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1.
Warming climate and thawing permafrost have profound impacts on groundwater flow regimes in cold regions because of the shrinkage or disappearance of the confining unit formed by the permafrost layers and improving hydraulic connections. Numerical simulations of coupled groundwater flow and heat transfer are often used to characterize the changing permafrost hydrogeology. In this study, a number of scenarios for different hydraulic gradients and lake-water depths have been used to simulate the concordant permafrost evolution and groundwater movement using a two-dimensional cylindrical coordinate model at time scales of decades to centuries in response to a warming climate. The model is applied to a representative headwater catchment in the south-central headwater area of the Yellow River on the northeastern Qinghai-Tibet Plateau, China. The results show that the presence and movement of groundwater and the deeper subpermafrost aquifer can substantially accelerate permafrost degradation, and the disappearance of residual permafrost at depth can result in the sudden establishment of deep groundwater flow paths. All hydrological impacts will become evident after the stabilization of the hydrothermal and flow fields at 100–200 years. The stable discharge rate of groundwater flow varies from 8.0 to 12.4 m3 s−1, and the stable velocity of groundwater flow varies from 1.6 × 10−7 to 4.4 × 10−7 m s−1 under different scenarios within the model domain. The modeling results also demonstrate that flow velocity and discharge rate in local groundwater flow systems can be enhanced by an increased hydraulic conductivity, leading to an accelerated degradation of isolated permafrost bodies. 相似文献
2.
The variable polyrhythmicity observed in natural, technical, and humanitarian spheres can be the result of mutual desynchronization of conjugate rhythmic processes. One example of desynchronization in medicine is fibrillations of heart ventricles. To bring a patient out of this state, electroshock is applied, which frequently leads to defibrillation and recovery of normal heart rhythm (resynchronization). This phenomenon has analogies in other fields of science. It is known that lunar–solar tides cause subsurface seismic noise. We give an example of detecting such noise in the Ashkhabad seismic survey area. This noise can appear and disappear, and the reason may be certain shock impacts, in particular, earthquakes. Similar results have been obtained in studying lunar seismicity, where tidal phenomena are more strongly pronounced than on Earth. 相似文献
3.
The results of experimental studies and scientific substantiation of an effect of directional change in the chemical and phase composition of the surface and increase in the contrast of physicochemical and electrical properties of tantalite, columbite, and zircon in the course of treatment with anolyte (pH < 5) and a hydrochloric acid solution (HCl, pH 3–3.5) are reported. The mechanism of structural and chemical transformations of the mineral surface in the process of leaching with acid solutions are studied. This mechanism includes the activation of oxidation of iron atoms in the surface layer of tantalite and columbite with the transition from Fe(II) to Fe(III), destruction of the zircon surface with the formation of oxygen–vacancy defects of the SiO
2-3
- and SiO
02
-types, and intense dissolution of iron- and silicate-bearing films from the surface of rare-metal minerals. 相似文献
4.
The water framework directive (WFD) is applied within the Guadalhorce river basin, a Western Mediterranean basin in the Málaga
province (South Spain). Criteria defining different surface and groundwater bodies are described. The basic hydrographic network
is constituted of low-mountain and low-altitude Mediterranean mineralized rivers. Heavily modified surface water bodies correspond
(1) to areas where dams regulate the main watercourses, (2) to areas downstream of reservoirs, where river flow is reduced,
and (3) to the coastal sector of the river where artificial channelling has caused morphological variations. Groundwater bodies
are related to carbonate and porous aquifers and, locally, to aquifers influenced by dissolution of evaporites. The main impacts
to water bodies are irrigated lands and livestock farming. There are also point sources of pollution, such as wastewater,
landfills, golf courses, industrial zones, quarries and petrol stations. In addition, groundwater is frequently pumped for
human supply and irrigation. Qualitative status of groundwater bodies was done by chemical analysis of samples from a monitoring
network and the quantitative status by examining variations in piezometric levels. Both revealed the existence of water bodies
at risk of not meeting the environmental objectives of the WFD. The main indicators of pollution are nitrates related to agricultural
activities, and total organic carbon (TOC), PO 43− and NH 4+ in relation to wastewater. 相似文献
5.
