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Articles 1 - 18 of 18
Full-Text Articles in Physical Sciences and Mathematics
Pystprism: Tools For Voxel-Based Space–Time Prisms, Rebecca Loraamm, Joni A. Downs, James Anderson, David S. Lamb
Pystprism: Tools For Voxel-Based Space–Time Prisms, Rebecca Loraamm, Joni A. Downs, James Anderson, David S. Lamb
School of Geosciences Faculty and Staff Publications
The observed movements of humans and animals are realizations of complex spatiotemporal processes. Recent advances in location-aware technologies have rendered trajectory data ubiquitous. Examining the sequenced, instantaneous locations found in movement trajectory data for information reconstructing the location or state of the mover between observed points comprises a primary focus in Time Geography and related disciplines. The PySTPrism toolbox introduced in this paper provides a straightforward and open-source implementation of the Probabilistic Space Time Prism, in addition to related tools from Time Geography. PySTPrism is implemented in Python using the ArcPy module in ArcGIS Pro Desktop.
Novel Quantification Of Shallow Sediment Compaction By Gps Interferometric Reflectometry And Implications For Flood Susceptibility, Makan A. Karegar, Kristine M. Larson, Jurgen Kusche, Timothy H. Dixon
Novel Quantification Of Shallow Sediment Compaction By Gps Interferometric Reflectometry And Implications For Flood Susceptibility, Makan A. Karegar, Kristine M. Larson, Jurgen Kusche, Timothy H. Dixon
School of Geosciences Faculty and Staff Publications
Estimates of flood susceptibility and land loss in the world's coastal regions depend on our knowledge of sea level rise (SLR) from increases in ocean mass and volume, as well as knowledge of vertical land motion. Conventional approaches to the latter include tide‐gauge and Global Positioning System (GPS) measurements relative to well‐anchored monuments few meters below the surface. However, in regions of rapid Holocene sedimentation, compaction of this material can add a significant component to the surface lowering. Unfortunately, this process has been difficult to quantify, especially for the shallowest material above the monument. Here we use a new technique, …
Seafloor Geodesy In Shallow Water With Gps On An Anchored Spar Buoy, Surui Xie, Jason Law, Randy Russell, Timothy H. Dixon, Chad Lembke, Rocco Malservisi, Melanie Rodgers, Giovanni Iannaccone, Sergio Guardato, D. F. Naar
Seafloor Geodesy In Shallow Water With Gps On An Anchored Spar Buoy, Surui Xie, Jason Law, Randy Russell, Timothy H. Dixon, Chad Lembke, Rocco Malservisi, Melanie Rodgers, Giovanni Iannaccone, Sergio Guardato, D. F. Naar
School of Geosciences Faculty and Staff Publications
Measuring seafloor motion in shallow coastal water is challenging due to strong and highly variable oceanographic effects. Such measurements are potentially useful for monitoring near‐shore coastal subsidence, subsidence due to petroleum withdrawal, strain accumulation/release processes in subduction zones and submerged volcanoes, and certain freshwater applications, such as volcano deformation in caldera‐hosted lakes. We have developed a seafloor geodesy system for this environment based on an anchored spar buoy topped by high‐precision GPS. Orientation of the buoy is measured using a digital compass that provides heading, pitch, and roll information. The combined orientation and GPS tracking data are used to recover …
Theory And Application Of Geophysical Geodesy For Studying Earth Surface Deformation, Makan A. Karegar
Theory And Application Of Geophysical Geodesy For Studying Earth Surface Deformation, Makan A. Karegar
USF Tampa Graduate Theses and Dissertations
An interdisciplinary approach at the interface between geodesy and geophysics has recently resolved several Earth science problems at regional and global scales. I use the term “geophysical geodesy” to distinguish the technical and theoretical aspect of geodesy from geophysical applications of geodetic techniques. Using a wide range of Earth observation data, I study the spatio-temporal characteristics of Earth surface deformation in the United States associated with several geophysical processes, including natural and anthropogenic subsidence and uplift, regional relative sea-level rise, and continental hydrological loading. The theoretical portion of this dissertation applies loading theory and develops a new hybrid method to …
A New Hybrid Method For Estimating Hydrologically Induced Vertical Deformation From Grace And A Hydrological Model: An Example From Central North America, Makan A. Karegar, Timothy H. Dixon, Jurgen Kusche, Don P. Chambers
A New Hybrid Method For Estimating Hydrologically Induced Vertical Deformation From Grace And A Hydrological Model: An Example From Central North America, Makan A. Karegar, Timothy H. Dixon, Jurgen Kusche, Don P. Chambers
School of Geosciences Faculty and Staff Publications
Hydrologically induced deformation of Earth's surface can be measured with high precision geodetic techniques, which in turn can be used to study the underlying hydrologic process. For geodetic study of other Earth processes such as tectonic and volcanic deformation, or coastal subsidence and its relation to relative sea level rise and flood risk, hydrological loading may be a source of systematic error, requiring accurate correction. Accurate estimation of the hydrologic loading deformation may require consideration of local as well as regional loading effects. We present a new hybrid approach to this problem, providing a mathematical basis for combining local (near …
