Multiple scattering ofSH waves in 2-D media with many cavities

Voids and Rock Friction at Subseismic Slip Velocity

“…The theoretical consideration by Hudson (1981) predicted that inverse of quality factor (Q -1 ) is proportional to (ak) 3 in 3-D isotropic medium when cracks (or cavities) are distributed randomly and ak ( 1. Then, the numerical experiments using 2-D SH model (Yamashita 1990;Benites et al 1992;Kelner et al 1999) and 2-D P-SV model (Kawahara and Yamashita 1992) confirmed this feature. Under this condition, it is also known that wave velocity does not significantly change due to scattering, which is consistent with our experiments (Fig.…”

“…This difference might be related to the temporal variation of the thickness of the layer, which we could not monitor accurately at this moment. It should also be noted that the void does not have to be empty inside but can be filled with liquid material (Kikuchi 1981;Yamashita 1990;Benites et al 1992;Kelner et al 1999;Kawahara et al 2010). In this case, the theoretical prediction of the absolute values of Q -1 could be different but the general tendency with respect to ak does not change.…”

“…To interpret the above results, we referred to a theoretical investigation of scattering waves caused by cavities (Yamashita 1990;Benites et al 1992;Kelner et al 1999;Kawahara et al 2010). In the scattering theory, ak defines the type of scattering, where a is the characteristic size of scatterers and k is wavenumber (= 2p/k, where k is wavelength) (e.g., Aki 1973).…”

The seismology of geothermal regimes. Final report

“…This is our first attempt to use wave-theoretical approach for understanding the effect of Using the indirect boundary integral scheme for multiple scattering of seismic waves developed by Benites et al (1992), we compute SH-wave seismograms and measure frequencydependent characteristic of coda Q in 2-D random media with a flat layer over a half space. Many circular cavities are randomly distributed in both the upper layer and the half-space, down to a certain depth (called the lower layer), simulating the upper and lower crusts, as shown in Figure 1.…”

“…NumenLa modeling of SH wave seismograms in media whose material properties are prescribed by a random distribution of many perfectly elastic cavities and by intrinsic absorption of seismic energy (anelasticity) demonstrates that the main characteristics of the coda waves, namely amplitude decay and duration, are well described by singly scattered waves in an elastic media rather than by multiply scattered waves in either elastic of an elastic media. We use the Boundary Integral scheme developed by BENITES et al (1992) to compute the complete wave field and measure the values of the direct wave Q and coda waves Q in a wide range of frequencies, determining the spatial decay of the direct wave log-amplitude relation and the temporal decay of the coda envelope, respectively. The effects of both intrinsic absorption and pure scattering on the overall attenuation can be quantified separately by computing the Q values for corresponding models with (an elastic) and without (elastic) absorption.…”