A seismic sequence in central Italy from August 2016 to January 2017 affected groundwater dynamics in fractured carbonate aquifers. Changes in spring discharge, water-table position, and streamflow were recorded for several months following nine Mw 5.0–6.5 seismic events. Data from 22 measurement sites, located within 100 km of the epicentral zones, were analyzed. The intensity of the induced changes were correlated with seismic magnitude and distance to epicenters. The additional post-seismic discharge from rivers and springs was found to be higher than 9 m3/s, totaling more than 0.1 km3 of groundwater release over 6 months. This huge and unexpected contribution increased streamflow in narrow mountainous valleys to previously unmeasured peak values. Analogously to the L’Aquila 2009 post-earthquake phenomenon, these hydrogeological changes might reflect an increase of bulk hydraulic conductivity at the aquifer scale, which would increase hydraulic heads in the discharge zones and lower them in some recharge areas. The observed changes may also be partly due to other mechanisms, such as shaking and/or squeezing effects related to intense subsidence in the core of the affected area, where effects had maximum extent, or breaching of hydraulic barriers. 相似文献
6.
We present the estimated source parameters from SH-wave spectral modeling of selected 463 aftershocks (2002–06) of the 26 January 2001 Bhuj earthquake, the well-recorded largest continental intraplate earthquake. The estimated seismic moment (M o), corner frequency (f c), source radius (r) and stress drop (Δσ) for aftershocks of moment magnitude 1.7 to 5.6 range from 3.55×10 11 to 2.84×10 17 N-m, 1.3 to 11.83 Hz, 107 to 1515 m and 0.13 to 26.7 MPa, respectively, while the errors in f c and Δσ are found to be 1.1 Hz and 1.1 MPa, respectively. We also notice that the near surface attenuation factor (k) values vary from 0.02 to 0.03. Our estimates reveal that the stress drop values show more scatter (Mo 0.5 to 1 is proportional to Δσ) toward the larger M o values (≥10 14.5 N-m), while they show a more systematic nature (Mo 3 is proportional to Δσ) for smaller M o values (<10 14.5 N-m), which can be explained as a consequence of a nearly constant rupture radius for smaller aftershocks in the region. The large stress drops (= 10 MPa) associated with events on the north Wagad fault (at 15–30 km depth) and Gedi fault (at 3–15 km depth) can be attributed to the large stress developed at hypocentral depths as a result of high fluid pressure and the presence of mafic intrusive bodies beneath these two fault zones. 相似文献
7.
A two‐dimensional thermorheological model of the Central Alps along a north–south transect is presented. Thermophysical and rheological parameters of the various lithological units are chosen from seismic and gravity information. The inferred temperature distribution matches surface heat flow and results in Moho temperatures between 500 and 800 °C. Both European and Adriatic lithospheres have a ‘jelly‐sandwich’ structure, with a 15–20 km thick brittle upper crust overlying a ductile lower crust and a mantle lid whose uppermost part is brittle. The total strength of the lithosphere is of the order of 0.5–1.0 × 10 13 N m −1 if the upper mantle is dry, or slightly less if the upper mantle is wet. In both cases, the higher values correspond to the Adriatic indenter. 相似文献
8.
On the basis of the summarized results of multiannual deep soundings with the use of powerful controlled sources, it is suggested to subdivide the Earth’s crust, which is traditionally identified by seismic data, into two parts, namely, upper and lower. The upper crust of 10–15 km thick is more conductive and is the most actively involved in geologic processes. Its principal peculiarities are sharp horizontal heterogeneity and a wide range of variations of specific electric resistance for rocks (from 1 to 10 5 Ohm m), a higher brittleness, and the presence of fluids that drain the suprastructure from the day surface owing to the supply of meteor waters to depths. The lower crust (in the depth interval from 10–15 to 35–45 km) is distinctive by the high specific electric resistance (10 5–10 6 Ohm m) and horizontal homogeneity of electric properties. Electric conductivity of the lower crust is mostly determined by the influence of planetary physical-chemical parameters (pressure, temperature, viscosity), phase transitions of substances, and geodynamic peculiarities of evolution for different segments of the Earth, rather than by geologic processes observed near the day surface. 相似文献
9.
