Oregon Department of Geology and Mineral Industries

The proportion of fractures that occur in women without osteoporosis has not been fully described, and the characteristics of nonosteoporotic women who fracture are not well understood. We measured total hip bone mineral density (BMD) and baseline characteristics including physical activity, falls, and strength for 8065 women aged 65 yr or older participating in the Study of Osteoporotic Fractures and then followed these women for hip fracture for up to 5 yr after BMD measurement. Among all participants, 17% had osteoporosis (total hip BMD T-score < or = -2.5). Of the 243 women with incident hip fracture, 54% were not osteoporotic at start of follow-up. Nonosteoporotic women who fractured were less likely than osteoporotic women with fracture to have baseline characteristics associated with frailty. Nevertheless, among nonosteoporotic participants, several characteristics increased fracture risk, including advancing age, lack of exercise in the last year, reduced visual contrast sensitivity, falls in the last year, prevalent vertebral fracture, and lower total hip BMD. These findings call attention to the many older women who suffer hip fracture but do not have particularly low antecedent BMD measures and help begin to identify risk factors associated with higher bone density levels.

The first probabilistic tsunami flooding maps have been developed. The methodology, called probabilistic tsunami hazard assessment (PTHA), integrates tsunami inundation modeling with methods of probabilistic seismic hazard assessment (PSHA). Application of the methodology to Seaside, Oregon, has yielded estimates of the spatial distribution of 100‐ and 500‐year maximum tsunami amplitudes, i.e., amplitudes with 1% and 0.2% annual probability of exceedance. The 100‐year tsunami is generated most frequently by far‐field sources in the Alaska‐Aleutian Subduction Zone and is characterized by maximum amplitudes that do not exceed 4 m, with an inland extent of less than 500 m. In contrast, the 500‐year tsunami is dominated by local sources in the Cascadia Subduction Zone and is characterized by maximum amplitudes in excess of 10 m and an inland extent of more than 1 km. The primary sources of uncertainty in these results include those associated with interevent time estimates, modeling of background sea level, and accounting for temporal changes in bathymetry and topography. Nonetheless, PTHA represents an important contribution to tsunami hazard assessment techniques; viewed in the broader context of risk analysis, PTHA provides a method for quantifying estimates of the likelihood and severity of the tsunami hazard, which can then be combined with vulnerability and exposure to yield estimates of tsunami risk.

The El Niño-Southern Oscillation is the dominant mode of interannual climate variability across the Pacific Ocean basin, with influence on the global climate. The two end members of the cycle, El Niño and La Niña, force anomalous oceanographic conditions and coastal response along the Pacific margin, exposing many heavily populated regions to increased coastal flooding and erosion hazards. However, a quantitative record of coastal impacts is spatially limited and temporally restricted to only the most recent events. Here we report on the oceanographic forcing and coastal response of the 2015-2016 El Niño, one of the strongest of the last 145 years. We show that winter wave energy equalled or exceeded measured historical maxima across the US West Coast, corresponding to anomalously large beach erosion across the region. Shorelines in many areas retreated beyond previously measured landward extremes, particularly along the sediment-starved California coast.

Erosion along the West Coast of the United States is affected by climate controls that include a trend of increasing wave heights during at least the past 25 years that might be related to global warming and the El Niño Southern Oscillation (ENSO) range between El Niños and La Niñas that affects both annual wave conditions and monthly mean water levels that raise tidal elevations. These processes are analyzed for sites from Washington to south-central California, revealing a latitude dependence of the individual processes and how their combinations affect total water levels at the shore, which is important to beach and property erosion. Particularly significant on the coast of the Pacific Northwest (Washington and Oregon) has been the progressive decadal increases in deep-water wave heights and periods, which have increased breaker heights and elevated storm wave runup levels on beaches. Along the entire West Coast, the annual variations in wave conditions above and below any progressive decadal increase are controlled by the North Pacific index (NPI), the atmospheric pressure difference between the Hawaiian High and Aleutian Low, and the ENSO range, as demonstrated by a strong correlation with the multivariate ENSO index (MEI), with the highest wave conditions occurring during El Niños. In addition, the ENSO range is particularly important in controlling mean water levels, causing tides to reach their highest elevations during El Niños, again shown by correlations with MEIs along the entire West Coast. With El Niños producing increased deep-water wave heights, runup levels on beaches, and elevated tides, the total water levels at the shore from the combined processes are significantly higher compared with normal or La Niña years, resulting in episodes of major property erosion along the entire US West Coast.

