Open Access. Powered by Scholars. Published by Universities.®

Physical Sciences and Mathematics Commons™

Open Access. Powered by Scholars. Published by Universities.®

Portland State University

Series

2017

Earth Sciences

Articles 1 - 15 of 15

Full-Text Articles in Physical Sciences and Mathematics

Coastal Eolian Sand-Ramp Development Related To Paleo-Sea-Level Changes During The Latest Pleistocene And Holocene (21–0 Ka) In San Miguel Island, California, U.S.A., Curt D. Peterson, Jon M. Erlandson, Errol Stock, Steve W. Hostetler, David M. Price Sep 2017

Coastal Eolian Sand-Ramp Development Related To Paleo-Sea-Level Changes During The Latest Pleistocene And Holocene (21–0 Ka) In San Miguel Island, California, U.S.A., Curt D. Peterson, Jon M. Erlandson, Errol Stock, Steve W. Hostetler, David M. Price

Geology Faculty Publications and Presentations

Coastal eolian sand ramps (5–130 m elevation) on the northern slope (windward) side of the small San Miguel Island (13 km in W-E length) range in age from late Pleistocene to modern time, though a major hiatus in sand-ramp growth occurred during the early Holocene marine transgression (16–9 ka). The Holocene sand ramps (1–5 m measured thicknesses) currently lack large dune forms, thereby representing deflated erosional remnants, locally covering thicker late Pleistocene sand-ramp deposits. The ramp sand was initially supplied from the adjacent island-shelf platform, extending about 20 km north of the present coastline. The sand-ramp deposits and interbedded loess …

Go to article

A Finite Difference Method For Off-Fault Plasticity Throughout The Earthquake Cycle, Brittany A. Erickson, Eric M. Dunham, Arash Khosravifar Aug 2017

A Finite Difference Method For Off-Fault Plasticity Throughout The Earthquake Cycle, Brittany A. Erickson, Eric M. Dunham, Arash Khosravifar

Mathematics and Statistics Faculty Publications and Presentations

We have developed an efficient computational framework for simulating multiple earthquake cycles with off-fault plasticity. The method is developed for the classical antiplane problem of a vertical strike-slip fault governed by rate-and-state friction, with inertial effects captured through the radiationdamping approximation. Both rate-independent plasticity and viscoplasticity are considered, where stresses are constrained by a Drucker-Prager yield condition. The off-fault volume is discretized using finite differences and tectonic loading is imposed by displacing the remote side boundaries at a constant rate. Time-stepping combines an adaptive Runge-Kutta method with an incremental solution process which makes use of an elastoplastic tangent stiffness tensor …

Go to article

The Geography Of Glaciers And Perennial Snowfields In The American West, Andrew G. Fountain, Bryce Glenn, Hassan J. Basagic Aug 2017

The Geography Of Glaciers And Perennial Snowfields In The American West, Andrew G. Fountain, Bryce Glenn, Hassan J. Basagic

Geology Faculty Publications and Presentations

A comprehensive mid-20th century inventory of glaciers and perennial snowfields (G&PS) was compiled for the American West, west of the 100° meridian. The inventory was derived from U.S. Geological Survey 1:24,000 topographic maps based on aerial photographs acquired during 35 years, 1955–1990, of which the first 20 years or more was a cool period with little glacier change. The mapped features were filtered for those greater than 0.01 km2. Results show that 5036 G&PS (672 km2, 14 km3) populate eight states, of which about 1276 (554 km2, 12 km3) are glaciers. …

Go to article

High-Resolution Elevation Mapping Of The Mcmurdo Dry Valleys, Antarctica, And Surrounding Regions, Andrew G. Fountain, Juan C. Fernandez-Diaz, Maciej K. Obryk, Joseph Levy, Michael N. Gooseff, David J. Van Horn, Paul Morin, Ramesh Shrestha Jul 2017

High-Resolution Elevation Mapping Of The Mcmurdo Dry Valleys, Antarctica, And Surrounding Regions, Andrew G. Fountain, Juan C. Fernandez-Diaz, Maciej K. Obryk, Joseph Levy, Michael N. Gooseff, David J. Van Horn, Paul Morin, Ramesh Shrestha

