THE IMPACT OF TSUNAMI ON THE COASTLINE OF JERVIS BAY,SOUTHEASTERN AUSTRALIA     

Edward A. Bryant  Robert W. Young  David M. Price  David J. Wheeler  Mark I. Pease 《自然地理学》2013,34(5):440-459

The Jervis Bay area offers a diversity of landforms that do not fit within contemporary views of coastal evolution. Field evidence indicates that catastrophic tsunami have had a significant impact on the coast and its hinterland both within and outside the embayment. Runup has overtopped cliffs 80 m above sea level and deposited chevron-shaped ridges to elevations of 130 m on the southern headland. Boulders, up to 6 m in diameter, have been deposited in an imbricated fashion against cliffs, on clifftops, and along shoreline ramps. Bed-form features and the size of transported material indicate flow depths up to 10 m and velocities around 8 m s^-1. While significant Pleistocene material has been swept onto the coastline, mainly in the form of barriers, radiocarbon dating indicates that tsunami have occurred repetitively throughout the Holocene. The most recent event occurred just before European settlement over 200 years ago. [Key words: barrier beaches, coastal geomorphology, tsunami, Jervis Bay, Australia.]  相似文献   

Prediction and visualization of GPS multipath signals in urban areas using LiDAR Digital Surface Models and building footprints     

Jing Li  George Taylor  David Kidner  Mark Ware 《International journal of geographical information science》2013,27(11-12):1197-1218

This paper explains a ray tracing method which is applied to prediction and visualization of diffracted and reflected GPS signals in dense urban areas. Reflected and diffracted signals can have a detrimental effect on GPS positioning accuracy especially in highly built‐up areas. The ray tracing technique implemented in this paper is specially geared to LiDAR height pole data at 1‐m spatial resolution and 2D building footprints in raster and vector format, respectively. Such a simple data format allows for rapid implementation of 3D ray tracing in a GIS without further processing so that detailed 3D urban models in vector format are not required. Issues of spatial uncertainty in the data used are also addressed in relation to the identification of multipath signals. Some preliminary results obtained from fieldwork are presented and analysed in detail.  相似文献   

A Multiresolution topographic surface database     

J. Mark Ware  Christopher B. Jones 《International journal of geographical information science》2013,27(6):479-496

Abstract

Multiresolution data structures provide a means of retrieving geographical features from a database at levels of detail which are adaptable to different scales of representation. A database design is presented which integrates multi-scale storage of point, linear and polygonal features, based on the line generalization tree, with a multi-scale surface model based on the Delaunay pyramid. The constituent vertices of topologically-structured geographical features are thus distributed between the triangulated levels of a Delaunay pyramid in which triangle edges are constrained to follow those features at differing degrees of generalization. Efficient locational access is achieved by imposing a spatial index on each level of the pyramid.  相似文献   

Database design for a multi-scale spatial information system     

C. B. Jones  D. B. Kidner  L. Q. Luo  G. Ll. Bundy  J. M. Ware 《International journal of geographical information science》2013,27(8):901-920

Abstract

Growth in the available quantities of digital geographical data has led to major problems in maintaining and integrating data from multiple sources, required by users at differing levels of generalization. Existing GIS and associated database management systems provide few facilities specifically intended for handling spatial data at multiple scales and require time consuming manual intervention to control update and retain consistency between representations. In this paper the GEODYSSEY conceptual design for a multi-scale, multiple representation spatial database is presented and the results of experimental implementation of several aspects of the design are described. Object-oriented, deductive and procedural programming techniques have been applied in several contexts: automated update software, using probabilistic reasoning; deductive query processing using explicit stored semantic and spatial relations combined with geometric data; multiresolution spatial data access methods combining poini, line, area and surface geometry; and triangulation-based generalization software that detects and resolves topological inconsistency.  相似文献   

Modelling of solar quiet magnetic field variations near a conductivity anomaly     

E. B. Aronson  R. H. Ware  P. L. Bender 《Geophysical Journal International》1979,59(3):539-552

Summary. A simplified model of the solar quiet-time ionospheric current system is used to calculate the induced currents in a model earth. The conductivity is assumed to be constant below a depth of about 400 km and zero above that depth. The current induced in the north—south conductivity anomaly under the Rocky Mountains is then estimated from the time-varying potential difference between points at 30 and 45° latitude at the surface of the conducting sphere. The purpose of these calculations is to investigate whether variations in the latitude of the northern hemisphere current system vortex will substantially alter the relationship between the observed magnetic field components at the Earth's surface and the local magnetic field gradient caused by the conductivity anomaly. We find that a 10° shift in the latitude of the ionospheric current focus causes a change of 6 per cent or less in the transfer function from the field components to the gradient in the total field. Thus such latitude shifts cannot explain much of the magnetic field gradient variation at periods near 24 hr that has been observed near Boulder, Colorado.  相似文献   

Thermoluminescenge and Uranium‐Thorium chronologies of pleistocene coastal landforms of the Illawarra region,New South Wales     