Mining development sites occasionally host complicated aquifer systems with notable connections to natural surface water (SW) bodies. A low-altitude thermal infrared (TIR) imaging survey was conducted to identify hydraulic connections between aquifers and rivers and to map spatial surface temperature patterns along the subarctic rivers in the proximity of the Hannukainen mining development area, northern Finland. In addition to TIR data, stable isotopic compositions ( δ 18O, δD) and dissolved silica concentrations were used as tracers to verify the observed groundwater (GW) discharge into the river system. Based on the TIR survey, notable GW discharge into the main river channel and its tributaries (61 km altogether) was observed and over 500 GW discharge sites were located. On the basis of the survey, the longitudinal temperature patterns of the studied rivers were found to be highly variable. Hydrological and hydrogeological information is crucial in planning and siting essential mining operations, such as tailing areas, in order to prevent any undesirable environmental impacts. The observed notable GW discharge was taken into consideration in the planning of the Hannukainen mining development area. The results of this study support the use of TIR imagery in GW–SW interaction and environmental studies in extensive and remote areas with special concerns for water-related issues but lacking the baseline research. 相似文献
10.
The locations of areas prone to strong earthquakes (M ≥ 6.0) in the Altai–Sayan–Baikal region are determined. Based on a scheme of morphostructural zoning of the region and by using the CORA-3 pattern recognition algorithm, all intersections of morphostructural lineaments are separated into two classes: the highly seismic intersections in the vicinities of which strong earthquakes can occur and low seismic in the vicinities of which only earthquakes with M < 6.0 are possible. Recognition was performed for the vectors the components of which were measured values of the geological–geophysical characteristics describing the respective intersection. The result obtained allows the zones of high seismic hazard to be identified more reliably in the region. 相似文献
11.
The 1515 M7? Yongsheng earthquake is the strongest earthquake historically in northwest Yunnan. However, its time, magnitude and the seismogenic fault have long been a topic of dispute. In order to accurately define those problems, a 1:50000 active tectonic mapping was carried out along the northern segment of the Chenghai–Binchuan fault zone. The result shows that there is an at least 25 km–long surface rupture and a series of seismic landslides distributed along the Jinguan fault and the Chenghai fault. Radiocarbon dating of the ~(14) C samples indicates that the surface rupture should be a part of the deformation zone caused by the Yongsheng earthquake in the year 1515. The distribution characteristics of this surface rupture indicate that the macroscopic epicenter of the 1515 Yongsheng earthquake may be located near Hongshiya, and the seismogenic fault of this earthquake is the Jinguan–Chenghai fault, the northern part of the Chenghai–Binchuan fault zone. Striations on the surface rupture show that the latest motion of the fault is normal faulting. The maximum co–seismic vertical displacement can be 3.8 m, according to the empirical formula for the fault displacement and moment magnitude relationship, the moment magnitude of the Yongsheng earthquake was Mw 7.3–7.4. Furthermore, combining published age data with the ~(14) C data in this paper reveals that at least four large earthquakes of similar size to the 1515 Yongsheng earthquake, have taken place across the northern segment of the Chenghai–Binchuan fault zone since 17190±50 yr. BP. The in–situ recurrence interval of Mw 7.3–7.4 characteristic earthquakes in Yongsheng along this fault zone is possibly on the order of 6 ka. 相似文献
12.
