Thesis (M.S.)--University of Nevada, Reno, 2007. / "May, 2007." Includes bibliographical references (leaves 25-31). Online version available on the World Wide Web.

Thesis (Ph. D.)--Columbia University, 1968. / Includes bibliographical references (leaves 151-159).

Record sections from partially reversed refraction lines in northern British Columbia show that the amplitudes of upper mantle arrivals vary smoothly with distance. The pattern of crustal arrival amplitudes is not smooth. Normalization of the seismograms to remove the amplification caused by shot size and instrument response show the effects of recording sites on Pn amplitudes are minimal. Models derived from ray theory indicate a crust which thins from about 40 km in the Omineca Crystalline Belt to about 25 km in the Insular Trough. The average Pn velocity is 8.06 km/s. The average crustal velocity is 6.4 km/s. The secondary energy would indicate the models are greatly simplified. A time-term profile between the Omineca Crystalline Belt and the Coast Mountains suggests a Mohorovicic transition which is characterized by two significant topographic wavelengths. The shorter (200 km) wavelength correlates roughly with the Cordilleran structural elements of Wheeler et al. (1972). The larger (800 km) wavelength may have tectonic significance. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

No description available.

Thesis advisor: John E. Ebel / Degradation within an earth embankment structure is often unobservable from the surface. In order to evaluate the structural integrity of earth embankment dams and levees and identify subsurface zones of weakness that may result in future failures, various geophysical methods have been proposed as effective subsurface imaging tools. This study presents the results of using the horizontal-to-vertical spectral ratio (HVSR), seismic refraction analysis, and multi-channel analysis of surface waves (MASW) methods to estimate subsurface seismic structures for two earth embankment dams located in Chestnut Hill, MA, and Franklin Falls, NH. The estimated seismic velocity structures from the seismic refraction analysis and MASW performed in this study confirm the HVSR method is able to effectively estimate depth to bedrock at sites atop earth embankments using estimated fundamental frequencies. The MASW was found to resolve a low-velocity zone in the subsurface at the Chestnut Hill reservoir embankment that the seismic refraction method was unable to image, and this low-velocity zone is required to best fit a theoretical HVSR to an observed spectrum. Furthermore, the variation and uncertainty in fundamental frequency estimation were investigated by making repeated HVSR measurements at the Chestnut Hill embankment. / Thesis (BS) — Boston College, 2023. / Submitted to: Boston College. College of Arts and Sciences.. / Discipline: Departmental Honors. / Discipline: Earth and Environmental Sciences.

No description available.

Dryland salinity occurs extensively throughout the Spicers Creek Catchment in central west New South Wales, Australia. The extent of dryland salinity in the Spicers Creek Catchment has severely altered the landscape, having major environmental implication. Large area of the catchments has experienced soil erosion resulting from the saline groundwater in the surface soil causing the destruction of clay and soil structure. The objective of this study was to use seismic refraction methods to map in detail a shear zone, which was associated with an area of major dryland salination. In particular, both the width of shear zone and the rock fabric within it were to be mapped with two both compressional (P) and shear (S) waves using a three-dimensional (3D) array of three- component (3C) receivers. The seismic data was recorded across a shear zone which is associated with salination in the Spicers Creek Catchment using the Australian National Seismic Imaging Resources (ANSIR) 360-trace system. Three-component (3C) geophones were used to record shear waves as well as compressional wave. An IVI minivibrator T-15000 was used as the main source of energy for the seismic survey. The results of the three-dimensional three-component seismic refraction surveys at the Spicers Creek Catchment show that the shear zone exhibit the seismic geophysical anomaly of a shear zone, existing as a narrow region with low seismic velocities and increased depth of weathering. A detailed analysis of the refractor seismic velocities and amplitude show a number of linear features parallel to and cross-cutting the shear zone. Linear features cut the shear zones at each site. They have been interpreted as a series of recent faults which act as discharge zone bringing saline groundwater to the surface.

