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1.
Characterising youthful strike-slip fault systems within transtensional regimes is often complicated by the presence of tectonic geomorphic features produced by normal faulting associated with oblique extension. The Petersen Mountain fault in the northern Walker Lane tectonic province exhibits evidence of both normal and strike-slip faulting. We present the results of geologic and geomorphic mapping, and palaeoseismic trenching that characterise the fault's style and sense of deformation. The fault consists of two major traces. The western trace displaces colluvial, landslide, and middle to late Pleistocene alluvial fans and is associated with aligned range front saddles, linear drainages, and oversteepened range front slopes. The eastern trace is associated with a low linear bedrock ridge, a narrow graben, right deflected stream channels, and scarps in late Pleistocene alluvial fan deposits. A trench on the eastern trace of the fault exposed a clear juxtaposition of disintegrated granodiorite bedrock against sand and boulder alluvial fan deposits across a steeply east-dipping fault. The stratigraphic evidence supports the occurrence of at least one late Pleistocene earthquake with a component of lateral displacement. As such, the Petersen Mountain fault accommodates part of the ~7 mm/yr of dextral shear distributed across the northern Walker Lane.  相似文献   
2.
The thermal dehydration process of fibroferrite, FeOH(SO4)·5H2O, a secondary iron-bearing hydrous sulfate, was investigated by in situ high-temperature synchrotron X-ray powder diffraction (HT-XRPD), in situ high-temperature Fourier transform infrared spectroscopy (HT-FTIR) and thermal analysis (TGA-DTA) combined with evolved gas mass spectrometry. The data analysis allowed the determination of the stability fields and the reaction paths for this mineral as well as characterization of its high-temperature products. Five main endothermic peaks are observed in the DTA curve collected from room T up to 800 °C. Mass spectrometry of gases evolved during thermogravimetric analysis confirms that the first four mass loss steps are due to water emission, while the fifth is due to a dehydroxylation process; the final step is due to the decomposition of the remaining sulfate ion. The temperature behavior of the different phases occurring during the heating process was analyzed, and the induced structural changes are discussed. In particular, the crystal structure of a new phase, FeOH(SO4)·4H2O, appearing at about 80 °C due to release of one interstitial H2O molecule, was solved by ab initio real-space and reciprocal-space methods. This study contributes to further understanding of the dehydration mechanism and thermal stability of secondary sulfate minerals.  相似文献   
3.
Multipath remains one of the major challenges in Global Navigation Satellite System (GNSS) positioning because it is considered the dominant source of ranging errors, which can be classified into specular and diffuse types. We present a new method using wavelets to extract the pseudorange multipath in the time domain and breaking it down into the two components. The main idea is an analysis-reconstruction approach based on application of both continuous wavelet transform (CWT) and discrete wavelet transform (DWT). The proposed procedure involves the use of L1 code-minus-carrier (CMC) observable where higher-frequency terms are isolated as residuals. CMC residuals are analyzed by applying the CWT, and we propose the scalogram as a technique for discerning time–frequency variations of the multipath signal. Unlike Fourier transform, the potential of the CWT scalogram for examining the non-stationary and multifrequency nature of the multipath is confirmed as it simultaneously allows fine detection and time localization of the most representative frequencies of the signal. This interpretation of the CWT scalogram is relevant when choosing the levels of reconstruction with DWT, allowing accurate time domain extraction of both the specular and diffuse multipath. The performance and robustness of the method and its boundary applicability are assessed. The experiment was carried out using a receiver of Campania GNSS Network. The results are given in which specular multipath error is achieved using DWT level 7 approximation component and diffuse multipath error is achieved using DWT level 6 denoised detail component.  相似文献   
4.
We use the angular power spectrum of the cosmic microwave background, measured during the North American test flight of the Boomerang experiment, to constrain the geometry of the universe. Within the class of cold dark matter models, we find that the overall fractional energy density of the universe Omega is constrained to be 0.85相似文献   
5.
