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Compressional and shear body waves generated by a seismic source can be analyzed using vertical seismic profiling (VSP) data-acquisition procedures. If a goal of exploration geophysics is to study the physics and exploration applications of shear waves, it is important to know how much S-wave energy a source puts into the earth. To maximize S-wave created by a source, considerable effort has been expended to create surface sources that apply horizontally directed impulses to the earth (horizontal vibrators and horizontal impacts). In my project, radial shear (SR) and transverse shear (ST) waves generated by different types of sources and recorded by multicomponent receivers in a VSP well are examined and compared. The research question is ‘can a vertical-impact source create shear wave energy equivalent to the S-wave energy produced by standard horizontal-force shear-wave sources?’ To quantify the energy of shear-wave modes produced by different kinds of seismic sources, a VSP field test program was conducted at the Devine Test Site owned by The University of Texas at Austin. In the VSP data acquisition phase, the orientation of horizontal geophones is unknown because a borehole geophone rotates as it is lowered into a well, causing the horizontal geophones at each receiver station to be oriented in different azimuths. To study body waves, it is essential that all geophones in a vertical VSP array be oriented in a consistent azimuth. I mathematically rotated multi-component VSP sensors systems to change them from the inconsistent orientation they had at the time of data recording to a user-defined consistent-azimuth coordinate system. This rotation allowed ST and SR wave modes to be identified. After geophone rotation, direct-S wavelet amplitudes were analyzed in 90-ms windows starting at the first-break times of each arriving mode. Analysis of the rotated data showed that SR energy created by a vertical-impact source, a shot-hole explosive, and an inclined-impact source differ only slightly, and that there is essentially no difference in ST energy among these sources. Also, the signal frequency of SR and ST wave modes produced by horizontal-force shear wave sources are essentially the same as the frequency of SR and ST wave modes generated by a vertical-impact source. These test data show that vertical and horizontal vibrator sources produce shear wave modes having amplitudes 1000 times stronger than the other energy sources we tested. Considering the cost of using inclined-impact sources which is relatively expensive compared to using a vertical-impact source, and the difficulty of applying inclined-impacts in some land conditions, it is possible to obtain direct-S data of the same quality by using only a vertical-impact source or a shot-hole explosive. The arguments given above demonstrate that it is not necessary to use inclined-impact sources or horizontal vibrators to produce shear-wave data. S-wave data of the same quality produced by a horizontal-force source are provided by simple vertical-impact sources and shot-hole explosives. / text

Os principais impactos ambientais decorrentes de desmontes de rochas com explosivos estão associados à geração de vibrações no maciço circundante e pressão acústica. Para o monitoramento sismográfico apropriado, é fundamental que o sensor esteja bem acoplado ao meio, possibilitando a medição acurada da vibração do terreno. Devido à existência de diversas recomendações a respeito da montagem dos sensores de vibração (geofones) em campo, este estudo tem o intuito de avaliar os métodos de acoplamento de geofone mais comuns, determinando quais são aceitáveis para um adequado monitoramento sismográfico. Dessa forma, foi estudada a influência de quatro métodos de fixação nos parâmetros de vibração. Para este propósito, o primeiro geofone foi colocado sob um saco de areia, o segundo foi enterrado no solo, o terceiro foi cravado no solo e o quarto foi livremente colocado sobre o solo. Estes geofones foram dispostos lado a lado e as vibrações de desmontes com explosivos de uma mina de carvão a céu aberto foram monitoradas. As vibrações foram analisadas em termos de velocidade de vibração de partícula de pico, históricos temporais e frequência associada à vibração. Os resultados obtidos indicaram o desacoplamento do geofone sob saco de areia, descartando o método. O enterramento do geofone se mostrou preferível, entretanto, o uso de cravos registrou bom acoplamento. A colocação do geofone sobre o solo se mostrou aceitável de acordo com o nível de aceleração de vibração, decorrente do desmonte. / The main environmental impacts from rock blasting are ground vibrations and air overpressure. For proper blast vibration monitoring, it is critical that the sensor be coupled to the medium, enabling accurate measurement of ground vibration. Due to the existence of several recommendations regarding the mounting of vibration sensors (geophones) in the field, this study intends to evaluate the most common geophone coupling methods, determining which are acceptable for adequate vibration monitoring. The influence of four mounting methods on vibration parameters was studied. For this purpose, the first geophone was sandbagged, the second one was buried in soil, the third one was spiked and the fourth one was placed freely on the ground. These geophones were mounted side by side and ground vibrations at an opencast coal mine were monitored. The vibrations were analyzed in terms of peak particle velocity, time histories and frequency spectra. The results indicated the decoupling of the sandbagged geophone, discarding the method. The burial of the geophone proved to be preferable, however, the use of spikes recorded good coupling. The free placement of geophone proved to be acceptable according to the expected acceleration level.

