Estimation of coda and shear wave attenuation in the volcanic area in SE Sabalan Mountain, NW Iran

Rahimi, Habib; Hamzehloo, H.; Kamalian, N A

doi:10.2478/s11600-009-0023-8

Cited by 26 publications

(10 citation statements)

References 32 publications

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“…Aki and Chouet (1975) stated that seismically active regions have Qc values at 1 Hz lower than 200. Some examples of quantitative comparable estimations referred to in the present study are by Akıncı and Eyidoğan (1996) for the Erzincan region in eastern Turkey, Sertçelik (2012) for the East Anatolian Fault Zone (EAFZ) and its five subregions, Sertçelik and Güleroğlu (2017) on the easternmost segments of the North Anatolian Fault Zone (NAFZ), and Rahimi et al (2009Rahimi et al ( , 2010 on Mt. Sabalan and the Alborz region in Iran.…”

Section: Introductionsupporting

confidence: 53%

Frequency-dependent body-Q and coda-Q in Karlıova Triple Junction and its vicinity, Eastern Turkey

2019

Turkish J Earth Sci

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A dataset obtained from six broadband stations of 111 small-to moderate-sized local events that occurred between 2010 and 2018 was analyzed to reveal the frequency-dependent seismic body (body-Q) and coda (coda-Q) wave attenuation characteristics of three tectonic branches of the Karlıova Triple Junction: the Varto Fault Zone (VFZ), North Anatolian Fault Zone (NAFZ), and East Anatolian Fault Zone. The magnitude range was between 2.8 and 6.1 with shallow (<10 km) focal depths. The maximum station-event distance was selected as not to exceed 120 km. Frequency-dependent Qc functions were determined using the single back-scattering model with four lapse time lengths (20, 30, 40, 50 s) while the extended coda normalization method was performed to estimate the body wave attenuation functions for seven central frequencies varying from 1.5 Hz to 18 Hz. The minimum and maximum Qp values were 7 at 1.5 Hz for the VFZ and 739 at 18 Hz for the NAFZ, respectively. Qs values were observed between a minimum of 26 for VFZ and maximum of 1259 for NAFZ. Additionally, coda-Q results show a strong lapse time dependency between Q 0 and n; exhibiting a decrease in n by an increase in Q 0 , with an ascending lapse time. Comparing the three subregions of the Karlıova Triple Junction, VFZ appears to have a significantly higher attenuation for all Q types and Qs/Qp ratios while the NAFZ has relatively low attenuation.

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Section: Introductionsupporting

confidence: 53%

Frequency-dependent body-Q and coda-Q in Karlıova Triple Junction and its vicinity, Eastern Turkey

2019

Turkish J Earth Sci

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“… Comparison of Q c of the Alborz Region and central Iran with those reported from other regions of the world. The plots for other regions are, respectively, obtained from Mukhopadhyay et al (2006), Frankel (1991), Mandal & Rastogi (1998), Woodgold (1990), Kumar et al (2005), Zelt et al (1999), Hazarika et al (2009), Maka et al (2004), Yun et al (2007), Rahimi & Hamzehloo (2008, 2009) and Ma’hood & Hamzehloo (2009). …”