Abstract Comparison of histories of great earthquakes and accompanying tsunamis at eight coastal sites suggests plate-boundary ruptures of varying length, implying great earthquakes of variable magnitude at the Cascadia subduction zone. Inference of rupture length relies on degree of overlap on radiocarbon age ranges for earthquakes and tsunamis, and relative amounts of coseismic subsidence and heights of tsunamis. Written records of a tsunami in Japan provide the most conclusive evidence for rupture of much of the plate boundary during the earthquake of 26 January 1700. Cascadia stratigraphic evidence dating from about 1600 cal yr B.P., similar to that for the 1700 earthquake, implies a similarly long rupture with substantial subsidence and a high tsunami. Correlations are consistent with other long ruptures about 1350 cal yr B.P., 2500 cal yr B.P., 3400 cal yr B.P., 3800 cal yr B.P., 4400 cal yr B.P., and 4900 cal yr B.P. A rupture about 700–1100 cal yr B.P. was limited to the northern and central parts of the subduction zone, and a northern rupture about 2900 cal yr B.P. may have been similarly limited. Times of probable short ruptures in southern Cascadia include about 1100 cal yr B.P., 1700 cal yr B.P., 3200 cal yr B.P., 4200 cal yr B.P., 4600 cal yr B.P., and 4700 cal yr B.P. Rupture patterns suggest that the plate boundary in northern Cascadia usually breaks in long ruptures during the greatest earthquakes. Ruptures in southernmost Cascadia vary in length and recurrence intervals more than ruptures in northern Cascadia.

Abstract Detailed information about landslide occurrence is the foundation for advancing process understanding, susceptibility mapping, and risk reduction. Despite the recent revolution in digital elevation data and remote sensing technologies, landslide mapping remains resource intensive. Consequently, a modern, comprehensive map of landslide occurrence across the United States (USA) has not been compiled. As a first step toward this goal, we present a national-scale compilation of existing, publicly available landslide inventories. This geodatabase can be downloaded in its entirety or viewed through an online, searchable map, with parsimonious attributes and direct links to the contributing sources with additional details. The mapped spatial pattern and concentration of landslides are consistent with prior characterization of susceptibility within the conterminous USA, with some notable exceptions on the West Coast. Although the database is evolving and known to be incomplete in many regions, it confirms that landslides do occur across the country, thus highlighting the importance of our national-scale assessment. The map illustrates regions where high-quality mapping has occurred and, in contrast, where additional resources could improve confidence in landslide characterization. For example, borders between states and other jurisdictions are quite apparent, indicating the variation in approaches to data collection by different agencies and disparity between the resources dedicated to landslide characterization. Further investigations are needed to better assess susceptibility and to determine whether regions with high relief and steep topography, but without mapped landslides, require further landslide inventory mapping. Overall, this map provides a new resource for accessing information about known landslides across the USA.

[1] High-resolution beach morphology data collected along much of the U.S. West Coast are synthesized to evaluate the coastal impacts of the 2009–10 El Niño. Coastal change observations were collected as part of five beach monitoring programs that span between 5 and 13 years in duration. In California, regional wave and water level data show that the environmental forcing during the 2009–10 winter was similar to the last significant El Niño of 1997–98, producing the largest seasonal shoreline retreat and/or most landward shoreline position since monitoring began. In contrast, the 2009–10 El Niño did not produce anomalously high mean winter-wave energy in the Pacific Northwest (Oregon and Washington), although the highest 5% of the winter wave-energy measurements were comparable to 1997–98 and two significant non-El Niño winters. The increase in extreme waves in the 2009–10 winter was coupled with elevated water levels and a more southerly wave approach than the long-term mean, resulting in greater shoreline retreat than during 1997–98, including anomalously high shoreline retreat immediately north of jetties, tidal inlets, and rocky headlands. The morphodynamic response observed throughout the U.S. West Coast during the 2009–10 El Niño is principally linked to the El Niño Modoki phenomena, where the warm sea surface temperature (SST) anomaly is focused in the central equatorial Pacific (as opposed to the eastern Pacific during a classic El Niño), featuring a more temporally persistent SST anomaly that results in longer periods of elevated wave energy but lower coastal water levels.