Os principais impactos ambientais decorrentes de desmontes de rochas com explosivos estão associados à geração de vibrações no maciço circundante e pressão acústica. Para o monitoramento sismográfico apropriado, é fundamental que o sensor esteja bem acoplado ao meio, possibilitando a medição acurada da vibração do terreno. Devido à existência de diversas recomendações a respeito da montagem dos sensores de vibração (geofones) em campo, este estudo tem o intuito de avaliar os métodos de acoplamento de geofone mais comuns, determinando quais são aceitáveis para um adequado monitoramento sismográfico. Dessa forma, foi estudada a influência de quatro métodos de fixação nos parâmetros de vibração. Para este propósito, o primeiro geofone foi colocado sob um saco de areia, o segundo foi enterrado no solo, o terceiro foi cravado no solo e o quarto foi livremente colocado sobre o solo. Estes geofones foram dispostos lado a lado e as vibrações de desmontes com explosivos de uma mina de carvão a céu aberto foram monitoradas. As vibrações foram analisadas em termos de velocidade de vibração de partícula de pico, históricos temporais e frequência associada à vibração. Os resultados obtidos indicaram o desacoplamento do geofone sob saco de areia, descartando o método. O enterramento do geofone se mostrou preferível, entretanto, o uso de cravos registrou bom acoplamento. A colocação do geofone sobre o solo se mostrou aceitável de acordo com o nível de aceleração de vibração, decorrente do desmonte. / The main environmental impacts from rock blasting are ground vibrations and air overpressure. For proper blast vibration monitoring, it is critical that the sensor be coupled to the medium, enabling accurate measurement of ground vibration. Due to the existence of several recommendations regarding the mounting of vibration sensors (geophones) in the field, this study intends to evaluate the most common geophone coupling methods, determining which are acceptable for adequate vibration monitoring. The influence of four mounting methods on vibration parameters was studied. For this purpose, the first geophone was sandbagged, the second one was buried in soil, the third one was spiked and the fourth one was placed freely on the ground. These geophones were mounted side by side and ground vibrations at an opencast coal mine were monitored. The vibrations were analyzed in terms of peak particle velocity, time histories and frequency spectra. The results indicated the decoupling of the sandbagged geophone, discarding the method. The burial of the geophone proved to be preferable, however, the use of spikes recorded good coupling. The free placement of geophone proved to be acceptable according to the expected acceleration level.

Os principais impactos ambientais decorrentes de desmontes de rochas com explosivos estão associados à geração de vibrações no maciço circundante e pressão acústica. Para o monitoramento sismográfico apropriado, é fundamental que o sensor esteja bem acoplado ao meio, possibilitando a medição acurada da vibração do terreno. Devido à existência de diversas recomendações a respeito da montagem dos sensores de vibração (geofones) em campo, este estudo tem o intuito de avaliar os métodos de acoplamento de geofone mais comuns, determinando quais são aceitáveis para um adequado monitoramento sismográfico. Dessa forma, foi estudada a influência de quatro métodos de fixação nos parâmetros de vibração. Para este propósito, o primeiro geofone foi colocado sob um saco de areia, o segundo foi enterrado no solo, o terceiro foi cravado no solo e o quarto foi livremente colocado sobre o solo. Estes geofones foram dispostos lado a lado e as vibrações de desmontes com explosivos de uma mina de carvão a céu aberto foram monitoradas. As vibrações foram analisadas em termos de velocidade de vibração de partícula de pico, históricos temporais e frequência associada à vibração. Os resultados obtidos indicaram o desacoplamento do geofone sob saco de areia, descartando o método. O enterramento do geofone se mostrou preferível, entretanto, o uso de cravos registrou bom acoplamento. A colocação do geofone sobre o solo se mostrou aceitável de acordo com o nível de aceleração de vibração, decorrente do desmonte. / The main environmental impacts from rock blasting are ground vibrations and air overpressure. For proper blast vibration monitoring, it is critical that the sensor be coupled to the medium, enabling accurate measurement of ground vibration. Due to the existence of several recommendations regarding the mounting of vibration sensors (geophones) in the field, this study intends to evaluate the most common geophone coupling methods, determining which are acceptable for adequate vibration monitoring. The influence of four mounting methods on vibration parameters was studied. For this purpose, the first geophone was sandbagged, the second one was buried in soil, the third one was spiked and the fourth one was placed freely on the ground. These geophones were mounted side by side and ground vibrations at an opencast coal mine were monitored. The vibrations were analyzed in terms of peak particle velocity, time histories and frequency spectra. The results indicated the decoupling of the sandbagged geophone, discarding the method. The burial of the geophone proved to be preferable, however, the use of spikes recorded good coupling. The free placement of geophone proved to be acceptable according to the expected acceleration level.

As human settlement expands into the natural habitats of wild animals, the conflict between humans and wildlife increases. The human-elephant conflict is one that causes a tremendous amount of damage, often to poor villages close to the savannah. In this master's thesis, a system is developed, that is intended to detect, localise and track elephants from seismic vibrations generated from footsteps. The system consists of multiple devices, with three geophones, and a microprocessor each. To detect the footsteps, two different methods are evaluated. One that analyses features consistion of the normalised standard deviation, frequency peak, spectral centroid and low compared to high frequency content of a signal. These features of the signal are then compared to those of an elephant footstep. The other one compares the frequency content of the seismic wave from a footstep to an computed average of known elephant footsteps. The signal feature method performed the best with an accuracy of 89 %, and detecting 54 % of the footsteps. The detected footstep is sent to a backend where further calculations are done. With one device, estimations of the direction of arrival (DOA) angle can be made. This is done using a delay and sum algorithm. By using a Kalman filter on the DOA estimates, the bearing to the elephant can be tracked over time. From the detected elephant footsteps it has been shown that it is possible to estimate the direction of an elephant with quite high performance and by applying a Kalman filter to track the elephant, it has been shown that the filter gives better and more reasonable estimates. With two devices, a location can be estimated with triangulation and also an elephant's position can be tracked. With triangulation, where the easting position estimated to some extent, but the northing position did not give good results. By using these localisations estimates in a Kalman filter the elephant could be tracked in most of the cases with high enough performance and especially when there weren't too many high northing estimates. By using separate DOA estimations in an extended Kalman filter the easting position could be tracked fairly well, while the northing updates had some strange behaviours, most probably because of implementation error. / Project Ngulia

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