Geophysical Prospecting Techniques Research Articles

An attempt to use convolutional neural network to recover layered-earth structure from electrical resistivity tomography survey

The Electrical Resistivity Tomography (ERT) method is a geophysical prospecting technique for determining subsurface structure in terms of electrical resistivity distribution. Direct current is injected into the ground through a pair of electrodes, and the potential difference is measured using another pair of electrodes. The estimated resistivity model of the subsurface is then obtained using a mathematical optimization algorithm called the inversion algorithm, which incorporates multiple measured potential differences from different electrode configurations as the input data. The inverted resistivity model serves as a resource for the interpretation process of the survey. Specialists employ the model and the prior geological information in the area to extract the subsurface geological structure under the data measurement profile. The inverted model can be treated as a two-dimensional image in which each element represents resistivity. The image can be visualized as a blurred or distorted version of the actual resistivity image of the subsurface. We, therefore, developed a post-inversion image enhancement code using a neural network aiming to recover the true subsurface model with predetermined features. We employed the convolutional neural network (CNN) that uses the inverted models as input and returns an enhanced model as output. We tested our developed neural network with a case study that utilized the proposed method to recover the layered earth structure which is often found in real surveys. The electrode spacing was 5 meters in the Schlumberger array configuration. The true subsurface resistivity models of training data and validating data for evaluating the neural network were randomly generated based on the predetermined feature of the layered structure. We then generated their respective inverted models from those data through simulated inversion routine. As a result, 94.75% of the enhanced models in the validation dataset exhibited a lower loss metric compared to the original inverted models in the same validation dataset. We also applied the proposed method to practical field data to recover the subsurface layers and compared them with stratigraphic information from a borehole in each area. The result showed that the proposed method gives well-resolved structures in the enhancement process after the typical inversion.

Fine detection of large-scale complex geological structures based on geophysical prospecting techniques

Fine detection of large-scale complex geological structures based on geophysical prospecting techniques

Research on Comprehensive Exploration Technology of Underground Soil Karst Cave

Underground soi-karst caves are widely developed in China, especially in the southwestern region, and are relatively typical geological structures in limestone areas. It may cause adverse geological disasters such as landslides, ground fissures, ground collapses, mountain collapses, karst leaks, water loss, water inrush and mud out of mine pits, etc., which bring great hidden dangers to the survey and construction of foundation engineering. We analyze the mechanism of bad geological bodies for underground soil-karst caves, discuss the characteristics of several commonly used geophysical prospecting techniques for soil-karst cave exploration, such as high-density resistivity method, five-pole electric sounding method, and geological radar. Through the engineering examples, it is shown that the location and distribution of soil-karst caves can be effectively detected by using the above comprehensive exploration techniques, which take advantage of the differences in the electrical and magnetic properties of soil-karst caves.

Geophysical Prospecting Using ERT and IP Techniques to Locate Galena Veins

The aim of this study is to prove the effectiveness of two electrical geophysical prospecting techniques, namely electrical resistivity tomography (ERT) and induced polarization (IP), in locating thin vein structures of metal sulphides embedded in Palaeozoic materials underlying a sedimentary cover. For this purpose, a Quaternary basin known as La Garza was selected, located in the mining district of Linares-La Carolina (Southern Spain). Galena (PbS) veins appear abundantly throughout this area, hosted in the Palaeozoic granitic bedrock. The studied veins show thicknesses from 0.5 to 2.0 m, and most present a vertical planar distribution. The veins lose their continuity below the sedimentary cover due to normal fractures that control the subsidence of the basin. During the 1980s, geophysical research campaigns were carried out in La Garza using vertical electrical sounding and failed in detecting the hidden veins. For this reason, to carry out this study, a closed regular mesh was designed, composed by eight ERT and IP profiles, with variable lengths between 315 and 411 metres. An electrode spacing between 5 and 7 metres was selected, thus allowing the granite bedrock to be reached without significantly reducing the resolution capabilities of the method. Even though ERT and IP are well-known geophysical techniques for mapping ore deposits, this is a case study that shows the advantages of the simultaneous use of both techniques (ERT and IP), over their individual application. ERT allows for reconstructing the morphology of the basin and the fractures that control it due to high-resistivity contrast between the overlying sedimentary cover and the underlaying granitic basement. However, it cannot provide any insights about their degree of mineralization. At this point, it is the IP technique that makes it possible to differentiate which are the mineralized structures. Some of these fractures produce high (above 50 mV/V) and moderate (below 50 mV/V) chargeability values, suggesting the existence of several unexploited metal veins. Furthermore, the derived models enable researchers to analyse the morphology of this sedimentary basin controlled by normal faults.

