. The low velocity metasedimentary layer in the QF is about 1.5 km thick.

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“…But the uniform distribution of energies around the station-pairs only occurs in rare cases. Recent studies regarding noise source distribution (e.g., Stutzmann et al, 2009;Safarkhani and Shirzad 2019) overcome the problem via separating stationary sources, and performing stacking for these signals.…”

Section: Introductionmentioning

confidence: 99%

Shear wave velocity model in the Quadrilátero Ferrífero: Preliminary Results

2021

Proceeding of the 17th International Congress of the Brazilian Geophysical

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We applied a combination of the ambient seismic noise and classical source-receiver techniques to characterize the subsurface shear wave velocities in the Quadrilátero Ferrífero to a depth of about 4 km. Ambient seismic noise data were recorded by two arrays of 16 stations deployed in the study area. To enhance the SNR of the extracted EGF signals, we divided ambient seismic records into shorter 10 min time window with 70% overlapping before correlation and stacking. To ensure retrieval EGF signals are accurate, we compared our results (obtained from ambient seismic noise) with an earthquake results occurred near to FABR station. By inspection of the 1D VS models, we inferred two main layers including upper and lower sedimentary layers. 2D mapped VS models indicate a low velocity anomaly around Engenho and Moeda faults.

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Improving C1 and C3 empirical Green’s functions from ambient seismic noise in NW Iran using RMS ratio stacking method

Cited by 8 publications

References 60 publications

Crustal Structure of the Collision-Subduction Zone in South of Iran Using Virtual Seismometers

Crustal Structure of the Collision-Subduction Zone in South of Iran Using Virtual Seismometers

Shear wave velocities in the upper crust of the Quadrilátero Ferrífero, Minas Gerais: Rayleigh-wave tomography

Shear wave velocity model in the Quadrilátero Ferrífero: Preliminary Results

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