Comparison of field and laboratory seismic velocity anisotropy measurement (scaling factor)
| Autor: | Vilhelm, Jan |
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| Další autoři: |
Živor, Roman, 1958-
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| Jazyk: | angličtina |
| Předmět: | |
| Druh dokumentu: | Non-fiction |
| ISSN: | 1214-9705 |
| Abstrakt: | Abstract: P-wave velocity anisotropy of rocks is often investigated by laboratory methods. The extrapolation of the laboratory results to larger rock units requires comparison with direct field measurements. Physical properties of deep-originated rocks were performed on mantle-derived peridotite from the Ivrea zone (N orthwestern Italy). These rock s were exhumed by tectonic processes during collision orogeny up to the Earth’s surface. The direct surface seismic measurements of elastic waves velocity were realized by means of shallow seismic refraction method on the outcrop of peridotite. The measuring base was about 10 m long. Laboratory seismic anisotropy measurement was realized on rock samples from the same outcrop. The geographically oriented spherical samples with diameter 50 mm were radiated by elastic waves in 132 directions under confining stress from atmospheric level up to 200 MPa. Laboratory and field values of the anisotropy of seismic wave ve locities were compared and different scales of measurements were evaluated. The field measuremen ts used frequency about 1 kHz whereas the laboratory measur ement used 700 kHz radiation. Field measurements proved relatively high value of anisotropy P-wave propagation - 25%, while laboratory experiments only 1.5%. This difference is caused by different reason of anisotropy. Laboratory samples contain only microcraks, which represents nearly continuum with rega rd to ultrasound wave length (11 mm). Rock massif, however, contains beside mickrocraks also cracks with comparable size of applied seismic wave length (10 m). |
| Databáze: | Katalog Knihovny AV ČR |
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