The impact of seismic noise produced by wind turbines on seismic borehole measurements
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Abstract. Seismic signals produced by wind turbines can have an adverse effect on seismological measurements up to distances of several kilometres. Based on numerical simulations of the emitted seismic wave field, we study the effectivity of seismic borehole installations as a way to reduce the incoming noise. We analyse the signal amplitude as a function of sensor depth and investigate effects of seismic velocities, damping parameters and geological layering in the subsurface. Our numerical approach is validated by real data from borehole installations affected by wind turbines. We demonstrate that a seismic borehole installation with an adequate depth can effectively reduce the impact of seismic noise from wind turbines in comparison to surface installations. Therefore, placing the seismometer at greater depth represents a potentially effective measure to improve or retain the quality of the recordings at a seismic station. However, the advantages of the borehole decrease significantly with increasing signal wavelength.Keywords:
Seismic Noise
Seismometer
Vertical seismic profile
Passive seismic
Abstract. Seismic signals produced by wind turbines can have an adverse effect on seismological measurements up to distances of several kilometres. Based on numerical simulations of the emitted seismic wavefield, we study the effectivity of seismic borehole installations as a way to reduce the incoming noise. We analyse the signal amplitude as a function of sensor depth and investigate effects of seismic velocities, damping parameters and geological layerings in the subsurface. Our numerical approach is validated by real data from borehole installations affected by wind turbines. We demonstrate that a seismic borehole installation with an adequate depth can effectively reduce the impact of seismic noise from wind turbines in comparison to surface installations. Therefore, placing the seismometer at greater depth represents a potentially effective measure to improve or retain the quality of the recordings at a seismic station. However, the advantages of the borehole decrease significantly with increasing signal wavelength.
Seismometer
Seismic Noise
Vertical seismic profile
Passive seismic
SIGNAL (programming language)
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We investigated the use of seismic sensors as small seismic sources. A voltage signal is applied to a geophone that forces the mass within the geophone to move. The movement of the mass generates a seismic wavefield that was recorded with an array of geophones operating in the conventional sense. We observed higher-frequency (25 Hz and above) surface and body waves propagating from the geophone source at offsets of 10 s of meters. We further found that the surface waves emitted from geophone sources can be used to generate a surface-wave group velocity map. We discuss potential developments and future applications.
Geophone
Vertical seismic profile
Seismic velocity
Passive seismic
SIGNAL (programming language)
Seismic Noise
Seismic array
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Abstract. Seismic signals produced by wind turbines can have an adverse effect on seismological measurements up to distances of several kilometres. Based on numerical simulations of the emitted seismic wave field, we study the effectivity of seismic borehole installations as a way to reduce the incoming noise. We analyse the signal amplitude as a function of sensor depth and investigate effects of seismic velocities, damping parameters and geological layering in the subsurface. Our numerical approach is validated by real data from borehole installations affected by wind turbines. We demonstrate that a seismic borehole installation with an adequate depth can effectively reduce the impact of seismic noise from wind turbines in comparison to surface installations. Therefore, placing the seismometer at greater depth represents a potentially effective measure to improve or retain the quality of the recordings at a seismic station. However, the advantages of the borehole decrease significantly with increasing signal wavelength.
Seismic Noise
Seismometer
Vertical seismic profile
Passive seismic
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Passive seismic plays an important role in the investigation of the interior structure of the Earth. Passive seismic is a 3-D seismic imaging of the target geology without using artificial surface sources. It uses multi-component seismic receivers to take advantage of shear wave energy generated by the microearthquakes thereby delivering a shear wave (Vs) velocity distribution estimate of the subsurface in addition to the conventional compressional (Vp) image. Recently, the passive seismic tomography surveys became an essential tool for the oil industry and modern reservoir management. The passive seismic technology is applied to investigate the relatively shallow depths that lie in hydrocarbon exploration window. In addition, some of the problems that are encountered in the conventional seismic explorations, for example salt domes effects, are solved using this technique. Passive Seismic Method constitutes the passive seismic transmission tomography in which 3-D images are created using the observed travel time of seismic signals originating from micro-earthquakes occurring below the target; and passive seismic emission tomography where the micro-seismic activity itself becomes the imaging target. The most straight-forward approach is to observe and record the direct arrivals of the seismic waves from these events and to map the distribution of hypocenter locations. Passive seismic technology, as an imaging and processing technique, challenges the following issues:<br>1. Identification of anisotropic flow and well targeting.<br>2. Determination of the three-dimensional VP and VP/VS velocity structure.<br>3. Analyzing the seismicity.<br>4. Getting under salt formations.<br>5. Description of the deformation processes of the reservoir.<br>6. Delineation of leaky fault structures, mapping active and conductive fractures of faults, at an<br>intermediate scale between borehole imaging and 3-D seismic imaging.<br>7. Predictive reservoir models thus Reducing uncertainty.<br>The Gulf of Suez, Egypt, is characterized by its high hydrocarbon potentialities where most of Egypt oil production comes from. The basic problems in exploration at the Gulf of Suez come from its complex geologic structural setting as well as the presence of anhydrites that mask the structures below. Therefore, Passive seismic transmission tomography (PSTT) creates 3-D images using the observed travel time of seismic signals originating from micro-earthquakes occurring below the so masked structures. The cost/benefit justification of 3D seismic applies to Passive Seismic. Deeper pool tests drilled with this coverage will have a much higher success rate. Coverage will provide risk-reducing information content. For example: new interpretation could prevent drilling of unsuccessful step-out wells ($1 MM savings per well). Additionally, PSTT may be the only viable seismic option for certain areas. One of the most important parts of the passive tomography investigation is the quality control of the results. This can be done using many different procedures and their correlation can lead to safe conclusions about the resolution power of the dataset and therefore the quality of the tomographic inversion results. The method used does not only verify the estimation of their accuracy, but also points out the areas of higher and lower analysis precision, thus making it easier to control the interpretation of the results. This paper represents the passive seismic technology as an alternative to the conventional seismic exploration for delineating the structures that are masked by salt domes and Anhydrites in the Gulf of Suez and other regions, as well.
