Diversity of the 2014 Iquique’s foreshocks and aftershocks: clues about the complex rupture process of a Mw 8.1 earthquake     

Sergio León-Ríos  Sergio Ruiz  Andrei Maksymowicz  Felipe Leyton  Amaya Fuenzalida  Raúl Madariaga 《Journal of Seismology》2016,20(4):1059-1073

We study the foreshocks and aftershocks of the 1 April 2014 Iquique earthquake of Mw 8.1. Most of these events were recorded by a large digital seismic network that included the Northern Chile permanent network and up to 26 temporary broadband digital stations. We relocated and computed moment tensors for 151 events of magnitude Mw?≥?4.5. Most of the foreshocks and aftershocks of the Iquique earthquake are distributed to the southwest of the rupture zone. These events are located in a band of about 50 km from the trench, an area where few earthquakes occur elsewhere in Chile. Another important group of aftershocks is located above the plate interface, similar to those observed during the foreshock sequence. The depths of these events were constrained by regional moment tensor (RMT) solutions obtained using the records of the dense broad band network. The majority of the foreshocks and aftershocks were associated to the interplate contact, with dip and strike angles in good agreement with the characteristics of horst and graben structures (>2000 m offset) typical of the oceanic Nazca Plate at the trench and in the outer rise region. We propose that the spatial distribution of foreshocks and aftershocks, and its seismological characteristics were strongly controlled by the rheological and tectonics conditions of the extreme erosive margin of Northern Chile.  相似文献   

Removal of Arsenic by Alumina: Effects of Material Size,Additives, and Water Contaminants          下载免费PDF全文

Victor K. Tchieda  Emilio D'Amato  Agostina Chiavola  Mariapaola Parisi  Angelo Chianese  Mohamed Amamra  Andrei Kanaev 《洁净——土壤、空气、水》2016,44(5):496-505

  相似文献   

Digital filtering as a tool for the study of some flysch deposits from the East Carpathians (Romania)     

Radu Botezatu  Mircea Dumitriu 《Mathematical Geology》1972,4(2):103-113

Results from the application of digital filtering (simple and weighted averaging) to the analysis of sedimentary series are given. Two flysch sequences from the East Carpathians (Upper Eocene, Damacua Valley; and Lower Cretaceous, Sbrancani Valley) were studied. Individual components, affecting the conditions of deposition, were separated, and establishment of the geological significance of the components separated by digital filtering was investigated.  相似文献   

Traveltime computation by wavefront-orientated ray tracing   总被引：1，自引：0，他引：1  

Radu Coman  Dirk Gajewski 《Geophysical Prospecting》2005,53(1):23-36

For multivalued traveltime computation on dense grids, we propose a wavefront‐orientated ray‐tracing (WRT) technique. At the source, we start with a few rays which are propagated stepwise through a smooth two‐dimensional (2D) velocity model. The ray field is examined at wavefronts and a new ray might be inserted between two adjacent rays if one of the following criteria is satisfied: (1) the distance between the two rays is larger than a predefined threshold; (2) the difference in wavefront curvature between the rays is larger than a predefined threshold; (3) the adjacent rays intersect. The last two criteria may lead to oversampling by rays in caustic regions. To avoid this oversampling, we do not insert a ray if the distance between adjacent rays is smaller than a predefined threshold. We insert the new ray by tracing it from the source. This approach leads to an improved accuracy compared with the insertion of a new ray by interpolation, which is the method usually applied in wavefront construction. The traveltimes computed along the rays are used for the estimation of traveltimes on a rectangular grid. This estimation is carried out within a region bounded by adjacent wavefronts and rays. As for the insertion criterion, we consider the wavefront curvature and extrapolate the traveltimes, up to the second order, from the intersection points between rays and wavefronts to a gridpoint. The extrapolated values are weighted with respect to the distances to wavefronts and rays. Because dynamic ray tracing is not applied, we approximate the wavefront curvature at a given point using the slowness vector at this point and an adjacent point on the same wavefront. The efficiency of the WRT technique is strongly dependent on the input parameters which control the wavefront and ray densities. On the basis of traveltimes computed in a smoothed Marmousi model, we analyse these dependences and suggest some rules for a correct choice of input parameters. With suitable input parameters, the WRT technique allows an accurate traveltime computation using a small number of rays and wavefronts.  相似文献   

