Shallow crustal structures of the Tehran basin in Iran resolved by ambient noise tomography

Shirzad, Taghi; Shomali, Zaher‐Hossein

doi:10.1093/gji/ggt449

Cited by 38 publications

(14 citation statements)

References 29 publications

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“…Surface wave tomography based on ambient noise has been widely used to investigate regional crustal structure in the past decade [e.g., Shapiro et al , ; Sabra et al , ; Yao et al , ; Yang et al , ; Lin et al , ] using a period band of 5–40 s. Moreover, recent studies show that shorter period (∼1 s, using station spacing of ∼20 km or less) surface waves can also be retrieved from ambient noise cross correlation [e.g., Picozzi et al , ; Huang et al , ; Young et al , ; Pilz et al , ; Lin et al , ; Shirzad and Shomali , ]. Because the depth sensitivity depends on frequency, shorter period surface waves are more sensitive to the near‐surface velocity and are thus particularly useful to resolve shallow V s structure.…”

Section: Introductionmentioning

confidence: 99%

A new algorithm for three‐dimensional joint inversion of body wave and surface wave data and its application to the Southern California plate boundary region

et al. 2016

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We introduce a new algorithm for joint inversion of body wave and surface wave data to get better 3‐D P wave (Vp) and S wave (Vs) velocity models by taking advantage of the complementary strengths of each data set. Our joint inversion algorithm uses a one‐step inversion of surface wave traveltime measurements at different periods for 3‐D Vs and Vp models without constructing the intermediate phase or group velocity maps. This allows a more straightforward modeling of surface wave traveltime data with the body wave arrival times. We take into consideration the sensitivity of surface wave data with respect to Vp in addition to its large sensitivity to Vs, which means both models are constrained by two different data types. The method is applied to determine 3‐D crustal Vp and Vs models using body wave and Rayleigh wave data in the Southern California plate boundary region, which has previously been studied with both double‐difference tomography method using body wave arrival times and ambient noise tomography method with Rayleigh and Love wave group velocity dispersion measurements. Our approach creates self‐consistent and unique models with no prominent gaps, with Rayleigh wave data resolving shallow and large‐scale features and body wave data constraining relatively deeper structures where their ray coverage is good. The velocity model from the joint inversion is consistent with local geological structures and produces better fits to observed seismic waveforms than the current Southern California Earthquake Center (SCEC) model.

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Section: Introductionmentioning

confidence: 99%

A new algorithm for three‐dimensional joint inversion of body wave and surface wave data and its application to the Southern California plate boundary region

et al. 2016

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“…The higher velocity in this area is due to the low thickness of the sediments, as well as the presence of geological units such as andesitic tuffs, limestone, and shale. At the periods of the 2‐ and 3‐second group velocity maps, the range of the depth sensitivity is broad from 450 to 850 m (Shirzad and Shomali ). These two periods are influenced by the sediments and represent the Love and Rayleigh waves’ group velocities in the sediments.…”

Section: Resultsmentioning

confidence: 99%

The imaging of the near‐surface features using earthquakes and ambient noise in the Tehran region

Asadi

Rahimi

Fard

2017

Near Surface Geophysics

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Seismic surface wave tomography of short-period dispersion curves is a useful method for studying the shallow structures of the Earth. In this research, the continuous records of ten seismographs of the Tehran Disaster Mitigation and Management Organization for a period of 8 months have been used to calculate the Green's function for Love and Rayleigh waves. Dispersion curves are calculated using the cross-correlation of the ambient noise signal recorded at station pairs. In order to improve the ray coverage in the Tehran region, dispersion curves of Love and Rayleigh waves are derived from the seismic events recorded by a temporary network run by Parsian Company. The epicentral distance and magnitude of earthquakes are less than 100 km and larger than 1.5, respectively. The dispersion curves are calculated in the period range between 2 seconds and 5 seconds, which correspond to the top sedimentary cover. Surface wave tomography has also been performed to estimate the two-dimensional group velocity maps of Love and Rayleigh waves in the region. Based on the ray coverage inside the 0.1° × 0.1° cells in the region, the estimated minimum dimension of distinct heterogeneities was about 6 km. Based on the derived velocity model, the western and the central parts of the Tehran plain show low anomalies that could be due to the large thickness of alluvial sedimentary cover over the basement. The high-velocity anomaly in the southeastern part of the region can be attributed to the tapering of the alluvial cover towards the rock units where the southeastern mountains of Tehran are present.

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“…A similar procedure introduced by Shirzad and Shomali () to extract Rayleigh and Love wave EGFs was applied to process the recorded three‐component raw data. All data were windowed into 5‐second‐length segments before processing (Cho et al ; Shirzad, Shomali, and Riahi ). The mean and trend of the three components (E, N, Z) of 5‐second windowed raw data were first removed.…”

Section: Data Processing Methodsmentioning

confidence: 99%

“…The root‐mean‐square (RMS) values were calculated for velocities ranging from 300 m/s to 650 m/s, as expected for the fundamental mode of surface wave signals. We applied an RMS‐stacking method as described by Shirzad and Shomali () to enhance the signal‐to‐noise ratio (hereafter, SNR) of the EGFs. Changes in the gradient of the RMS curve (see Fig.…”

Section: Data Processing Methodsmentioning

confidence: 99%

Near‐surface V_S structure by inversion of surface wave estimated from ambient seismic noise

Shirzad

Shomali

Naghavi

et al. 2015

Near Surface Geophysics

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In this study, 20 hours of ambient seismic noise recorded from a small‐scale inter‐station distance was used to obtain near‐surface shear wave velocity structures at a local test site in Tehran (Iran). High‐resolution group velocity dispersion curves using fundamental mode of surface waves were calculated for all possible combinations of station pairs at frequencies ranging from 1 Hz to 25 Hz. Unlike most previous studies regarding ambient seismic noise, which observe very little coherent noise at frequencies larger than 1 Hz, the empirical Green’s functions were extracted using a root‐mean‐square stacking method showing more coherent signals. Our results indicate that ambient seismic noise is a viable technique at a frequency range of 1 Hz–25 Hz even when different sensor types are present. One‐dimensional VSV and VSH models from the near surface were then assessed by inverting the calculated Rayleigh and Love waves’ dispersion measurements. We observed that the calculated shear wave velocity model agrees with the available downhole model and shows three distinct layers in the upper 25 m of the test site.

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Shallow crustal structures of the Tehran basin in Iran resolved by ambient noise tomography

Cited by 38 publications

References 29 publications

A new algorithm for three‐dimensional joint inversion of body wave and surface wave data and its application to the Southern California plate boundary region

A new algorithm for three‐dimensional joint inversion of body wave and surface wave data and its application to the Southern California plate boundary region

The imaging of the near‐surface features using earthquakes and ambient noise in the Tehran region

Near‐surface V_S structure by inversion of surface wave estimated from ambient seismic noise

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Shallow crustal structures of the Tehran basin in Iran resolved by ambient noise tomography

Cited by 38 publications

References 29 publications

A new algorithm for three‐dimensional joint inversion of body wave and surface wave data and its application to the Southern California plate boundary region

A new algorithm for three‐dimensional joint inversion of body wave and surface wave data and its application to the Southern California plate boundary region

The imaging of the near‐surface features using earthquakes and ambient noise in the Tehran region

Near‐surface VS structure by inversion of surface wave estimated from ambient seismic noise

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Near‐surface V_S structure by inversion of surface wave estimated from ambient seismic noise