Since 2002 the Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS) in Udine (Italy), the Agencija Republike Slovenije za Okolje (ARSO) in Ljubljana (Slovenia) and the Zentralanstalt für Meteorologie und Geodynamik (ZAMG) in Vienna (Austria), are collecting, analyzing, archiving and exchanging seismic data in real time, initially in the framework of the EU Interreg IIIa Italia-Austria project “Trans-national seismological networks in the South-Eastern Alps”. As outcome of the successful cooperation, in the 2013 OGS, ARSO and ZAMG decided to officially merge their seismic monitoring efforts into the “Central and Eastern European Earthquake Research Network—CE3RN”. This work reports the results of a nine-month real-time test of the earthquake early warning (EEW) algorithm probabilistic and evolutionary early warning system carried out at the CE3RN. The study allowed identifying the actions to be implemented in order to let the CE3RN become in the next future an efficient cross-border EEW system. 相似文献
13.
A novel high-resolution (2–4 m source and receiver spacing) reflection and refraction seismic survey was carried out for aquifer characterization and to confirm the existing depositional model of the interlobate esker of Virttaankangas, which is part of the Säkylänharju-Virttaankangas glaciofluvial esker-chain complex in southwest Finland. The interlobate esker complex hosting the managed aquifer recharge (MAR) plant is the source of the entire water supply for the city of Turku and its surrounding municipalities. An accurate delineation of the aquifer is therefore critical for long-term MAR planning and sustainable use of the esker resources. Moreover, an additional target was to resolve the poorly known stratigraphy of the 70–100-m-thick glacial deposits overlying a zone of fractured bedrock. Bedrock surface as well as fracture zones were confirmed through combined reflection seismic and refraction tomography results and further validated against existing borehole information. The high-resolution seismic data proved successful in accurately delineating the esker cores and revealing complex stratigraphy from fan lobes to kettle holes, providing valuable information for potential new pumping wells. This study illustrates the potential of geophysical methods for fast and cost-effective esker studies, in particular the digital-based landstreamer and its combination with geophone-based wireless recorders, where the cover sediments are reasonably thick. 相似文献
14.
ABSTRACTNew analysis of the geophysical data of the ultraslow-spreading Mohns Ridge and its off-axis structure reveals a distinctive asymmetric structure. We calculate residual bathymetry (RB) and residual mantle Bouguer gravity anomaly (RMBA) and decompose the anomalies into symmetric and asymmetric components between the ridge conjugates. The western flank of the Mohns Ridge at crustal age of ~50–15 Ma is characterized by a broad zone of elevated RB and more negative RMBA, which we term the Vesteris Plateau (VP). The VP anomaly has a surface area of ~1.12 × 10 5 km 2 and an excess crust volume of ~2.33 × 10 5 km 3, making it a significant anomaly comparable to other anomalies such as the Bermuda Rise. Extending north of the Kolbeinsey Ridge for more than 500 km, the VP lies above an anomalous upper mantle region of low shear-wave seismic velocity, indicating that the VP might represent the northernmost reach of the Iceland-Jan Mayen mantle anomaly. In addition, the western ridge flank of the Mohns Ridge at crustal age of 6–0 Ma is associated with higher RB and more positive RMBA relative to the eastern conjugate, indicating tectonic uplift and associated exposure of lower crust and upper mantle near the ridge axis. 相似文献
15.
AbstractDistinctions between cave morphologies originating from seismic or active tectonics and those generated by natural clastic breakdown or by human activity must be made using unambiguous interpretative criteria.Easily accessible caves in particular, which may have been visited for centuries or millennia, or caves located near engineering works or quarries using great quantities of explosives, may have broken speleothems, breakdowns or detachment joints unrelated to seismic events or tectonic movements.Zambujal cave lies near neotectonic and seismic structures associated with a Plio-Quatemary 200 m uplift of the Arrábida chain and has suffered impacts resulting from quarrying, followed by possible vandalism. It is thus an example for which it is difficult to decipher morphological agents as there is the possibility that identical forms have been generated by several causes, which may have repeated at different episodes of its evolution. However, a careful morphological interpretation makes it possible to accept the existence of two seismic episodes, an “ancient” one and a “modern” one. The detection of other episodes between these is only possible using absolute dating. © Elsevier, Paris 相似文献
16.