Geology Faculty Publications and Presentations

We present detailed surface elevation measurements for the McMurdo Dry Valleys, Antarctica derived from aerial lidar surveys flown in the austral summer of 2014–2015 as part of an effort to understand geomorphic changes over the past decade. Lidar return density varied from 2 to > 10 returns m−2with an average of about 5 returns m−2. Vertical and horizontal accuracies are estimated to be 7 and 3 cm, respectively. In addition to our intended targets, other ad hoc regions were also surveyed including the Pegasus flight facility and two regions on Ross Island, McMurdo Station, Scott Base (and surroundings), and the coastal …

Go to article

Origins Of Late- Pleistocene Coastal Dune Sheets, Magdalena And Guerrero Negro, From Continental Shelf Low-Stand Supply (70-20 Ka), Under Conditions Of Southeast Littoral- And Eolian-Sand Transport, In Baja California Sur, Mexico, Curt D. Peterson, Janette Murillo-Jiminez, Errol Stock, David M. Price, Steve W. Hostetler, David Percy Jul 2017

Origins Of Late- Pleistocene Coastal Dune Sheets, Magdalena And Guerrero Negro, From Continental Shelf Low-Stand Supply (70-20 Ka), Under Conditions Of Southeast Littoral- And Eolian-Sand Transport, In Baja California Sur, Mexico, Curt D. Peterson, Janette Murillo-Jiminez, Errol Stock, David M. Price, Steve W. Hostetler, David Percy

Geology Faculty Publications and Presentations

Shallow morpho-stratigraphic sections (n = 11) in each of two large coastal dune sheets including the Magdalena (7000 km2) and Guerrero Negro (8000 km2) dune sheets, from the Pacific Ocean side of Baja California Sur, Mexico, have been analyzed for dune deposit age. The shallow morpho-stratigraphic sections (∼2-10 m depth) include 11 new TL and 14C ages, and paleosol chronosequences, that differentiate cemented late Pleistocene dune deposits (20.7 ± 2.1 to 99.8 ± 9.4 ka) from uncemented Holocene dune deposits (0.7 ± 0.05 to at least 3.2 ± 0.3 ka). Large linear dune ridges (5-10 m …

Go to article

Time Varying Parameter Models For Catchments With Land Use Change: The Importance Of Model Structure, Sahani Pathiraja, Daniela Anghileri, Paolo Burlando, Ashish Sharma, Lucy Marshall, Hamid Moradkhani Jul 2017

Time Varying Parameter Models For Catchments With Land Use Change: The Importance Of Model Structure, Sahani Pathiraja, Daniela Anghileri, Paolo Burlando, Ashish Sharma, Lucy Marshall, Hamid Moradkhani

Civil and Environmental Engineering Faculty Publications and Presentations

Rapid population and economic growth in South-East-Asia has been accompanied by extensive land use change with consequent impacts on catchment hydrology. Modelling methodologies capable of handling changing land use conditions are therefore becoming ever more important, and are receiving increasing attention from hydrologists. A recently developed Data Assimilation based framework that allows model parameters to vary through time in response to signals of change in observations is considered for a medium sized catchment (2880 km²) in Northern Vietnam experiencing substantial but gradual land cover change. We investigate the efficacy of the method as well as the importance of the chosen …

Go to article

Cascadia Subduction Tremor Muted By Crustal Faults, Ray E. Wells, Richard J. Blakely, Aaron G. Wech, Patricia A. Mccrory, Andrew Michael Jun 2017

Cascadia Subduction Tremor Muted By Crustal Faults, Ray E. Wells, Richard J. Blakely, Aaron G. Wech, Patricia A. Mccrory, Andrew Michael

Geology Faculty Publications and Presentations

Deep, episodic slow slip on the Cascadia subduction megathrust of western North America is accompanied by low-frequency tremor in a zone of high fluid pressure between 30 and 40 km depth. Tremor density (tremor epicenters per square kilometer) varies along strike, and lower tremor density statistically correlates with upper plate faults that accommodate northward motion and rotation of forearc blocks. Upper plate earthquakes occur to 35 km depth beneath the faults. We suggest that the faults extend to the overpressured megathrust, where they provide fracture pathways for fluid escape into the upper plate. This locally reduces megathrust fluid pressure and …