A framework for modeling uncertainty in regional climate change     

Erwan Monier  Xiang Gao  Jeffery R. Scott  Andrei P. Sokolov  C. Adam Schlosser 《Climatic change》2015,131(1):51-66

  相似文献   

Coherent Structures at a Forest Edge: Properties, Coupling and Impact of Secondary Circulations   总被引：1，自引：1，他引：0  

Fabian Eder  Andrei Serafimovich  Thomas Foken 《Boundary-Layer Meteorology》2013,148(2):285-308

Little is known about the influence of coherent structures on the exchange process, mainly in the case of forest edges. Thus, in the framework of the ExchanGE processes in mountainous Regions (EGER) project, measurements of atmospheric turbulence were taken at different heights between a forest and an adjacent clear cutting using sonic anemometers and high-frequency optical gas analyzers. From these turbulence data, dominant coherent structures were extracted using an already existing wavelet methodology, which was developed for homogeneous forest canopies. The aim of this study is to highlight differences in properties of coherent structures between a forest and a clear cutting. Distinct features of coherent exchange at the forest edge are presented and a careful investigation of vertical and horizontal coupling by coherent structures around the surface heterogeneity is made. Within the forest, coherent structures are less frequent but possess larger time scales, indicating that only the largest coherent motions can penetrate through the forest canopy. At the forest edge, there is no crown layer that can hinder the vertical exchange of coherent structures, because these exhibit similar time scales at all heights. In contradiction to that, no improved vertical coupling was detected at the forest edge. This is mainly because the structures captured by the applied routine contribute less to total turbulent fluxes at the edge than within the forest. Thus, coherent structures with time scales between 10 and 40 s are not the dominant exchange mechanism at the forest edge. With respect to the horizontal direction, a consistent picture of coherent transport could be derived: along the forest edge there is mainly good coupling by coherent structures, whereas perpendicular to the forest edge there is mainly decoupling. Finally, it was found that there is a systematic modulation of coherent structures directly at the forest edge: strong ejection motions appear in all time series during the daytime, whereas strong sweeps dominate at night. An effect of wind direction relative to the forest edge is excluded. Consequently, it is hypothesized that this might be an indication of a quasi-stationary secondary circulation above the clear cutting that develops due to differences in surface temperature and roughness. Such circulations might be a relevant turbulent transport mechanism for ecosystem-atmosphere exchange in heterogeneous landscapes.  相似文献   

Quantitative modelling of seismic site amplification in an earthquake-endangered capital city: Bucharest,Romania     