Many scientific studies have been conducted on the Cretaceous-Paleogene boundary (KTB) in the Gulf coast region and, in particular, the Brazos River section in Falls County, Texas. Despite this, there remains much to be learned about the KTB and its depositional environment. Study of the KTB has been multidisciplinary, primarily in the fields of sedimentology and paleontology. Some researchers in these disciplines have questioned the consensus view of the placement of the KTB and subsequent interpretation of the timing of depositional events and mass extinction events. Geophysical methods have potential to provide additional understanding of the physical properties of the KTB. To date, study of the KTB has relied on point data and borehole information to create cross sections of the complex. Seismic refraction surveys can provide spatially continuous information on susburface horizons located adjacent to the KTB. In this study, seismic first-arrival traveltimes are processed with a tomographic modeling program to map the top of the hummocky cross-bedded sandstone (HCS), which is a key indicator of the deposition environment at the time of KTB boundary complex placement. The survey area is located at Cottonmouth Creek, a tributary of the Brazos River. Three seismic lines were surveyed, one across Cottonmouth Creek, and two parallel to the creek on either side. The data from the two parallel lines were processed using the 2-D seismic refraction tomography algorithm of Zelt and Smith. The reconstructed depth to the HCS in the survey area is approximately 6 m, with layer seismic velocities of 364, 1800, and 2200 m/s, respectively. Seismic tomography successfully mapped the HCS layer and reveals approximately 1 m amplitude undulations vertically and undulations on the order of several m horizontally. These variations are consistent with exposed surfaces of the HCS in the creek bed. Seismic refraction has been utilized successfully herein to map a key buried indicator, namely the top of the HCS layer, associated with the KTB complex. A detailed 3-D seismic refraction survey at this site is recommended to generate a high-resolution 2-D terrain map of the top of the HCS layer.

No description available.

Στη συγκεκριμένη διατριβή περιλαμβάνεται όλη η απαραίτητη θεωρία της σεισμικής τομογραφίας όπως και ιστορική αναδρομή των μεθόδων που προηγήθηκαν αυτής που παρουσιάζεται στην ανα χείρας μελέτη. Γίνεται σύγκριση των μεθόδων ειδικά σε δεδομένα από επιφανειακά πειράματα και μελετάται η αντίδραση των αλγορίθμων σε περιπτώσεις εντόνου αντιθέσεως στη ταχύτητα των σεισμικών κυμάτων, αναλυτική μεθοδολογία ανάλυσης αβεβαιοτήτων με στατιστικές μεθόδους, θεωρητική ανάπτυξη του ευθέους αλλά και του αντιστρόφου προβλήματος, χρήση για πρώτη φορά σε ανάλογα προβλήματα των αλγορίθμων Kohonen, μεθοδολογία βέλτιστης λήψης δεδομένων σε δυσχερείς συνθήκες και τέλος λήψη, ανάλυση, ποιοτικός έλεγχος, επεξεργασία και ερμηνεία ενός μεγάλου όγκου σεισμικών δεδομένων, αλλά και ορισμένων γεωηλεκτρικών που έδρασαν συνεπικουρικά, πάνω σε ένα γεωτεχνικό πρόβλημα. Η καινοτομία της διατριβής έγκειται στην εισαγωγή γεωμετρίας Finsler για την επίλυση των προβλημάτων που δημιουργούνται στα επιφανειακά προβλήματα από τις έντονες αντιθέσεις των σεισμικών κυμάτων. / In this PhD we include all the necessary theory on seismic tomography as well as an historical review of older methods. We compare these methods especially on shallow experiments data, we compare the uncertainties with statistical methods, we develop new methods on forward and inverse problem, we use also Kohonen algorithms. The data we gathered apart from seismic ones were also downhole and electrical data in order to compare the validity of the method. We also applied Finsler geometry in order to overpass the problems that occur in shallow experiments.