Passive seismic
Hypocenter
Seismic Tomography
Geophysical Imaging
Vertical seismic profile
Seismic anisotropy
Synthetic seismogram
Seismic to simulation
Geophone
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In this study, a method for characterizing ambient seismic noise in an urban park using a pair of Tromino3G+ seismographs simultaneously recording high-gain velocity along two axes (north-south and east-west) is presented. The motivation for this study is to provide design parameters for seismic surveys conducted at a site prior to the installation of long-term permanent seismographs. Ambient seismic noise refers to the coherent component of the measured signal that comes from uncontrolled, or passive sources (natural and anthropogenic). Applications of interest include geotechnical studies, modeling the seismic response of infrastructure, surface monitoring, noise mitigation, and urban activity monitoring, which may exploit the use of well-distributed seismograph stations within an area of interest, recording on a days-to-years scale. An ideal well-distributed array of seismographs may not be feasible for all sites and therefore, it is important to identify means for characterizing the ambient seismic noise in urban environments and limitations imposed with a reduced spatial distribution of stations, herein two stations. The developed workflow involves a continuous wavelet transform, peak detection, and event characterization. Events are classified by amplitude, frequency, occurrence time, source azimuth relative to the seismograph, duration, and bandwidth. Depending on the applications, results can guide seismograph selection (sampling frequency and sensitivity) and seismograph placement within the area of interest.
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Passive seismic
Ambient noise level
Seismic Noise
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This paper analyzed the applicability of the seismic wave pre-stack reverse-time migration technology on the migration of data from different seismic observation models,such as surface seismic,borehole seismic and crosswell seismic.Taking velocity model with different dip angle and Marmousi velocity model as examples,we synthesized several common shot gathers corresponding to observation models,and carried out numerical experiments on reverse-time migration further.The results show that the reverse-time migration method is suitable for these seismic observation models,and can get perfect imaging results;the S/N ratio can be further improved by low-frequency noise suppression method.The direct wave and refracted wave of the surface seismic observation model must be finely cut,and the first-arrival wave field(down propagating direct wave) must be preserved of the borehole seismic and crosswell seismic observation model.In this way,the wave field energy transformation relation between the reflection and transmission can be remained unchanged,and it can depict detailed features the geological structure to a maximum extent.
Seismic migration
Vertical seismic profile
Reflection
Seismic energy
Passive seismic
Seismic Noise
Synthetic seismogram
Geophysical Imaging
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Geophone
Seismometer
Rayleigh Wave
Vertical seismic profile
Seismic refraction
Dispersive body waves
Shadow zone
Seismogram
Synthetic seismogram
Reflection
Passive seismic
Microseism
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In The Nankai Trough seismogenic zone, cabled real-time observation system, DONET and IODP C0002G borehole observatory, have been operating to monitor seismic activity, crustal deformation and tsunami propagation since Aug. 2011 and Jan. 2013, respectively. For elucidating dynamic processes from preseismic state to the generation of mega-thrust earthquake, which occurs repeatedly in subduction zones, it is important to observe and monitor the stress state, i.e., a key parameter governing its fault dynamics in the vicinity of seismogenic fault. In this study, we performed active and passive seismic data processing to obtain seismic anisotropy, as a proxy of stress state, by using dataset acquired by three-component seismometers installed in the DONET and IODP C0002G observatories. In the passive data processing, we applied a seismic interferometry method to ambient noise records acquired by horizontal components of each seismometer. After the application of cross-dipole analysis to the acquired records, several coherent events have become visible. These events were perceived to be reflected S-wave from each layer below seafloor, and S-wave splitting caused by seismic anisotropy was observed. We then estimated anisotropy direction and amplitude beneath each seismometer in shallow sediment layer. For the active seismic dataset that was acquired in azimuthally aligned airgun shot locations for each seismometer performed in Nov. 2013, we steered horizontal records for each pair of shot and seismometer to form radial and transverse components to each shot location at a distance of ca. 3km from the seismometer. In the steered records, P-S converted waves from bottom of shallow sediments were clearly visible. The horizontal axis of symmetry to fast S-wave direction was estimated through the fitting of a simple sinusoidal curve to the aximuthal amplitude distribution in radial and transverse components for S-wave anisotropy in the shallow sediments in the Nankai Trough. We finally compared the obtained S-wave anisotropy from the passive data with the active one. The comparison in the order of anisotropy and the orientation of the horizontal axis of symmetry showed good agreement with each other, especially in landward area. Some differences in the complicated structure zone were probably caused by the signal-to-noise ratio deterioration due to the influence of the dimensionality of the sub-seafloor structure and the seafloor topography around the observatory in the active dataset, and to the contamination of seafloor microseisms in the passive data. We now plan to develop a new scheme including layer stripping method, 3-D rotation method, etc., to improve the quality of our analysis.
Seismometer
Vertical seismic profile
Passive seismic
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