Andrei Bala 《Natural Hazards》2014,72(3):1429-1445

Bucharest, the capital city of Romania, with more than 2 million inhabitants, is considered as a natural disaster hotspot by a recent global study of the World Bank and the Columbia University (Dilley M et al. Natural disaster hotspots: a global risk analysis. International Bank for Reconstruction and Development/The World Bank and Columbia University, Washington, DC in 2005). Therefore, it is classified as the second metropolis in Europe, after Istanbul, subjected to important losses in the case of a destructive Vrancea earthquake with moment magnitude greater than seven. Four major earthquakes with moment magnitudes between 6.9 and 7.7 hit Bucharest in the last 68 years. The most recent destructive earthquake on March 4, 1977, with a moment magnitude of 7.4, caused about 1,500 casualties in the capital alone. All disastrous intermediate-depth earthquakes are generated within a small epicentral area—the Vrancea seismogenic region—about 150 km northeast of Bucharest. Thick unconsolidated sedimentary layers below Bucharest amplify the arriving seismic waves causing severe destruction. Ten 50-m-deep boreholes are drilled in the metropolitan area of Bucharest in order to obtain a unique, homogeneous dataset of seismic, soil-mechanic and elasto-dynamic parameters. Cores for dynamic tests were extracted, and vertical seismic profiles were performed to obtain an updated site amplification model related to earthquakes waves. The boreholes are placed near former or existing seismic station sites to allow a direct comparison and calibration of the borehole data with previous seismological measurements. A database containing geological characteristics for each sedimentary layer, geotechnical parameters measured on rock samples, P- and S wave velocity and density for each sedimentary layer is set up, as a result of previous papers with this subject. Direct data obtained by the geophysical methods in the new boreholes drilled in Bucharest City, as well as from laboratory measurements, are used as input data in the program SHAKE2000. Results are obtained in the form of spectral acceleration response, and peak acceleration in depth is computed for every site in which in situ measurements were performed. The acceleration response spectra correspond to the shear-wave amplifications due to the models of sedimentary layers down to (a) 50 m depth; (b) 70 m depth; and (c) 100 m depth. A comparison of the acceleration response spectra obtained by modelling at surface with a real signal recorded at surface is obtained in three sites, as test sites for the three depths considered, in order to calibrate the results obtained by equivalent linear method of the seismic site response.  相似文献   

Dissociation constants and speciation in aqueous Li₂SO₄ and K₂SO₄ from measurements of electrical conductance to 673 K and 29 MPa     

Andrei V. Sharygin  Robert H. Wood  Victor N. Balashov 《Geochimica et cosmochimica acta》2006,70(20):5169-5182

The electrical conductivities of aqueous solutions of Li₂SO₄ and K₂SO₄ have been measured at 523-673 K at 20-29 MPa in dilute solutions for molalities up to 2 × 10⁻² mol kg⁻¹. These conductivities have been fitted to the conductance equation of Turq, Blum, Bernard, and Kunz with a consensus mixing rule and mean spherical approximation activity coefficients. In the temperature interval 523-653 K, where the dielectric constant, ε, is greater than 14, the electrical conductance data can be fitted by a solution model which includes ion association to form , , and , where M is Li or K. The adjustable parameters of this model are the first and second dissociation constants of the M₂SO₄. For the 673 K and 300 kg m⁻³ state point where the Coulomb interactions are the strongest (dielectric constant, ε = 5), models with more extensive association give good fits to the data. In the case of the Li₂SO₄ model, including the multi-ion associate, , gave an extremely good fit to the conductance data.  相似文献   

Impact of spatial correlation of ground motions on seismic damage for residential buildings in Bucharest,Romania     

Pavel  Florin  Vacareanu  Radu  Calotescu  Ileana  Sandulescu  Ana-Maria  Arion  Cristian  Neagu  Cristian 《Natural Hazards》2017,87(2):1167-1187

Natural Hazards - This paper focuses on the investigation of seismic risk for residential buildings situated in Bucharest, the capital city of Romania. With a population of nearly 2 million...  相似文献   

The Late Pleistocene megafauna of the Chulym River basin,southeastern West Siberian Plain: chronology and stable isotope composition     

Yaroslav V. Kuzmin  Andrei V. Shpansky 《第四纪科学杂志》2023,38(1):2-7

New data were obtained for the Chulym River basin in the southeastern part of the West Siberian Plain, one of the understudied parts of Siberia in terms of age and composition of carbon and nitrogen stable isotopes for Late Pleistocene megafauna. The ¹⁴C dates from the Sergeevo outcrop, the most complete section of Late Quaternary deposits in the region, are mostly greater than ~30 550 bp. Other localities yielded ¹⁴C values in the range from >44 500 to ~19 300 bp. The finite date of ~42 270 bp for the Khozarian steppe elephant (Mammuthus trogontherii chosaricus) from Asino is intriguing because previously it was not detected in the Late Pleistocene of Siberia after the last interglacial (Marine Isotope Stage 5e), ~115 000–130 000 years ago. Stable isotope data show both similarities and differences compared to the pre-Last Glacial Maximum megafaunal species in other parts of Siberia.  相似文献