Detection of the water level in fractured phreatic aquifers using nuclear magnetic resonance (NMR) geophysical measurements

Correlation of geophysical data collected using the NMR method in the Negev Desert, Israel, with hydrogeological data from nearby observation wells is presented. The experiment was conducted near Kibbutz Revivim in the Besor drainage system (Fig. 1). The objective of the survey was to detect groundwater layers in the Quaternary cover filling and Eocene fractured aquifers down to a depth of 100 m. The experiment was performed using a combination of two different geophysical techniques, namely the NMR and time domain electromagnetic (TDEM) methods. The geophysical results were verified by measuring the water level in three observation wells, two of which were drilled several months after the geophysical survey was carried out.The water level measured in these follow-up observation wells shortly after drilling did not coincide with the geophysical data. However, it settled over a period of time and finally stabilized at a depth very similar to that obtained from the NMR measurements. This phenomenon is caused by the fractured nature of the phreatic aquifer. Since the flow of water in such aquifers is confined by the fractures, the appearance of water in the well during or shortly after drilling is determined solely by the intersection of the well and the fracture. Our experiments showed that geophysical measurements in fractured phreatic aquifers may have a distinct advantage over direct borehole measurements, since the former average the depth to the water table over large areas (several thousand square meters) while the latter are limited by the area of the borehole cross-section (several tens of square centimeters).     

川滇菱形块体顺时针转动的构造学与古地磁学证据

川滇菱形块体内部受NE向丽江 -小金河断裂的切割 ,可进一步划分为川西北次级块体和滇中次级块体等南北 2个部分 ;各次级块体东边界断裂有规律地左旋滑动、西边界断裂的右旋滑动及其滑动速率值的差异 ,反映出新生代时期各次级块体作向SE的水平滑移叠加绕垂直轴顺时针转动的复合运动。其中 ,川西北次级块体SE向的水平滑移速率 5mm/a ,顺时针转动角速度 1 4°/Ma ;滇中次级块体SE向的水平滑移速率 3 5mm/a ,顺时针转动角速度约 1 5°/Ma。在滇中次级块体内部姚安、大姚、永仁、昆明北马街等地采集到约 90个古新世地层的定向样品 ,通过交变退磁和热退磁获得了它们各自的剩磁矢量 (实验磁偏角和磁倾角 ) ,由实测磁偏角与期望磁偏角相比可知川滇地区滇中次级块体中新世早期以来的顺时针转动累积量可达 30°～ 4 8°。次级块体的整体转动与块边活动断裂的左旋滑动符合左旋走滑断裂作用区块体作顺时针转动的运动学模式     

Die halbtägige Welle des Iuftelektrischen Potentialgefälles

Zusammenfassung Die Tagesgänge des luftelektrischen Potentialgefälles an Festlandstationen kann man in ihrem ortszeitgebundenen Anteil auffassen als einfache Schwingung mit einem Mindestwert in den frühen Morgen- und einem Maximalwert in den Nachmittagsstunden, über die eine im Laufe des Jahres schwankende und von Ort zu Ort verschiedene austauschbedingte Einsenkung während des Tages überlagert ist. Es läßt sich zeigen, daß die Tiefe dieser Einsenkung um so größer sein, muß, je größer der mittlere Kern- und Großionengehalt des Meßortes ist. Damit finden die Unterschiede im Gang des Potentialgefälles benachbarter Stationen sowie die Änderungen dieses Charakters in Davos von 1909/10 zur Meßperiode 1923/26 eine qualitative Erklärung.

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Summary The diurnal variations of the potential gradient of atmospheric electricity at continental stations can be interpreted, in their share connected to local time, as a simple oscillation with a minimum in the early morning and a maximum in the afternoon; above this oscillation a depression is superposed during the day, caused by turbulence exchange, showing fluctuations in the course of the year and different from place to place. It can be shown that the amplitude of this depression must be so much greater the greater is the average content of nuclei and large ions of the place of measurements. Therewith the differences of the gradient's variation of neighbouring stations and the alteration of their character from 1909/10 at Davos to the period of measurements in 1923/26 find a qualitative explanation.

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Résumé On peut considérer la variation diurne du gradient de potentiel électrique de l'atmosphère dans les stations terrestres, du moins celle qui est liée au temps local, comme une oscillation simple avec un minimum tôt le matin et un maximum l'après-midi; une baisse diurne, variable suivant le moment de l'année et le lieu d'observation, vient s'y superposer. On peut montrer que cette baisse est d'autant plus accusée que la teneur moyenne en noyaux et en gros ions est plus élevée. Cela permet d'expliquer les divergences de variation diurne du gradient électrique entre stations rapprochées, ainsi que la différence constatée dans les séries d'observations de 1909/10 et 1923/26 à Davos.

