Natural Hazards - Inner Mongolia, located in the northern China, is a natural disaster-prone region. This study is dedicated to making a comprehensive and quantitative analysis of the... 相似文献
In the years 2001–2003, we accomplished the experimental phase of the project CEMES by collecting long-period magnetotelluric
data at positions of eleven permanent geomagnetic observatories situated within few hundreds kilometers along the south-west
margin of the East European Craton. Five teams were engaged in estimating independently the magnetotelluric responses by using
different data processing procedures. The conductance distributions at the depths of the upper mantle have been derived individually
beneath each observatory. By averaging the individual cross-sections, we have designed the final model of the geoelectrical
structure of the upper mantle beneath the CEMES region. The results indicate systematic trends in the deep electrical structure
of the two European tectonic plates and give evidence that the electrical structure of the upper mantle differs between the
East European Craton and the Phanerozoic plate of west Europe, with a separating transition zone that generally coincides
with the Trans-European Suture Zone. 相似文献
A rectangular flume with dimensions of length 180 cm, height 60 cm and width 20 cm was used to observe the entry angle (i.e. angle between the interface and the centerline of the slot) of a two-layer flow withdrawal by a line sink. Saline water was used to form a bottom density current and red dye was applied. Based on the experimental data, one could see that the dimensionless discharge is more influential on the entry angle than the depth-averaged concentration of the lower-layer flow. Thus, the influence of concentration on experimental conditions is negligible for evaluation of the entry angle. The absolute values of entry angles increase with the absolute values of the dimensionless discharge. Almost all absolute values of the theoretical angle are bigger than that of the measured angle with a deviation bounded within 0.15 rad. The influence on the entry angle from the dimensionless discharge is symmetrical between the drawdown curve (interface above the slot) and the suck-up curve (interface below the slot). This phenomenon can be seen from a simplified form of a theoretical formula. 相似文献
This paper summarizes the available geological and geophysical material for faults as regards their role in the seismic process. The entirety of the geological and geophysical evidence is used to reveal hidden faults, which are important in influencing the spatial distribution of earthquakes, and to produce a map of the major earthquake-generating faults and lineaments in the Russian northeast. As well as the occurrence of earthquakes at known faults that have surface expression, we find that seismicity tends to occur at the hidden faults and lineaments we have identified, as well as at intersections of faults. We made a quantitative assessment of the relationship of seismicity to tectonic fragmentation of the crust, correlating the density and discordance measure for faults to indicators of seismic activity (rate and energy release of earthquakes per unit area) for the southeast flank of the Okhotsk-Lena seismic region. The results obtained in this study revealed some features in the spatial distribution of earthquakes occurring on land in the Okhotsk-Lena seismic region: the maximum level of seismic activity occurs in areas with moderate values of the discordance measure for faults (12 < ‖D‖ ≤ 18) as identified from gravity data and in zones of increased horizontal gradients of the lines of equal discordance. At these locations, the greatest probability of earthquake occurrence for events of energy class K ≥ 12 corresponds to moderate values of the density of faults visible at the surface (0.12 < τ ≤ 0.16 km?1). 相似文献
The Xiangshuyuan Formation (middle Rhuddanian to middle Aeronian stages of the Llandovery Series, lower Silurian) records a shelly fauna representing recovery after the end-Ordovician mass extinction in a well-oxygenated shallow carbonate platform of the Upper Yangtze region, South China Block. Carbon isotope stratigraphy is documented from limestone sequences of the formation at the Qiankou section, northeast Guizhou. The early Aeronian carbon isotope excursion (EACIE, with an amplitude of about 2 ‰ and peak value of 2.44 ‰) is identified in the middle and upper parts of the formation (Ozarkodina obesa conodont Biozone). The EACIE recorded herein correlates well with those in Baltica, Canada, and the United States; together with its records from organic material (δ13Corg) the data verify that the EACIE is a global event. The beginning of the EACIE can be used as a chemostratigraphic marker defining the Rhuddanian/Aeronian boundary in strata that lack high-resolution biostratigraphic constraints. 相似文献