Analyses of hourly measurements of ocean wave heights along the U.S. East Coast, collected since the 1970s by three buoys of the National Data Buoy Center, document a progressive increase during the summer months when hurricanes are most important to wave generation. In contrast, the waves measured during the winter, generated by extratropical storms, have not experienced a statistically significant change. Summer waves with significant wave heights greater than 3 m, which can be directly attributed to specific hurricanes, have increased at a rate of 0.059 m/y (1.8 m in 30 years) according to records from buoy 41002 offshore from Charleston, South Carolina, with a lower rate of 0.024 m/y (0.7 m in 30 years) recorded by the Cape Hatteras buoy (41001); both trends are statistically significant at the 90% level. A still lower rate is found for the Cape May buoy (44004), 0.017 m/y, suggesting that there is a systematic latitude variation. Histograms of the ranges of significant wave heights measured during the hurricane season show that the most extreme occurrences during the 1996–2005 decade are both higher and more common than occurred 30 years ago, at the beginning of buoy measurements, having increased from about 7 m to higher than 10 m. The waves recorded by the buoys depend on the annual numbers of hurricanes that followed tracks northward into the central Atlantic, how close their tracks approached the buoys, and the intensities (categories) of those hurricanes. Examinations of the storms that have occurred since 1980 indicate that the primary explanation for the progressive increase in wave heights has been an intensification of the hurricanes, with increased numbers of storms a contributing factor.

Abstract A recent 35‐year endpoint shoreline change analysis revealed significant counterclockwise rotations occurring in north‐central Oregon, USA, littoral cells that extend 10s of kilometers in length. While the potential for severe El Niños to contribute to littoral cell rotations at seasonal to interannual scale was previously recognized, the dynamics resulting in persistent (multidecadal) rotation were unknown, largely due to a lack of historical wave conditions extending back multiple decades and the difficulty of separating the timescales of shoreline variability in a high energy region. This study addresses this question by (1) developing a statistical downscaling framework to characterize wave conditions relevant for longshore sediment transport during data‐poor decades and (2) applying a one‐line shoreline change model to quantitatively assess the potential for such large embayed beaches to rotate. A climate IN dex was optimized to capture variability in longshore wave power as a proxy for potential LO ngshore S ediment T ransport (LOST_IN), and a procedure was developed to simulate many realizations of potential wave conditions from the index. Waves were transformed dynamically with Simulating Waves Nearshore to the nearshore as inputs to a one‐line model that revealed shoreline rotations of embayed beaches at multiple time and spatial scales not previously discernible from infrequent observations. Model results indicate that littoral cells respond to both interannual and multidecadal oscillations, producing comparable shoreline excursions to extreme El Niño winters. The technique quantitatively relates morphodynamic forcing to specific climate patterns and has the potential to better identify and quantify coastal variability on timescales relevant to a changing climate.