Development of a distributed hybrid seismic–electrical data acquisition system based on the Narrowband Internet of Things (NB-IoT) technology

Abstract. The ambiguity of geophysical inversions, which is based on a single geophysical method, is a long-standing problem in geophysical exploration. Therefore, multi-method geophysical prospecting has become a popular topic. In multi-method geophysical prospecting, the joint inversion of seismic and electric data has been extensively researched for decades. However, the methods used for hybrid seismic–electric data acquisition that form the base for multi-method geophysical prospecting techniques have not yet been explored in detail. In this work, we developed a distributed, high-precision, hybrid seismic–electrical data acquisition system using advanced Narrowband Internet of Things (NB-IoT) technology. The system was equipped with a hybrid data acquisition board, a high-performance embedded motherboard based on field-programmable gate array, an advanced RISC machine, and host software. The data acquisition board used an ADS1278 24 bit analog-to-digital converter and FPGA-based digital filtering techniques to perform high-precision data acquisition. The equivalent input noise of the data acquisition board was only 0.5 µV with a sampling rate of 1000 samples per second and front-end gain of 40 dB. The multiple data acquisition stations of our system were synchronized using oven-controlled crystal oscillators and global positioning system technologies. Consequently, the clock frequency error of the system was less than 10−9 Hz at 1 Hz after calibration, and the synchronization accuracy of the data acquisition stations was ±200 ns. The use of sophisticated NB-IoT technologies allowed the long-distance wireless communication between the control center and the data acquisition stations. In validation experiments, it was found that our system was operationally stable and reliable, produced highly accurate data, and it was functionally flexible and convenient. Furthermore, using this system, it is also possible to monitor the real-time quality of data acquisition processes. We believe that the results obtained in this study will drive the advancement of prospective integrated seismic–electrical technologies and promote the use of IoT technologies in geophysical instrumentation.

Detection and treatment of water inflow in karst tunnel: A case study in Daba tunnel

In a karst tunnel, fissures or cracks that are filled with weathered materials are a type of potential water outlet as they are easily triggered and converted into groundwater outlets under the influence of high groundwater pressure. A terrible water inrush caused by potential water outlets can seriously hinder the project construction. Potential water outlets and water sources that surrounding the tunnel must be detected before water inflow can be treated. This paper provides a successful case of the detection and treatment of water inflow in a karst tunnel and proposes a potential water outlet detection (PWOD) method in which heavy rainfall (>50 mm/d) is considered a trigger for a potential water outlet. The Daba tunnel located in Hunan province, China, has been constructed in a karst stratum where the rock mass has been weathered intensely by the influence of two faults. Heavy rain triggered some potential water outlets, causing a serious water inrush. The PWOD method was applied in this project for the treatment of water inflow, and six potential water outlets in total were identified through three heavy rains. Meanwhile, a geophysical prospecting technique was also used to detect water sources. The connections between water outlets and water sources were identified with a 3-D graphic that included all of them. According to the distribution of water outlets and water sources, the detection area was divided into three sections and separately treated by curtain grouting.

A Manifold Approach for the Investigation of Early and Middle Neolithic Settlements in Thessaly, Greece

The IGEAN (Innovative Geophysical Approaches for the study of Early Agricultural villages of Neolithic) Thessaly project focused on Early and Neolithic settlements in Thessaly, Central Greece. The aim of the project was to highlight in an extensive way differences in settlement layouts while investigating commonalities as a way to understand Neolithic use of space. To accomplish this, a suite of geophysical prospection techniques (geomagnetic, electromagnetic induction, and Ground Penetrating Radar (GPR)), aerial platforms (historic aerial imagery and Remotely Piloted Aerial Systems (RPAS)) as well as very high resolution spaceborne sensors were integrated to acquire comprehensive pictures of settlements. Results of the IGEAN project provide archaeological information on the dynamic character of enclosures, the structure of architectural features and open spaces within sites as an indication of economic or communal spaces. At the same time, they demonstrated the importance of employing a suite of different geophysical techniques to reveal different aspects of the hindered prehistoric settlements that could not be highlighted with a single geophysical approach.

