Uncertainties in the estimation of earthquake magnitudes in Greece   总被引：1，自引：0，他引：1  

B.C. Papazachos  V.G. Karakostas  A.A. Kiratzi  B.N. Margaris  C.B. Papazachos  E.M. Scordilis 《Journal of Seismology》2002,6(4):557-570

Instrumental magnitudes in Greece have been reported as: a) Mmagnitudes based on the records of the Wiechert or Mainka seismographs,b) M_LGR magnitudes based on the records of the Wood-Anderson(WA) seismographs (T_o = 0.8 sec, V_effective 1000) or othershort period seismographs calibrated against WA records and,c) M_LSM magnitudes based on strong motion records(accelerograms). Comparison of such magnitudes with momentmagnitudes, M_w, for 329 earthquakes, with epicenters in thebroader Aegean area, performed in this study, showedthat M, M_LGR+0.5 and M_LSM are practically equalto M_w, with a small overall standard error ( = 0.23).Therefore, equivalent moment magnitudes, M_w ^*,estimated from these magnitudes and reported in the catalogues of theGeophysical Laboratory of the University of Thessaloniki are equal tomoment magnitudes for all practical purposes with reasonable uncertainties.It has been further shown that surface wave magnitudes, M_s,for M_s <6.0, can be also transferred into momentmagnitudes, M_w ^*, but the larger uncertaintiesencountered make its use rather problematic.  相似文献   

Single crystal Raman spectrum of uvarovite, Ca3Cr2Si3O12     

Anastasia Chopelas 《Physics and Chemistry of Minerals》2005,32(8-9):525-530

Single-crystal Raman spectra of synthetic end-member uvarovite (Ca₃Cr₂Si₃O₁₂) and of a binary solution (59% uvarovite, 41% andradite) have been measured using single crystal techniques. For each of these garnets, 22 and 21 of the 25 Raman modes were located, respectively. The spectra for uvarovite garnets closely resemble those of the other calcic garnets, grossular, and andradite. The modes for uvarovites do not fit into the same trends as established by the other five anhydrous end-member garnets: the high energy “internal” Si–O modes do not depend on lattice constant in uvarovite. They exceed frequencies for both andradite and grossular. This is likely due to the large crystal field stabilization energy of trivalent chromium. The low energy and midrange modes are at similar frequencies to the other calcic garnets.  相似文献   

Modeling the thermodynamic parameters of six endmember garnets at ambient and high pressures from vibrational data     

Anastasia Chopelas 《Physics and Chemistry of Minerals》2006,33(6):363-376

Raman and infrared spectroscopic data at ambient and high pressures were used to compute the lattice contribution to the heat capacities and entropies of six endmember garnets: pyrope, almandine, spessartine, grossular, andradite and uvarovite. Electronic, configurational and magnetic contributions are obtained from comparing available calorimetric data to the computed lattice contributions. For garnets with entropy in excess of the computed lattice contribution, the overwhelming majority is found in the subambient temperature regime. At room temperature, the non-lattice entropy is approximately 11.5 J/mol-K for pyrope, 49 J/mol-K for almandine, and 19 J/mol-K for andradite. The non-lattice entropy for pyrope and some for almandine cannot be accounted for by magnetic or electronic contributions and is likely to be configurational in nature. Estimates of low temperature non-lattice entropies for both spessartine and uvarovite are made in absence of calorimetric measurements and are based on low temperature calorimetry of other minerals containing the Mn²⁺ and Cr³⁺ cations as well as on solid solution garnets containing these cations. The estimate for uvarovite non-lattice entropy is approximately 18 J/mol-K, while for spessartine, approximately 45 J/mol-K. Neither of these cations is expected to provide electronic contributions to the entropy. For both iron-bearing garnets, a small electronic or magnetic entropy contribution continues above ambient temperatures. High pressure data on pyrope, grossular and andradite permit calculation of the thermodynamic parameters at high pressures, which are important for computation of processes in the Earth’s mantle. Thermal expansion coefficients of these materials were found to be 1.6, 1.5, 1.6×10⁻⁵ K⁻¹ at 298 K, respectively, using a Maxwell relation. These closely match the literature values at ambient conditions.  相似文献