Go to article

Evidence For Distributed Clockwise Rotation Of The Crust In The Northwestern United States From Fault Geometries And Focal Mechanisms, Thomas M. Brocher, Ray E. Wells, Andrew P. Lamb, Craig S. Weaver May 2017

Evidence For Distributed Clockwise Rotation Of The Crust In The Northwestern United States From Fault Geometries And Focal Mechanisms, Thomas M. Brocher, Ray E. Wells, Andrew P. Lamb, Craig S. Weaver

Geology Faculty Publications and Presentations

Paleomagnetic and GPS data indicate that Washington and Oregon have rotated clockwise for the past 16 Myr. Late Cenozoic and Quaternary fault geometries, seismicity lineaments, and focal mechanisms provide evidence that this rotation is accommodated by north directed thrusting and right-lateral strike-slip faulting in Washington, and SW to W directed normal faulting and right-lateral strike-slip faulting to the east. Several curvilinear NW to NNW trending high-angle strike-slip faults and seismicity lineaments in Washington and NW Oregon define a geologic pole (117.7°W, 47.9°N) of rotation relative to North America. Many faults and focal mechanisms throughout northwestern U.S. and southwestern British Columbia …

Go to article

Slope, Grain Size, And Roughness Controls On Dry Sediment Transport And Storage On Steep Hillslopes, Roman A. Dibiase, Michael P. Lamb, Vamsi Ganti, Adam M. Booth Apr 2017

Slope, Grain Size, And Roughness Controls On Dry Sediment Transport And Storage On Steep Hillslopes, Roman A. Dibiase, Michael P. Lamb, Vamsi Ganti, Adam M. Booth

Geology Faculty Publications and Presentations

Existing hillslope sediment transport models developed for low-relief, soil-mantled landscapes are poorly suited to explain the coupling between steep rocky hillslopes and headwater channels. Here we address this knowledge gap using a series of field and numerical experiments to inform a particle-based model of sediment transport by dry ravel—a mechanism of granular transport characteristic of steep hillslopes. We find that particle travel distance increases as a function of the ratio of particle diameter to fine-scale (1m) topographic variability associated with rocky landscapes. Applying a 2-D dry-ravel-routing model to lidar-derived surface topography, we show how spatial patterns of local and nonlocal …

Go to article

Analyzing Glacier Surface Motion Using Lidar Data, Jennifer W. Tellig, Craig Glennie, Andrew G. Fountain, David C. Finnegan Mar 2017

Analyzing Glacier Surface Motion Using Lidar Data, Jennifer W. Tellig, Craig Glennie, Andrew G. Fountain, David C. Finnegan

Geology Faculty Publications and Presentations

Understanding glacier motion is key to understanding how glaciers are growing, shrinking, and responding to changing environmental conditions. In situ observations are often difficult to collect and offer an analysis of glacier surface motion only at a few discrete points. Using light detection and ranging (LiDAR) data collected from surveys over six glaciers in Greenland and Antarctica, particle image velocimetry (PIV) was applied to temporally-spaced point clouds to detect and measure surface motion. The type and distribution of surface features, surface roughness, and spatial and temporal resolution of the data were all found to be important factors, which limited the …

Go to article

The Influence Of Föhn Winds On Glacial Lake Washburn And Palaeotemperatures In The Mcmurdo Dry Valleys, Antarctica, During The Last Glacial Maximum, Maciej Obryk, Peter Doran, Ed Waddington, Chris Mckay Mar 2017

The Influence Of Föhn Winds On Glacial Lake Washburn And Palaeotemperatures In The Mcmurdo Dry Valleys, Antarctica, During The Last Glacial Maximum, Maciej Obryk, Peter Doran, Ed Waddington, Chris Mckay

Geology Faculty Publications and Presentations

Large glacial lakes, including Glacial Lake Washburn, were present in the McMurdo Dry Valleys, Antarctica, during the Last Glacial Maximum (LGM) despite a colder and drier climate. To address the mechanism capable of generating enough meltwater to sustain these large lakes, a conceptual model was developed based on the warming potential of infrequent contemporary föhn winds. The model suggests that föhn winds were capable of generating enough meltwater to sustain large glacial lakes during the LGM by increasing degree days above freezing (DDAF) and prolonging the melt season. A present-day relationship between infrequent summer föhn winds and DDAF was established. …

