Attenuation of seismic waves in dry and saturated rocks: II. Mechanisms

Johnston, David H.; Toksöz, M. Nafi; Timur, A.

doi:10.1190/1.1440970

Cited by 441 publications

(262 citation statements)

References 26 publications

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“…17) calculated from the Q values shown in Table 2. For OBS records within the 10-120 km distance interval, where the waves travel at shallow depths, the crust contains microcracks, and the rocks are fluid saturated (e.g., Johnston et al, 1979;Winkler and Nur, 1982), we find that P waves attenuate more than S waves for frequencies between 0.6 and 12.6 Hz. On the contrary, we find for the 120-220 km interval (for deeper travel paths) that S waves attenuate more than P waves up to 3.5 Hz, indicating that in the lower crust and upper mantle the temperature must be higher and the rocks probably less fractured.…”

Section: Resultsmentioning

confidence: 97%

An Attenuation Study of Body Waves in the South-Central Region of the Gulf of California, Mexico

Vidales-Basurto¹,

Castro²,

Huerta³

et al. 2014

Bulletin of the Seismological Society of America

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We studied the seismic attenuation of body waves in the south-central region of the Gulf of California (GoC) with records from the Network of Autonomously Recording Seismographs of Baja California (NARS-Baja), from the Centro de Investigación Científica y de Educación Superior de Ensenada's Broadband Seismological Network of the GoC (RESBAN), and from the ocean-bottom seismographs (OBS) deployed as part of the Sea of Cortez Ocean Bottom Array experiment (SCOOBA). We examine 27 well-located earthquakes reported in Sumy et al. (2013) that occurred from October 2005 to October 2006 with magnitudes (M w ) between 3.5 and 4.8. We estimated S-wave site effects by calculating horizontal-to-vertical spectral ratios and determined attenuation functions with a nonparametric model by inverting the observed spectral amplitudes of 21 frequencies between 0.13 and 12.59 Hz for the SCOOBA (OBS) stations and 19 frequencies between 0.16 and 7.94 Hz for NARS-Baja and RESBAN stations. We calculated the geometrical spreading and the attenuation (1=Q) factors for two distance intervals (10-120 and 120-220 km, respectively) for each frequency considered. The estimates of Q obtained with the SCOOBA (OBS) records for the interval 10-120 km indicate that the P waves attenuate more than S waves (Q P 34 1:2f 0:820:10 , Q S 59 1:1f 0:900:03 ) for frequencies between 0.6 and 12.6 Hz; whereas for the 120-220 km interval, where ray paths travel deeper, S waves attenuate more than P waves (Q P 117 1:3f 0:440:19 , Q S 51 1:2f 1:120:11 ). The estimates of Q obtained using NARS-Baja and RESBAN records, within 10-120 km, indicate that P waves attenuate more than S waves (Q P 69 1:2f 0:870:16 , Q S 176 1:4f 0:610:26 ) at frequencies between 0.3 and 6.3 Hz; whereas at the 120-220 km distance interval S waves attenuate slightly more than P waves (Q P 39 1:1f 0:640:06 , Q S 48 1:1f 0:370:07 ) at high frequencies (f > 3 Hz). These results, based on a unique OBS dataset, provide an indirect mean to constrain future models of the thermal structure beneath the GoC.

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Section: Resultsmentioning

confidence: 97%

An Attenuation Study of Body Waves in the South-Central Region of the Gulf of California, Mexico

Vidales-Basurto¹,

Castro²,

Huerta³

et al. 2014

Bulletin of the Seismological Society of America

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“…De nombreuses études expérimentales aussi bien in situ qu'au laboratoire ont montré la validité de cette affir mation. Citons pour mémoire TOKSÔZ et al (1979), JOHNSTON et TOKSÖZ (1980aet 1980b), STACEY et GLADWIN (1981) et BLAIR et al (1984. Le para mètre le plus couramment utilisé pour caractériser l'atténuation est le facteur de qualité (Q).…”

Section: Mesures De L'atténuation Des Ondes P Et Sunclassified

Mesures in situ de vitesse et d’atténuation des ondes P et S dans un massif granitique

Talebi

1987

Rev. Fr. Geotech.

