Potential loess landslide deformation monitoring using L-band SAR interferometry

Multi-temporal InSAR technique can implement continuous earth surface deformation detection with long time scale and wide geographical coverage. In this paper, we first employ the Small Baseline Subset method to survey potential landslides in Guide County, Qinghai Province, which is identified as a loess landslide prone area for geological and climate conditions. Two anomalous deformation regions are detected by L-band Phased Array and L-band Synthetic Aperture Radar stacks. Then, qualitative and quantitative evaluations of the measuring points are given for understanding the distribution regularity of deformation. Finally, preliminary correlation between the time-series deformation and triggering factors is analyzed to explore the driving mechanism for landslide movement. The results demonstrate that L-band SAR has high potential in landslide monitoring applications and can be used as the basis for landslide recognizing, precursory information extracting, and early warning.     

MULTINATIONAL ENTERPRISES IN BRAZIL: LOCATIONAL PATTERNS AND IMPLICATIONS FOR REGIONAL DEVELOPMENT

The long-established role of foreign interests in Latin America, and specifically Brazil, has been perpetuated since 1945 by multinational corporations. This article analyzes five industries where foreign direct investment has been especially important. These industries tend toward spatial concentration, particulary in metropolitan locations and at growth poles offering special attractions. A comparative study of private Brazilian enterprises suggests that these may offer greater opportunities for regional development than do the MNC's but that such concerns are dependent to some extent upon both MNC's and governmental assistance for their growth.     

Post-glacial loess deposition in a montane environment: South Thompson River valley,British Columbia,Canada

In the late Wisconsinan, the South Thompson River valley, British Columbia, was occupied by an ice-dammed lake. After the lake drained, the exposed lacustrine silt became the source material for a Holocene loess. The purpose of this paper is to establish the stratigraphic, depositional and geomorphic framework of loess occurring along the South Thompson River valley immediately east of Kamloops, British Columbia. This montane environment of loess deposition was characterised by active slope and fluvial processes depositing sediments contemporaneously with the accumulation of loess. The loess reaches an average of 4 m in thickness in the central part of the valley and thins towards the valley sides. Two tephras—Mount St Helens Y (3.4 ka) and Mount Mazama (6.8 ka)— occur in the loess and are invaluable stratigraphic markers. Most of the loess was probably deposited between 8.2 ka and 3.4 ka, a period coinciding with mid-Holocene increased summer temperatures and decreased precipitation in south-central British Columbia. Debris flows and small streams, originating on the valley sides, flowed out on to the loess depositing sand and gravel beds. These deposits form a definite proximal—distal relation across valley with the slope-derived sediments decreasing and the loess increasing in thickness towards the centre of the valley. The lactustrine silt particles were mobilised by diurnal mountain and valley, gravity, and canalised winds flowing within the South Thompson valley. An analysis of contemporary wind-flow data was undertaken to provide a possible analogue for valley wind flows in the mid-Holocene.     

Bacteria,fungi and biokarst in Lechuguilla Cave,Carlsbad Caverns National Park,New Mexico

Lechuguilla Cave is a deep, extensive, gypsumand sulfur-bearing hypogenic cave in Carlsbad Caverns National Park, New Mexico, most of which (>90%) lies more than 300 m beneath the entrance. Located in the arid Guadalupe Mountains, Lechuguilla's remarkable state of preservation is partially due to the locally continuous Yates Formation siltstone that has effectively diverted most vadose water away from the cave. Allocthonous organic input to the cave is therefore very limited, but bacterial and fungal colonization is relatively extensive: (1)Aspergillus sp. fungi and unidentified bacteria are associated with iron-, manganese-, and sulfur-rich encrustations on calcitic folia near the suspected water table 466 m below the entrance; (2) 92 species of fungi in 19 genera have been identified throughout the cave in oligotrophic (nutrient-poor) soils and pools; (3) cave-air condensate contains unidentified microbes; (4) indigenous chemoheterotrophicSeliberius andCaulobacter bacteria are known from remote pool sites; and (5) at least four genera of heterotrophic bacteria with population densities near 5×10⁵ colony-forming units (CFU) per gram are present in ceiling-bound deposits of supposedly abiogenic condensation-corrosion residues. Various lines of evidence suggest that autotrophic bacteria are present in the ceiling-bound residues and could act as primary producers in a unique subterranean microbial food chain. The suspected autotrophic bacteria are probably chemolithoautotrophic (CLA), utilizing trace iron, manganese, or sulfur in the limestone and dolomitic bedrock to mechanically (and possibly biochemically) erode the substrate to produce residual floor deposits. Because other major sources of organic matter have not been detected, we suggest that these CLA bacteria are providing requisite organic matter to the known heterotrophic bacteria and fungi in the residues. The cavewide bacterial and fungal distribution, the large volumes of corrosion residues, and the presence of ancient bacterial filaments in unusual calcite speleothems (biothems) attest to the apparent longevity of microbial occupation in this cave.     

Pre-Set Delay Electronic Detonators: Merits Opposite Programmable Systems

The South African mining industry first experienced en-masse use of electronic detonators in the Narrow Reef environment using AEL's Electrodet™ pre-set delay system. In recent years, programmable systems such as AEL's Smartdet™ have also established their position, and within both AEL and the mines there has been important learning around the strengths and weaknesses of these systems. In general, the fixed delay systems tend to be more easily appreciated by less-skilled work teams, and are very well suited to simple layouts, especially long, narrow blasts. However, development of programmable row controllers and series delay inserts has greatly expanded the field of usefulness of these systems while retaining most of the simplicity of use. The programmable systems are immensely flexible and therefore able to function under any condition, but require a higher level of discipline and knowledge. Much has been done to address this issue and make the systems user friendly, so the systems have converged to some extent. These systems are both valuable tools for achieving control over blasting in underground and surface applications. The choice of system is very dependent on the prevailing conditions. Accurate timing with electronic enhancements continues to show an increasing range of benefits to mining operations. There is a strong parallel with non-electronic initiation systems which helps to understand the appropriate use of the systems.     

Migration of recharge waters downgradient from the Santa Catalina Mountains into the Tucson basin aquifer, Arizona, USA

 Aquifers in the arid alluvial basins of the southwestern U.S. are recharged predominantly by infiltration from streams and playas within the basins and by water entering along the margins of the basins. The Tucson basin of southeastern Arizona is such a basin. The Santa Catalina Mountains form the northern boundary of this basin and receive more than twice as much precipitation (ca. 700 mm/year) as does the basin itself (ca. 300 mm/year). In this study environmental isotopes were employed to investigate the migration of precipitation basinward through shallow joints and fractures. Water samples were obtained from springs and runoff in the Santa Catalina Mountains and from wells in the foothills of the Santa Catalina Mountains. Stable isotopes (δD and δ¹⁸O) and thermonuclear-bomb-produced tritium enabled qualitative characterization of flow paths and flow velocities. Stable-isotope measurements show no direct altitude effect. Tritium values indicate that although a few springs and wells discharge pre-bomb water, most springs discharge waters from the 1960s or later. Received, February 1997 · Revised, September 1997 · Accepted, September 1997