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671.
Electrical triggering of earthquakes: results of laboratory experiments at spring-block models
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Victor A. Novikov Vladimir I. Okunev Vadim N. Klyuchkin Jing Liu Yuri Ya. Ruzhin Xuhui Shen 《地震科学(英文版)》2017,30(4):167-172
Recently published results of field and laboratory experiments on the seismic/acoustic response to injection of direct current(DC) pulses into the Earth crust or stressed rock samples raised a question on a possibility of electrical earthquake triggering. A physical mechanism of the considered phenomenon is not clear yet in view of the very low current density(10~(-7)–10~(-8) A/m~2) generated by the pulsed power systems at the epicenter depth(5–10 km) of local earthquakes occurred just after the current injection. The paper describes results of laboratory‘‘earthquake' triggering by DC pulses under conditions of a spring-block model simulated the seismogenic fault. It is experimentally shown that the electric triggering of the laboratory ‘‘earthquake'(sharp slip of a movable block of the spring-block system) is possible only within a range of subcritical state of the system, when the shear stress between the movable and fixed blocks obtains 0.98–0.99 of its critical value. The threshold of electric triggering action is about 20 A/m~2 that is 7–8 orders of magnitude higher than estimated electric current density for Bishkek test site(Northern Tien Shan, Kirghizia) where the seismic response to the man-made electric action was observed. In this connection, the electric triggering phenomena may be explained by contraction of electric current in the narrow conductive areas of the faults and the corresponding increase in current density or by involving the secondary triggering mechanisms like electromagnetic stimulation of conductive fluid migration into the fault area resulted in decrease in the fault strength properties. 相似文献
672.
Florent Gimbert Brian M. Fuller Michael P. Lamb Victor C. Tsai Joel P. L. Johnson 《地球表面变化过程与地形》2019,44(1):219-241
Recent advances in fluvial seismology have provided solid observational and theoretical evidence that near-river seismic ground motion may be used to monitor and quantify coarse sediment transport. However, inversions of sediment transport rates from seismic observations have not been fully tested against independent measurements, and thus have unknown but potentially large uncertainties. In the present study, we provide the first robust test of existing theory by conducting dedicated sediment transport experiments in a flume laboratory under fully turbulent and rough flow conditions. We monitor grain-scale physics with the use of ‘smart rocks’ that consist of accelerometers embedded into manufactured rocks, and we quantitatively link bedload mechanics and seismic observations under various prescribed flow and sediment transport conditions. From our grain-scale observations, we find that bedload grain hop times are widely distributed, with impacts being on average much more frequent than predicted by existing saltation models. Impact velocities are observed to be a linear function of average downstream cobble velocities, and both velocities show a bed-slope dependency that is not represented in existing saltation models. Incorporating these effects in an improved bedload-induced seismic noise model allows sediment flux to be inverted from seismic noise within a factor of two uncertainty. This result holds over nearly two orders of magnitude of prescribed sediment fluxes with different sediment sizes and channel-bed slopes, and particle–particle collisions observed at the highest investigated rates are found to have negligible effect on the generated seismic power. These results support the applicability of the seismic-inversion framework to mountain rivers, although further experiments remain to be conducted at sediment transport near transport capacity. © 2018 John Wiley & Sons, Ltd. 相似文献
673.
In October 1991 a high magnitude rainstorm flood, estimated return period 40 years, occurred in Nahal Zin, a 1400 km2 catchment in the hyperarid Negev Desert. The meso-scale structure of the storm was a curved squall line that developed from a thunderstorm in accordance with the topography of the catchment divide, by which it was strongly affected. Tropical moisture reached the area via the subtropical jet stream, in conjunction with a lower level northward intrusion of the Red Sea trough (RST-N) into the Mediterranean Sea. Rainfall, as measured at the few and sparse gauging stations, was much too small to account for the resulting large flood. Peak flow and other hydraulic characteristics of the flood were indirectly reconstructed. The techniques of palaeoflood hydrology used were based on sedimentological evidence of fine-grained flood sediments deposited in back-flooded tributaries, as well as on other stage indicators. The HEC-2 procedure was employed to determine water surface profiles. The spatial and temporal characteristics of the event were studied through a combination of rainstorm analysis, remote sensing, hydrological and sedimentological data; they jointly explain the magnitude and timing of tributary contributions producing the integrated flood in the main channel. The flood as reconstructed reveals a three-peak hydrograph: two peaks were generated by the same storm but had different floodwave arrival times in the main channel; the third resulted from a local rainstorm which occurred on the following day and covered only one tributary. The curved structure of the storm and its dynamics in relation to catchment orientation resulted in storm move- ment in tandem with the floodwave. The synchronous contribution from all main tributaries preserved evidence of the floodwave both in stage and volume by replacing the transmission losses in the sections with thick alluvium. Other high magnitude floods on record for the large Negev Desert catchments are caused by a cold upper air incursion associated with the RST-N. Most of them occur in the autumn and are caused by storms with high-intensity rainfall. This is in stark contrast with the flooding behaviour of the semi-arid zone further north, which is linked primarily to the core of the Mediterranean winter. The complexities involved in the generation of a large desert flood, as revealed by this study, illustrate the fallacy of applying routine hydrological modelling to such events, and underline the need to study the processes involved in adequate detail. © 1998 John Wiley & Sons, Ltd. 相似文献
674.
