1 edition of On seismic wave attenuation in an hydrated crust found in the catalog.
Written in English
|Statement||by Pierre Michel Rouleau|
|Contributions||University of Alberta. Dept. of Physics|
|The Physical Object|
|Pagination||[xi], 71 leaves ;|
|Number of Pages||71|
Seismic attenuation without Q – I. Concept and model for mantle Love waves Igor B. Morozov Department of Geological Sciences, University of Saskatchewan, Saskatoon, SK S7N 5E2 Canada [email protected] Summary The attenuation quality parameter (Q) is . Earthquake - Earthquake - Properties of seismic waves: At all distances from the focus, mechanical properties of the rocks, such as incompressibility, rigidity, and density, play a role in the speed with which the waves travel and the shape and duration of the wave trains. The layering of the rocks and the physical properties of surface soil also affect wave characteristics.
It has been documented that the presence of magma within the crust can bend seismic waves, thus resulting in distorted seismic raypaths given the locations of the hypocenters with respect to the stations (e.g., Steck and Prothero, ; Yeguas et al., ; Galluzzo and La Rocca, ). This can modify the results of seismic studies that rely. Our results depict that seismic wave attenuation is an effective attribute to identify gas hydrates. 1. Introduction. With the enhancement of exploration technology for gas hydrate resources, research on wave attenuation in hydrate-bearing sediments is being paid more and more attention.
In considering specific examples, we find that for ocean basins worldwide the lower oceanic crust is partially hydrated . Whitman et al. () have examined patterns of high-frequency seismic wave attenuation under the central Andean plateau. High- and low-Q regions in the upper plate and wedge were mapped in three dimensions, with a thin low-Q region just above the slab (similar to Sack and Okada, ) or a variable asthenospheric window being proposed to vary.
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Seismic magnitude scales are used to describe the overall strength or "size" of an earthquake. These are distinguished from seismic intensity scales that categorize the intensity or severity of ground shaking (quaking) caused by an earthquake at a given location. Magnitudes are usually determined from measurements of an earthquake's seismic waves as recorded on a seismogram.
In the Kanto region, analysis of Hi-net waveform data from earthquakes occurring in the subducting crust of the Philippine Sea plate revealed strong lateral variation in the characteristics of high-frequency trapped P and S waves.
Strong distortion of the trapped wave envelopes was observed in those regions where the Philippine Sea plate exists Cited by: 4. Snapshots of the seismic wave propagation at lapse times of t = 4, 8, 12 and 16 s, derived from 2-D FDM simulations in (a) model A1 and (b) model A2 along profile A-B.
Assumed P-wave velocity. Seismic wave fields are recorded by a seismometer, hydrophone (in water), or accelerometer. The propagation velocity of seismic waves depends on density and elasticity of the medium as well as the type of wave. Velocity tends to increase with depth through Earth's crust and mantle, but drops sharply going from the mantle to the outer core.
attenuation of wave in case of earthquake (EQ) occurrence in the nearby region. The attenuation study is also important for ground motion prediction5 and seismic hazard analysis. The attenuation of wave is defined by the inverse of quality factor (−1) while quality factor () File Size: KB.
This paper is devoted to the study of the time decay of the coda of seismograms. We consider a conceptual model of the Earth upper layers: a diffractive crust overlying an almost homogeneous mantle. We simulate the multiple scattering of the seismic waves using the classical radiative transfer equation in a scalar approximation.
Shear wave velocity, seismic attenuation, and thermal structure temperature T: Q−1 = Aταexp(−αE∗/RT), (1) where E∗ is the activation energy, R is the gas constant, τ is the oscillation period, A is a scaling constant and the exponent α is approximately – as.
The Q-factor estimates of the Earth’s crust and upper mantle as the functions of frequency (Q(f)) are obtained for the seismic S-waves at frequencies up to ~35 Hz.
The estimates are based on the data for ~40 earthquakes recorded by the Kislovodsk seismic station since The magnitudes of these events are M W >the sources are located in the depth interval from 1 to km, and the. Attenuation of seismic waves. Seismic waves decay as they radiate away from their sources, partly for geometric reasons because their energy is distributed on an expanding wave front, and partly because their energy is absorbed by the material they travel through.