E. A. Bryant  R. W. Young  D. M. Price  S. A. Short 《The Australian geographer》1990,21(2):101-112

TL determinations of the ages of aeolian sands and U/Th determinations of the ages of crusts on rock platforms in the Illawarra region, especially at Red Point, indicate that these techniques give considerable promise of a major advance in deciphering the Pleistocene coastal record in Australia. The methods of dating are outlined, and problems of laboratory and field interpretation are considered. The longstanding debate as to whether the +2 m level of platforms is modern or is a Pleistocene relict has been resolved for the Illawarra coast, where these platforms can be shown to have been formed during the Last Interglacial high stand of the sea. By inference, the +4 m level must be of at least the same age. The +6 to 7 m level was cut by about 300Ka and may be as old as Pliocene. Four aeolian units at Red Point reworked from nearby barrier beach complexes date from c. 25Ka, 45Ka, 125Ka, and 300 to >400Ka. Reconnaissance surveys and dating indicate that aeolian sands of similar ages occur elsewhere along the New South Wales coast.  相似文献   

The detection and interpretation of hydrogen in fault gases   总被引：1，自引：0，他引：1  

Randolph H. Ware  Christian Roecken  Max Wyss 《Pure and Applied Geophysics》1984,122(2-4):392-402

Hydrogen gas can be released by chemical and mechanical changes in crustal rocks. Once released, it is highly mobile, buoyant, and almost insoluble in groundwater. A fault system may act as a conduit, allowing hydrogen to accumulate in soil gases near a surface expression. Since hydrogen is scarce in ambient air, its presence at elevated levels in soil gases may be a tool for fault mapping. In order to evaluate this tool, we surveyed eleven different faults by measuring the concentration of hydrogen and methane in 2 to 21 soil-gas samples that were collected near each of them. The sense of motion at four of those faults is normal (western United States, Greece), at five it is strike-slip or dip-slip (California, Colorado, Japan), and at two it is thrusting (California). At four of these faults (Hebgen Lake, Yellowstone, Yamasaki, Burro Mountain) maximum concentrations of hydrogen ranged from 80 ppm to 70% and methane from 300 ppm to 5%. All other sites showed ambient levels of both gases, except for one sample taken at Mt. Borah, Idaho, that was 2% methane. From this preliminary study it is not clear whether the presence of hydrogen is correlated uniquely to the location of faults or whether it occurs randomly. The conditions required to produced and accumulate hydrogen are also not clear. Excess hydrogen may well be produced by different mechanisms in different geological regimes. For example, if ferrous hydroxide is present in local rocks, it may react to produce hydrogen. Detailed and extensive studies are needed to clarify the connection between hydrogen and tectonic faulting.  相似文献   

North American farmland protection strategies in retrospect     

C. R. Bryant  Prof. Dr. L. H. Russwurm 《GeoJournal》1982,6(6):501-511

The arenas in which farmland protection strategies have developed in North America vary in terms of perceptions of the farmland resource and the role of planning, and in terms of administrative structures. Administratively, farmland protection strategies have developed in a variety of structures, ranging from the very decentralized ones of many US states to the more centralized, though still mixed, ones found in some Canadian provinces. Farmland protection strategies can thus be investigated in terms of how they address a variety of fundamental issues. Difficult questions are raised by policy evaluation, e.g. are objectives coherent, how do objectives relate to goals and objectives for other land uses and what would have happened in the absence of the program? It is argued that, while it is essential to encourage more analyses of how results, e.g. farmland removal rates, relate to stated objectives, it is equally important to study the decision-making process of implementation to establish both stated and implied objectives and therefore how farmland protection strategies relate to the broader land use planning and management context for other land uses.  相似文献   

Geological Indicators of Large Tsunami in Australia   总被引：1，自引：0，他引：1  

Bryant  E. A.  Nott  J. 《Natural Hazards》2001,24(3):231-249

Tsunami waves can produce four general categories of depositional and erosional signatures that differentiate them from storm waves. Combinations of items from these categories uniquely define the impact of palaeo-tsunami on the coastal landscape. The largest palaeo-tsunami waves in Australia swept sediment across the continental shelf and obtained flow depths of 15–20 m at the coastline with velocities in excess of 10 m ^-1. In New South Wales, along the cliffs of Jervis Bay, waves reachedelevations of more than 80 m above sea-level with evidence of flow depths in excess of 10 m. These waves swept 10 km inland over the Shoalhaven delta. In northern Queensland, boulders more than 6 m in diameter and weighing 286 tonnes were tossed alongshore above cyclone storm wave limits inside the Great Barrier Reef. In Western Australia waves overrode and breached 60 m high hills up to 5 km inland. Shell debris and cobbles can be found within deposits mapped as dunes, 30 km inland. The array of signatures provide directional information about the origin of the tsunami and, when combined with radiocarbon dating, indicate thatat least one and maybe two catastrophic events have occurred during the last 1000 years along these three coasts. Only the West Australian coast hashistorically been affected by notable tsunami with maximum run-up elevations of 4–6 m. Palaeo-tsunami have been an order of magnitude greater than this. These palaeo-tsunami are produced most likely by large submarine slides on the continental slope or the impactof meteorites with the adjacent ocean.  相似文献   

Geotechnical sampling and testing of gas-charged marine sediments atin situ pressures     

Mark W. Johns  Elliott Taylor  William R. Bryant 《Geo-Marine Letters》1982,2(3-4):231-236

Gas-charged marine sediments were sampled using a pressure core barrel and a new technique involving standard wireline sampling procedures. Pressure core barrel sampling provides sediments atin situ pressures with no degassing. Analysis of gas content, geotechnical properties and microfabric were performed for samples atin situ pressures and compared with degassed results. Methane concentrations ranged from 3,450 to 137,140 ppm for pressurized samples. Microfabric analyses reveal highly nonoriented clay particles and grains in degassed samples. Degassing of these methane-rich sediments increases porosities and compression indices, while reducing undrained shear strengths and computed preconsolidation pressures.  相似文献