Subsidence Along The Atlantic Coast Of North America: Insights From Gps And Late Holocene Relative Sea Level Data, Makan A. Karegar, Timothy H. Dixon, Simon E. Engelhart
Subsidence Along The Atlantic Coast Of North America: Insights From Gps And Late Holocene Relative Sea Level Data, Makan A. Karegar, Timothy H. Dixon, Simon E. Engelhart
School of Geosciences Faculty and Staff Publications
The Atlantic Coast of North America is increasingly affected by flooding associated with tropical and extratropical storms, exacerbated by the combined effects of accelerated sea‐level rise and land subsidence. The region includes the collapsing forebulge of the Laurentide Ice Sheet. High‐quality records of late Holocene relative sea‐level (RSL) rise are now available, allowing separation of long‐term glacial isostatic adjustment‐induced displacement from modern vertical displacement measured by GPS. We compare geological records of late Holocene RSL to present‐day vertical rates from GPS. For many coastal areas there is no significant difference between these independent data. Exceptions occur in areas of recent …
Space Geodetic Observation Of The Deformation Cycle Across The Ballenas Transform, Gulf Of California, Christina Plattner, Rocco Malservisi, Falk Amelung, Timothy H. Dixon, Matthias Hackl, Alessandro Verdecchia, Peter Lonsdale, Francisco Suarez-Vidal, Javier Gonzalez-Garcia
Space Geodetic Observation Of The Deformation Cycle Across The Ballenas Transform, Gulf Of California, Christina Plattner, Rocco Malservisi, Falk Amelung, Timothy H. Dixon, Matthias Hackl, Alessandro Verdecchia, Peter Lonsdale, Francisco Suarez-Vidal, Javier Gonzalez-Garcia
School of Geosciences Faculty and Staff Publications
The Gulf of California, Mexico, accommodates ~90% of North America‐Pacific plate relative motion. While most of this motion occurs on marine transform faults and spreading centers, several fault segments in the central Gulf come close to peninsular Baja California. Here we present Global Positioning System and interferometric synthetic aperture radar data near the Ballenas transform fault, separating the peninsula from Angel de la Guarda Island. We observe interseismic motion between June 2004 and May 2009 and displacements associated with the 3 August 2009 Mw 6.9 earthquake. From the interseismic data we estimate a locking depth of 9–12.5 km and a …
Earthquake And Tsunami Forecasts: Relation Of Slow Slip Events To Subsequent Earthquake Rupture, Timothy H. Dixon, Yan Jiang, Rocco Malservisi, Robert Mccaffrey, Nicholas Voss, Marino Protti, Victor Gonzalez
Earthquake And Tsunami Forecasts: Relation Of Slow Slip Events To Subsequent Earthquake Rupture, Timothy H. Dixon, Yan Jiang, Rocco Malservisi, Robert Mccaffrey, Nicholas Voss, Marino Protti, Victor Gonzalez
School of Geosciences Faculty and Staff Publications
The 5 September 2012 Mw 7.6 earthquake on the Costa Rica subduction plate boundary followed a 62-y interseismic period. High-precision GPS recorded numerous slow slip events (SSEs) in the decade leading up to the earthquake, both up-dip and down-dip of seismic rupture. Deeper SSEs were larger than shallower ones and, if characteristic of the interseismic period, release most locking down-dip of the earthquake, limiting down-dip rupture and earthquake magnitude. Shallower SSEs were smaller, accounting for some but not all interseismic locking. One SSE occurred several months before the earthquake, but changes in Mohr–Coulomb failure stress were probably too small to …
Insights Into Distributed Plate Rates Across The Walker Lane From Gps Geodesy, Zachery M. Lifton, Andrew V. Newman, Kurt L. Frankel, Christopher W. Johnson, Timothy H. Dixon
Insights Into Distributed Plate Rates Across The Walker Lane From Gps Geodesy, Zachery M. Lifton, Andrew V. Newman, Kurt L. Frankel, Christopher W. Johnson, Timothy H. Dixon
School of Geosciences Faculty and Staff Publications
Contemporary geodetic slip rates are observed to be approximately two times greater than late Pleistocene geologic slip rates across the southern Walker Lane. Using a dense GPS network, we compare the present‐day crustal velocities to observed geologic slip rates in the region. We find that the Walker Lane is characterized by a smooth transition from westward extension in the Basin and Range to northwestward motion of the Sierra Nevada block. The GPS velocity field indicates that (1) plate parallel (N37°W) velocities define a velocity differential of 10.6 ± 0.5 mm/yr between the western Basin and Range and the Sierra Nevada …
Detailed Data Available For Recent Costa Rica Earthquake, Timothy H. Dixon, Susan Schwartz, Marino Protti, Victor Gonzalez, Andrew Newman, Jeff Marshall, Jim Spotila
Detailed Data Available For Recent Costa Rica Earthquake, Timothy H. Dixon, Susan Schwartz, Marino Protti, Victor Gonzalez, Andrew Newman, Jeff Marshall, Jim Spotila
School of Geosciences Faculty and Staff Publications
On 5 September 2012 a magnitude 7.6 earthquake occurred beneath the Nicoya Peninsula of northwestern Costa Rica, rupturing the subduction zone between the Cocos and Caribbean plates. In most subduction zones the locus of seismic slip lies far offshore, making it difficult to infer interface seismogenic processes from on-shore observations. In contrast, the Nicoya Peninsula lies close to the trench (within 70 kilometers), allowing observations directly over the earthquake rupture zone.