The energy absorbtion depends on the material properties. Attenuation of seismic waves has been measured for many years. However, it is only recently that sufficient precision has been achieved and analytical techniques have been evolved which make possible the inversion of the experimental data [Anderson and Archambeau, ; Anderson and Kovach, ; Knopoff, ].The resultant distribution of attenuation versus depth (usually expressed by the.
The low-velocity zone (LVZ) in the upper mantle is characterized by low seismic wave velocities, high seismic energy attenuation, and high electrical conductivity.
The bottom of the LVZ, sometimes referred to as the Lehmann discontinuity, has been identified from the study of surface wave and S-wave data in some continental areas (Figure Attenuation values were derived between and Hz using the P-wave quality factor,QP, the inverse of the internal friction.
By assuming constant attenuation along the seismic line we obtained. Attenuation of seismic waves in dry and saturated rocks: II. Mechanisms 0. Johnston*, M. Tokst)z*, and A. Timur$ Theoretical models based on several hypothesized attenuation mechanisms are discussed in relation to pub- lished data on the effects of pressure and fluid saturation on attenuation.
These mechanisms include friction. Chapter 1: Seismic Wave Attenuation 1 Chapter 1 Seismic Wave Attenuation In this chapter a brief introduction on seismic wave attenuation is given.
A discussion on coda waves and their properties is also included in this chapter. The back scattering model (Aki and Chouet, ) is also discussed, which is a way to model coda wave excitation. Seismic wave attenuation in carbonates L. Adam,1,2 M. Batzle,3 K. Lewallen,4 and K. van Wijk1 Received 23 June ; revised 7 December ; accepted 22 January ; published 25 June  The effect of pore fluids on seismic wave attenuation in carbonate rocks is important.
for the deterministic seismic hazard studies and to point out lateral variations of the seismic wave attenuation in the crust in the study region.
METHOD The modeling of the wave attenuation in the Vrancea region and the adjacent zones is approached in relation with the study of the seismic source by local seismogram inversion. The attenuation of upper crustal seismic waves that are refracted with a velocity of about 6 kilometers per second varies greatly among profiles in the area of the New Madrid seismic zone in the central Mississippi Valley.
The waves that have the strongest attenuation pass through the seismic trend along the axis of the Reelfoot rift in the area of the Blytheville arch. a primary wave, or compression wave; a seismic wave that causes particles of rock to move in a back-and-forth direction parallel to the direction in which the wave is traveling; they are the fastest seismic waves and can travel through solids, liquids, and gases.
As the waves move into shallower water, the angle between the wave crests and shoreline decreases and the crests become more parallel with the shoreline ____________ are coastal structures designed to keep tidal and harbor inlets from shifting location or filling with sand.
1 Introduction. Small-scale heterogeneities randomly distributed in the Earth generate incoherent wave trains called as coda waves, which arrive at the seismogram after direct P and S waves. The coda is thought to be due to scattering of direct waves from heterogeneities in the crust and mantle ().A number of models explain the generation of coda waves involving scattering of seismic waves.
Shear wave splitting measurements provide robust evidence of seismic anisotropy and can potentially be used to map out the presence of serpentine and its alignment in the mantle wedge. Figure 1 The range of possible Vp/Vs values and seismic velocities (Vp and Vs) for different proportions of serpentinization taking into account the anisotropy.Seismic waves reflect and refract from geologically distinct layers: the crust, the upper mantle, the lower mantle, and the core.
The speed of seismic waves depends on the elastic properties and density of the material through which they travel. Cold, stiff rocks allow seismic waves to travel quickly, whereas soft, molten rocks slow them down.A seismic metamaterial, is a metamaterial that is designed to counteract the adverse effects of seismic waves on artificial structures, which exist on or near the surface of the earth.
Current designs of seismic metamaterials utilize configurations of boreholes, trees or proposed underground resonators to act as a large scale material.
Experiments have observed both reflections and bandgap.