Emerson Rodrigo Almeida

Microwave Tomography-Enhanced GPR in Forensic Surveys: The Case Study of a Tropical Environment

Ground penetrating radar (GPR) is a geophysical tool currently adopted by police forces to locate buried objects and missing human bodies. However, a systematic assessment of its achievable imaging capabilities is still an open issue. In addition, sometimes, conventional data processing tools do not provide accurate and reliable information, thus leading to a misinterpretation of the location and geometry estimation of the target. In this framework, this paper deals with a case study referred to a tropical environment, and investigates the imaging capabilities offered by a linear microwave tomography approach. The results of three experiments, referred to the same organic target and carried out at different times by means of 270- and 900-MHz antennas, are presented. The comparison between the microwave tomographic approach and the widely used Kirchhoff migration suggests that the former procedure allows improved performances in locating both the target and the grave.

New magnetotelluric data trough the boundary between the Ossa Morena and Centroiberian Zones

The south-western part of the Iberian Peninsula, including the southern branch of the Iberian Massif, has recently been the subject of several magnetotelluric (MT) studies. This area is made up of three different tectonic terranes: the South Portuguese Zone (SPZ), the Ossa Morena Zone (OMZ) and the Central Iberian Zone (CIZ). The boundaries between these zones are considered to be sutures, which appear as high electrical conductivity anomalies in the MT surveys. The OMZ is characterised by a conductive layer at middle-lower crustal levels. To investigate the continuity of this conductive layer into the CIZ, a new MT profile was carried out. This 75-km long ENE profile goes through the boundary between the OMZ and the CIZ. The results of a two-dimensional magnetotelluric inversion revealed a high-conductivity anomaly in the transition OMZ/CIZ (the so-called Central Unit), which is interpreted as due to interconnected graphite along shear planes. High-conductivity anomalies appeared in the middle crust of the CIZ, whose geometry and location are consistent with the conductive layer previously found in the OMZ, thus confirming the prolongation of the conductive layer into the CIZ. The top of this layer correlated spatially with a broad reflector detected by a seismic profile previously acquired in the same area. This, together with other geological and petrological evidence, points to a common origin for both features.

Role of high mountain areas in catchment hydromineral resources - Northern/Central Portugal: environmental issues.

This study summarizes the results of geological, geomorphological, tectonic, geochemical, geophysical, hydrogeological and isotopic techniques in hydromineral resources assessment (issue temperature between 27oC and 45oC). Two case studies are presented: i) Serra da Estrela mountain region, the highest mountain in Portuguese mainland and ii) Serra do Marao mountain region. A special emphasis is dedicated to the recharge and discharge processes and the role of snowmelt as a source of hydromineral resources. Since local Spas are particularly dependent on water quality, the existence of mixing between hydromineral waters and local shallow groundwaters is also considered.

GPR data analysis enhanced by microwave tomography for forensic archaeology

GPR has been used worldwide to help the police enforcement to search for missing bodies. In this paper, microwave tomography is considered as an advanced data processing technique in order to enhance the visualization and thus improve the interpretation of GPR images for forensic purposes. In particular, we discuss on an experiment that was carried out by using a pig to simulate a human body buried in a tropical environment. A system equipped with 270 MHz and 900 MHz antennas was used to survey the area. The microwave tomography approach applied to the 270 MHz data allowed to get a good identification of the edges of the target, as well as to determine its position in the area of the experiment. The tomographic reconstruction of 900 MHz data allowed a better visualization of the grave itself.

Contributions of TDEM Survey in a Seismic Activity Area Triggered by Wells in Paraná Basin, Brazil - Preliminary Results

This article present TDEM results on a seismic activity area triggered by groundwater exploitation from deep wells. The study area is situated at Parana basin, Sao Paulo state, Brazil. Stations were individually arranged next to wells and along profiles. Preliminary result showed the geoelectrical stratigraphy of Parana basin. 1st geoelectrical layer is constituted by sedimentary aquifer, followed by top of basalt layer that occur ~60-80 m depth. A fractured zone filled with water within of the basaltic layer was found between 100-300 m depth, which agree to the depth estimated for more than 3000 micro earthtremor hypocenter in the studied region. The bottom of the basalt layer was estimated between ~400-650 m depth. The last geoelectrical layer is characterized by Botucatu sandstone. Results suggest that the high water flow in some wells seems to be related to the presence of fractured zones filled with water founded in the middle of basalt layer. Moreover, there are a good correlation between the seismic activities area and the fractured zones filled with water, which some wells presented the high flux of groundwater. This is a good result which suggest that the shallow seismic activity, can probably is being triggered by water wells drilling.

1D Joint Inversion of DC and TEM Data for Hydrogeological Applications - Preliminary Results

Electrical (DC) and transient electromagnetic (TEM) soundings have been used in great number of hydrological,environmental, and mining exploration studies. The data interpretation usually is done individually by 1D models resulting in ambiguous results. This fact can be explained by how the two different methodologies observe the medium below the surface. The vertical electrical sounding (VES) is good at marking very resistive structures, while the transient electromagnetic sounding (TEM) is very sensitive to map conductive structures. Another difference is that VES is better to detects shallow structures, while TEM soundings can reach deeper layers. In this way, a Matlab program for joint inversion of VES and TEM soundings was developed aiming explore the best of the both methods. Initially, the algorithm was tested with synthetic data and after was used real data from Parana Sedimentary Basin in Bebedouro region, Sao Paulo State, Brazil. The geoelectrical model obtained from joint inversion of VES and TEM data are more similar to the real geological condition and ambiguities were minimized. The results with synthetic and real data shows that joint inversion of VES/TEM is better for recovering the simulated models and shows a great potential in geological studies, particularly in hydrogeological studies.

Shallow geoelectric structure of eastern part of Terceira Island (Acores) from AMT soundings

The Terceira Island is located at the plate boundary between the Eurasian and African plates. This plate boundary usually referred to as the Terceira axis, is a highly complex, non conventional ridge system morphologically defined by a succession of deep rhombic basins and shallow volcanic banks or islands materializing domains of higher magmatic budget (Lourenco et al., 1998).