Research Article| May 01, 2000 Stratigraphic and structural evolution of the middle Miocene synvolcanic Oregon-Idaho graben Michael L. Cummings; Michael L. Cummings 1Department of Geology, Portland State University, P.O. Box 751, Portland, Oregon 97207, USA Search for other works by this author on: GSW Google Scholar James G. Evans; James G. Evans 2U.S. Geological Survey, West 904 Riverside, Room 202, Spokane, Washington 99210, USA Search for other works by this author on: GSW Google Scholar Mark L. Ferns; Mark L. Ferns 3Oregon Department of Geology and Mineral Industries, 1831 First Street, Baker City, Oregon 97814, USA Search for other works by this author on: GSW Google Scholar Kate R. Lees Kate R. Lees 4Department of Earth Sciences, Open University, Milton Keynes, UK Search for other works by this author on: GSW Google Scholar Author and Article Information Michael L. Cummings 1Department of Geology, Portland State University, P.O. Box 751, Portland, Oregon 97207, USA James G. Evans 2U.S. Geological Survey, West 904 Riverside, Room 202, Spokane, Washington 99210, USA Mark L. Ferns 3Oregon Department of Geology and Mineral Industries, 1831 First Street, Baker City, Oregon 97814, USA Kate R. Lees 4Department of Earth Sciences, Open University, Milton Keynes, UK Publisher: Geological Society of America Received: 23 Jun 1997 Revision Received: 04 May 1999 Accepted: 11 May 1999 First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (2000) 112 (5): 668–682. https://doi.org/10.1130/0016-7606(2000)112<668:SASEOT>2.0.CO;2 Article history Received: 23 Jun 1997 Revision Received: 04 May 1999 Accepted: 11 May 1999 First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Michael L. Cummings, James G. Evans, Mark L. Ferns, Kate R. Lees; Stratigraphic and structural evolution of the middle Miocene synvolcanic Oregon-Idaho graben. GSA Bulletin 2000;; 112 (5): 668–682. doi: https://doi.org/10.1130/0016-7606(2000)112<668:SASEOT>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The Oregon-Idaho graben is a newly identified north-south–trending synvolcanic graben in southeastern Oregon and southwestern Idaho within the middle Miocene backarc rift system that extends 1100 km from southern Nevada to southeastern Washington. The graben formed along the western margin of the North American craton shortly after the largest volumes of tholeiitic flood basalt erupted (Columbia River Basalt Group, Steens-Pueblo Basalt, basalt of Malheur Gorge, basalt and latite unit of Ekren et al., 1981). Rhyolite flows and ash-flow tuffs (16.1–14.0 Ma) erupted from northeastern Oregon (Dooley Volcanics) to northern Nevada (McDermitt volcanic field) shortly after the flood basalt was emplaced. Subsidence of the Oregon-Idaho graben (15.5–15.3 Ma) coincides with eruption of rhyolite flows and caldera-related ash-flow tuffs from vents along the margins and within the graben. Mafic and silicic intragraben volcanism accompanied sedimentation from about 15.3 to 10.5 Ma. Sedimentary and volcanic rocks from extrabasinal sources, especially southwestern Idaho, were introduced periodically.After initial subsidence, the evolution of the Oregon-Idaho graben is divided into three stages. Stage 1 (15.3–14.3 Ma) followed intragraben caldera collapse and was marked by deposition of fluvial and lacustrine sediment across the graben. Stage 2 (14.3–12.6 Ma) movement on intragraben fault zones divided the graben into distinct subbasins and marked the onset of calc-alkalic volcanism. Fine-grained tuffaceous sediment derived from glassy rhyolite and pyroclastic deposits and basalt tuff cones interbedded with rhyolite ash and lapilli-fall deposits and locally erupted basalt hydrovolcanic deposits predominated during synvolcanic subsidence. Synsedimentary hot-spring alteration and precious-metals mineralization of graben fill were controlled by the same intragraben fault zones that served as magmatic conduits. During stage 3 (12.6–10.5 Ma) the subbasins were filled, and graben-wide fluviatile and lacustrine sedimentation resumed. At about the same time, renewed rhyolitic volcanism occurred on both flanks, and tholeiitic volcanism resumed within the Oregon-Idaho graben. Subsidence in the Oregon-Idaho graben ceased as west-northwest–striking faults related to the formation of the western Snake River plain became active. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

The volcanic origin of the Samoan archipelago can be explained by one of three models, specifically, by a hot spot forming over a mantle plume, by lithospheric extension resulting from complex subduction tectonics in the region, or by a combination of these two processes, either acting sequentially or synchronously. In this paper, we present results of 36 high-resolution 40Ar/39Ar incremental heating age analyses for the initial (submarine) phase of Samoan volcanoes, ranging from 13.2 Ma for the westernmost Samoan seamounts to 0.27 Ma in the eastern Samoan volcanic province. Taken as a whole, our new age data point to a hot spot origin for the shield-building volcanism in the Samoan lineament, whereby seamounts younger than 5 Ma are consistent with a model of constant 7.1 cm/yr plate motion, analogous to GPS measurements for the Pacific Plate in this region. This makes our new 40Ar/39Ar ages of the submarine basalts all older compared to recent absolute plate motion (APM) models by Wessel et al. (2008), which are based on the inversion of twelve independent seamount trails in the Pacific relative to a fixed reference frame of hot spots and which predict faster plate motions of around 9.3 cm/yr in the vicinity of Samoa. The Samoan ages are also older than APM models by Steinberger et al. (2004) taking into account the motion of hot spots in the Pacific alone or globally. The age systematics become more complicated toward the younger end of the Samoan seamount trail, where its morphology bifurcates into two en echelon subtracks, termed the VAI and MALU trends, as they emanate from two eruptive centers at Vailulu'u and Malumalu seamount, respectively. Spaced ∼50 km apart, the VAI and MALU trends have distinct geochemical characters and independent but overlapping linear 40Ar/39Ar age progressions since 1.5 Ma. These phenomena are not unique to Samoa, as they have been observed at the Hawaiian hot spot, and can be attributed to a geochemical zoning in its underlying mantle source or plume. Moreover, the processes allowing for the emergence of two distinct eruptive centers in the Samoan archipelago, the stepped offset of these subtracks, and their slight obliqueness with respect to the overall seamount trail orientation may very well be controlled by local tectonics, stresses, and extension, also causing the rejuvenated volcanism on the main islands of Savai'i, Upolu, and Tutuila since 0.4 Ma.