Rb/Sr whole rock as well as K/Ar whole rock and mineral age determinations have been carried out on drill core samples obtained from the crystalline basement underlying the Amazonas and Maranhão Basins in Brazil. The data confirm the existence of an ancient basement under the Upper and Middle Amazonas Basin. The primary age of the granitic rocks is estimated at about 1560 Ma which correlates with recent age data obtained on granitic rocks on both sides of the Amazonas syneclise. In some areas the K/Ar ages show a decrease probably due to the effect of the Nickerie thermal episode described previously in the Guayana Shield.In the basement of the interconnected Lower Amazonas and Maranhão Basins Late Precambrian (Caririan) metamorphism and igneous activity seems to have been pervasive. The data allow the continuation of the Brazilian age province known in northeastern Brazil under the Maranhão Basin, linking this province to the Brasilia-Paraguay orogenic belt of similar age.  相似文献   
6.
7.
Photometric data on 17 binary near-Earth asteroids (15 of them are certain detections, two are probables) were analysed and characteristic properties of the near-Earth asteroid (NEA) binary population were inferred. We have found that binary systems with a secondary-to-primary mean diameter ratio Ds/Dp?0.18 concentrate among NEAs smaller than 2 km in diameter; the abundance of such binaries decreases significantly among larger NEAs. Secondaries show an upper size limit of Ds=0.5-1 km. Systems with Ds/Dp?0.5 are abundant but larger satellites are significantly less common. Primaries have spheroidal shapes and they rotate rapidly, with periods concentrating between 2.2 to 2.8 h and with a tail of the distribution up to ∼4 h. The fast rotators are close to the critical spin for rubble piles with bulk densities about 2 g/cm3. Orbital periods show an apparent cut-off at Porb∼11 h; closer systems with shorter orbital periods have not been discovered, which is consistent with the Roche limit for strengthless bodies. Secondaries are more elongated on average than primaries. Most, but not all, of their rotations appear to be synchronized with the orbital motion; nonsynchronous secondary rotations may occur especially among wider systems with Porb>20 h. The specific total angular momentum of most of the binary systems is similar to within ±20% and close to the angular momentum of a sphere with the same total mass and density, rotating at the disruption limit; this suggests that the binaries were created by mechanism(s) related to rotation near the critical limit and that they neither gained nor lost significant amounts of angular momentum during or since formation. A comparison with six small asynchronous binaries detected in the main belt of asteroids suggests that the population extends beyond the region of terrestrial planets, but with characteristics shifted to larger sizes and longer periods. The estimated mean proportion of binaries with Ds/Dp?0.18 among NEAs larger than 0.3 km is 15±4%. Among fastest rotating NEAs larger than 0.3 km with periods between 2.2 and 2.8 h, the mean proportion of such binaries is (66+10−12)%.  相似文献   
8.
The South-American continent is constituted of three major geologic–geotectonic entities: the homonym platform (consolidated at the end of the Cambrian), the Andean chain (essentially Meso-Cenozoic) and the Patagonian terrains, affected by tectonism and magmatism through almost all of the Phanerozoic. The platform is constituted by a series of cratonic nuclei (pre-Tonian, fragments of the Rodinia fission) surrounded by a complex fabric of Neoproterozoic structural provinces.  相似文献   
9.
The Mako bimodal volcanic belt of the Kédougou–Kéniéba inlier is composed of volcanic basalts and peridotites interbedded by quartzites and limestones intruded by different generations of granitoïds. The early volcanic episode of the belt is constituted of submarine basalts with peridotite similar to those of the oceanic abyssal plains. It is intruded by the Badon Kakadian TTG?granitic batholite dated around 2200 Ma. The second volcanic phase is constituted of basaltic, andesitic, and felsitic flows exhibit structures of aerial volcanic rocks. It is intruded by granites dated between 2160 and 2070 Ma. The general pattern of trace element variation of submarine volcanic rocks is consistent with those of basalts from oceanic plateaus which are the modern equivalent of the Archean greenstones belts. The Nd and Sr isotopic systematics typical of juvenile material indicates that the source of these igneous rocks is derived from a depleted mantle source. These results are consistent with the idea of a major accretion within the West African Craton occurring at about 2.1 Ga and corresponding to an important process of mantle–oceanic lithosphere differentiation.  相似文献   
10.
Studies on persistence are important for the clarification of statistical properties of the analyzed time series and for understanding the dynamics of the systems which create these series. In climatology, the analysis of the autocorrelation function has been the main tool to investigate the persistence of a time series. In this paper, we propose to use a more sophisticated econometric instrument. Using this tool, we obtain an estimate of the persistence in global land and ocean and hemispheric temperature time series.  相似文献   
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