Current research in urban hydrogeology – A review

Urban groundwater is a heritage at risk because urban land use practises puts enormous and highly complex pressure on this resource. In this article, we review urban groundwater studies in the context of urban water management, discuss advances in hydrogeological investigation, monitoring and modelling techniques for urban areas and highlight the challenges. We present how techniques on contaminant concentration measurements, water balancing and contaminant load estimation were applied and further developed for the special requirements in urban settings. To fully understand and quantify the complex urban water systems, we need to refine these methods and combine them with sophisticated modelling approaches. Only then we will be able to sustainably manage our water resources in and around our urban areas especially in light of growing cities and global climatic change. We believe that over the next few years much more effort will be devoted to research in urban hydrogeology.     

The heterogeneous characteristics of crust-mantle structures and the seismic activities in the northwest Beijing region

Introduction Zhangjiakou-Bohai seismic zone is a major active seismic zone that passes through the north-ern part of North China. Zhangjiakou-Beijing area, the northwest part of North China, is located at the intersection position of Yanshan, Taihangshan uplift, and Shanxi down-faulted zone, and the geological structures in this area are extremely complicated. Many researchers in the geoscience circle always pay close attention to this region because Yanqing-Huailai region is located in th…     

The deep structures and oil-gas prospect evaluation in the Qiangtang Basin, Tibet

The Qiantang Basin is now one of the topics of general interest in petroleum exploration in China. This paper reports a comprehensive study of geophysical and geological survey data recently obtained in this area and, combined with INDEPTH-3 deep survey results, comes to the following conclusions： 1） The hydrocarbon source formations, reservoirs, and overlying strata and their association within the basin are quite good, local structures are developed, and, therefore, the region is favorable for forming and preserving oil and gas accumulations. Faults are not a fatal problem. The future main target strata are the middle-deep structural strata composed of Upper-Triassic and middle Jurassic rocks; 2） A new classification has been made for second-order tectonic sequences inside the basin to disavow the central Qingtang uplift. It is noted that the main structures at the surface are orientated NW-SE and the crustal structure can be described as three depressions, three risees, and one deep depression, of which the prospective zone with the most potential is the inner main subsided belt and its two sides; 3） Comparatively intensive interaction between the crust and mantle and volcanic and thermal activities in the northern basin play a very important role in petroleum evaluation. The southern deeper sedimentation and less thermal activity make this area a more perfect zone for oil exploration; 4） Currently, the most important objective is determining the physical properties of the deep strata, the status of oil and gas accumulations, the source of the hydrocarbons, and the relationship between the upper and lower structures; and 5） The Lunpola Tertiary basin may be favorable for oil accumulations because petroleum may migrate from marine strata on two sides.     

Deformation Patterns and Shortening Rates in the East Part of the Kalpin Thrust System in the Southwest Tianshan Mountains During the Late Quaternary

Deformation patterns, shortening amounts and rates in the late Quaternary across the Kalpin thrust system have received little attention in the past. This paper attempts to discuss them, mainly in the eastern part of the thrust system by doing field investigation along the faults and folds, measuring geomorphic deformation, excavating trenches in several important sites where young alluvial fans were obviously displaced and dating young deposits of alluvial terraces. There are two types of deformation in the surface and near surface for the Kalpin thrust system in the late Quaternary. They are movement of thrust faults on lower angles and bending of young folds. Both kinds of deformation are shown by shortening and uplifting of young geomorphic surfaces. The surface ages of 3 stages are calculated by dating 20 examples using the TL method in the study area and comparing the results of our predecessors on the deposition and incision times of alluvial terraces in the Tianshan mountain which are 100ka B.P., 33～18ka B.P. and 6.6～8.2ka B.P. respectively for the large-scale deformed alluvial surfaces: T_3, T_2 and T_1 in the Kalpin region. Then, 19 sets of shortening amounts and rates are obtained in 13 sites along 4 rows of anticlines in front of the Kalpin thrust system and Piqiang fold. The shortening amounts and rates show that there are two sections where deformation is stronger than others. The two sections consist of two arcs that are towards the south. The shortening rates near the top of arcs are 1.32mm/a in the west and 1.39mm/a in the east across the thrust system, respectively. In addition, deformation is stronger in the front rows than the rear ones for bifurcate folds.     