Automatic Identification Of Points Of Interest In Global Navigation Satellite System Data: A Spatial Temporal Approach, Khoa Anh Tran
Automatic Identification Of Points Of Interest In Global Navigation Satellite System Data: A Spatial Temporal Approach, Khoa Anh Tran
USF Tampa Graduate Theses and Dissertations
In addition to the emergence of smartphones and tablets in recent years, the rise of Global Navigation Satellite Systems (GNSS) has allowed mobile tracking applications to become popular and be put into many uses. Analyzing tracking records to identify points of interest (POIs) is useful for both prediction applications and research such as human behavior analysis, transportation planning, and especially travel surveys. Past research in travel surveys has shown that a GPS mobile phone-based survey is a useful tool for collecting information about individuals. Moreover, a passive travel survey collection is preferred to an active travel survey method by the …
Active Deformation Near The Nicoya Peninsula, Northwestern Costa Rica, Between 1996 And 2010: Interseismic Megathrust Coupling, Lujia Feng, Andrew V. Newman, Marino Protti, Victor Gonzalez, Yan Jiang, Timothy H. Dixon
Active Deformation Near The Nicoya Peninsula, Northwestern Costa Rica, Between 1996 And 2010: Interseismic Megathrust Coupling, Lujia Feng, Andrew V. Newman, Marino Protti, Victor Gonzalez, Yan Jiang, Timothy H. Dixon
School of Geosciences Faculty and Staff Publications
We use campaign and continuous GPS measurements at 49 sites between 1996 and 2010 to describe the long-term active deformation in and near the Nicoya Peninsula, northwestern Costa Rica. The observed deformation reveals partial partitioning of the Cocos-Caribbean oblique convergence into trench-parallel forearc sliver motion and less oblique thrusting on the subduction interface. The northern Costa Rican forearc translates northwestward as a whole ridge block at 11 ± 1 mm/yr relative to the stable Caribbean. The transition from the forearc to the stable Caribbean occurs in a narrow deforming zone of ∼16 km wide. Subduction thrust earthquakes take 2/3 of …
Basal Graph Structures For Geometry Based Organization Of Wide-Baseline Image Collections, Aveek Shankar Brahmachari
Basal Graph Structures For Geometry Based Organization Of Wide-Baseline Image Collections, Aveek Shankar Brahmachari
USF Tampa Graduate Theses and Dissertations
We propose algorithms for organization of images in wide-area sparse-view datasets. In such datasets, if the images overlap in scene content, they are related by wide-baseline geometric transformations. The challenge is to identify these relations even if the images sparingly overlap in their content. The images in a dataset are then grouped into sets of related images with the relations captured in each set as a basal (minimal and foundational) graph structures. Images form the vertices in the graph structure and the edges define the geometric relations between the images. We use these basal graphs for geometric walkthroughs and detection …
Estimation Of Velocity Uncertainties From Gps Time Series: Examples From The Analysis Of The South African Trignet Network, Matthias Hackl, Rocco Malservisi, Urs Hugentobler, Richard Wonnacott
Estimation Of Velocity Uncertainties From Gps Time Series: Examples From The Analysis Of The South African Trignet Network, Matthias Hackl, Rocco Malservisi, Urs Hugentobler, Richard Wonnacott
School of Geosciences Faculty and Staff Publications
We present a method to derive velocity uncertainties from GPS position time series that are affected by time‐correlated noise. This method is based on the Allan variance, which is widely used in the estimation of oscillator stability and requires neither spectral analysis nor maximum likelihood estimation (MLE). The Allan variance of the rate (AVR) is calculated in the time domain and hence is not too sensitive to gaps in the time series. We derived analytical expressions of the AVR for different kinds of noises like power law noise, white noise, flicker noise, and random walk and found an expression for …
A Tremor And Slip Event On The Cocos‐Caribbean Subduction Zone As Measured By A Global Positioning System (Gps) And Seismic Network On The Nicoya Peninsula, Costa Rica, Kimberly Outerbridge, Timothy H. Dixon, Susan Y. Schwartz, Jacob I. Walter, Marino Protti, Victor Gonzalez, J. Biggs, Martin Thorwart, Wolfgang Rabbel