Application of geophysical prospecting techniques to evaluate geological-mining heritage: The Sinapismo mine (La Carolina, Southern Spain)

Geological-mining heritage is a valuable resource that deserves proper attention given its educational, scientific, landscape, and cultural worth. The significant geological and mining wealth of the abandoned metallogenic district of La Carolina (Southern Spain) is particularly interesting in this regard. This study is focused on one of the emblematic veins of this district, the Sinapismo vein, and more specifically, on the “La Paloma” drainage adit, stretching a total length of 1170m.A geological and geophysical study was conducted in the interior of this drainage structure to assess its heritage value as well as the condition of the mine voids with a view to converting the mine into a site open to the public. Electrical Resistivity Imaging (ERI) provides a general characterization of the mine, highlighting the vergence of the geological structure and the main faults and veins. Ground Penetrating Radar (GPR) offers higher resolution but provides a limited depth of penetration (less than 3m in this case). Profiles have been constructed using 500MHz and 250MHz shielded antennas to assist the analysis of the lithological alternance (quartzites and phyllites), layer dip, and the various associated fault and vein families.The position of the Sinapismo shaft with respect to the La Paloma drainage adit will permit an itinerary for visitors to be designed along the first 480m of the tunnel because it will allow for the proper location of two evacuation points (the shaft and the entrance to the adit). According to the results obtained from ERI and GPR studies, access to the rest of the drainage tunnel by visitors is inadvisable for safety reasons due to the existing fracture networks and the presence of veining.The two geophysical techniques applied in this study (ERI and GPR) provide, on the one hand, complementary information to the geological observations, which can be used to evaluate the geo-mining heritage. On the other hand, they offer information about the geomechanical conditions of the rock mass, thus permitting a safety assessment of access to the La Paloma adit.

Seismic exploration for volcanogenic massive sulphides: The DeGrussa copper-gold mine, Western Australia

Traditional geophysical prospecting techniques used for mineral exploration rarely provide either the depth of penetration or resolution required to accurately target orebodies at depth. Based on this, the seismic reflection method was trialled over a known VMS orebody at the DeGrussa copper-gold mine, Western Australia, in the hope of providing a viable exploration tool for deeper depths of investigation. However, a structurally complex geologic setting and a thick, highly variable regolith caused significant challenges in the processing of the seismic data. An initial 3D survey was not successful in imaging the orebody, so a follow-up downhole and 2D survey was acquired to address the potential issues. After verifying the in-situ seismic properties of the orebody through zero-offset Vertical Seismic Profiling (VSP) and increasing the down-dip offset range in the follow-up 2D survey it was found that the target provided a clear and unambiguous seismic response. However, a deep and variable regolith continued to cause significant issues during the imaging phase. This was overcome by applying a tomography-derived velocity field to a Kirchhoff migration, which produced outstanding results. Numerous tests and extensive data analyses eventually verified the seismic technique as a viable exploration tool for the region, with the direct detection of the target orebody.

Sinkhole risk assessment by ERT: The case study of Sirino Lake (Basilicata, Italy)

The presence of natural or artificial lakes and reservoirs that can drain because of natural phenomena can generate catastrophic events affecting urban and agricultural areas next to the source area.Therefore, geophysical prospecting techniques have been applied in the study of Sirino Lake, which, during the last century, was affected by the sudden opening of small sinkholes, resulting in the almost total draining of the lake and in the sudden increase of water flow rates of distal springs. Two electrical resistivity tomographies (ERTs) were carried out across the lake, using electrode arrays located on land and across the water body. Self-potential (SP) data were acquired around the lake shore and the surrounding area. The geophysical prospecting contributed significant data toward explaining the unique hydrogeological characteristics of the lake. Integration of geophysical, geological, hydrogeological, and geomorphological data allowed us to estimate the thickness of the lacustrine deposits beneath the lake, to describe the main patterns of the subsurface fluid flows in the area, and to identify possible water escape routes causing the piping phenomena.