New empirical relations are derived for source parameters of the Koyna–Warna reservoir-triggered seismic zone in Western India using spectral analysis of 38 local earthquakes in the magnitude range M L 3.5–5.2. The data come from a seismic network operated by the CSIR-National Geophysical Research Institute, India, during March 2005 to April 2012 in this region. The source parameters viz. seismic moment, source radius, corner frequency and stress drop for the various events lie in the range of 10 13–10 16 Nm, 0.1–0.4 km, 2.9–9.4 Hz and 3–26 MPa, respectively. Linear relationships are obtained among the seismic moment ( M 0), local magnitude ( M L), moment magnitude ( M w), corner frequency (fc) and stress drop (? σ). The stress drops in the Koyna–Warna region are found to increase with magnitude as well as focal depths of earthquakes. Interestingly, accurate depths derived from moment tensor inversion of earthquake waveforms show a strong correlation with the stress drops, seemingly characteristic of the Koyna–Warna region. 相似文献
17.
In this study kamacite was experimentally grown in taenite grains of Fe-Ni-P alloys containing between 5 and 10 wt% Ni and 0 and 1.0 wt% P. Both isothermal heat treatments and non-isothermal heat treatments at cooling rates of 2 to 5°C/day were carried out. Analytical electron microscopy was used to examine the orientation and chemical composition of the kamacite and the surrounding taenite matrix. The kamacite so produced is spindle or rod shaped and has a Widmanstätten pattern orientation. The presence of heterogeneous sites such as phosphides is necessary for the nucleation of the intergranular kamacite. During kamacite growth both Ni and P partition between kamacite and taenite with chemical equilibrium at the two phase interface. The growth kinetics are limited by the diffusion of Ni in taenite. Additional diffusion experiments showed that the volume diffusion coefficient of Ni in taenite is raised by a factor of 10 at 750°C in the presence of only 0.15 wt% P.A numerical model to simulate the growth of kamacite in Fe-Ni-P alloys, based on our experimental results, was developed and applied to estimate the cooling rates of the iron meteorites. The cooling rates predicted by the new model are two orders of magnitude greater than those of previous studies. For example the cooling rates of chemical groups I, IIIAB and IVA are 400–4000°C/10 6years, 150–1400°C/ 10 6 years and 750–6000°C/10 6years respectively. Previous models gave 1–4°C/10 6 years, 1–10°C/10 6 years and 3–200°C/10 6 years. Such fast cooling rates can be interpreted to indicate that meteorite parent bodies need only be a few kilometers in diameter or that iron meteorites can be formed near the surface of larger asteroidal bodies. 相似文献
18.
Landslides are the main secondary effects of earthquakes in mountainous areas. The spatial distribution of these landslides is controlled by the local seismic ground motion and the local slope stability. While gravitational instabilities in arid and semi-arid environments are understudied, we document the landslides triggered by the Sarpol Zahab earthquake (November 12, 2017, Mw7.3, Iran/Iraq border), the largest event ever recorded in the semi-arid Zagros Mountains. An original earthquake-induced landslide inventory was derived, encompassing landslides of various sizes and velocities (from rapid disrupted rockfalls to slow-moving coherent landslides). This inventory confirms the low level of triggered landslides in semi-arid environments. It also displays clear differences in the spatial and volumetric distributions of earthquake-induced landslides, having 386 rockfalls of limited size triggered around the epicenter, and 9 giant (areas of ca. 106 m2) active and ancient deep-seated landslides coseismically accelerated at locations up to 180 km from the epicenter. This unusual distant triggering is discussed and interpreted as an interaction between the earthquake source properties and the local geological conditions, emphasizing the key role of seismic ground motion variability at short spatial scales in triggering landslides. Finally, the study documents the kinematics of slow-moving ancient landslides accelerated by earthquakes, and opens up new perspectives for studying landslide triggering over short (~?1–10 years) and long-time (~?1000–10,000 years) periods.
相似文献
19.
