Seismic attenuation in partially saturated dime-shaped cracks

Citation
H. Schutt et al., Seismic attenuation in partially saturated dime-shaped cracks, PUR A GEOPH, 157(3), 2000, pp. 435-448
Citations number
7
Categorie Soggetti
Earth Sciences
Journal title
PURE AND APPLIED GEOPHYSICS
ISSN journal
00334553 → ACNP
Volume
157
Issue
3
Year of publication
2000
Pages
435 - 448
Database
ISI
SICI code
0033-4553(200003)157:3<435:SAIPSD>2.0.ZU;2-A
Abstract
We have examined the effect of surface contamination on the attenuation and stiffness of compressional seismic waves in artificial cylindrical glass c racks that are partially saturated with water. The compression of the gap p erpendicularly to its plane reduces the gap volume and forces the water to redistribute within the gap (conservation of volume of an incompressible li quid). On clean surfaces, the water can flow without significant resistance across the glass. This leads to a very low and almost constant attenuation over a wide frequency range (approx. 3 mHz to 10 Hz), while the sample sti ffness is constant. In the case of propanol contaminated surfaces, both the attenuation and the stiffness are considerably higher than in the clean ca se, and display a considerable frequency dependence. Both effects can be ex plained with the Restricted Meniscus Motion Model. In this model, the redis tribution of the liquid in the gap first leads to a change (increase) of th e contact angle. The change of the meniscus curvature results in an increas e of the pressure in the liquid and thus to a stiffening of the sample. Whe n the resistive force, that prevents the contact line from sliding along th e surface, is finally overcome, the contact line starts moving across the c ontaminated surface. The motion against the resistive force dissipates ener gy and increases the attenuation. The calculated data are in good agreement for both the clean and the contaminated case; the model parameters fall in the range that was established by independent experiments (e.g. WAITE et a l., 1997).