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Mit 2 Textabbildungen.     

Shear Strength Development with Burial in Eel River Margin Slope Sediments

As part of the STRATAFORM project, a series of cores were obtained from the Eel River Margin area of Eureka, California. The geotechnical analysis of intact specimens and of reconstituted samples provides some insight on the development of shear strength with burial. The results show the effect of bioturbation in the early part of the lifetime of a sediment. SEDCON tests were used to proposed various relationships which help predict the changes in density, liquidity index, and strength as a function of depth. These relationships are found useful from near the water sediment-interface down to a depth of at least 400 m in the sediment column.     

Smallholder Farmers’ perception and adaptation to climate variability and change in Fincha sub-basin of the Upper Blue Nile River Basin of Ethiopia

GeoJournal - Climate variability and change make agricultural sector a risky venture for smallholders’ farmers. This paper presents an assessment of smallholder farmers’ perceptions of...     

X-ray and optical-to-infrared follow-up observations of the transient X-ray burster SAX J1810.8–2609

We have performed a ROSAT follow-up observation of the X-ray transient SAX J1810.8–2609 on 1998 March 24 and detected a bright X-ray source (named RX J1810.7–2609) which was not detected during the ROSAT all-sky survey in September 1990. Optical-to-infrared follow-up observations of the 10" radius ROSAT HRI X-ray error box revealed one variable object ( R =19.5±0.5 on March 13, R >21.5 on 1998 August 27) which we tentatively propose as the optical/IR counterpart of RX J1810.7–2609≡SAX J1810.8–2609.     

Fast Upscaling of the Hydraulic Conductivity of Three-Dimensional Fractured Porous Rock for Reservoir Modeling

Mathematical Geosciences - A fast upscaling procedure for determining the equivalent hydraulic conductivity of a three-dimensional fractured rock is presented in this paper. A modified...     

Can the pattern of juvenile recruitment and population structure of the speckled swimming crab Arenaeus cribrarius (Decapoda: Brachyura) be determined by geographical variations?

This study evaluated the effect of environmental stimuli and selective pressures in different geographical areas along a latitudinal gradient, on the juvenile recruitment, population structure, and sex ratio of the speckled swimming crab Arenaeus cribrarius. Samples were collected monthly during 1 year in three locations along the Brazilian coast: Macaé, state of Rio de Janeiro (MAC, 22°47′ S, 41°45′ W); Ubatuba, São Paulo (UBA, 23°27′ S, 44°58′ W); and São Francisco do Sul, Santa Catarina (SFS, 26°08′ S, 48°34′ W). The specimens of A. cribrarius were identified, counted, sexed, and measured for maximum carapace width (CW). The largest juvenile found was in UBA (47.7 ± 1.36 mm); and the largest adult females and males in MAC (74.26 ± 0.93 and 77.04 ± 0.79 mm, respectively). Recruitment in MAC was continuous, whereas in UBA and SFS, recruitment showed seasonal characteristics. The sex ratio was skewed toward females only in UBA; in MAC and SFS, males and females were present in equal proportions. These results indicate that geographical variations can cause differences in the recruitment and population structure of A. cribrarius. These regional differences call attention to the necessity for improved management plans and control of shrimp fishing, which can affect population patterns such as juvenile recruitment, population structure and life history of the target species and species that are caught in bycatch from shrimping, such as the swimming crab A. cribrarius.     

Annama H chondrite—Mineralogy,physical properties,cosmic ray exposure,and parent body history

The fall of the Annama meteorite occurred early morning (local time) on April 19, 2014 on the Kola Peninsula (Russia). Based on mineralogy and physical properties, Annama is a typical H chondrite. It has a high Ar‐Ar age of 4.4 Ga. Its cosmic ray exposure history is atypical as it is not part of the large group of H chondrites with a prominent 7–8 Ma peak in the exposure age histograms. Instead, its exposure age is within uncertainty of a smaller peak at 30 ± 4 Ma. The results from short‐lived radionuclides are compatible with an atmospheric pre‐entry radius of 30–40 cm. However, based on noble gas and cosmogenic radionuclide data, Annama must have been part of a larger body (radius >65 cm) for a large part of its cosmic ray exposure history. The ¹⁰Be concentration indicates a recent (3–5 Ma) breakup which may be responsible for the Annama parent body size reduction to 30–35 cm pre‐entry radius.