Victor Vasylevich Rybkin Nicolai Petrovich Nastechik Ruslan Volodymyrovych Marcul 《寒旱区科学》2013,5(5):0654-0658
This paper describes the economic and technological benefits of installing continuous welded rail(CWR) track on sharp(radius ≤ 300 m) railway curves. A new form of prestressed concrete sleepers developed by the V. Lazaryan Dnipropetrovsk National University of Railway Transport is shown to improve the lateral shift resistance of CWR track in sharp curves and the use of anchor sleepers on tangents is shown to make it possible to lower the fastening temperature of the CWR track in order to increase the rail lifespan. 相似文献
675.
The Stern Review has played an enormous role in making the world of business aware of the challenge of long-term climate change. In order to make real progress on the basis of this awareness, it is important to pay attention to the difference between human suffering and losses of gross domestic product (GDP). The Review has compared climate change to experiences of suffering like World War I. That war, however, hardly affected global GDP. The long-term damages to be expected from business-as-usual greenhouse gas emissions include loss of the coastal cities of the world over the next millennia. This would be an act of unprecedented barbarism, regardless of whether it would slow down economic growth or perhaps even accelerate it. Business leaders worried about climate change need to pay attention to the tensions between ethical and economic concerns. Otherwise, a credibility crisis threatens global climate policy. An important step to establish the credibility needed for effective climate policy will be to gradually move towards a regime where emission permits are auctioned, not handed out as hidden subsidies. The revenues generated by permit auctions should be used to establish a global system of regional climate funds. 相似文献
676.
Bui Xuan-Nam Choi Yosoon Atrushkevich Victor Nguyen Hoang Tran Quang-Hieu Long Nguyen Quoc Hoang Hung-Thang 《Natural Resources Research》2020,29(2):771-790
Natural Resources Research - Predicting and reducing blast-induced ground vibrations is a common concern among engineers and mining enterprises. Dealing with these vibrations is a challenging issue... 相似文献
677.
INTRODUCTIONThe underground m ine prospecting work seem s to be oneof the m ajor tasks for the mining industry.The key to thesuccessful com pletion of the task is the im provem ent in tech-nology and method engineering.The method engineering onthe surface is characterized by the increasing combination ofan individual process with space and tim e,which is the basisfor the development of m ethod engineering for cutting.Theexperience of Yakutsk and Magadan Geological Surveys isused to compi… 相似文献
678.
679.
Luis M. Farfán Eurico J. D’Sa Kam-biu Liu Victor H. Rivera-Monroy 《Estuaries and Coasts》2014,37(6):1388-1402
Tropical cyclones (TCs) are large-scale natural disturbances that generate strong winds and heavy rainfall, impacting coastal and inland environments. TCs also influence biogeochemical and hydrological cycles controlling aquatic primary productivity in tropical and subtropical coastal ecosystems. We assessed TC landfall activity and identified sites along the Mexican east and west coasts with high frequency in the period 1970–2010 and evaluated TCs with significant precipitation. Changes in chlorophyll-a (Chl-a) concentrations before and after storm impacts were estimated using remotely sensed ocean color. There were 1,065 named TCs with a wide diversity in tracks. Three states with the highest number of landfalls were identified: Baja California Sur and Sinaloa on the west coast and Quintana Roo on the east coast. While a relative increase in Chl-a values following TC landfalls in the Baja California and Yucatán Peninsula regions appeared to be strongly linked to TC strength, the intensity of precipitation, the spatial scales of the two peninsulas, and the relative movement of TCs appeared to have contributed to Chl-a variability. Satellite estimates of Chl-a in the nearshore coastal waters following TC passage were likely enhanced by coastal morphology and water discharge along with constituents such as suspended particulate, colored dissolved organic matter and nutrients from rivers, tributaries, and groundwater. 相似文献
680.
Marked, 19th‐century kiln bricks and rocks from Caledonia Springs (CS) have black glass coatings that can easily be mistaken for glass produced at the elusive CS glassworks (c. 1844–1846). The glass‐on‐brick material, however, is more aluminous (nearly 20% Al2O3) than virtually any analyzed historical glass, and the glass‐on‐rock is compositionally similar to the rock itself, which shows clear signs of having undergone extensive melting. Mineral thermometry (Cpx‐Ol, Pl‐melt) indicates that parts of the kiln‐achieved temperatures of approximately 1200–1300°C. The CS samples show that caution must be exercised when identifying seemingly obvious waste glass near defunct glassworks sites. © 2005 Wiley Periodicals, Inc. 相似文献