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31.
Ambiguous Moment Tensors and Radiation Patterns in Anisotropic Media with Applications to the Modeling of Earthquake Mechanisms in W-Bohemia 总被引:3,自引:0,他引:3
Anisotropic material properties are usually neglected during inversions for source parameters of earthquakes. In general anisotropic media, however, moment tensors for pure-shear sources can exhibit significant non-double-couple components. Such effects may be erroneously interpreted as an indication for volumetric changes at the source. Here we investigate effects of anisotropy on seismic moment tensors and radiation patterns for pure-shear and tensile-type sources. Anisotropy can significantly influence the interpretation of the source mechanisms. For example, the orientation of the slip within the fault plane may affect the total seismic moment. Also, moment tensors due to pure-shear and tensile faulting can have similar characteristics depending on the orientation of the elastic tensor. Furthermore, the tensile nature of an earthquake can be obscured by near-source anisotropic properties. As an application, we consider effects of inhomogeneous anisotropic properties on the seismic moment tensor and the radiation patterns of a selected type of micro-earthquakes observed in W-Bohemia. The combined effects of near-source and along-path anisotropy cause characteristic amplitude distortions of the P, S1 and S2 waves. However, the modeling suggests that neither homogeneous nor inhomogeneous anisotropic properties alone can explain the observed large non-double-couple components.The results also indicate that a correct analysis of the source mechanism, in principle, is achievable by application of anisotropic moment tensor inversion. 相似文献
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Average recurrence intervals of strong earthquakes and potential risky segments along the Taiyuan-Linfen portion of the Shanxi graben system 总被引:1,自引:0,他引:1
Introduction In AD 1303, the great Hongtong, Shanxi, earthquake of magnitude 8 caused a very serious disaster, which killed over one hundred thousands people at least (Department of Earthquake Dis- *aster Prevention, State Seismological Bureau, 1995). On the occasion of commemorating this ca-tastrophe having occurred for 700 years, we have important problems that need to be answered: How long the average recurrence interval of the grea… 相似文献
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Jan
ílený 《Tectonophysics》2004,383(3-4):133-147
The retrieval of earthquake moment tensor (MT) requires the response of the medium, in which seismic waves travel from the hypocenter to the stations, to be known. In inverting long-period (LP) seismic data (teleseismic and LP regional records), a gross earth model is sufficient; with decreasing periods, a more detailed model is needed. This is the case when waveforms of weak earthquakes at regional distances are to be inverted. Regional moment tensors (RMTs) of mostly Mediterranean earthquakes are determined on a routine basis by the Swiss Seismological Survey (SED) by using averaged models of the earth's crust. By inverting broad-band records of the Mw=4.8 earthquake near Udine, N Italy, on Feb. 14, 2002, we tested the sensitivity of the MT solution with respect to possible errors in the earth model used and in the location of the hypocenter depth. We perturbed the P and S velocities and the thickness in the 1-D earth model in the range from 3% to 30% of the parameter values and constructed estimates of confidence regions of the MT and error bars of the source time function (STF) and scalar moment in three frequency bands. Similarly, these error characteristics were determined assuming a mislocation in the hypocenter depth. We found that, in the band of periods from 25 to 50 s, the mechanism is resolved well (at the confidence level 95% at least) up to an earth model uncertainty of 30%, in the passband 10–25 s up to about 10%, but it is undetermined completely at periods of 5–10 s. An error in hypocenter depth of as much as double the value reported by the location procedure does not destroy the resolution of the mechanism at periods above 10 s. In the RMT catalog of the SED, earthquakes of Mw greater than about 3.5 are processed at periods above 30 s; thus, the solutions for these events are robust with respect to a possible uncertainty in the earth model used. Mechanisms of weaker earthquakes, retrieved from short periods, should be interpreted with caution. 相似文献
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Introduction The acceleration response spectrum and peak ground acceleration are the necessary and im-portant parameters in earthquake-resistant design at present. They are still active research field. With the increase of digital high accurate strong motion observation data, especially the earth-quakes of Loma Prieta (M=7.0) in 1989; Landers (M=7.3) in 1992; Big Bear (M=6.4) in 1994 and Northridge (M=6.7) in 1994 in USA; Kozani (M=6.6) earthquake and afteshocks in 1995 in Greece; Dinar… 相似文献
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