The work you do
Contenido
El geofísico realiza un trabajo que podría considerarse de gran interés por dos motivos principales: por un lado, porque con su trabajo contribuye a la investigación de lo que está oculto y, por otro, porque su aportación es muy útil para numerosos especialistas en la materia, es decir, que tiene una contribución multidisciplinar.
Una vez realizadas estas dos indicaciones que permiten evaluar de forma muy generalista el trabajo del geofísico, conviene concretar el tipo de tareas que lleva a cabo para poder conocer mejor su labor técnica y científica. El grueso de este trabajo consiste en la implantación de diferentes dispositivos sobre el terreno para, una vez obtenidas las lecturas pertinentes, procesar la información de estos datos e interpretarlos con el fin de aportar algo de «luz» al «oscuro» ambiente que es el subsuelo. Pero, como antes se ha indicado, esto es solamente una de las etapas, la correspondiente a la adquisición y procesado que, ni mucho menos, se presentan de forma aislada sino acompañada de otras etapas. En mayor o en menor medida, todas ellas contribuyen al trabajo final del geofísico y todas ellas son importantes.
Ordenadas de forma cronológica todas estas etapas, quedarían relacionadas de la siguiente manera:.
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- Obtención de información sobre la zona de trabajo.
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- Selección del método geofísico más adecuado.
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- Campaña de adquisición de datos del subsuelo.
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- Procesado de los datos adquiridos.
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- Integración de toda la información e interpretación de los resultados.
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- Redacción del informe final.
1. Information about the work area
This phase constitutes, logically, the first of all and is the one in which the geophysicist investigates the "databases" of a given area with the purpose of obtaining a first knowledge of the characteristics of the area where the work has to be carried out. These characteristics that must be known are very varied and could be differentiated into logistical and geological characteristics.
From a logistical point of view, the geophysicist should never neglect the work of general recognition of the area he intends to investigate, that is, knowing if there are access points and what they are like; see if the terrain is steep or practicable; See if there is vegetation that prevents the placement of the devices or if this vegetation is dispersed enough to be able to move between it.
From the geological point of view, the geophysicist has a very important job: trying to know what the main geological features of the study area are since it is very important to know in what depth range the target is located, if there is fracturing or another series of aspects that must be taken into consideration when proposing the devices, such as the preferred direction of this fracturing as well as stratification and folding. To do this, a compilation of the existing documentation must be made as exhaustive as possible. This phase may take some time but there is no doubt that the information you are able to provide will help so much that the duration of this first stage should not be a concern if it extends too long. Logically, once everything necessary has been collected, an analysis of all that information must be carried out.
2. Selection of the geophysical method
It consists of selecting the geophysical method or methods that are considered most appropriate to cover the objective. The most logical and common thing is that this phase of work can be carried out but, on numerous occasions, the prospective method is requested by the client which implies an advantage and a disadvantage. The advantage is due to the fact that you do not have to dedicate time to this phase since it is already covered by the client as he is the one who directly proposes or requests the type of research he wants to cover the objective. The drawback, however, lies in the difficulty or impossibility of changing the requested method for another different geophysical method that better suits the needs of the objective or the characteristics of the work area.
In any case, it is convenient for the geophysicist to analyze the characteristics of the objective pursued and determine which is the most appropriate method or methods to achieve it, either by the type of objective, by the depth at which it is expected to be found, or by its dimensions, or even by the budget available to undertake the work.
3. Data acquisition campaign
This stage could be considered the most important as it is the moment in which the geophysicist proceeds to obtain the field data that, after processing, will allow information about the characteristics of the subsoil. To carry out this data acquisition campaign in the field, the geophysicist must carry out a series of complementary tasks, as is the case, sometimes requesting and managing the necessary permits to be able to carry out the work in the study area. Even if they are simply permits of passage, on numerous occasions the geophysicist has to notify his intention to carry out a series of works to avoid prohibitions on the execution of measures that, with the displaced equipment and even the devices implanted in the field, sometimes the geophysicist is forced to comply. If it is private property, you will need to discuss your intentions with the owner; If they are public, with the city council involved. If it involves passing or crossing roads, sometimes you must notify the relevant town hall, county council or autonomous community. In short, administrative procedures do not escape the scope of work of a geophysicist.