Integrated geophysical investigations at a sacred Hittite Area in Central Anatolia, Turkey

In this paper, an integrated geophysical investigation of a sacred area in the archaeological site of Šapinuwa is presented. Šapinuwa was one of the important cities in the Hittite Empire. The archaeological site of Šapinuwa is located in the Çorum region of Central Anatolia, Turkey. The goal of the here presented integrative archaeological prospection investigation was to explore buried structures inside the so‐called sacred Taşdöşem area (Taşdöşem means “the stone pavement”) by employing a number of different near‐surface geophysical prospection methods. To this purpose, magnetic gradiometry, ground‐penetrating radar, electrical resistivity tomography, seismic refraction tomography, and multi‐channel analysis of surface wave tomography were applied in this specific area. Overall, the results of the individual geophysical investigations were superimposed in order to obtain more detailed and comprehensive integrative interpretations on the burials contained inside this sacred area. Electrical tomography depth slices revealed the presence of an important structure buried inside the Taşdöşem area. Surprisingly, the velocity variations observed in the depth slices of the multi‐channel analysis of surface wave tomography provided important information on the character of the burial structure. Additionally, seismic refraction tomography sections and depth slices confirmed the presence of the structures in the same locations. The result of the ground‐penetrating radar investigation did not present sufficient certainty regarding the possible deeper burials, whereas the magnetic gradiometry survey gave some insight into near‐surface structures. The combination of the employed geophysical prospection techniques was successfully able to characterize the structures that are assumed to have been buried within the Taşdöşem area. It is concluded that the integrated non‐invasive geophysical archaeological prospection study conducted at Šapinuwa provides a good example on how to approach the investigation and documentation of sites similar to the Taşdöşem.

Borehole seismoelectric logging using a shear-wave source: Possible application to CO2 disposal?

The behaviour of CO2 deposition sites – and their surroundings – during and after carbon dioxide injection has been matter of study for several years, and several geophysical prospection techniques like surface and crosshole seismics, geoelectrics, controlled source electromagnetics among others, have been applied to characterize the behaviour of the gas in the reservoirs. Until now, Seismolectromagnetic wave conversions occurring in poroelastic media via electrokinetic coupling have not been tested for this purpose. In this work, by means of numerical experiments using Pride's equations – extended to deal with partial saturations – we show that the seismoelectric and seismomagnetic interface responses (IR) generated at boundaries of a layer containing carbon dioxide are sensitive to its CO2 content. Further, modeling shear wave sources in surface to borehole seismoelectric layouts and employing two different models for the saturation dependence of the electrokinetic coefficient, we observe that the IR are sensitive to CO2 saturations ranging between 10% and 90%, and that the CO2 saturation at which the IR maxima are reached depends on the aforementioned models. Moreover, the IR are still sensitive to different CO2 saturations for a sealed CO2 reservoir covered by a clay layer. These results, which should be complemented by the analysis of the IR absolute amplitude, could lead, once confirmed on the field, to a new monitoring tool complementing existing ones.

Influence of measurement conditions on the resolution of electrical resistivity imaging: The example of abandoned mining dams in the La Carolina District (Southern Spain)

The La Carolina district, which is located in Jaen (Southern Spain), has experienced important mining activity for centuries. These long-standing mining activities, which have been associated with the presence of a philonian network of metallic sulfides, have generated vast accumulations of mine wastes—primarily tailings impoundments—that contain high levels of heavy metals from ore concentration plants. In this paper, the resolution of electrical resistivity imaging (ERI) is analyzed to determine the internal structure of these tailings dams and to assess the influence of the tailings over groundwater and surface water. The “La Manzana” dam, which is one of the largest sludge dams in the district, was selected to achieve this objective.First, old aerial photographs that were taken prior to the existence of the tailings dam were examined. Second, probing was performed using mechanical drilling, which enabled the identification of the features of the fill material, the thicknesses of the mine tailings and the contact zone between the mining structure and the basement. Third, the probe acts as a piezometer, which is an excellent tool to correlate the geophysical prospecting techniques. The characterization of the internal geometry of this structure has been performed by two ERI surveys, in which electric profiles were obtained under different moisture conditions. During the dry season, this methodology has been effective for identifying the morphology of the structures, contact with the substratum, variations in the vertical and horizontal distribution of the deposited material, and the fracture zones, as well as the contact between the tailings and the substratum on which they are deposited. Conversely, during the wet season, this contact was not distinct in the profile; however, variations in the saturation degree of these deposits, preferential infiltration areas and water flow through the interior of the tailings dam were observed. Last, the ERI survey confirmed the absence of waterproofing measures in the dump areas, which represents a high risk of soil and water pollution in the surrounding areas.

