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Articles 1 - 8 of 8
Full-Text Articles in Physical Sciences and Mathematics
Comparisons Of Gravity Anomalies At Pseudofaults, Fracture Zones, And Nontransform Discontinuities From Fast To Slow Spreading Areas, Sarah E. Kruse, Sarah F. Tebbens, David F. Naar, Qingyuan Y. Lou, Robert T. Bird
Comparisons Of Gravity Anomalies At Pseudofaults, Fracture Zones, And Nontransform Discontinuities From Fast To Slow Spreading Areas, Sarah E. Kruse, Sarah F. Tebbens, David F. Naar, Qingyuan Y. Lou, Robert T. Bird
Geology Faculty Publications
Published mechanisms for rift tip propagation at spreading centers include extensional deformation and an initial period of slow spreading. We investigate whether the gravity signal and inferred crustal structure at pseudofaults formed in medium to superfast spreading environments resemble the gravity signal at fracture zones or nontransform discontinuities formed in slow spreading environments. We find that altimetry-based gravity anomalies on the Mathematician, Bauer, Easter, Juan Fernandez, and northern Chile Ridge pseudofaults, located in 75–150 mm/yr (full rate) seafloor spreading environments, are similar in amplitude and form to Atlantic fracture zones with 20–30 mm/yr spreading rates. A 5–15 mGal positive mantle …
Comparative Ecosystem Analysis Of Hydrologic Restoration Of Tates Hell Swamp, Chris Robert, Thomas Crisman, Loren Anderson, Carolyn Kendell
Comparative Ecosystem Analysis Of Hydrologic Restoration Of Tates Hell Swamp, Chris Robert, Thomas Crisman, Loren Anderson, Carolyn Kendell
School of Geosciences Faculty and Staff Publications
No abstract provided.
Aseismic Inflation Of Westdahl Volcano, Alaska, Revealed By Satellite Radar Interferometry, Zhong Lu, Charles Wicks, Daniel Dzurisin, Wayne Thatcher, Jeffrey T. Freymuller, Stephen R. Mcnutt, Dorte Mann
Aseismic Inflation Of Westdahl Volcano, Alaska, Revealed By Satellite Radar Interferometry, Zhong Lu, Charles Wicks, Daniel Dzurisin, Wayne Thatcher, Jeffrey T. Freymuller, Stephen R. Mcnutt, Dorte Mann
School of Geosciences Faculty and Staff Publications
Westdahl volcano, located at the west end of Unimak Island in the central Aleutian volcanic arc, Alaska, is a broad shield that produced moderate-sized eruptions in 1964, 1978–79, and 1991–92. Satellite radar interferometry detected about 17 cm of volcano-wide inflation from September 1993 to October 1998. Multiple independent interferograms reveal that the deformation rate has not been steady; more inflation occurred from 1993 to 1995 than from 1995 to 1998. Numerical modeling indicates that a source located about 9 km beneath the center of the volcano inflated by about 0.05 km³ from 1993 to 1998. On the basis of the …
Application Of Wave-Theoretical Seismoacoustic Models To The Interpretation Of Explosion And Eruption Tremor Signals Radiated By Pavlof Volcano, Alaska, Milton A. Garces, Stephen R. Mcnutt, Roger A. Hansen, John C. Eichelberger
Application Of Wave-Theoretical Seismoacoustic Models To The Interpretation Of Explosion And Eruption Tremor Signals Radiated By Pavlof Volcano, Alaska, Milton A. Garces, Stephen R. Mcnutt, Roger A. Hansen, John C. Eichelberger
School of Geosciences Faculty and Staff Publications
Tremor and explosion signals recorded on September 29 during the Fall 1996 Pavlof eruption are interpreted using video images, field observations, and seismic data. Waveform analysis of tremor and explosions provided estimates of the melt's volcano-acoustic parameters and the magma conduit dimensions. Initial mass fractions of 0.25% water and 0.025% carbon dioxide in the melt can explain the resonance characteristics of the tremor and explosion pulses inferred from seismic data. The magma conduit is modeled as a three-section rectangular crack. We infer that the tremor-radiating region consists of the lowermost two sections, both with cross-sectional areas of ∼10 m2 …
Present-Day Motion Of The Sierra Nevada Block And Some Tectonic Implications For The Basin And Range Province, North American Cordillera, Timothy H. Dixon, Meghan Miller, Frederic Farina, Hongzhi Wang, Daniel Johnson
Present-Day Motion Of The Sierra Nevada Block And Some Tectonic Implications For The Basin And Range Province, North American Cordillera, Timothy H. Dixon, Meghan Miller, Frederic Farina, Hongzhi Wang, Daniel Johnson