Another of the complementary stages, but which must also be carried out prior to the data acquisition work, is the clearing of the undergrowth that, sometimes very densely, covers the areas where the measurements must be carried out, for which it will be necessary to open passageways with sufficient dimensions to allow the passage of personnel and equipment.
The third activity that the geophysicist must be aware that he must carry out in a complementary manner is the signaling of the work carried out in the field. Although there are currently a series of tools that facilitate this task, it is often advisable to also mark the measurements made (measurement points, beginnings and ends of profiles, etc.) directly on the ground, as is the case with markings with reflective and biodegradable paint, as well as with construction tape. The previously indicated tools that facilitate signaling of the status of the work are, for example, portable GPS signal receivers to obtain the more or less exact coordinates of the measured points. It is also possible to indicate it on maps of different scales and, what is usually more interesting, on aerial photographs.
Signaling as exhaustively as possible the position of the work carried out is, therefore, the fundamental task of the geophysicist, while good data and good results would be of no value if they are not correctly referenced.
Regarding the measurement of data in the field itself, which is what constitutes the main activity of the geophysicist in this phase of the study, a series of important facets should be highlighted such as the calibration of the devices, the implementation of the devices, measurement and verification. It is logical to think that, to obtain good measurements in the field, that is, coherent and real measurements, the recording devices must be calibrated, an activity that must be done regularly in order to keep the sensors in accordance with the manufacturer's technical requirements.
4. Data processing
At this stage, the geophysicist usually takes a laptop computer to the field in order to carry out a first processing and check, in a first inspection, whether the recorded data is of good quality or has suffered alterations of some kind that have caused apparently erroneous files to be obtained. In this case, this first processing actually consists of a review of the quality of the geophysical data obtained. Once confirmed that the files are acceptable, the geophysicist will archive them for subsequent treatment in the office, which constitutes the final processing.
This processing requires the application of different computer programs (currently the manual activity of data processing is unthinkable, a phase that previously took a long time due to the need to compare the data with tables, graphs, etc.). These programs are usually specific to each device or, sometimes, for a more general application. In any case, the geophysicist will be familiar with these programs in order to be able to get the most out of the data obtained.
5. Integration of all information and interpretation of results
Interpretation, that is, the formulation of the response to the problem posed. To do this, the geophysical document must be converted into a document with geological expression, so at this stage the contribution of experts in the geological topic contemplated is once again essential, who together with the geophysicist will be able to carry out the best interpretation of the results; It must be taken into account that geophysical instruments measure magnitudes related to the physical properties of rocks, but they do not know anything about lithology, stratigraphy, tectonics, etc., which are or are not possible at the place of measurements. Data processing and interpretation often form an inseparable couple; The process can provide various solutions compatible from a physical-mathematical point of view with the measurements taken, and greater priority in the choice should be given to the geological viability of the interpretation than to the smallest numerical error of the process. It is worth remembering that computers do not perform interpretations, and this activity is currently the preserve of the human brain. In any case, the term interpretation already implies its subjective nature.
6. Writing the final report
The task of writing the final report should not be considered the least important since the geophysicist must have sufficient ease to be able to express what work has been carried out, describe the methodology used, develop the chapter corresponding to the results obtained and express in a clear and concise manner the conclusions reached in order to establish the pertinent recommendations.
All this in itself seems obvious but it is important that the geophysicist makes an effort to take care of both the writing and the presentation of the results. To understand and evaluate these indications, it is enough not to forget that the writing of the final report constitutes the presentation of all the work carried out in the previous phases.
Among all this set of activities carried out by the geophysicist it would be unfair not to include another work that is carried out to a greater or lesser extent and that is commercial activity. He is the technician who best knows what he does, how he does it and why he does it and, therefore, he is the technician who will best be able to "sell" your product. Geophysical prospecting enjoys a good opinion by many professionals but, at the same time, it suffers from lack of knowledge, a "bad reputation" and even contempt from many. It is a task of great importance to make known the existence of geophysical prospecting and the possibilities it offers as well as its advantages and disadvantages.