Section: Resultsmentioning

confidence: 99%

Variation of coda wave attenuation in the Alborz region and central Iran

Rahimi¹,

Motaghi²,

Mukhopadhyay

et al. 2010

Geophysical Journal International

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S U M M A R YMore than 340 earthquakes recorded by the Institute of Geophysics, University of Tehran (IGUT) short period stations from 1996 to 2004 were analysed to estimate the S-coda attenuation in the Alborz region, the northern part of the Alpine-Himalayan orogen in western Asia, and in central Iran, which is the foreland of this orogen. The coda quality factor, Q c , was estimated using the single backscattering model in frequency bands of 1-25 Hz. In this research, lateral and depth variation of Q c in the Alborz region and central Iran are studied. It is observed that in the Alborz region there is absence of significant lateral variation in Q c. The average frequency relation for this region is Q c = 79 ± 2f 1.07±0.08 . Two anomalous high-attenuation areas in central Iran are recognized around the stations LAS and RAZ. The average frequency relation for central Iran excluding the values of these two stations is Q c = 94 ± 2f 0.97±0.12 . To investigate the attenuation variation with depth, Q c value was calculated for 14 lapse times (25, 30, 35, . . . 90s) for two data sets having epicentral distance range R < 100 km (data set 1) and 100 < R < 200 km (data set 2) in each area. It is observed that Q c increases with depth. However, the rate of increase of Q c with depth is not uniform in our study area. Beneath central Iran the rate of increase of Q c is greater at depths less than 100 km compared to that at larger depths indicating the existence of a high attenuation anomalous structure under the lithosphere of central Iran. In addition, below ∼180 km, the Q c value does not vary much with depth under both study areas, indicating the presence of a transparent mantle under them.The attenuation of short-period S waves, expressed as the inverse of the quality factor (Q −1 ), helps in understanding the physical laws related to the propagation of the elastic energy of an earthquake through the lithosphere. Seismic waves in the Earth attenuate with distance at rates greater than predicted by geometrical spreading. The contributing factors are intrinsic attenuation due to the medium anelasticity, and scattering attenuation associated with the inhomogeneities. Knowledge of the relative contributions of scattering (Q s −1 ) and intrinsic (Q i −1 ) attenuation is important for appropriate subsurface material identification, tectonic interpretations and quantification of the ground motion (e.g. Hoshiba 1993; Akinci et al. 1995;Del Pezzo et al. 1995;Bianco et al. 1999Bianco et al. , 2002. Attenuation inferred from the decay rate of the coda (Aki & Chouet 1975;Singh & Herrmann 1983;Sato & Fehler 1998) is a combination of scattering and intrinsic attenuations. The intrinsic attenuation is associated with small-scale crystal dislocations, friction, and movement of interstitial fluids. The scattering attenuation, associated with an elastic process of redistributing wave energy by reflection, refraction and conversion at irregularities in the medium, is often characterized by an exponential attenuation quality factor, Q s...

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“…To invert phase and group velocity dispersions, we used the average Q S structural models to avoid anelastic dispersion effect. The average values of Q S are taken from the literature as ∼25 and ∼55 for crust and upper mantle (Cong and Mitchell, 1998;Motazedian, 2006;Rahimi and Hamzehloo, 2008;Ma'hood et al, 2009;Rahimi et al, 2009Rahimi et al, , 2010.…”

Section: Constructing the Starting Modelmentioning

confidence: 99%

Shear-Wave Velocity Tomography of the Lithosphere-Asthenosphere System beneath the Iranian Plateau

Rahimi¹,

Hamzehloo²,

Vaccari³

et al. 2014

Bulletin of the Seismological Society of America

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We conducted a tomographic inversion of Rayleigh-wave dispersion to obtain 2D phase and group velocity tomographic images in the 10-100 s period range and shear-wave velocity structures for the Iranian plateau. For this purpose, the fundamental mode of Rayleigh waves, recorded along 1586 paths by 29 broadband stations, was identified by applying the frequency time analysis (FTAN) to each epicenter-station path which simultaneously satisfies the two-station method conditions. The fundamental modes identified by FTAN have been used to determine the path-average interstation phase and group velocities at selected periods. With this procedure, 243 group and phase velocity dispersion curves were processed to obtain tomographic maps by applying the Yanovskaya-Ditmar formulation for periods in the 10-100 s range. Averaged dispersion curves of phase and group velocities, which represent six rather homogeneous regions, are computed. Finally, we used a fully nonlinear inversion procedure to derive tomographic images of the elastic structure of the lithosphere and asthenosphere of the six main structural and seismotectonic features of the Iranian plateau. The dense path coverage in the Iranian plateau permits us to produce images that have substantially higher lateral resolution compared to images currently available from global and regional group velocity studies. Tomographic maps at high frequencies are well correlated with the upper crust structure, especially with sediment layers thickness. Estimated shear-wave velocity structures are well correlated with the shield-like lithosphere structure in Zagros. A low-velocity zone (LVZ) is not detected in Alborz or the south Caspian basin, which can imply thrusting of the oceanic crust of the southern Caspian Sea under the Alborz to the south. LVZs are derived for the region east of Iran, central Iran, and Kopeh Dagh.

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Estimation of coda and shear wave attenuation in the volcanic area in SE Sabalan Mountain, NW Iran

Cited by 26 publications

References 32 publications

Frequency-dependent body-Q and coda-Q in Karlıova Triple Junction and its vicinity, Eastern Turkey

Frequency-dependent body-Q and coda-Q in Karlıova Triple Junction and its vicinity, Eastern Turkey

Variation of coda wave attenuation in the Alborz region and central Iran

Shear-Wave Velocity Tomography of the Lithosphere-Asthenosphere System beneath the Iranian Plateau

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