Spectral characteristics of magnetogravity waves generated by high-energy mass source in the equatorial region of the atmosphere,Part I

The possibility of magnetogravity wave (MGW) propagation in the equatorial ionosphere taking into account the finite conductivity is analyzed. The dispersion relation shows the existence of two propagating MGW modes in ionospheric layer F2: high-frequency (HF MGW) and low frequency (LF MGW). The dispersion relations for them are executed and the characteristic frequencies and propagation velocities are determined. In this part of research the spectral features of disturbances in components of environment displacement for HF MGW, generated by a mass source, is carried out. The results are applied to estimate the values of density, pressure and magnetic field spectral components of magnetogravity disturbances caused by horizontal meteor sweep. They may be useful in the analysis of ionospheric disturbances excited by high energy geophysical sources.     

Hydrological regime of the Rhône Delta and dynamics of its coastline

Specific features of the hydrological regime of the Rhône River and the nearshore zone of its mouth are discussed. The processes of seawater intrusion into the delta branches are described. The information on the history of the delta evolution and development is presented along with the reconstruction of the Holocene evolution of the Rhône Delta and analysis of formation peculiarities of the present-day delta. Channel processes in the Rhône Delta and the dynamics of the delta coastline are described; characteristics of the deep-water fan are discussed, and the data on sediment balance are given.     

The bedrock topography of the botany basin,New South Wales

The bedrock topography of the Botany Basin has been determined from seismic‐sparker records made in Botany Bay and Bate Bay, and from seismic‐refraction and gravity measurements on the Kurnell Peninsula. Supplementary information has been obtained from boreholes both on land and in the sea.

The Cooks and Georges Rivers formerly constituted the main drainage of the Basin and flowed generally southeastwards (beneath the present Kurnell Peninsula) and joined the Port Hacking River east of Cronulla. The depth of the bedrock channel of the former Georges River is 75–80 m b.s.l. at Taren Point, 90–95 m beneath the Kurnell Peninsula and 110–115 m at its junction with the Port Hacking River channel. The bedrock channel of the former Cooks River is about 30 m b.s.l. at Kyeemagh, its present entrance to Botany Bay, and it joined the Georges River at a location now 90 m b.s.l. beneath the Kurnell Peninsula.

A second drainage system existed in the north and east of Botany Bay and generated the present mouth beneath which the bedrock is now 110 m b.s.l. This channel followed a southeasterly course parallel to the present northern shore of Botany Bay and was separated from that of the ‘Cooks and Georges Rivers’ by a bedrock ridge which extended from beneath Sydney Airport to the northern extremity of the Kurnell Peninsula. Over much of its length this divide had a depth of about 30 m b.s.l.

The formation of the Kurnell Peninsula tombolo led to the diversion of the ‘Cooks/Georges River’ through the mouth of Botany Bay and subsequently led to the development of the bay. This change in the drainage system occurred when the sea was less than 30 m below the present sea level.     

Challenges associated with pre-border management of biofouling on oil rigs

The potential for oil rigs to transport diverse, reef-like communities around the globe makes them high risk vectors for the inadvertent spread of non-indigenous species (NIS). This paper describes two case studies where a suite of pre-border management approaches was applied to semi-submersible drilling rigs. In the first case study, a drilling rig was defouled in-water prior to departure from New Zealand to Australia. Risk mitigation measures were successful in reducing biosecurity risks to the recipient region, but they resulted in the unintentional introduction of the non-indigenous brown mussel (Perna perna) to New Zealand when the rig was defouled in-water by divers. In the second case study, lessons learned from this high-profile incursion resulted in a more structured approach to pre-border management, and this serves as a useful template for future rig transfers.     

Discontinuity controlled probabilistic slope failure risk maps of the Altindag (settlement) region in Turkey

The evaluation of potential rock slope problems using stereographic projection techniques known as kinematic analysis is one of the most important parts of a slope stability investigation to be carried out in jointed rock media. In conventional stereoprojection techniques for the assessment of possible rock slope failures, the peak orientations of joints together with the slope geometry and the friction angle of the weakness planes are used. Other possible joint orientations which may be encountered in the rock media are ignored, although they belong to the group of joint peak orientations. In this study, nearly vertical jointed andesites cropped out at the Altindag settlement region in Ankara were studied in order to evaluate the relevance of this ignored discontinuity orientation data on slope stability. As a result, probabilistic risk maps for planar, toppling and wedge failures were produced using the kinematic rules and digital elevation model of the study area. The comparison of the distribution of the actual failures in the area and the probabilistic risk maps prepared for the study area revealed that all of the identified failures are found to be located in the higher risk zones on the probabilistic risk maps.     

Current trends in Great Lakes shipping

Shipping on the Great Lakes has changed rapidly in recent years. Internal Great Lakes traffic consists almost entirely of bulk movements, primarily of iron ore, coal, limestone, and grain. Ore shipments are mainly of taconite concentrate. Low-sulfur coal from the western areas of the United States is now moving downbound through the lakes, a movement in the opposite direction from the predominantly upbound movement of Appalachian coal. Opening of a larger lock in 1970 between lakes Superior and Huron has initiated a new generation of lake vessels, which are three times the size of the previous lake ships, and are too large to transit the Welland Canal and the St. Lawrence Seaway; for the first time since 1959 the largest “lakers” are land-locked. General cargo traffic between the Great Lakes and overseas has been declining rapidly since 1970, largely as the result of the rapid development of container ships, and the Interstate highway system, which increases the competitive advantages of salt-water ports.