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Articles 1 - 10 of 10
Full-Text Articles in Geophysics and Seismology
Spatial Variations Of Stochastic Noise Properties In Gps Time Series, Xiaoxing He, Michael Simon Bos, Jean-Philippe Montillet, Rui Fernandes, Timothy I. Melbourne, Weiping Jiang, Wudong Li
Spatial Variations Of Stochastic Noise Properties In Gps Time Series, Xiaoxing He, Michael Simon Bos, Jean-Philippe Montillet, Rui Fernandes, Timothy I. Melbourne, Weiping Jiang, Wudong Li
Geological Sciences Faculty Scholarship
The noise in position time series of 568 GPS (Global Position System) stations across North America with an observation span of ten years has been investigated using solutions from two processing centers, namely, the Pacific Northwest Geodetic Array (PANGA) and New Mexico Tech (NMT). It is well known that in the frequency domain, the noise exhibits a power-law behavior with a spectral index of around −1. By fitting various noise models to the observations and selecting the most likely one, we demonstrate that the spectral index in some regions flattens to zero at long periods while in other regions it …
Tidal And Structural Controls On Seismic Events Near The Grounding Line At Beardmore Glacier, Antarctica, Jade Cooley
Tidal And Structural Controls On Seismic Events Near The Grounding Line At Beardmore Glacier, Antarctica, Jade Cooley
All Master's Theses
Here I report seismic events occurring over a three-week period during the 2013-2014 austral summer near the grounding line of Beardmore Glacier, Antarctica. The ~24000 events over this time frame had a noticeable temporal pattern that correlates well with the principally diurnal tides of Antarctica. Falling and rising tide each accounted for nearly equal occurrence of events, and most (~42%) events occurred in the last third of any tidal cycle. Event epicenters were located using beamforming, and display a spatial pattern of two distinct clusters. Appearance of event location clusters differ on rising and falling tide. I theorize that, due …
Real-Time Monitoring Of Tectonic Displacements In The Pacific Northwest Through An Array Of Gps Receivers, Răzvan Popovici, Răzvan Andonie, Walter M. Szeliga, Timothy I. Melbourne, Craig W. Scrivner
Real-Time Monitoring Of Tectonic Displacements In The Pacific Northwest Through An Array Of Gps Receivers, Răzvan Popovici, Răzvan Andonie, Walter M. Szeliga, Timothy I. Melbourne, Craig W. Scrivner
All Faculty Scholarship for the College of the Sciences
The Pacific Northwest Geodesic Array at Central Washington University collects telemetered streaming data from 450 GPS stations. These real-time data are used to monitor and mitigate natural hazards arising from earthquakes, volcanic eruptions, landslides, and coastal sea-level hazards in the Pacific Northwest. The displacement measurements are performed at millimeter-scale, and require stringent analysis and parameter estimation techniques. Recent improvements in both accuracy of positioning measurements and latency of terrestrial data communication have led to the ability to collect data with higher sampling rates, of up to 1 Hz. For seismic monitoring applications, this means 1350 separate position streams from stations …
Clockwise Rotation Of The Brahmaputra Valley Relative To India: Tectonic Convergence In The Eastern Himalaya, Naga Hills, And Shillong Plateau, Philippe Vernant, R. Bilham, Walter Szeliga, D. Drupka, S. Kalita, A. K. Bhattacharyya, V. K. Gaur
Clockwise Rotation Of The Brahmaputra Valley Relative To India: Tectonic Convergence In The Eastern Himalaya, Naga Hills, And Shillong Plateau, Philippe Vernant, R. Bilham, Walter Szeliga, D. Drupka, S. Kalita, A. K. Bhattacharyya, V. K. Gaur
All Faculty Scholarship for the College of the Sciences
GPS data reveal that the Brahmaputra Valley has broken from the Indian Plate and rotates clockwise relative to India about a point a few hundred kilometers west of the Shillong Plateau. The GPS velocity vectors define two distinct blocks separated by the Kopili fault upon which 2–3 mm/yr of dextral slip is observed: the Shillong block between longitudes 89 and 93°E rotating clockwise at 1.15°/Myr and the Assam block from 93.5°E to 97°E rotating at ≈1.13°/Myr. These two blocks are more than 120 km wide in a north‐south sense, but they extend locally a similar distance beneath the Himalaya and …
Interseismic Strain Accumulation Along The Western Boundary Of The Indian Subcontinent, Walter Szeliga, Roger Bilham, Din Mohammad Kakar, Sarosh H. Lodi
Interseismic Strain Accumulation Along The Western Boundary Of The Indian Subcontinent, Walter Szeliga, Roger Bilham, Din Mohammad Kakar, Sarosh H. Lodi
All Faculty Scholarship for the College of the Sciences
