Investigation of coda and body wave attenuation functions in Central Asia

Sedaghati, Farhad; Nazemi, Nima; Pezeshk, Shahram; Ansari, Anooshiravan; Daneshvaran, Siamak; Zaré, Mehdi

doi:10.1007/s10950-019-09854-x

“…Thus, we will be able to regionalize almost the entire territory of Georgia according to the Q parameter. ; line 2-Erzincan, Turkey [5]; line 3-Yunnan Province, China [57]; line 4-Racha, Georgia [46]; line 5-the Javakheti plateau, Georgia [51]; line 6-Arunachal Himalaya [8]; line 7-Tbilisi region (this study); line 8-the Bam region, Iran [58]; line 9-Northwest Caucasus [21]; line 10-Central Asia [59]; line 11-the Andaman Sea [7]. ; line 2-Umbria-Marche, Italy [41]; line 3-Racha, Georgia [46]; line 4-Arunachal Himalaya [8]; line 5-Tbilisi region (this study); line 6-W. Greece [60]; line 7-Andaman Sea [7]; line 8-Bam region, Iran [58]; line 9-Delhi, India [61]; line 10-Alborz region, Iran [62].…”

Section: Discussionmentioning

confidence: 78%

“…Figure 9: Comparison of Q c for different regions: line 1-Etna, Italy[56]; line 2-Erzincan, Turkey[5]; line 3-Yunnan Province, China[57]; line 4-Racha, Georgia[46]; line 5-the Javakheti plateau, Georgia[51]; line 6-Arunachal Himalaya[8]; line 7-Tbilisi region (this study); line 8-the Bam region, Iran[58]; line 9-Northwest Caucasus[21]; line 10-Central Asia[59]; line 11-the Andaman Sea[7].…”

mentioning

confidence: 78%

Attenuation of Coda and Body Waves for Tbilisi and Surrounding Area, Georgia

Shengelia,

Jorjiashvili,

Godoladze

et al. 2024

International Journal of Geophysics

0

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The attenuation of high-frequency seismic waves was investigated in the crust beneath Tbilisi and the surrounding territory by analysing 225 local earthquakes that occurred from 2008 to 2020 and were recorded by eight seismic stations. The quality factors of coda waves QC and direct P and S waves, QP and QS, were estimated using the single backscattering model and the extended coda normalization method, respectively. The separation of intrinsic quality factors Qi from scattering quality factor QSC was fulfilled by Wennerberg’s method. Observed results show that all evaluated attenuation parameters are frequency-dependent in the frequency range of 1-32 Hz and increase with increasing frequency. Coda QC values increase also with increasing lapse time window from 20 s to 50 s and vary from 91±5 at 1.5 Hz to 1779±108 at 24 Hz, respectively. P waves attenuate slightly faster than S waves, and the ratio of QS/QP is more than unity and varies in a range of 1.5-1.8. The intrinsic and scattering quality factors are expressed by the following power laws: Qi=77±4f0.930±0.046 and QSC=219±6f0.924±0.050. The results show that Qi is close to QC, but QSC is larger than Qi, which means that intrinsic attenuation has a dominant role compared with the scattering effect. Our results were compared with those obtained in two other seismically active regions of Georgia, as well as with regions of the world. In general, the observed quality factors and their frequency-dependent relationships follow a similar trend, characterizing seismically active regions with complex tectonics. The calculated attenuation parameters characterize the entire earth’s crust under Tbilisi and the surrounding area. The results obtained will be useful in future seismological studies since the Q parameters are estimated for the first time for the given region.

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“…Our results are slightly lower than the S-wave quality factor Q 212.6 f 0.71 at frequencies of 1-20 Hz obtained by Zhao et al (2011) for the northwest Tarim Basin using the hinged trilinear geometrical spreading model proposed by Atkinson and Mereu (1992). After defining a geometrical spreading function as R −1 , Sedaghati et al (2019) also demonstrated strong anelastic attenuation for the Tajikistan-Kyrgyzstan region in Central Asia, west and northwest of our study region, according to the S-wave quality factor Q 152 f 0.856 at frequencies of 1-20 Hz determined by the multiple-station coda normalization method. The much stronger anelastic attenuation (low Q) verified in our study may be majorly attributed to the enormous scattering from the prominent interaction of seismic wave propagation with the highly inhomogeneous crust.…”

Section: Figure 4 | (A)mentioning

confidence: 76%

“…(C) Calculated Q values (circles) and the regressed Q model (solid line) in our study. The Q models for the northwest Tarim Basin proposed by Zhao et al (2011) and the Tajikistan-Kyrgyzstan region west and northwest of our study region proposed by Sedaghati et al (2019) are also plotted. spectral decay observed above f max is universally considered to be path-and site-dependent at present (Campbell, 2009;Ktenidou et al, 2013;Lai et al, 2016) and modeled by exp (−πfκ) where κ indicates the high-frequency decay parameter.…”

