Gpr

The case study presented is a prime example of integrated geophysical–archaeological prospection. The aerial photographs available are complemented by non-destructive geomagnetic and geoelectric surveys with a reading distance of 0.5 m or less. To gain depth information and provide higher resolution, ground-penetrating radar (GPR) data are integrated. The GPR data were collected in a 0.5 × 0.05 m raster and visualized as black-and-white time or depth slices. The developments presented allow us to incorporate GPR into the standardized interpretation process of archaeological prospection based on a geographical information system (Grs). Using GPR and all the other prospection data available as a basis, a detailed three-dimensional interpretation model of the monument detected, the southern part of the forum of the civil town of Roman Carnuntum, is created. Copyright © 2002 John Wiley & Sons, Ltd.

The Murray Basin is a low-lying but extensive intracratonic depocentre in southeastern Australia, preserving an extraordinary record of Late Neogene sedimentation. New stratigraphic and sedimentologic data allow the long-term evolution of the basin to be re-evaluated and suggest a significant role for: (1) tectonism in controlling basin evolution, and (2) progressive and step-wise climatic change beginning in the early Pleistocene. Tectonic change is associated with regional uplift, occurring at approximately the same rate from the early Pliocene until the present day, and possibly associated with changing mantle
circulation patterns or plate boundary processes. This uplift led to the defeat and re-routing of the Murray River, Australia’s major continental drainage system. Key to our interpretation is recognition of timing relationships between four prominent palaeogeographic features e the Loxton-Parilla Sands strandplain, the Gambier coastal plain, palaeo megalake Bungunnia and the Kanawinka Escarpment.  Geomorphic and stratigraphic evidence suggest that during the Early Pliocene the ancestral Murray River
was located in western Victoria, flowing south along the Douglas Depression. Relatively small amounts of regional uplift (<200 m) defeated this drainage system, dramatically changing the palaeogeography of southeastern Australia and forming Plio-Pleistocene megalake Bungunnia. At its maximum extent Lake
Bungunnia covered more than 50,000 km2, making it one of the largest known palaeo- or modern-lakes in an intracontinental setting. Magnetostratigraphic constraints suggest lake formation c. 2.4 Ma. The formation of Lake Bungunnia influenced the Pliocene coastal dynamics, depriving the coastline of a sediment source and changing the coastal system from a prograding strandline system to an erosional one. Erosion during this period formed the Kanawinka Escarpment, a palaeo sea-cliff and one of the most prominent and laterally extensive geomorphic features in southeastern Australia. Marine sediments c. 800 ka to c. 1.16 Ma represent the time of re-establishment of depositional coastal dynamics and of a permanent outlet for the Murray River. This age range is consistent with our best estimate of the age of the youngest Lake Bungunnia sediments and points towards an early Pleistocene age for the demise of the lake system. The youngest Lake Bungunnia sediment, present on a number of distinct terraces, suggests that progressive, step-wise climatic change played a role in the demise of the lake. However, in order for the ancestral Murray River system to have been able to breach the pre-existing tectonic dam, it is likely that tectonic change and/or temporarily enhanced discharge was also significant. This scenario indicates that the modern Murray River has only been in existence for at most 700 ka.

1] The discovery of rock glacier-like features on Mars suggests the presence of flowing, or once-flowing, ice-rock mixtures. These landforms, which include lobate debris aprons, concentric crater fill, and lineated valley fill, hold significant promise as reservoirs of stored water ice that could be used as fuel sources for human exploration of Mars and provide a frozen record of the climatic history of the planet. To understand the deformation and distribution of ice within these landforms, fundamental descriptions of their internal structure and development are required. To this end, a ground-penetrating radar investigation was initiated using rock glaciers in the San Juan Mountains of Colorado as surrogates for similar Martian landforms. Results obtained from one of these rock glaciers show that the interior of the landform is composed of a layered permafrost matrix of ice, sediment, and ice lenses that comprise thicker depositional units formed through highmagnitude debris falls. Folds in the uppermost layers correspond to the surface expression of ridges and furrows, suggesting that compressive stresses originating in the accumulation zone are transmitted downslope through the rock glacier. Rock glacier features on Mars may also consist of layered permafrost, which would suggest a history of development involving seasonal frost accumulation and/or water influx from below. In terms of water storage within Martian analogs, consideration must include the possibility that some water ice may be stored in relatively pure form within lenses and vein networks such as observed in the surrogate rock glacier of this study.

Ground-penetrating radar (GPR) has shown good potential in providing valuable information for the evaluation of masonry structures. We used GPR to survey several stone arch bridges located in the Galician territory in Spain. The results revealed previously unknown geometrical data and hidden characteristics of the interiors of the bridges, including the presence of internal voids, ancient arches, and restorations. However, many factors can adversely affect a GPR survey, such as ringing noise and signal attenuation. These factors can make data interpretation complex. To assist in the interpretation, we employed numerical modelling because it can play a very important role in extracting valid and useful information from GPR data sets. The expected electromagnetic wave response can be simulated through the use of modelling tools. The obtained information can be useful for engineers, as it provides better structural knowledge of the bridge.► A GPR survey methodology to assess stone masonry arch bridges is presented. ► The GPR results revealed unknown construction details and modifications over time. ► More realistic FDTD modelling was used to assess in the radar data interpretation. ► This work provided promising information to make decisions about stability.

Identifying underground utilities and predicting their depth are fundamental when it comes to civil engineering excavations, for example, to install or repair water, sewer, gas, electric systems and others. The accidental rupture of these systems can lead to unplanned repair costs, delays in completing the service, and risk injury or death of workers. One way to detect underground utilities is using the GPR-Ground Penetrating Radar geophysical method. To estimate depth, the travel time (two-way travel time) information provided by a radargram is used in conjunction with ground wave velocity, which depends on the dielectric constant of materials, where it is usually assumed to be constant for the area under investigation. This procedure provides satisfactory results in most cases. However, wrong depth estimates can result in damage to public utilities, rupturing pipes, cutting lines and so on. These cases occur mainly in areas that have a marked variation of water content and/or soil li-thology, thus greater care is required to determine the depth of the targets. The present work demonstrates how the interval velocity of Dix (1955) can be applied in radargram to estimate the depth of underground utilities compared to the conventional technique of constant velocity applied to the same data set. To accomplish this, synthetic and real GPR data were used to verify the applicability of the interval velocity technique and to determine the accuracy of the depth estimates obtained. The studies were carried out at the IAG/USP test site, a controlled environment, where metallic drums are buried in known positions and depths allowing the comparison of real to estimated depths. Numerical studies were also carried out aiming to simulate the real environment with variation of dielectric constant in depth and to validate the results