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Petroleum Seismological Survey
Published in Muhammad Abdul Quddus, Petroleum Science and Technology, 2021
Seismology is the study of earthquakes. Seismic waves are naturally generated during earthquakes and accompanied by movement or vibration of the earth’s crust. The crust vibration is due to the traveling wave energy through the underground structure. Petroleum seismology is the study of the geological characteristics of underground sedimentary rock, through artificially created seismic waves. The seismic wave or energy produced at the surface travels into the ground and results in a variety of reflected, refracted, head refracted and transmitted waves. The reflected and head refracted waves appear back at the surface, whereas the refracted and transmitted waves travel deep into the ground and are lost. The study of reflected and head refracted waves lead to information on the path traveled through the subsurface rock strata in terms of change in the characteristics of the seismic wave. The nature of the strata affects the traveling seismic wave. Change in the characteristics of wave is related to the subsurface rock structure. Petroleum seismology for oil/gas prospecting gives more certain and reliable information than the other geophysical survey methods. The survey is close to the geological reality of the subsurface structure. Besides petroleum prospecting, other areas where seismology is employed are ground engineering, environmental, coal, minerals, hydrology and geothermal studies. The study ranges from shallow to deep earth crust.
Minimizing the seismic effects of blasting works on the environment in the mining of raw materials
Published in Vladimir Litvinenko, Topical Issues of Rational Use of Natural Resources 2019, 2019
The velocity of the seismic waves is measured by seismographs – devices for seismic signal recording and modification. Their main aim is to register the mechanical vibrations of the ground particles induced by seismic wave transfer from the source to individual geophones and to record the arrival time and the course of the wave. To measure the particle velocity of the seismic wave during blasting operations, vibration monitors are used. We consider as vibration monitors a complex of devices for registration of the seismic signal created by blasts. The main goal of the vibration monitor is to record the mechanical vibration of the ground particles induced by seismic wave arrival from the source to the geophones and to record the peak particle velocity and course of the seismic wave on the monitored standpoint. (Pandula and Kondela, 2010, Knejzlik at all., 2012).
Field Investigation Techniques for Potentially Contaminated Sites
Published in Kofi Asante-Duah, Management of Contaminated Site Problems, 2019
Seismic waves travel at different velocities depending on the soil and rock types present and their specific hardness, elasticity and density. In general, solid, denser, and water-saturated materials tend to display higher velocities. Refraction (or signal “bending”) often occurs at the interface between layers with differing wave propagation properties. For instance, if a denser layer with a higher velocity (e.g., bedrock) exists below surface soils, a portion of the seismic waves will be refracted as they enter the denser layer, similar to the refraction of light in accordance with Snell’s law. Some of these refracted waves cross the interface at a critical angle and then move parallel to the top of the dense layer at the higher velocity of the denser layer. The seismic wave traveling along this interface will continually release energy back into the upper layer by refraction. These waves may then be detected by geophones emplaced at the surface at various distances from the wave source along the path of propagation.
Seismic Earth Pressure Due to Rayleigh Waves in Viscoelastic Media
Published in Journal of Earthquake Engineering, 2022
In terms of seismic waves in soil, earthquakes produce two main types of waves: body waves and surface waves. Body waves travel through the inner layers of the Earth. Contrarily, a surface wave exists only in the surficial layers and reach the site after the arrival of body waves due to its relatively low propagation velocity. Surface waves can be more destructive than body waves as they propagate at a slower rate and can have a much larger amplitude in strong earthquakes. Also, surface waves geometrically attenuate at a much slower rate than body waves, with the attenuation rates being proportional to and for the body waves and surface waves (Lowrie, 2007), respectively. Body waves include Primary waves (P-waves) and Secondary waves (S-waves), while Surface waves include Rayleigh waves and Love waves. Figure 1 shows both types of waves and elucidates the difference in the magnitudes and the arrival times.
Modal Identification of a Soil-subway System with Emphasis on Scattering of Seismic Waves Induced by Uniform and Non-uniform Support Excitations
Published in Journal of Earthquake Engineering, 2022
Mohsen Isari, Majid Damadipour, Abbasali Taghavi Ghalesari, Seyyed Kazem Razavi, Reza Tarinejad
In dynamic analysis of structures, it is typically assumed that the excitation caused by an earthquake is applied to the structure uniformly and simultaneously. This assumption can be verified if (i) the wave propagation speed is indefinite (ii) the propagation of seismic waves is constant and uniform. The first assumption is an ideal assumption that cannot be attained in reality and the second assumption contradicts the topographic amplification observed in seismic records made during earthquakes (Alves 2005). One of the main reasons of damages caused by an earthquake is the amplification of seismic waves as they travel through soil layers of variable material, dynamic properties, stratification, and the existing joints and embedded structures with different size and direction. These geologic and geometric irregularities as well as topographic features can cause disturbance of seismic waves that may result in resonance of seismic waves, change in frequency content and thus, delayed time of vibration. In other words, scattering of seismic waves causes a non-uniform excitation that differs in amplitude and phase from one point to another. Therefore, considering the non-uniform support excitation is an important factor influencing the accuracy of the study of soil-underground structure system.
Directional Components of a Seismic Design Accelerogram
Published in Journal of Earthquake Engineering, 2022
Lanlan Yang, Wei Chau Xie, Weiya Xu, Binh-Le Ly, Huanling Wang, Qingxiang Meng
When an earthquake occurs, different types of seismic waves are produced: body waves (including P-waves and S-waves) and surface waves (including Rayleigh and Love waves) (Xie et al. 2019). To simplify the discussion, the propagation of seismic waves could be imagined as water ripples, emancipating from the epicenter in concentric circles. Unless recordings of the ground motions are taken in the radial and the tangential directions of these concentric circles, the data will be correlated (Beyer and Bommer 2007). The measured intensities in the radial and the tangential directions are anisotropic. However, the orientation of a reactor building in the transversal direction (AC direction) and the longitudinal direction (BD direction), in relation to the directions of seismic waves cannot be predicted or designed. The picture of ground motions is further complicated by decomposition of the motions into the AC and the BD direction, not to mention that the angle between the two Cartesian coordinate systems is unknown.