Section: Source Characteristicsmentioning

confidence: 92%

“…The determined f lc values were in the range of 0.10-0.95 Hz. In order to avoid the nonlinear soil behavior potentially occurring under strong ground shaking (Beresnev and Wen, 1996;Wu et al, 2010) and reduce the contamination of the surface wave and/or Lg wave to the applied S-wave as much as possible (McNamara et al, 2012;Sedaghati et al, 2019), recordings with R > 120 km or PGA > 100 cm/s 2 were first eliminated. Moreover, to ensure data redundancy, we adopted a minimum three-recording criterion requiring each selected earthquake to be recorded by at least three selected stations, each of which recorded at least three selected earthquakes.…”

Section: Datasetmentioning

confidence: 99%

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Earthquake Source Characteristics and S-Wave Propagation Attenuation in the Junction of the Northwest Tarim Basin and Kepingtage Fold-and-Thrust Zone

Wang

¹

,

Wen

²

2020

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We separated the propagation path attenuation and source spectra from the S-wave Fourier amplitude spectra of the observed ground motions recorded during 46 small-to-moderate earthquakes in the junction of the northwest Tarim Basin and Kepingtage fold-and-thrust zone, mainly composed of two Jiashi seismic sequences in 2020 and 2018. Slow seismic wave decay was observed as the distance increased, while the quality factor regressed as 60.066 f0.988 for frequency f = 0.254–30 Hz reflects the strong anelastic attenuation in the study region. We estimated the stress drops for the 46 earthquakes under investigation from the preferred corner frequencies and seismic moments by fitting the inverted source spectra and the theoretical ω-square model. The relationship between seismic moment and corner frequency and the dependence of the stress drop on the moment magnitude reveal the breakdown of earthquake self-similar scaling for the events in this study. The temporal variation in stress drops indicates that the mainshock plays a short-term role in the source characteristics of the surrounding earthquakes. Aftershocks immediately following the mainshock show a low stress release and then gradually recover in a short time. The healing process for the fractured fault in the mainshock may be one reason for the stress drop recovery of the aftershock. The foreshock with the low stress release occurring in the high-heterogeneity fault zone may motivate the following occurrence of the largest magnitude mainshock with a high stress drop. We inferred that the foreshock-mainshock behavior, including several moderate events, may be predisposed to occur in our study region characterized by an inhomogeneous crust.

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Machine learning regression implementation for high-frequency seismic wave attenuation estimation in the Aswan Reservoir area, Egypt

Moustafa

¹

,

Mohamed

²

,

El-Hadidy

³

et al. 2023

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Attenuation characteristics have been estimated to understand the effect of the heterogeneity in the tectonically active Aswan Reservoir, the southern part of Egypt using data collected by a ten-station local seismological network operating across the reservoir. The quality factor was estimated from 350 waveform spectra of P- and S-waves from 50 earthquakes. By applying a spectral ratio technique to bandpass-filtered seismograms, obtained results show variations in both P-waves attenuation ($$Q_\alpha$$ Q α ) and corresponding S-waves ($$Q_\beta$$ Q β ) as a function of frequency, according to the power law $$Q=Q_0 \times f^n$$ Q = Q 0 × f n , with n ranging between 0.85 and 1.19 for P-waves and between 0.92 and 1.18 for S-waves. A supervised machine learning algorithm known as Orthogonal distance regression was utilized to fit the attenuation power law functions. Estimates of $$Q_\alpha$$ Q α and $$Q_\beta$$ Q β show a clear dependence on frequency. The frequency-dependent attenuation is found to be $$Q_\alpha = (11.22 \pm 2.2) \times f^{(1.09 \pm 0.07)}$$ Q α = ( 11.22 ± 2.2 ) × f ( 1.09 ± 0.07 ) and $$Q_\beta = (9.89 \pm 1.89) \times f^{(1.14 \pm 0.07)}$$ Q β = ( 9.89 ± 1.89 ) × f ( 1.14 ± 0.07 ) for P- and S-waves, respectively. The average ratio $$Q_\alpha /Q_\beta$$ Q α / Q β is higher than unity, which is commonly observed in tectonically active regions characterized by a high degree of heterogeneity of the crustal structure of the area. Final results indicate that seismic wave attenuation in the AHDR region is highly frequency-dependent. Moreover, estimated low values of $$Q_0$$ Q 0 clearly highlight the heterogeneity of the AHDR with considerably high seismic activity. These findings will be useful in any future assessment of seismic hazards and the damage pattern of earthquakes.

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Investigation of coda and body wave attenuation functions in Central Asia

Cited by 7 publications

References 82 publications

Attenuation of Coda and Body Waves for Tbilisi and Surrounding Area, Georgia

Attenuation of Coda and Body Waves for Tbilisi and Surrounding Area, Georgia

Earthquake Source Characteristics and S-Wave Propagation Attenuation in the Junction of the Northwest Tarim Basin and Kepingtage Fold-and-Thrust Zone

Machine learning regression implementation for high-frequency seismic wave attenuation estimation in the Aswan Reservoir area, Egypt

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