Analyses of the progressive multidecadal trends and climate-controlled annual variations in mean sea levels are presented for nine tide-gauge stations along the coast of the U.S. Pacific Northwest: Washington, Oregon, and Northern California. The trends in relative sea levels are strongly affected by the tectonics of this region, characterized by significant alongcoast variations in changing land elevations measured by benchmarks and global positioning system data. These combined data sets document the existence of both submergent and emergent stretches of shore. The Pacific Northwest sea levels are also affected by variations in the monthly mean seasonal cycles, with its extreme water levels occurring in the winter during strong El Niños. To quantify this climate control and to derive improved multidecadal sea-level trends, separate evaluations of the winter and summer-averaged measured water levels have been undertaken. The resulting pair of linear regressions for each tide gauge shows a consistent difference in the mean water levels over the years, at their highest during the winters, reflecting the total magnitude in the seasonal cycle of water levels. Of importance, the degree of scatter in the summer averages is reduced compared with the annual averages, yielding sea-level trends that generally have the highest statistical significance. In contrast, the winter records emphasize the extreme water levels associated with strong El Niños, yielding a predictive correlation with the Multivariate El Niño/Southern Oscillation Index. Both trends in relative sea levels and extremes in the winter monthly elevations produced by El Niños are important to the Pacific Northwest coastal hazard assessments, combining with the multidecade increase in wave heights measured by buoys. With these multiple processes and their climate controls, the erosion hazards are projected to significantly increase in future decades.

Characterizations of tsunami hazards along the Cascadia subduction zone hinge on uncertainties in megathrust rupture models used for simulating tsunami inundation. To explore these uncertainties, we constructed 15 megathrust earthquake scenarios using rupture models that supply the initial conditions for tsunami simulations at Bandon, Oregon. Tsunami inundation varies with the amount and distribution of fault slip assigned to rupture models, including models where slip is partitioned to a splay fault in the accretionary wedge and models that vary the updip limit of slip on a buried fault. Constraints on fault slip come from onshore and offshore paleoseismological evidence. We rank each rupture model using a logic tree that evaluates a model's consistency with geological and geophysical data. The scenarios provide inputs to a hydrodynamic model, SELFE, used to simulate tsunami generation, propagation, and inundation on unstructured grids with <5-15 m resolution in coastal areas. Tsunami simulations delineate the likelihood that Cascadia tsunamis will exceed mapped inundation lines. Maximum wave elevations at the shoreline varied from ~4 m to 25 m for earthquakes with 9-44 m slip and M w 8.7-9.2. Simulated tsunami inundation agrees with sparse deposits left by the A.D. 1700 and older tsunamis. Tsunami simulations for large (22-30 m slip) and medium (14-19 m slip) splay fault scenarios encompass 80%-95% of all inundation scenarios and provide reasonable guidelines for landuse planning and coastal development. The maximum tsunami inundation simulated for the greatest splay fault scenario (36-44 m slip) can help to guide development of local tsunami evacuation zones.

Abstract Much research has been done on water‐rich mass flows, but the distinction between hyperconcentrated flows and debris flows, and whether the two are indeed different processes, continue to be debated. Here, we contribute to the ongoing discussion of these phenomena by describing and interpreting the deposit of a large landslide‐induced mass flow in the eastern Swiss Alps. About 9400 years ago, 10‐12 km 3 of limestone detached from the wall of the Vorderrhein River valley and rapidly fragmented while sliding towards the valley bottom. The rock mass struck the valley floor with enormous force and liquefied at least 1 km 3 of valley‐fill sediments. A slurry of liquefied sediment – the ‘Bonaduz gravel’ – traveled tens of kilometres down the Vorderrhein valley from the impact site, carrying huge fragments of rockslide debris that became stranded on the valley floor, forming hills termed ‘tomas’. Part of the flow was deflected by a cross‐valley barrier and traveled 14 km up a tributary of the Vorderrhein valley. The Bonaduz gravel is &gt;65 m thick and fines upward from massive sandy cobble gravel at its base to silty sand at its top. Sedimentologic and geomorphic evidence indicates that Bonaduz gravel was transported as a hyperconcentated flow, likely above a basal carpet of coarse diamictic sediment that behaved as a debris flow. The large amount of water involved in the flow indicates that at least part of the Flims rockslide entered a lake. The Bonaduz deposit shares many properties with sediments left by hyperconcentrated flows generated in flumes, including normal grading and elutriation pipes produced by the rapid escape of fluids when the flow comes to rest. These properties are characteristic of non‐Newtonian laminar flows with high sediment concentrations. Our study reinforces laboratory and theoretical studies showing that debris flows and hyperconcentrated flows are different processes. © 2017 The Authors. Earth Surface Processes and Landforms published by John Wiley &amp; Sons Ltd.