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mesures in situ de vitesse et d'atténuation des ondes P et S dans un massif granitiquein situ measurements of velocity and attenuation of P and S waves in a granitic rock mass Sh. TALEBI Rock Physics Laboratory, Queen's University* RésuméLes propriétés acoustiques du massif granitique du Mayet-de-Montagne (Allier), à savoir la vitesse et l'atténuation des ondes P et S, ont été mesurées à partir de signaux engendrés par des tirs de dynamite dans différents forages du site. Les valeurs de vitesse obtenues varient de 4,88 km/s à 5,87 km/s pour les ondes P et de 3,13 km/s à 3,27 km/s pour les ondes S. Un coefficient de Poisson de 0,27 a été obtenu. La projection équiaréale des vitesses des ondes P fait ressor tir une anisotropie ayant trois plans de symétrie et donc un système orthorhombique. Dans le plan horizontal, la direction de Vmax est cohérente avec celles de la contrainte principale maximum et de la fracturation naturelle du massif. De même, la direction de Vmin est cohérente avec celle de la contrainte principale minimum. Les valeurs minimum, intermédiaire et maximum de vitesse des ondes P retenues pour cette analyse sont de 5,25 km/s, 5,55 km/s et 5,75 km/s, soit un degré d'anisotropie de 9 %. Le champ de fracturation naturelle semble avoir le rôle prépondérant dans cette anisotropie. L'atténuation a été mesurée par deux méthodes : le rapport spectral et le temps de montée du signal. La première donne Qp = 10 à 40 (1 000/Qp = 25 à 100) et Qs = 20 à 35 (1 000/Qs = 30 à 50) où Qp et Qs sont les facteurs de qualité des ondes P et S. L'application de la deuxième méthode fournit Qp = 51 ± 4 (1 000/Qp = 20 ± 2) et Qs = 59 ± 13 (1 000/Qs = 17 ± 4). AbstractAcoustic properties of the granitic rock mass of«le Mayet-de-Montagne»(French Massif Central) Qp = 51 ± 4 (1 000/Qp = 20 ± 2) and Qs = 59 ± 13 (1 000/Qs = 17 ± 4).

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“…[Knopoff, 1971]. In porous and/or densely fractured media permeated by fluids, seismic attenuation depends in a complicated way on different factors as the degree of saturation, fluid type, and static pressure [Johnston et al, 1979]. In rock volumes saturated with a low viscosity fluid (e.g., water and oil), laboratory measurements at ultrasonic frequencies using a pulse amplitude technique found Q P < Q S for partially saturated rock samples .…”

Section: P and S Wave Shallow Crustal Attenuationmentioning

confidence: 99%

Source parameter scaling and radiation efficiency of microearthquakes along the Irpinia fault zone in southern Apennines, Italy

2014

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We analyzed the P and S wave displacement spectra of 717 microearthquakes in the moment range 4 × 10 9 À 2 × 10 14 N m recorded at the dense networks operating in southern Apennines (Italy) and deployed along the 1980 M s 6.9 Irpinia earthquake fault zone. Source, attenuation, and site parameters are estimated by using a parametric modeling approach, which is combined with a multistep, nonlinear inversion strategy. We found that in the analyzed frequency band, an attenuation model with constant Q has to be preferred to frequency-dependent Q models. Consistent estimates of the median P and S quality factors e Q P ¼ 167 (90; 296) and e Q S ¼ 226 (114; 417) are obtained from two different techniques and relatively high values of Q S /Q P (median value 1.3, (0.8; 2.1)) are found in the same depth range where high V P /V S and a peak in seismicity distribution are observed. This is the evidence for a highly fractured, partially, or completely fluid-saturated medium embedding the Irpinia fault zone, down to crustal depths of 15-20 km. A nearly constant stress drop ( f Δσ ¼ 1:4 MPa, (0.4; 5.0)) and apparent stress (e τ a ¼ 0:1 MPa, (0.03, 0.4)) scaling of P and S corner frequencies and seismic energies is observed above a seismic moment value of about 10 11 N m. The measured radiation efficiency is low (g η SW ¼ 0:06; 0:03; 0:13 ð Þ ), e.g., the radiated energy is only a small fraction of the whole energy spent by friction and fracture development. A large positive dynamic overshoot (high dynamic shear strength) can be the dominant mechanism controlling the microearthquake fractures along the Irpinia fault zone.

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Attenuation of seismic waves in dry and saturated rocks: II. Mechanisms

Cited by 441 publications

References 26 publications

An Attenuation Study of Body Waves in the South-Central Region of the Gulf of California, Mexico

An Attenuation Study of Body Waves in the South-Central Region of the Gulf of California, Mexico

Mesures in situ de vitesse et d’atténuation des ondes P et S dans un massif granitique

Source parameter scaling and radiation efficiency of microearthquakes along the Irpinia fault zone in southern Apennines, Italy

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