Despite an overall sinistral slip rate of ≈3 cm/yr, few major earthquakes have occurred in the past 200 years along the Chaman fault system, the western boundary of the India Plate with the Eurasia Plate. GPS and InSAR data reported here indicate sinistral shear velocities of 8–17 mm/yr across the westernmost branches of the fault system, suggesting that a significant fraction of the plate boundary slip is distributed in the fold and fault belt to the east. At its southernmost on‐land segment (≈26°N), near the triple junction between the Arabia, Eurasia, and India Plates, we find the velocity across the …
Moment Release Rate Of Cascadia Tremor Constrained By Gps, Ana C. Aguiar, Timothy I. Melbourne, Craig W. Scrivner
Moment Release Rate Of Cascadia Tremor Constrained By Gps, Ana C. Aguiar, Timothy I. Melbourne, Craig W. Scrivner
All Faculty Scholarship for the College of the Sciences
A comparison of GPS and seismic analyses of 23 distinct episodic tremor and slip events, located throughout the Cascadia subduction zone over an 11-year period, yields a highly linear relationship between moment release, as estimated from GPS, and total duration of nonvolcanic tremor, as summed from regional seismic arrays. The events last 1–5 weeks, typically produce ~5 mm of static forearc deformation, and show cumulative totals of tremor that range from 40 to 280 h. Moment released by each event is estimated by inverting GPS-measured deformation, which is sensitive to all rates of tremor-synchronous faulting, including aseismic creep, for total …
Energy Budget Analysis Of Slow-Slip Tremor Events Along The Cascadia Subduction Zone Using Continuous Gps Array Data, James Steven Chapman
Energy Budget Analysis Of Slow-Slip Tremor Events Along The Cascadia Subduction Zone Using Continuous Gps Array Data, James Steven Chapman
All Master's Theses
Seismic hazards poised to cities by subduction zones are strongly controlled by fault slip along the deeper extent of the two plate interaction closest to population densities. In Cascadia, where Mw=9 size events are known to occur from a variety of sources, modeling of leveling data has suggested that the region of maximum slip lies well offshore and diminishes rapidly inland. However, over two dozen slow slip distributions have been imaged using Global Positioning System (GPS) along the lower reaches of the northern Cascadia locked zone between 30 and 40 km in depth. Averaged over many episodic tremor and slip …
Seismic Constraints On Slow Slip Events Within The Cascadia Subduction Zone, Ana Cristina Aguiar
Seismic Constraints On Slow Slip Events Within The Cascadia Subduction Zone, Ana Cristina Aguiar
All Master's Theses
Reanalysis of geodetic GPS time series from the Cascadia subduction zone have revealed at least 30 resolvable slow slip events along the megathrust, ranging from northern California to southern British Columbia, since 1997. Many of the smaller and more recent events are barely resolvable with GPS, but stand out clearly as tremor sequences. Since tremor bursts lasting less than 10-seconds are often visible across multiple stations, they offer the highest resolution for studying moment release through time. To test the hypothesis that tremor and transient deformation are two manifestations of the same faulting process, and to quantify the relative contribution …
Transient Detection And Modeling Of Continuous Geodetic Data, Walter Michael Szeliga
Transient Detection And Modeling Of Continuous Geodetic Data, Walter Michael Szeliga
All Master's Theses
Transient surface deformation has been observed by continuously operating Global Positioning System stations in the Puget Sound area during the past decade. This surface deformation is associated with processes occurring on or near the subducting plate boundary between the Juan de Fuca and North American plates. This thesis is composed of two studies of transient deformation along the Cascadia plate margin and a discussion of the methodologies employed in these studies. We model one 7-week episode of transient deformation that occurred during 2003 beneath the Puget Sound area. Additionally, we utilize a combination of continuous Global Positioning System and seismic …
Error Analysis Of Continuous Gps Position Time Series, Simon D. P. Williams, Yehuda Bock, Peng Fang, Paul Jamason, Rosanne M. Nikolaidis, Linette Prawirodirdjo, Meghan Miller, Daniel J. Johnson
Error Analysis Of Continuous Gps Position Time Series, Simon D. P. Williams, Yehuda Bock, Peng Fang, Paul Jamason, Rosanne M. Nikolaidis, Linette Prawirodirdjo, Meghan Miller, Daniel J. Johnson
All Faculty Scholarship for the College of the Sciences
A total of 954 continuous GPS position time series from 414 individual sites in nine different GPS solutions were analyzed for noise content using maximum likelihood estimation (MLE). The lengths of the series varied from around 16 months to over 10 years. MLE was used to analyze the data in two ways. In the first analysis the noise was assumed to be white noise only, a combination of white noise plus flicker noise, or a combination of white noise plus random walk noise. For the second analysis the spectral index and amplitude of the power law noise were estimated simultaneously …