A Tremor And Slip Event On The Cocos‐Caribbean Subduction Zone As Measured By A Global Positioning System (Gps) And Seismic Network On The Nicoya Peninsula, Costa Rica, Kimberly Outerbridge, Timothy H. Dixon, Susan Y. Schwartz, Jacob I. Walter, Marino Protti, Victor Gonzalez, J. Biggs, Martin Thorwart, Wolfgang Rabbel
School of Geosciences Faculty and Staff Publications
In May 2007 a network of global positioning systems (GPS) and seismic stations on the Nicoya Peninsula, of northern Costa Rica, recorded a slow-slip event accompanied by seismic tremor. The close proximity of the Nicoya Peninsula to the seismogenic part of the Cocos-Caribbean subduction plate boundary makes it a good location to study such events. Several centimeters of southwest motion were recorded by the GPS stations over a period of several days to several weeks, and the seismic stations recorded three distinct episodes of tremor during the same time span. Inversion of the surface displacement data for the depth and …
Fore-Arc Motion And Cocos Ridge Collision In Central America, Peter Lafemina, Timothy Dixon, Rob Govers, Edmundo Norabuena, Henry Turner, Armando Saballos, Glen Mattioli, Marino Protti, Wilfried Strauch
Fore-Arc Motion And Cocos Ridge Collision In Central America, Peter Lafemina, Timothy Dixon, Rob Govers, Edmundo Norabuena, Henry Turner, Armando Saballos, Glen Mattioli, Marino Protti, Wilfried Strauch
School of Geosciences Faculty and Staff Publications
We present the first regional surface velocity field for Central America, showing crustal response to interaction of the Cocos and Caribbean plates. Elastic half-space models for interseismic strain accumulation on the dipping subduction plate boundary fit the GPS data well and show strain accumulation offshore and beneath the Nicoya and Osa peninsulas in Costa Rica but not in Nicaragua. Since large subduction zone earthquakes occur in Nicaragua, we suggest that interseismic locking in Nicaragua and some other parts of Central America occurs but is mainly shallow, depth, too far offshore to be detected by our on-land GPS measurements. Our data …
Kinematics Of The Nicaraguan Forearc From Gps Geodesy, Henry L. Turner, Peter Lafemina, Armando Saballos, Glen S. Mattioli, Pamela E. Jansma, Timothy H. Dixon
Kinematics Of The Nicaraguan Forearc From Gps Geodesy, Henry L. Turner, Peter Lafemina, Armando Saballos, Glen S. Mattioli, Pamela E. Jansma, Timothy H. Dixon
School of Geosciences Faculty and Staff Publications
Campaign GPS data from a network in the Nicaraguan forearc show a strong component of arc-parallel motion indicating northwest translation of a nearly rigid forearc sliver. Our measured mean velocity for forearc sites of 15.1 mm yr−1 agrees well with the arc-parallel sliver motion predicted previously by DeMets (2001) derived from closure constraints on oblique convergence between the Cocos and Caribbean plates. The lack of a northeasterly oriented arc-normal component of motion in forearc velocities indicates that there are complexities involved beyond a simple interpretation of sliver motion being driven by oblique convergence. The forearc is reasonably well-fit by …
Revel: A Model For Recent Plate Velocities From Space Geodesy, Giovanni F. Sella, Timothy H. Dixon, Ailin Mao
Revel: A Model For Recent Plate Velocities From Space Geodesy, Giovanni F. Sella, Timothy H. Dixon, Ailin Mao
School of Geosciences Faculty and Staff Publications
We present a new global model for Recent plate velocities, REVEL, describing the relative velocities of 19 plates and continental blocks. The model is derived from publicly available space geodetic (primarily GPS) data for the period 1993–2000. We include an independent and rigorous estimate for GPS velocity uncertainties to assess plate rigidity and propagate these uncertainties to the velocity estimates. The velocity fields for North America, Eurasia, and Antarctica clearly show the effects of glacial isostatic adjustment, and Australia appears to depart from rigid plate behavior in a manner consistent with the mapped intraplate stress field. Two thirds of tested …