Go to article

Ground-Rupturing Earthquakes On The Northern Big Bend Of The San Andreas Fault, California, 800 A.D. To Present, Katherine Scharer, Ray J. Weldon Ii, Glenn Biasi, Ashley Streig, Thomas Fumal Mar 2017

Ground-Rupturing Earthquakes On The Northern Big Bend Of The San Andreas Fault, California, 800 A.D. To Present, Katherine Scharer, Ray J. Weldon Ii, Glenn Biasi, Ashley Streig, Thomas Fumal

Geology Faculty Publications and Presentations

Paleoseismic data on the timing of ground-rupturing earthquakes constrain the recurrence behavior of active faults and can provide insight on the rupture history of a fault if earthquakes dated at neighboring sites overlap in age and are considered correlative. This study presents the evidence and ages for 11 earthquakes that occurred along the Big Bend section of the southern San Andreas Fault at the Frazier Mountain paleoseismic site. The most recent earthquake to rupture the site was the Mw7.7–7.9 Fort Tejon earthquake of 1857. We use over 30 trench excavations to document the structural and sedimentological evolution of a small …

Go to article

Watershed Response To Climate Change And Fire-Burns In The Upper Umatilla River Basin, Usa, Kimberly Crystal Yazzie, Heejun Chang Feb 2017

Watershed Response To Climate Change And Fire-Burns In The Upper Umatilla River Basin, Usa, Kimberly Crystal Yazzie, Heejun Chang

Geography Faculty Publications and Presentations

This study analyzed watershed response to climate change and forest fire impacts in the upper Umatilla River Basin (URB), Oregon, using the precipitation runoff modeling system. Ten global climate models using Coupled Intercomparison Project Phase 5 experiments with Representative Concentration Pathways (RCP) 4.5 and 8.5 were used to simulate the effects of climate and fire-burns on runoff behavior throughout the 21st century. We observed the center timing (CT) of flow, seasonal flows, snow water equivalent (SWE) and basin recharge. In the upper URB, hydrologic regime shifts from a snow-rain-dominated to rain-dominated basin. Ensemble mean CT occurs 27 days earlier in …

Go to article

Holocene History Of Deep-Seated Landsliding In The North Fork Stillaguamish River Valley From Surface Roughness Analysis, Radiocarbon Dating, And Numerical Landscape Evolution Modeling, Adam M. Booth, Sean R. Lahusen, Alison R. Duvall, David R. Montgomery Feb 2017

Holocene History Of Deep-Seated Landsliding In The North Fork Stillaguamish River Valley From Surface Roughness Analysis, Radiocarbon Dating, And Numerical Landscape Evolution Modeling, Adam M. Booth, Sean R. Lahusen, Alison R. Duvall, David R. Montgomery

Geology Faculty Publications and Presentations

Documenting spatial and temporal patterns of past landsliding is a challenging step in quantifying the effect of landslides on landscape evolution. While landslide inventories can map spatial distributions, lack of dateable material, landslide reactivations, or time, access, and cost constraints generally limit dating large numbers of landslides to analyze temporal patterns. Here we quantify the record of the Holocene history of deep-seated landsliding along a 25 km stretch of the North Fork Stillaguamish River valley, Washington State, USA, including the 2014 Oso landslide, which killed 43 people. We estimate the ages of more than 200 deep-seated landslides in glacial sediment …

Go to article

Mapping The Nonstationary Internal Tide With Satellite Altimetry, Edward Zaron Jan 2017

Mapping The Nonstationary Internal Tide With Satellite Altimetry, Edward Zaron

Civil and Environmental Engineering Faculty Publications and Presentations

t Temporal variability of the internal tide has been inferred from the 23 year long combined records of the TOPEX/Poseidon, Jason-1, and Jason-2 satellite altimeters by combining harmonic analysis with an analysis of along-track wavenumber spectra of sea-surface height (SSH). Conventional harmonic analysis is first applied to estimate and remove the stationary components of the tide at each point along the reference ground tracks. The wavenumber spectrum of the residual SSH is then computed, and the variance in a neighborhood around the wavenumber of the mode-1 baroclinic M2 tide is interpreted as the sum of noise, broadband nontidal processes, and …

Go to article