The Martabe Au–Ag deposit, North Sumatra Province, Indonesia, is a high sulfidation epithermal deposit, which is hosted by Neogene sandstone, siltstone, volcanic breccia, and andesite to basaltic andesite of Angkola Formation. The deposit consists of six ore bodies that occurred as silicified massive ore (enargite–luzonite–pyrite–tetrahedrite–tellurides), quartz veins (tetrahedrite–galena–sphalerite–chalcopyrite), banded sulfide veins (pyrite–tetrahedrite–sphalerite–galena) and cavity filling. All ore bodies are controlled by N–S and NW–SE trending faults. The Barani and Horas ore bodies are located in the southeast of the Purnama ore body. Fluid inclusion microthermometry, and alunite‐pyrite and barite‐pyrite pairs sulfur isotopic geothermometry show slightly different formation temperatures among the ore bodies. Formation temperature and salinity of fluid inclusions of the Purnama ore body range from 200 to 260 C and from 6 to 8 wt.% NaCl equivalent, respectively. Formation temperature and salinity of fluid inclusions of the Barani ore body range from 200 to 220 °C and from 0 to 2.5 wt.% NaCl equivalent and those of the Horas ore body range from 240 to 275 °C and from 2 to 3 wt.% NaCl equivalent, respectively. The Barani and Horas ore bodies are less silicified and sulfides are less abundant than the Purnama ore body. A relationship between enthalpy and chloride content indicates mixing of hot saline fluids with cooler dilute fluids during the mineralization of each of the ore bodies. The δ 18O values of quartz samples from the southeast ore bodies exhibit a wide range from +4.2 to +12.9‰ with an average value of +7.0‰. The δ 18O values of H 2O estimated from δ 18O values of quartz, barite and calcite confirm the oxygen isotopic shift to near meteoric water trend, which support the incorporation of meteoric water. Salinity of the fluid inclusions decrease from >5 wt.% NaCl equivalent in the Purnama ore body to <3 wt.% NaCl equivalent in the Barani ore body, indicating different fluid systems during mineralization. The δ 34S values of sulfide and sulfate in Purnama range from ? 4.2 to +5.5‰ and from +1.2 to +26.7‰, those in the Barani range from ? 4.3 to +26.4‰ and from +3.9 to +18.5‰ and those in the Horas ore body range from ? 11.8 to +3.5‰ and from +1.4 to +25.7‰, respectively. The δ 34S of total bulk sulfur in southeastern ore bodies (Σδ 34S) was estimated to be approximately +6‰. The estimated sulfur fugacity during formation of the Purnama and Horas ore bodies is relatively high. It was between 10 ?4.8 and 10 ?10.8 atm at 220 to 260 °C. Tellurium fugacity was between 10 ?7.8 and 10 ?9.5 atm at 260 °C and between 10 ?9 and 10 ?10.6 atm at 220 °C in the Purnama ore body. The Barani ore body was formed at lower fS 2, lower than about 10 ?14 atm at 200 to 220 °C based on the presence of arsenopyrite and pyrrhotite in the early stage, and between 10 ?14 and 10 ?12 atm based on the existence of enargite and tennantite in the last stage. © 2016 The Society of Resource Geology 相似文献
20.
Interpretation of 2500 km of newly processed 2D seismic and regional potential field data has led to the identification of two new Miocene–Oligocene sedimentary basins in the northern part of offshore Egypt. The western part of the basin is deeper and has thick sedimentary cover. The upper part of the Miocene section is tested in its southern part through two wells, where the eastern subbasin is still virgin and is located at the intersection between Temsah basins and southeastern end of the Levantine basin. The main sedimentary unit of the basin is the Miocene–Oligocene sedimentary section, which was proven by the exploration and production activities in Nile Delta to be one of the hydrocarbon-generating facies. This fact is supported by 1D basin analysis using the average parameter values, which shows a hydrocarbon window, extending from lower Miocene to upper Miocene. The basin dimensions are more than 2000 km2 area and more than 4000 m of thickness, with variable petroleum system parameters’ potentialities, starting from Tortonian–Serravallian to lower Oligocene section. 相似文献
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