Kinematics of throughgoing fractures in jointed rocks

Throughgoing fractures play a major role in subsurface fluid flow yet the kinematics of their formation, which directly impact rock flow properties, are often difficult to establish. We investigate throughgoing fractures in the Monterey Formation of California that developed by the coalescence of pre-existing joints. At Lompoc Landing, throughgoing fractures fall into three main groups: linked, linked with aperture, and breccia zones. The segmented nature of their walls provides numerous piercing points to firmly establish the sense of displacement. Analysis of displacement vectors derived from piercing points demonstrates that the NW–SE trending throughgoing fractures, often interpreted as strike–slip faults, are in fact extensional structures in origin. We suggest that this method may be applied to throughgoing fractures that form by the same mechanism in other geologic settings. Establishing kinematics of throughgoing fractures will lead to a better understanding of their contribution to subsurface fluid flow.     

New potentially industrial sulfide indium-manganese ore type

Doklady Earth Sciences -     

Hypoxic events in Narragansett Bay, Rhode Island, during the summer of 2001

Bottom water hypoxic events were observed in Narragansett Bay, Rhode Island during the summer of 2001 using a towed sensor, vertical casts at fixed stations, and continuous monitoring buoys. This combination of approaches allowed for both extensive spatial and temporal sampling. Oxygen concentrations below the U.S. Environmental Protection Agency (EPA) acute hypoxia criterion of 2.3 mg l^?1 were observed in the northern parts of Narragansett Bay, including the Providence River. We estimate 39% of the area of the Providence River was affected by acute hypoxia between July and September 2001. All other regions experienced only small areas of acute hypoxia (<5%), and no acute hypoxia was observed from Quonset Point south. The area encompassing oxygen concentrations below the EPA chronic hypoxia criterion of 4.8 mg l^?1 was much more extensive in the upper half of Narragansett Bay, sometimes covering the majority of the region, though it is unclear whether exposure to concentrations below this criterion persisted long enough to significantly affect marine species in these areas. Vertical profiles of dissolved oxygen typically exhibited a mid water oxygen minimum near the pycnocline, followed by a slight increase in oxygen with depth. The surface waters above the pycnocline were typically supersaturated with oxygen. The northern portions of the Bay where the most extensive hypoxia was observed corresponded to the regions with both the greatest thermohaline stratification, the highest nutrient inputs, and the highest primary productivity.     

Analysis of Blast Vibration Characteristics Across a Trench and a Pre-Split Plane

This paper presents the influence of various discontinuities, natural or artificial, on magnitude and frequencies of blast induced ground vibrations. These discontinuities were geological faults, a pond, a shaft incline, a trench and a pre-split plane interposed in the path of vibration propagation. In the post-trench region, ground vibrations in terms of peak particle velocity were significantly reduced and dominant frequencies in higher bands were consequently observed. Depth of trench with respect to blastholes were varied and consequent vibration characteristics were analyzed. The techniques of creating a trench and pre-split plane were successfully implemented in controlling vibration and in increasing the explosives charge to meet the scheduled production target of an opencast mine. Comparisons of ground vibration characteristics affected by a trench and a pre-split plane of the same depth are described in the text. The findings lead to the conclusion that such experimental data are necessary for production blasting in open cast mines under constrained conditions.     

Evaluation of ground water potential in the environs of Jhansi city,Uttar Pradesh using hydrogeomorphological assessment by satellite remote sensing technique

An attempt has been made to delineate different hydrogeomorphological units in and around the immediate environs of Jhansi city with a view to attempt a correlation between the well yields and hydrogeomorphic units using satellite remote sensing technique. In general, a positive correlation is observed between the geomorphic units and the borewell yields with overlapping yields at the margin. The pediment residual hill complex is observed to provide wells with discharges ranging from 100 gallons per hour (gph) to 5000 gph, while the wells drilled in shallow weathered, buried pediplain has yields in the range of 2000 to 10000 gph moderately weathered, buried pediplain has discharges in the range of 8000 to 12000 gph, and deeply weathered, buried pediplain has discharges in excess of 12000 gph.     

A distance-drawdown aquifer test method for aquifers with areal anisotropy

A new distance-drawdown method for aquifers with anisotropy on the horizontal plane is presented. The method uses scalar transformation to convert to an equivalent, isotropic medium, thus permitting application of the Cooper-Jacob Method. The method is applicable to cases where at least one ellipse of equal drawdown can be delineated but can also be applied where no ellipse can be discerned from the data. In the latter case, a least-squares regression approach can be employed to estimate the orientation and magnitude of the anisotropy. The regression R2 value provides a quantitative assessment of the degree to which the drawdown data are indicative of a systematic areal anisotropy in the aquifer or whether the data simply reflect natural aquifer heterogeneity. In addition to confined aquifers, this methodology, like the Cooper-Jacob Method, is also applicable to unconfined aquifers either before the onset of delayed drainage or following the completion of delayed drainage provided that the u value meets the recommended criterion.     

THE LAUSANNE CONGRESS

The International Society for Photogrammetry held the Xlth International Congress at Lausanne during July 1968. The authors review the activities of five of the seven I.S.P. Commissions.