Search

Coda-Q is used to estimate the attenuation and scattering properties of the Earth. So far focus has been on earthquake data at frequencies above 1 Hz, as the high noise level in the first and second microseismic peak, and possibly lower scattering coefficient, hinder stable measurements at lower frequencies. In this work, we measure and map coda-Q in the period bands 2.5-5 s, 5-10 s and 10-20 s in the greater Alpine region using noise cross-correlations between station pairs, based on data from permanent seismic stations and from the temporary AlpArray experiment. The observed coda-Q for short interstation distances is independent of azimuth so there is no indication of influence of the directivity of the incoming noise field on our measurements. In the 2.5-5 s and 5-10 s period bands, our measurements are self-consistent, and we observe stable geographic patterns of low and high coda-Q in the period bands 2.5-5 s and 5-10 s. In the period band 10-20 s, the dispersion of our measurements increases and geographic patterns become speculative. The coda-Q maps show that major features are observed with high resolution, with a very good geographical resolution of for example low coda-Q in the Po Plain. There is a sharp contrast between the Po Plain and the Alps and Apennines where coda-Q is high, with the exception a small area in the Swiss Alps which may be contaminated by the low coda-Q of the Po Plain. The coda of the correlations is too short to make independent measurements at different times within the coda, so we cannot distinguish between intrinsic and scattering Q. Measurements on more severely selected data sets and longer time-series result in identical geographical patterns but lower numerical values. Therefore, high coda-Q values may be overestimated, but the geographic distribution between high and low coda-Q areas is respected. Our results demonstrate that noise correlations are a promising tool for extending coda-Q measurements to frequencies lower than those analysed with earthquake data.

Multiferroics are materials where magnetic and ferroelectric order coexist. This opens a possibility of control of magnetic order by both magnetic and electric field which makes these materials potentially technologically important. CuO is quasi-one-dimensional S=1/2 system which is also multiferroic. CuO has three magnetically ordered phases: below T_N1=213 K it is collinear antiferromagnet (AFM1 phase), between T_N1 < T < T_N2 (T_N2 = 229.3 K) it is incommensurable spiral antiferromagnet(AFM2 phase) and also multiferroic, and between T_N2 < T < T_N3 (T_N3 = 230 K) it is incommensurable collinear antiferromagnet (AFM3 phase). Theoretical calculations have shown that CuO could be multiferroic at room temperature under high pressures. Multiferroic state of CuO is still widely studied and not completely understood. Anisotropic interactions, i.e. Dzayloshinskii-Moriya, is expected to play an important role in multiferroic phase [5]. Measuring magnetic anisotropy is thus crucial for understanding of mechanism responsible for multiferroicity in CuO. Macroscopic anisotropy of CuO is studied with torque magnetometry in low magnetic fields in the temperature range 4.2 K – 300 K. All three magnetic phase transitions are observed in torque

A review of the recent achievements of the innovative neo-deterministic approach for seismic hazard assessment through realistic earthquake scenarios has been performed. The procedure provides strong ground motion parameters for the purpose of earthquake engineering, based on the deterministic seismic wave propagation modelling at different scales— regional, national and metropolitan. The main advantage of this neo-deterministic procedure is the simultaneous treatment of the contribution of the earthquake source and seismic wave propagation media to the strong motion at the target site/region, as required by basic physical principles. The neo-deterministic seismic microzonation procedure has been successfully applied to numerous metropolitan areas all over the world in the framework of several international projects. In this study some examples focused on CEI region concerning both regional seismic hazard assessment and seismic microzonation of the selected metropolitan areas are shown.

A hybrid technique consisting of modal summation and subsequent ®nite differences modelling is applied for the computation of synthetic accelerograms along a pro®le crossing the city of Zagreb, the capital of Croatia. Assuming the source geometry is known, the ampli®cation properties of the underlying soil may be determined by comparison of synthetics and their response spectra computed for a bedrock model with the ones obtained under the assumption of a realistic laterally varying local model. The peak ground acceleration is larger by a factor of up to 3.5 than the value obtained for the bedrock model. The ampli®cation of the response spectra is most prominent for frequencies below 2 Hz, and increases sharply to the SW from the mapped fault running through the centre of the city. q 2002 Published by Elsevier Science Ltd.

We present an electron spin resonance (ESR) study of single-crystalline spin chain-system CuSe$_2$O$_5$ in the frequency range between 9 GHz and 450 GHz. In a wide temperature range above the N\'{e}el temperature $T_N=17$ K we observe strong and anisotropic frequency dependence of a resonance linewidth. Although sizeable interchain interaction $J_{IC}\approx 0.1 J$ ($J$ is the intrachain interaction) is present in this system, the ESR results agree well with the Oshikawa-Affleck theory for one-dimensional $S=1/2$ Heisenberg antiferromagnet. This theory is used to extract the anisotropies present in CuSe$_2$O$_5$. We find that the symmetric anisotropic exchange $J_c=(0.04 \pm 0.01) \:J$ and the antisymmetric Dzyaloshinskii-Moriya (DM) interaction $D=(0.05\pm 0.01)\:J$ are very similar in size in this system. Staggered-field susceptibility induced by the presence of the DM interaction is witnessed in the macroscopic susceptibility anisotropy., Comment: 8 pages, 7 figures, 2 tables, published in Phys. Rev. B

Report submitted to the International Association of Seismology and Physics of the Earth’s Interior of the International Union of Geodesy and Geophysics

A hybrid technique consisting of modal summation and subsequent modelling is applied for the computation of synthetic accelerograms along a profile crossing the city of Zagreb, the capital of Croatia.

xx

Features of the earthquake sequence which occurred in the region of the Central Adriatic sea during January and February 1986 have been analysed.