Characteristics of Tectonic Deformation and Mechanisms for the Active Maxianshan-Xinglongshan Fault System in the Lanzhou Area

A detailed investigation permitted us to obtain quantitative data concerning fine geometric structures of 4 faults of the active Maxianshan-Xinglongshan fault system and the latest movement along them. Of them the northern Maxianshan border fault is a large-scale, strongly active Holocene reverse sinistral strike-slip fault, the other 3 faults, the southern Maxianshan border fault and the southern Xinglongshan border and the northern Xinglongshan border faults are the accompanying active late-Pleistocene thrust faults, which are incorporated into the main strike-slip fault, the northern Maxianshan border fault at depth. It is the most important earthquake-controlling fault in the Lanzhou area, the fault influences and constrains the seismic activity in the area.     

Application of the third generation of coherent cube inrecognizing faults and fractures

Three-dimensionalcoherentcubeisanextremelyeffectivenewtechniqueforinterpretingseismicdata.Ithasobviousadvantagesinmanyaspectscomparedwiththeconventional3Ddatavolume,suchasrecognizingfaultsandfractures,interpretingancientchannels,andedgedetectionofoil-gasreservoir.Coherentcubeistocondenseandextractinformationaroundacertainpointin3Ddatavolume,andthenhighlighttheoriginalcharacteristicsofthegeologicbodyatthispoint.Therefore,intermsofitsessence,coherentcubeisaspecialseismicattributecubeandthosepoi…     

Evaluation of the Capacity of Comprehensive Earthquake Prevention System in a Region and Its Countermeasures

A model for evaluating the capacity of the comprehensive prevention system in a region in terms of economic losses is established in this paper by using fuzzy mathematics.The authors have explored the weak links of the system mentioned above and suggested an effective procedure of increasing the capacity of earthquake resistance and disaster prevention in a region.Through taking suitable means of decision making,the mathematical model presented in this paper can be used for reference during establishing the comprehensive prevention system in a region to reduce the earthquake disasters.     

Location of Moderate-Sized Earthquakes Recorded by the NARS�CBaja Array in the Gulf of California Region Between 2002 and 2006

We relocated the hypocentral coordinates of small to moderate-sized earthquakes reported by the National Earthquake Information Center (NEIC) between April 2002 and August 2006 in the Gulf of California region and recorded by the broadband stations of the network of autonomously recording seismographs (NARS?CBaja array). The NARS?CBaja array consists of 19 stations installed in the Baja California peninsula, Sonora and Sinaloa, Mexico. The events reported by the preliminary determinations of epicenters (PDE) catalog within the period of interest have moment magnitudes (M _w) ranging between 1.1 and 6.7. We estimated the hypocentral location of these events using P and S wave arrivals recorded by the regional broadband stations of the NARS?CBaja and the RESBAN (Red Sismológica de Banda Ancha) arrays and using a standard location procedure with the HYPOCENTER code (Lienert and Havskov in Seism Res Lett 66:26?C36, 1995) as a preliminary step. To refine the location of the initial hypocenters, we used the shrinking box source-specific station term method of Lin and Shearer (J Geophys Res 110, B04304, 2005). We found that most of the seismicity is distributed in the NW?CSE direction along the axis of the Gulf of California, following a linear trend that, from north to south, steps southward near the main basins (Wagner, Delfin, Guaymas, Carmen, Farallon, Pescadero and Alarcon) and spreading centers. We compared the epicentral locations reported in the PDE with the locations obtained using regional arrival times, and we found that earthquakes with magnitudes in the range 3.2?C5.0?mb differ on the average by as much as 43?km. For the M _w magnitude range between 5 and 6.7 the discrepancy is less, differing on the average by about 25?km. We found that the relocated epicenters correlate well with the main bathymetric features of the Gulf.     