Ground-based archaeological prospection: Case studies from Greece

Nikos Papadopoulos, Gregory Tsokas, Apostolos Sarris, Panagiotis Tsourlos and George Vargemezis assess the preservation of standing monuments and ancient water management facilities. Archaeological prospection or archaeogeophysics includes the diverse geophysical methods employed either in planned excavations to guide the archaeological research in advance of and during the excavation process or in salvage excavations to provide a rapid assessment during the development of infrastructure in urban or rural environments. On a more general basis, these techniques are also applicable to support regional archaeological surveys by locating areas of archaeological interest and contributing to the settlement pattern analysis (Sarris and Jones, 2000). Unlike the destructive nature of the archaeological excavations, geophysical prospection techniques are non-invasive, providing at the same time a rapid reconnaissance of a site without disturbing the ground or the monuments themselves. The success or the failure of these techniques strongly depends on the contrasting physical properties that exist between the archaeological buried targets and the hosting material.

Combination of geophysical prospecting techniques into areas of high protection value: Identification of shallow volcanic structures

Timanfaya National Park is a volcanic area located in the southwest of Lanzarote Island (Canary Islands, Spain). Several lava tubes have been found in the lava flows but many others remain unknown. Its location and identification are important to mitigate collapse hazards in this touristic area. We present a new study about the location of recent lava tubes by the analysis and joint interpretation of around penetrating radar (GPR), microgravity and electromagnetic induction (EMI) data along the same profile over an area not previously surveyed. GPR data display a complex pattern of reflections up to ~10 m depth. The strongest hyperbolic reflections can be grouped in four different areas. Visual inspections carried out in the field allow confirming the occurrence of lava tubes at two of them. These reflections have been interpreted as the effect of the roof and bottom interfaces of several lava tubes. The microgravity survey defines a wide gravity low with several over-imposed minor highs and lows. Using the GPR data, a 2.5D gravity model has been obtained revealing four lava tubes. EMI data have been used to obtain an inverted resistivity model that displays four high resistivity areas that closely match the locations of the lava tubes derived from the previous methods. This resistivity model exhibits the lower resolution although reaches a deeper investigation depth (~20 m). The comparison of the results has revealed that joint interpretation of GPR, microgravity and EMI methods provides reliable models useful for the detection of unknown shallow lava tubes

Geologic remote sensing for geothermal exploration: A review

This paper is a comprehensive review of the potential for remote sensing in exploring for geothermal resources. Temperature gradients in the earth crust are typically 25–30°C per kilometer depth, however in active volcanic areas situated in subduction or rift zones gradients of up to 150°C per kilometer depth can be reached. In such volcanic areas, meteoric water in permeable and porous rocks is heated and hot water is trapped to form a geothermal reservoir. At the Earth's surface hot springs and fumaroles are evidence of hot geothermal water. In low enthalpy systems the heat can be used for heating/cooling and drying while in high enthalpy systems energy is generated using hot water or steam. In this paper we review the potential of remote sensing in the exploration for geothermal resources. We embark from the traditional suite of geophysical and geochemical prospecting techniques to arrive at parameters at the Earth surface that can be measured by earth observing satellites. Next, we summarize direct and indirect detection of geothermal potential using alteration mineralogy, temperature anomalies and heat fluxes, geobotanical anomalies and Earth surface deformation. A section of this paper is dedicated to published remote sensing studies illustrating the principles of mapping: surface deformation, gaseous emissions, mineral mapping, heat flux measurements, temperature mapping and geobotany. In a case study from the La Pacana caldera (Chili) geothermal field we illustrate the cross cutting relationships between various surface manifestations of geothermal reservoirs and how remotely sensed indicators can contribute to exploration. We conclude that although remote sensing of geothermal systems has not reached full maturity, there is great potential for integrating these surface measurements in a exploration framework. A number of recommendations for future research result from our analysis of geothermal systems and the present contributions of remote sensing to studying these systems. These are grouped along a number of question lines: ‘how reproducible are remote sensing products’, ‘can long term monitoring of geothermal systems be achieved’ and ‘do surface manifestations link to subsurface features’?

