The effect of saturation on velocity in low porosity rocks

Nur, Amos; Simmons, Gene

doi:10.1016/0012-821x(69)90035-1

Cited by 577 publications

(302 citation statements)

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“…(ii) Pore form is among the most important factors for seismic properties (Nur and Simmons, 1969;Toksöz et al, 1976;Wang, 2001) and the most difficult one to quantify (Wang, 2001). Pore form determines pressure susceptibility (Takeuchi and Simmons, 1973;Toksöz et al, 1976) and ice effects (Toksöz et al, 1976) while pore linkage affects the saturation.…”

Section: Model Setup and Representativenessmentioning

confidence: 99%

“…Carcione and Seriani (1998) give an overview about existing modelling of permafrost based on seismic velocities mostly for unconsolidated porous media (King et al, 1988;Leclaire et al, 1994;Zimmerman and King, 1986). The influence of pressure on seismic velocities (Nur and Simmons, 1969) and porosity (Takeuchi and Simmons, 1973;Toksöz et al, 1976) is observed by many researchers (King, 1966;Wang, 2001). Two pressures can be distinguished, the confining or overburden pressure of the rock mass and the pore pressure of the fluid.…”

Section: Introductionmentioning

confidence: 99%

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P-wave velocity changes in freezing hard low-porosity rocks: a laboratory-based time-average model

Draebing

Krautblatter

2012

The Cryosphere

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Abstract. P-wave refraction seismics is a key method in permafrost research but its applicability to low-porosity rocks, which constitute alpine rock walls, has been denied in prior studies. These studies explain p-wave velocity changes in freezing rocks exclusively due to changing velocities of pore infill, i.e. water, air and ice. In existing models, no significant velocity increase is expected for low-porosity bedrock. We postulate, that mixing laws apply for high-porosity rocks, but freezing in confined space in low-porosity bedrock also alters physical rock matrix properties. In the laboratory, we measured p-wave velocities of 22 decimetre-large lowporosity (< 10 %) metamorphic, magmatic and sedimentary rock samples from permafrost sites with a natural texture (> 100 micro-fissures) from 25 • C to −15 • C in 0.3 • C increments close to the freezing point. When freezing, pwave velocity increases by 11-166 % perpendicular to cleavage/bedding and equivalent to a matrix velocity increase from 11-200 % coincident to an anisotropy decrease in most samples. The expansion of rigid bedrock upon freezing is restricted and ice pressure will increase matrix velocity and decrease anisotropy while changing velocities of the pore infill are insignificant. Here, we present a modified Timur's twophase-equation implementing changes in matrix velocity dependent on lithology and demonstrate the general applicability of refraction seismics to differentiate frozen and unfrozen low-porosity bedrock.

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Section: Model Setup and Representativenessmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

P-wave velocity changes in freezing hard low-porosity rocks: a laboratory-based time-average model

Draebing

Krautblatter

2012

The Cryosphere

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“…Generally, the Taiwan region can be divided into two major tectonic provinces, separated by a narrow, linear feature known as the Taitung Longitudinal Valley, which is considered to be the boundary of the Eurasian plate and the Philippine Sea plate (Yen, 1968;Biq, 1977;Ho, 1988 temperature are the important factors in changing VP/VS value. Nur and Simmons (1969) expressed that the P-wave velocity reduces accordingly with a decrease in water saturation in low porosity rock. Toksoz et al (1976) found that even a small amount of gas as an immusicible mixture in a brine can reduce the P-wave velocity.…”

Section: Velocity Structure and Its Tectonic Implicationmentioning

confidence: 99%

Three-Dimensional Seismic Velocity Structure of the Crust and Uppermost Mantle beneath Taiwan.

1996

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Taiwan is located in a complex, tectonically active region where the Philippine Sea. plate is subducting northwestward along the Ryukyu Trench while the Eurasian plate is subducting eastward along the Manila Trench. The Central Weather Bureau Seismographic Network (CWBSN), which is composed of 75 stations with three-component instruments, has been operated over the island of Taiwan since March of 1991. This dense seismic network provides high-quality P-and S-wave arrival times of local earthquakes, and, thus, gives us a good opportunity to determine the velocity structure of the crust and upper mantle structures beneath Taiwan. We have applied a new tomographic method to infer the fine 3-D P-and S-wave velocity structures beneath Taiwan. Results show the existence of a low velocity zone in the uppercrust of west Taiwan. This zone is consistent with the thick sediments in the area. A low-velocity zone has been inferred underneath the extinct volcano regions, and it is due to the remnant geothermal effect after past volcanic activities. A low-velocity zone with a relatively homogeneous distribution of P-wave velocities, extending to a depth of about 30-35 km, is found beneath the Central Range. We infer that this feature might have resulted from the heat intrusion from the oceanic upper mantle of the Philippine Sea plate, which has been colliding with the Eurasian plate, and the effect of partial melting. The thickness of the crust of Taiwan is estimated to be 30-35 km and that for the Philippine Sea plate is 15-20 km.

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“…It is well known that seismic velocities and anisotropy are modulated by 61 non-hydrostatic stress changes (e.g., Nur and Simmons, 1969;Zatsepin and 62 Crampin, 1997; Teanby et al, 2004b;Verdon et al, 2008a), so observations 63 of shear wave splitting -a key indicator of anisotropy -made on waves 64 generated by microseismic events can also be used to inform geomechanical 65 models. (White, 2009).…”

mentioning

confidence: 99%

Linking microseismic event observations with geomechanical models to minimise the risks of storing CO2 in geological formations

Verdon

Kendall

White

et al. 2011

Earth and Planetary Science Letters

119

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The effect of saturation on velocity in low porosity rocks

Cited by 577 publications

References 20 publications

P-wave velocity changes in freezing hard low-porosity rocks: a laboratory-based time-average model

P-wave velocity changes in freezing hard low-porosity rocks: a laboratory-based time-average model

Three-Dimensional Seismic Velocity Structure of the Crust and Uppermost Mantle beneath Taiwan.

Linking microseismic event observations with geomechanical models to minimise the risks of storing CO2 in geological formations

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