Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
Results
Showing 1 to 20 of 94 for “"Velocity model"”.
-
Earthquake location using a 3D velocity model : an example in Sichuan Province, China
… the benefits of applying three-dimensional velocity models to seismic event location. We develop a technique for three-dimensional seismic event location, utilizing a finite difference method for travel time calculation and a grid search method for location. We apply this technique to the …
-
Seismic Imaging and Velocity Model Building in the Thrace Region, Northwestern Turkey: A Case Study
… refine the velocities to get the final interval velocity. Having the final interval velocity, reverse-time migration was used. The tomographic velocity analysis was successful in yielding an accurate interval velocity. After application of all these imaging methods, I found that the RTM gave the …
-
Tomographic velocity model building in high-fidelity seismic depth imaging of near surface and VSP settings
… between the raypath distribution and the model parameterization scheme. A reasonable model parametrization is the key to successful tomography applications, especially when the ray coverage is poor and uneven. Motivated by a geologically plausible model parameterization, the multiscale …
-
Shallow 3D Shear Wave Velocity Model and Revised Site Period Prediction Map for the Mexico City Basin
… map and to develop a shallow 3D shear wave velocity model of the Mexico City Basin. To accomplish this goal, an extensive literature review was performed to compile as much pertinent shear wave velocity and site period data for the region. In total, 75 sites were used to revise the site …
-
Building Velocity Models for Steep-Dip Prestack Depth Migration through First Arrival Traveltime Tomography
… depth migration, and an excellent seismic velocity model. Poststack time migrated seismic images, normal moveout velocity analysis, well logs, and other geologic information are used to build the velocity model. In regions of interest outside of sedimentary basins, such as major strike-slip …
-
Applications of a fast helmholtz solver in exploration seismology
Seismic imaging techniques rely on a velocity model inverted from noisy data via a non-linear inverse problem. This inferred velocity model may be inaccurate and lead to incorrect interpretations of the subsurface. In this thesis, I combine a fast Helmholtz solver, the field expansion method, with …
-
Seismic imaging with traveltime and waveform inversion: Naga Thrust and Fold Belt, India
… India. I use both lines to demonstrate that a) a velocity model from traveltime inversion is suitable for pre-stack depth migration (PSDM) and can effectively serve as a starting model for frequency-domain full-waveform inversion; b) both PSDM and waveform inversion yield interpretable depth …
-
Kirchhoff Common Offset Migration Velocity Analysis via Differential Semblance
… and fast approach to obtain an accurate velocity model for seismic imaging. An accurate velocity model is prerequisite for obtaining the image that represents the true underground geological structure: major evidence to explore for potential reservoirs and indicate hydrocarbons. This …
-
Shifting Paradigms: Data-Centric Approach for Marine Statics Correction using Symmetric Autoencoding
… correcting marine statics has been based on a model-centric paradigm. This paradigm involves a series of transformations between non-commensurate spaces: first, inversion from seismic data space to velocity model space and second, forward modeling from velocity model space to seismic data …
-
Automating Pre-Stack Migration Enhancement and Image Quality Analysis
… migration image strongly depends on an accurate velocity model. However, the migration velocity model often contains errors causing artifacts that degrade seismic resolution and fidelity. Here, I propose a method to enhance the seismic migration image using processes in angle domain common image …
-
Geophone Array Optimization for Monitoring Geologic Carbon Sequestration using Double-Difference Tomography
… carbon sequestration injection site. Artificial velocity models were created that accounted for the expected velocity decrease due to the existence of a CO₂ plume after underground injection into a depleted petroleum reservoir. Seismic events were created to represent induced seismicity from …
-
Acoustic full-waveform to elastic pre-stack seismic inversion of the Yakutat Terrane, Gulf of Alaska
… formation. I generate a compressional velocity model of the Yakutat microplate using two-dimensional acoustic and isotropic time-domain full waveform inversion (FWI) of marine seismic reflection and refraction data from the STEEP project (ST. Elias Erosion/tectonics Project). FWI is a …
-
Crustal structure of the Eratosthenes Seamount, Cyprus and S. Turkey from an amphibian wide-angle seismic profile
… data leads to a first-arrival tomographic model. This model reveals (1) P-wave velocities lower than 6.5 km/s in the crust, (2) a variable crustal thickness of about 28 - 37 km and (3) an upper crustal reflection at 5 km depth beneath the ESM. Two land shots on Turkey, also recorded on …
-
Velocity Studies in the Deepwater Gulf of Mexico: Keathley Canyon and Walker Ridge Areas
Two different, yet related, velocity studies were undertaken in and around the Keathley Canyon and Walker Ridge areas of the Gulf of Mexico. The first is a compilation of wellbore-salt-body interval velocities (Vint) from 55 wells exhibiting interval compressional-wave velocity variation from …
-
An Analysis of Focal Parameters with Application to West Texas Micro-Earthquakes
… of microseismic events due to anisotropy in velocity models and micro-earthquake distribution, magnitudes and focal mechanism solutions in the Permian Basin. Seismic anisotropy, a typical property in fractured sedimentary rocks, may bias the identification of the location of microseismic …
-
Modeling the Near-Surface Using High-Resolution Seismic Data
… reservoir imaging, an accurate near-surface velocity model is required. In this dissertation, I review the regional geology and geomorphology and the existing methods used for velocity modeling. A new method is developed, which depends on acquiring high-resolution shallow seismic data. The …
-
Local Earthquake Tomography at Mt. Pinatubo, Philippines
A new high-resolution 3-dimensional P-wave velocity model for Mt. Pinatubo volcano was developed by tomographic inversion of P-wave arrivals from 3,007 earthquakes recorded during a four month period from May to August, 1991. The arrivals were recorded by a network of seismic stations, consisting …
-
Focal mechanisms for eastern Tennessee earthquakes, 1981-1983
… Information Center (TEIG) with a four layer velocity model (GCOl). A second velocity model (STEP2), developed to improve focal depth estimates and to acquire continuously varying departure angles, is used to relocate events for which SEFM and CFM solutions are obtained. The two different …
-
An Assessment of Hypocenter Errors Associated with the Seismic Monitoring of Induced Hydro-fracturing in Hydrocarbon Reservoirs
… data sets to investigate how the accuracy of the velocity model, starting hypocenter location, recording geometry, and arrival-time picking error affect final hypocenter locations. Hypocenter locations improved using a velocity model that closely matched the observed sonic log rather than a …
Page 1 of 5