Study on the Exploitation Potential of Emergency Groundwater Source in Coastal Area of Quanzhou

In order to prepare for the extraordinary dry year, this study focuses on the fault zones identified by radioactive geophysical prospecting and EH4 electromagnetic imaging technique in the adjacent area of Qingyuan Mountain in Quanzhou. We infer that the fault-adjacent area has great potential for groundwater exploitation and perform a numerical simulation study on it using FEFLOW. Results show that the groundwater head can be restored in the whole hydrological series by establishing emergency water source and exploring groundwater in the fault zones in extraordinary dry year. This work demonstrates that it is feasible to use the fault zones adjacent to Qingyuan Maintain as an emergency water source of Quanzhou.

Aplicación de tomografía de refracción sísmica y análisis de microtremores como técnicas de prospección geofísicas en estudios geotécnicos en edificación

Although the CTE facilitates the application of geophysical prospecting techniques as complementary information to mechanical borings for the geotechnical characterization of the ground, its use in building is little widespread, making appropriate studies that analyze the benefits of its use. This article presents a comparative analysis of the results obtained using an experimental campaign with geophysical and traditional prospecting techniques. The methodology used has consisted in the characterization of a ground by seismic refraction tomography with microtremor analysis and mechanical borings, comparing them with the data obtained during the subsequent implementation of a foundation underpinning on the same site.The results have allowed to evaluate the limitations of each method and advantages of their combination.In conclusion, the application of geophysical prospecting techniques complementary to mechanical borings has contributed to a better geotechnical characterization of the ground, improving the planning and estimation of building project costs.

A Noniterative Method for Locating Soft Faults in Complex Wire Networks

Reflectometry-based methods are the standard choice for fault-detection techniques in wire networks. While effective when dealing with simple networks and relatively hard faults, their results can be of more difficult interpretation if a network presents more than two branches. In this paper, we propose the use of an alternative technique based on a coherent multiport characterization of a network under test. The data thus collected are used to define excitation signals that will be focusing over the position of a fault, following a method already successfully applied in geophysical prospection techniques and nondestructive testing, namely, the DORT method, based on the synthesis of time-reversed signals. It is shown that a direct transposition of this technique to wire networks is not possible, due to the guided nature of wave propagation in wire networks, leading to the impossibility of assuming a dominant direction of propagation, as opposed to the case of propagation in open media. A differential version of the DORT method is introduced, enabling an accurate identification of the original position of faults. Numerical and experimental results are presented to demonstrate the feasibility of this approach.

City Map of AncientEpomanduodurum(Mandeure–Mathay, Franche‐Comté, Eastern France): Contribution of Geophysical Prospecting Techniques

ABSTRACTThis study presents the main results of the geophysical survey of ancientEpomanduodurum, at Mandeure–Mathay, Eastern France. In northeastern Gaul,Epomanduodurumis a site of a major scientific interest for the understanding of past settlements and territorial formation at the end of the Iron Age and during the Roman period. The site, including a Roman urban centre and two suburbs containing workshops, occupies more than 500 ha inside and beyond a meander of the River Doubs. From the beginning of survey in 2001, several methods (fast electrical imaging automatic resistivity profiling system, ground penetrating radar, magnetic and electromagnetic mapping) have been performed on a large scale in order to precisely identify the vast extent and structure of the Roman town. The interpretation of the geophysical data was carried out using a combination of different data sources, including ancient maps and excavations recently conducted on restricted areas. The overall organization of an artisan quarter of 8 ha was revealed along a main Roman road leading to the left bank of the River Doubs. On the other bank, a river fortification and a vast monumental religious complex were recognized in the southern part of the Roman town. The geophysical imaging shows that the sacred area includes several temples or groups of temples radiating from the theatre. Other new buried structures probably corresponding to annexes, chapels and altars were also detected within this sacred area of 10 ha bound on three sides by a wall enclosure with monumental passages. In a surveyed area of 70 ha, geophysical prospecting techniques provided a clear overall image of the Roman urbanism revealed through a rectangular road network and street system delimiting insulae of variable sizes. The detection along the River Doubs of buildings similar to storehouses attests to fluvial transport and also suggests the likely existence of a port. More generally, the combination on a large scale of geophysical prospecting, aerial photographs and excavations allowed a new plan of the urban structure of the ancient town ofEpomanduodurumto be produced for an area of over 300 ha. Copyright © 2012 John Wiley & Sons, Ltd.