Research Article| November 01, 2010 Analysis of Elevation Changes Detected from Multi-Temporal LiDAR Surveys in Forested Landslide Terrain in Western Oregon WILLIAM J BURNS; WILLIAM J BURNS 1Oregon Department of Geology and Mineral Industries, 800 NE Oregon Street, Portland, OR 97232 Search for other works by this author on: GSW Google Scholar JEFFREY A COE; JEFFREY A COE 2U.S. Geological Survey, Denver Federal Center, Mail Stop 966, Denver, CO 80225 Search for other works by this author on: GSW Google Scholar BASAK SENER KAYA; BASAK SENER KAYA 3Colorado School of Mines, Division of Engineering, Golden, CO 80401 Search for other works by this author on: GSW Google Scholar LINA MA LINA MA 4Oregon Department of Geology and Mineral Industries, 800 NE Oregon Street, Portland, OR 97232 Search for other works by this author on: GSW Google Scholar Author and Article Information WILLIAM J BURNS 1Oregon Department of Geology and Mineral Industries, 800 NE Oregon Street, Portland, OR 97232 JEFFREY A COE 2U.S. Geological Survey, Denver Federal Center, Mail Stop 966, Denver, CO 80225 BASAK SENER KAYA 3Colorado School of Mines, Division of Engineering, Golden, CO 80401 LINA MA 4Oregon Department of Geology and Mineral Industries, 800 NE Oregon Street, Portland, OR 97232 Publisher: Association of Environmental & Engineering Geologists First Online: 02 Mar 2017 Online ISSN: 1558-9161 Print ISSN: 1078-7275 Copyright © 2010 EEGS Environmental & Engineering Geoscience (2010) 16 (4): 315–341. https://doi.org/10.2113/gseegeosci.16.4.315 Article history First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation WILLIAM J BURNS, JEFFREY A COE, BASAK SENER KAYA, LINA MA; Analysis of Elevation Changes Detected from Multi-Temporal LiDAR Surveys in Forested Landslide Terrain in Western Oregon. Environmental & Engineering Geoscience 2010;; 16 (4): 315–341. doi: https://doi.org/10.2113/gseegeosci.16.4.315 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyEnvironmental & Engineering Geoscience Search Advanced Search Abstract We examined elevation changes detected from two successive sets of Light Detection and Ranging (LiDAR) data in the northern Coast Range of Oregon. The first set of LiDAR data was acquired during leaf-on conditions and the second set during leaf-off conditions. We were able to successfully identify and map active landslides using a differential digital elevation model (DEM) created from the two LiDAR data sets, but this required the use of thresholds (0.50 and 0.75 m) to remove noise from the differential elevation data, visual pattern recognition of landslide-induced elevation changes, and supplemental QuickBird satellite imagery. After mapping, we field-verified 88 percent of the landslides that we had mapped with high confidence, but we could not detect active landslides with elevation changes of less than 0.50 m. Volumetric calculations showed that a total of about 18,100 m3 of material was missing from landslide areas, probably as a result of systematic negative elevation errors in the differential DEM and as a result of removal of material by erosion and transport. We also examined the accuracies of 285 leaf-off LiDAR elevations at four landslide sites using Global Positioning System and total station surveys. A comparison of LiDAR and survey data indicated an overall root mean square error of 0.50 m, a maximum error of 2.21 m, and a systematic error of 0.09 m. LiDAR ground-point densities were lowest in areas with young conifer forests and deciduous vegetation, which resulted in extensive interpolations of elevations in the leaf-on, bare-earth DEM. For optimal use of multi-temporal LiDAR data in forested areas, we recommend that all data sets be flown during leaf-off seasons. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Pilot reports in January 1995 and geologic field observations from the summer of 1996 indicate that a relatively small explosive eruption of Makushin, one of the more frequently active volcanoes in the Aleutian arc of Alaska, occurred on 30 January 1995. Several independent radar interferograms that each span the time period from October 1993 to September 1995 show evidence of ∼7 cm of uplift centered on the volcano's east flank, which we interpret as preeruptive inflation of a ∼7‐km‐deep magma source (Δ V = 0.022 km 3 ). Subsequent interferograms for 1995–2000, a period that included no reported eruptive activity, show no evidence of additional ground deformation. Interferometric coherence at C band is found to persist for 3 years or more on lava flow and other rocky surfaces covered with short grass and sparsely distributed tall grass and for at least 1 year on most pyroclastic deposits. On lava flow and rocky surfaces with dense tall grass and on alluvium, coherence lasts for a few months. Snow and ice surfaces lose coherence within a few days. This extended timeframe of coherence over a variety of surface materials makes C band radar interferometry an effective tool for studying volcano deformation in Alaska and other similar high‐latitude regions.

