Abstract Ground penetrating radar (GPR) offers a high-resolution, shallow subsurface profiling technique for use in sedimentological and reservoir analogue studies. GPR is similar to seismic reflection profiling but uses electromagnetic radiation in the 50 to 500 MHz frequency range (in geological applications). By using these relatively high frequencies, high resolution data can be obtained. Short duration pulses of electromagnetic energy are transmitted into the ground, reflected from interfaces across which there are abrupt changes in dielectric properties, and are detected by a receiver. These received signals are displayed in nanoseconds two-way time and may be recorded digitally allowing subsequent processing. Some 1000 m of 2D GPR profiles were collected from a modern point bar on the Madison River, Montana USA and have been interpreted using an approach similar to seismic stratigraphic analysis. This has allowed identification of a number of radar sequences and radar facies. Radar sequence boundaries are identified by reflector terminations (onlap, downlap, toplap and erosional truncation) and represent episodes of erosion during the development of the point bar. In contrast, radar sequences and their component radar facies record phases of accretion of the point bar. Each radar sequence is linked to a discrete accretionary unit that can be mapped on the surface of the point bar. Mapping of the radar sequences and radar facies has allowed quantification of their 3D geometry.

Ground penetrating radar: Application to sandbody geometry and heterogeneity studies

Modelling and model building

This paper describes dielectric properties of asphalt pavement that were studied in the process of developing a roller mountable microwave asphalt pavement density sensor as part of the National Cooperative Highway Research Program IDEA project. This new sensor involves simultaneously measuring reflected microwave signals from the asphalt pavement in front of and behind the vibratory roller. As the reflected signal and penetration depth of microwaves depend on the dielectric properties of asphalt pavement, temperature, and frequency dependencies of the permittivity and loss of asphalt, samples of different densities were studied in the frequency range from 100 Hz to 12 GHz. Results show that (1) permittivity and loss depend on frequency and temperature; (ii) the higher the pavement density, the higher the permittivity; (iii) permittivity slightly increases with temperature; (iv) moisture strongly increases permittivity and loss at low frequencies and only slightly at microwave frequencies; and (v) the penetration depth of microwaves in asphalt pavement is about 1214 cm at 8 GHz and only about 4 cm at 30 GHz.

Dielectric Properties of Asphalt Pavement

Shallow electromagnetic (EM) and ground-penetrating radar (GPR) surveys were conducted in an area north of Auckland, New Zealand to assist the search for human remains. The body had been buried for almost 12 years in a plantation forest that was irregularly disrupted and modified by tree harvesting and the partial removal of stumps. EM identified anomalous areas of potential interest, because a target need only be nearby to generate an EM response. GPR was then used to map subsurface layering, layering disruption, and buried objects, immediately adjacent to an EM anomaly. Because of the nature of the site, numerous geophysical anomalies were present. GPR was particularly sensitive to site disturbance resulting from the forestry operations. An isolated EM anomaly on the fringes of an expanded survey area was coincident with the location of the body. Whether for criminal investigations or for archaeological work, a combination of geophysical techniques is recommended.

The search for "Yvonne": a case example of the delineation of a grave using near-surface geophysical methods.

Forensic investigations concern locating, identifying, collecting, and cataloging physical evidence for the purpose of presenting it in court. One aspect of forensic investigations concerns locating clandestine evidence which is often concealed in the subsurface. This task is typically guided by information provided by informants (pathological liars), witnesses, psychics, and sometimes suspects. Resultant searches may be time consuming and frustrating to understaffed departments. Often such searches lead to excavations that destroy evidence. Any nondestructive method used to reduce the time spent on searches and excavations and to increase the probability of locating physical evidence are of prime interest to the law enforcement community. Remote sensing methods, which are nondestructive, are currently being applied with promising results in forensic investigations. Some of the more promising methods, including infrared, magnetics, electromagnetics, and ground penetrating radar are discussed. Remote sensing methods when properly applied can provide the forensic investigator tremendous savings in time and cost in the search for physical evidence. The forensic investigator must be educated to understand that there is no remote sensing method that will consistently find a body or physical evidence. These methods locate anomalous areas, and the cause of these anomalies will only be fully understood upon examination by others.

Remote sensing applications in forensic investigations

In Japan, geophysical methods are normally used to estimate the distribution of cultural relics before digging. Objects of archaeological interest are usually located within a few meters of the surface. Therefore, geophysical methods suitable for archaeological exploration are those which provide high resolution at shallow depths. The most commonly used geophysical methods are ground‐probing radar, resistivity, and magnetometry. Of these methods, we used mainly ground‐probing radar and resistivity surveys in archaeological investigations at four sites. Three of the sites were in Gumma Prefecture (Japan); they were covered with volcanic deposits (loam or pumice). Using ground‐probing radar, we were able to locate ancient dwellings, burial mounds, and a distribution of archaeologically significant “culture layers.” At the other site, in Nara Prefecture, we located part of the remains of an ancient city. In this investigation, the resistivity method and ground‐probing radar were combined to determine the loc...

Takashi Kanemori

Papers

Use of ground-probing radar and resistivity surveys for archaeological investigations

Ground-Probing Radar And Resistivity Surveys Used In Archaeological Investigations

A new type of geophone, Eddy‐Seis: Theoretical study of its response characteristics and method of testing