S-Wave Velocities of the Lithosphere–Asthenosphere System in the Caribbean Region

An overview of the S-wave velocity (V _s) structural model of the Caribbean with a resolution of 2°?×?2° is presented. New tomographic maps of Rayleigh wave group velocity dispersion at periods ranging from 10 to 40?s were obtained as a result of the frequency time analysis of seismic signals of more than 400 ray-paths in the region. For each cell of 2°?×?2°, group velocity dispersion curves were determined and extended to 150?s by adding data from a larger scale tomographic study (Vdovin et al., Geophys. J. Int 136:324–340, 1999). Using, as independent a priori information, the available geological and geophysical data of the region, each dispersion curve has been inverted by the “hedgehog” non-linear procedure (Valyus, Determining seismic profiles from a set of observations (in Russian), Vychislitielnaya Seismologiya 4, 3–14. English translation: Computational Seismology (V.I. Keylis-Borok, ed.) 4:114–118, 1968), in order to compute a set of V _s versus depth models up to 300?km of depth. Because of the non-uniqueness of the solutions for each cell, a local smoothness optimization has been applied to the whole region in order to choose a three-dimensional model of V _s, satisfying this way the Occam's razor concept. Several known and some new main features of the Caribbean lithosphere and asthenosphere are shown on these models such as: the west directed subduction zone of the eastern Caribbean region with a clear mantle wedge between the Caribbean lithosphere and the subducted slab; the complex and asymmetric behavior of the crustal and lithospheric thickness in the Cayman ridge; the predominant oceanic crust in the region; the presence of continental type crust in Central America, and the South and North America plates; as well as the fact that the bottom of the upper asthenosphere gets shallower going from west to east.     

Analysis of Current Movements and Deformations of the Earth’s Crust in Fennoscandia from GNSS Data

Izvestiya, Physics of the Solid Earth - Abstract—An analysis of the displacement rates of GNSS points indicates that the values of current deformations gradually decrease from the center of...     

Current Status and Future Development of Integrated Geophysical Technology in China

The gap between China‘‘s integrated geophysical technology and the world‘‘s advanced technologies has been significantly narrowed as the result of developments in the last decade.The new technology has played a very important role in oil and gas exploration in China, especially for the purposes of targeting seismically opaque zones, decreasing exploration risk, and improving exploration efficiency in the western territories and complex areas in China. The current status and future development of non-seismic integrated geophysical teams in China is discussed.     

Earthquake-induced soft-sediment deformation structures in the Mesoproterozoic Wumishan Formation,North China,and their geologic implications

Soft-sediment structures are key to defining seismites. Two soft-sediment deformation horizons, bounded by undeformed carbonate strata, have been found in the Wumishan Formation in the Jumahe region, 175 km southwest of Beijing. One is in the lowest part of Wumishan Formation; and the other is in the uppermost part of Litho-member I. The soft-sediment structures in these two horizons fall into three categories: mould-and-sag structures, hydraulic shatterings and liquefaction dikes. The mould-and-sag structures are divided into two types: one developed in tidal-flat sediments, accompa-nied by many liquefaction-related structures and characterized by autochthonous post-earthquake sediments in sags, and the other type developed in deep-water environments, is not associated with liquefaction structures, and is overlain immediately by seismogenic tsunamites. The hydraulic shat-terings are composed of pockets of fluidization conglomerate, sand intrusions, and syndepositional faults. The liquefaction dikes fall into two categories: hydraulic-fracturing dikes and lateral-spreading dikes. The former are steep, planar, and pinch out upwards. The latter are snake-like and characterized by no diapir-related drag structures in surrounding rocks. Examination of the attitudes and strati-graphic positions of these structures suggests that these soft-sediment structures are seismogenic, and consequently, are seismites. Most seismites in the Wumishan Formation are developed near the former western, margin fault of Yanliao rift. This occurrence suggests that they could be related to movements on this fault. Other geological implications are discussed.     

A connection between the Lagrangian stochastic–convective and cumulant expansion approaches for describing solute transport in heterogeneous porous media

The equation describing the ensemble-average solute concentration in a heterogeneous porous media can be developed from the Lagrangian (stochastic–convective) approach and from a method that uses a renormalized cumulant expansion. These two approaches are compared for the case of steady flow, and it is shown that they are related. The cumulant expansion approach can be interpreted as a series expansion of the convolution path integral that defines the ensemble-average concentration in the Lagrangian approach. The two methods can be used independently to develop the classical form for the convection–dispersion equation, and are shown to lead to identical transport equations under certain simplifying assumptions. In the development of such transport equations, the cumulant expansion does not require a priori the assumption of any particular distribution for the Lagrangian displacements or velocity field, and does not require one to approximate trajectories with their ensemble-average. In order to obtain a second-order equation, the cumulant expansion method does require truncation of a series, but this truncation is done rationally by the development of a constraint in terms of parameters of the transport field. This constraint is less demanding than requiring that the distribution for the Lagrangian displacements be strictly Gaussian, and it indicates under what velocity field conditions a second-order transport equation is a reasonable approximation.     