Research Article| June 01, 1990 Major off-axis hydrothermal activity on the northern Gorda Ridge P. A. Rona; P. A. Rona 1NOAA/AOML, 4301 Rickenbacker Causeway, Miami, Florida 33149 Search for other works by this author on: GSW Google Scholar R. P. Denlinger; R. P. Denlinger 2U.S. Geological Survey, Oceanography WB-10, University of Washington, Seattle, Washington 98195 Search for other works by this author on: GSW Google Scholar M. R. Fisk; M. R. Fisk 3College of Oceanography, Oregon State University, Corvallis, Oregon 97331 Search for other works by this author on: GSW Google Scholar K. J. Howard; K. J. Howard 3College of Oceanography, Oregon State University, Corvallis, Oregon 97331 Search for other works by this author on: GSW Google Scholar G. L. Taghon; G. L. Taghon 3College of Oceanography, Oregon State University, Corvallis, Oregon 97331 Search for other works by this author on: GSW Google Scholar K. D. Klitgord; K. D. Klitgord 4U.S. Geological Survey, Woods Hole, Massachusetts 02543 Search for other works by this author on: GSW Google Scholar J. S. McClain; J. S. McClain 5Department of Geology, University of California, Davis, California 95616 Search for other works by this author on: GSW Google Scholar G. R. McMurray; G. R. McMurray 6Department of Geology and Mineral Industries, 910 State Office Building, Portland, Oregon 97201 Search for other works by this author on: GSW Google Scholar J. C. Wiltshire J. C. Wiltshire 7Department of Oceanography, University of Hawaii, 1000 Pope Road, Honolulu, Hawaii 96822 Search for other works by this author on: GSW Google Scholar Author and Article Information P. A. Rona 1NOAA/AOML, 4301 Rickenbacker Causeway, Miami, Florida 33149 R. P. Denlinger 2U.S. Geological Survey, Oceanography WB-10, University of Washington, Seattle, Washington 98195 M. R. Fisk 3College of Oceanography, Oregon State University, Corvallis, Oregon 97331 K. J. Howard 3College of Oceanography, Oregon State University, Corvallis, Oregon 97331 G. L. Taghon 3College of Oceanography, Oregon State University, Corvallis, Oregon 97331 K. D. Klitgord 4U.S. Geological Survey, Woods Hole, Massachusetts 02543 J. S. McClain 5Department of Geology, University of California, Davis, California 95616 G. R. McMurray 6Department of Geology and Mineral Industries, 910 State Office Building, Portland, Oregon 97201 J. C. Wiltshire 7Department of Oceanography, University of Hawaii, 1000 Pope Road, Honolulu, Hawaii 96822 Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1990) 18 (6): 493–496. https://doi.org/10.1130/0091-7613(1990)018<0493:MOAHAO>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation P. A. Rona, R. P. Denlinger, M. R. Fisk, K. J. Howard, G. L. Taghon, K. D. Klitgord, J. S. McClain, G. R. McMurray, J. C. Wiltshire; Major off-axis hydrothermal activity on the northern Gorda Ridge. Geology 1990;; 18 (6): 493–496. doi: https://doi.org/10.1130/0091-7613(1990)018<0493:MOAHAO>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract The first hydrothermal field on the northern Gorda Ridge, the Sea Cliff hydrothermal field, was discovered and geologic controls of hydrothermal activity in the rift valley were investigated on a dive series using the DSV Sea Cliff. The Sea Cliff hydrothermal field was discovered where predicted at the intersection of axis-oblique and axis-parallel faults at the south end of a linear ridge at mid-depth (2700 m) on the east wall. Preliminary mapping and smpling of the field reveal: a setting nested on nearly sediment-free fault blocks 300 m above the rift valley floor 2.6 km from the axis; a spectrum of venting types from seeps to black smokers; high conductive heat flow estimated to be equivalent to the convective flux of multiple black smokers through areas of the sea floor sealed by a caprock of elastic breccia primarily derived from basalt with siliceous cement and barite pore fillings; and a vent biota with Juan de Fuca Ridge affinites. These findings demonstrate the importance of off-axis hydrothermal activity and the role of the intersection of tectonic lineations in controlling hydrothermal sites at sea-floor spreading centers. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Abstract Large-magnitude earthquakes and hydrologic events in mountainous settings commonly trigger thousands of landslides, and slope failures typically constitute a significant proportion of the damage associated with these events. Large, dormant deep-seated landslides are ubiquitous in the Oregon Coast Range, western United States, yet a method for calculating landslide ages with the precision required to diagnose a specific triggering event, including the A.D. 1700 Cascadia earthquake, has remained elusive. Establishing a compelling connection between prehistoric slope instability and specific triggers requires landslide ages with precision greater than that provided by 14C dating of detrital materials. Tree-ring analysis is the only known method capable of determining landslide age with this precision. Dozens of landslide-dammed lakes in western Oregon present an opportunity to use tree rings from drowned snags, or “ghost forests,” to establish the year of death, and thus landsliding. We cross-dated tree-ring indices from drowned Douglas fir trees with live tree-ring records from the Oregon Coast Range that exhibit synchronous, time-specific patterns due to regional climate variations. Our analyses determined that the landslides responsible for creating Wasson and Klickitat Lakes occurred in A.D. 1819 and 1751, respectively. The 14C dates from selected tree rings and landslide deposit detritus are consistent with our tree-ring analysis, although the ages exhibit high variability, revealing the limitations of using 14C dating alone. Because dendrochronology provides annual precision for landsliding, sampling of tree rings at additional landslide-dammed lakes throughout the Oregon Coast Range can be used to constrain the potential effects of ground motion and major storms on Cascadia landscapes.