School of Geosciences Faculty and Staff Publications
Global Positioning System (GPS) data from five sites on the stable interior of the Sierra Nevada block are inverted to describe its angular velocity relative to stable North America. The velocity data for the five sites fit the rigid block model with rms misfits of 0.3 mm/yr (north) and 0.8 mm/yr (east), smaller than independently estimated data uncertainty, indicating that the rigid block model is appropriate. The new Euler vector, 17.0°N, 137.3°W, rotation rate 0.28 degrees per million years, predicts that the block is translating to the northwest, nearly parallel to the plate motion direction, at 13–14 mm/yr, faster than …
Geologic Factors Controlling Patterns Of Small‐Volume Basaltic Volcanism: Application To A Volcanic Hazards Assessment At Yucca Mountain, Nevada, Charles B. Connor, John A. Stamatakos, David A. Ferrill, Brittain E. Hill, Goodluck I. Ofoegbu, Michael Conway, Budhi Sagar, John Trapp
Geologic Factors Controlling Patterns Of Small‐Volume Basaltic Volcanism: Application To A Volcanic Hazards Assessment At Yucca Mountain, Nevada, Charles B. Connor, John A. Stamatakos, David A. Ferrill, Brittain E. Hill, Goodluck I. Ofoegbu, Michael Conway, Budhi Sagar, John Trapp
School of Geosciences Faculty and Staff Publications
The proposed high‐level radioactive waste repository at Yucca Mountain, Nevada, is located within an active volcanic field. Probabilistic volcanic hazard models for future eruptions through the proposed repository depend heavily on our understanding of the spatial controls on volcano distribution at a variety of scales. On regional scales, Pliocene‐Quaternary volcano clusters are located east of the Bare Mountain fault. Extension has resulted in large‐scale crustal density contrast across the fault, and vents are restricted to low‐density areas of the hanging wall. Finite element modeling indicates that this crustal density contrast can result in transient pressure changes of up to 7 …
Gps Geodetic Constraints On Caribbean-North America Plate Motion, Charles Demets, Pamela E. Jansma, Glen S. Mattioli, Timothy H. Dixon, Fred Farina, Roger Bilham, Eric Calais, Paul Mann
Gps Geodetic Constraints On Caribbean-North America Plate Motion, Charles Demets, Pamela E. Jansma, Glen S. Mattioli, Timothy H. Dixon, Fred Farina, Roger Bilham, Eric Calais, Paul Mann
School of Geosciences Faculty and Staff Publications
We describe a model for Caribbean plate motion based on GPS velocities of four sites in the plate interior and two azimuths of the Swan Islands transform fault. The data are well fit by a single angular velocity, with average misfits approximately equal to the 1.5–3.0 mm yr−1 velocity uncertainties. The new model predicts Caribbean-North America motion ∼65% faster than predicted by NUVEL-1A, averaging 18–20±3 mm yr−1 (2σ) at various locations along the plate boundary. The data are best fit by a rotation pole that predicts obliquely convergent motion along the plate boundary east of Cuba, but are …
Neotectonics Of Puerto Rico And The Virgin Islands, Northeastern Caribbean, From Gps Geodesy, Pamela E. Jansma, Glen S. Mattioli, Alberto Lopez, Charles Demets, Timothy H. Dixon, Paul Mann, Eric Calais
Neotectonics Of Puerto Rico And The Virgin Islands, Northeastern Caribbean, From Gps Geodesy, Pamela E. Jansma, Glen S. Mattioli, Alberto Lopez, Charles Demets, Timothy H. Dixon, Paul Mann, Eric Calais
School of Geosciences Faculty and Staff Publications
The boundary between the North American and Caribbean plates is characterized primarily by left-lateral motion along predominantly east-west striking faults. Seismicity and marine geophysical survey data are consistent with at least two, and possibly three, microplates in the diffuse boundary zone in the northeastern Caribbean: (1) the Gonave, (2) the Hispaniola, and (3) the Puerto Rico-northern Virgin Islands (PRVI). We discuss results from GPS geodetic measurements acquired since 1994 to test the microplate hypothesis, define PRVI translation and rotation within the boundary zone, and constrain PRVI neotectonics. GPS-derived velocities are analyzed with respect to both North American and Caribbean plate …