The impact of the planetary β-effect on the vertical structure of a coherent vortex in the South China Sea

Ocean Dynamics - Vertical axes of mesoscale eddies with the coherent structure were observed to tilt southwestward significantly from the sea surface to bottom in the South China Sea. The dynamic...     

Seasonal variation in Tsushima Warm Current paths over the shelf off the San’in coast,Japan

Using long-term sea surface temperature (SST) and acoustic Doppler current profiler (ADCP) data, we examined variations in the current axis of the Tsushima Warm Current (TWC) off the San’in coast of Japan, near the entrance to the Japan Sea. There were large horizontal temperature gradients along the shelf edge in the southwestern Japan Sea from October to May, suggesting that the second branch of the TWC appears not only in spring and autumn but also in winter. From the ADCP data analysis, we found that currents with speeds of approximately 20 cm s^?1 and greater appeared around the shelf edge off San’in coast in all seasons. The SST and ADCP data analyses suggested that the second branch of the TWC exists around the shelf edge off the San’in coast throughout the year. This finding differed from those of previous studies. A relatively strong current (speed greater than 15 cm s^?1) appeared on the shore side in all seasons, except at line W in winter. This current might be the first branch of the TWC. The first branch seemed to occur around in 100 m isobaths, but shifted northward and southward because the bottom topography around lines W and M was relatively flat and the shelf was broad. The first branch was very obscure, and it was difficult to define the two branches of the TWC off the San’in coast from the seasonally averaged vectors. However, snapshots of current distribution derived from the ADCP data clearly showed these branches. Hence, both the first and second branches might occur throughout the year off the San’in coast.     

The Role of Microorganisms in Uranium Behavior in the Water–Rock System

Geochemical processes involving redox reactions and leading to either formation or transformation of geochemical barriers may be largely induced or enhanced by microbial activity. The microbial reduction of uranium is studied as a strategy for rehabilitation of uranium-containing groundwater. The bioremediation mechanism converts dissolved uranium(VI) into low-solubility U(IV). The processes involving dissimilatory reducing bacteria, which facilitate the reduction and retention of U(VI) in soils and rocks, are considered. The diversity of microorganisms involved in anaerobic reduction of uranium is shown. The geochemical conditions that may affect the rate of microbial reduction of U(VI) are specified, i.e., the presence of nitrate ions, phosphate ions, calcium ions, and iron oxides. The mechanisms of their action are examined. Geochemical barriers with the participation of microorganisms are proposed for the rehabilitation of groundwater with uranium removed from groundwater and deposited locally as a result of microbial reduction of U(VI).     

Conduit-vent structures and related proximal deposits in the Las Cañadas caldera, Tenerife, Canary Islands

The Las Cañadas caldera wall and the outer slopes of the caldera provide three-dimensional exposures of numerous proximal-welded fallout deposits and have been mapped in detail. As a result, some parts of the Ucanca and Guajara Formations of the stratigraphy of Martí et al. (1994) have been divided into members that correspond to individual eruptions. Mapping has also revealed the occurrence of conduit-vent structures associated with proximal-welded fallout deposits. Conduit-vent structures consist of an upper flaring area and a lower narrow conduit. Conduit-vent geometry and dimensions include cylindrical plugs and eruptive fissures steeply dipping towards the caldera depression and elongated vents. The flaring area can be rather asymmetric and is usually filled by down-vent rheomorphic flow of the proximal fallout deposit. The lower conduits are filled by lava plug, agglutination of juveniles onto conduit walls and dyke intrusion with eventual dome extrusion. The eruption dynamics of welded fallout deposits and magma fragmentation within the conduit are consistent with an evolution from explosive to effusive. In this context conduit flow regimes evolve from turbulent to annular flow in which the conduit is progressively choked, and laminar flow leading to the final conduit closure.