Research Article| November 01, 2011 Landslide Stability: Role of Rainfall-Induced, Laterally Propagating, Pore-Pressure Waves GEORGE R PRIEST; GEORGE R PRIEST 1 Oregon Department of Geology and Mineral Industries, P.O. Box 1033, Newport, OR 97365 1Corresponding author email: george.priest@dogami.state.or.us. Search for other works by this author on: GSW Google Scholar WILLIAM H SCHULZ; WILLIAM H SCHULZ U.S. Geological Survey, Denver Federal Center Box 25046, MS 966, Denver, CO 80225-0046 Search for other works by this author on: GSW Google Scholar WILLIAM L ELLIS; WILLIAM L ELLIS U.S. Geological Survey, Denver Federal Center Box 25046, MS 966, Denver, CO 80225-0046 Search for other works by this author on: GSW Google Scholar JONATHAN A ALLAN; JONATHAN A ALLAN Oregon Department of Geology and Mineral Industries, P.O. Box 1033, Newport, OR 97365 Search for other works by this author on: GSW Google Scholar ALAN R NIEM; ALAN R NIEM Pacific Geology Northwest LLC, 6325 B Avenue, Otter Rock, OR 97369 Search for other works by this author on: GSW Google Scholar WENDY A NIEM WENDY A NIEM Pacific Geology Northwest LLC, 6325 B Avenue, Otter Rock, OR 97369 Search for other works by this author on: GSW Google Scholar Author and Article Information GEORGE R PRIEST 1 Oregon Department of Geology and Mineral Industries, P.O. Box 1033, Newport, OR 97365 WILLIAM H SCHULZ U.S. Geological Survey, Denver Federal Center Box 25046, MS 966, Denver, CO 80225-0046 WILLIAM L ELLIS U.S. Geological Survey, Denver Federal Center Box 25046, MS 966, Denver, CO 80225-0046 JONATHAN A ALLAN Oregon Department of Geology and Mineral Industries, P.O. Box 1033, Newport, OR 97365 ALAN R NIEM Pacific Geology Northwest LLC, 6325 B Avenue, Otter Rock, OR 97369 WENDY A NIEM Pacific Geology Northwest LLC, 6325 B Avenue, Otter Rock, OR 97369 1Corresponding author email: george.priest@dogami.state.or.us. Publisher: Association of Environmental & Engineering Geologists First Online: 02 Mar 2017 Online ISSN: 1558-9161 Print ISSN: 1078-7275 © 2011 Association of Environmental & Engineering Geologists Environmental & Engineering Geoscience (2011) 17 (4): 315–335. https://doi.org/10.2113/gseegeosci.17.4.315 Article history First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation GEORGE R PRIEST, WILLIAM H SCHULZ, WILLIAM L ELLIS, JONATHAN A ALLAN, ALAN R NIEM, WENDY A NIEM; Landslide Stability: Role of Rainfall-Induced, Laterally Propagating, Pore-Pressure Waves. Environmental & Engineering Geoscience 2011;; 17 (4): 315–335. doi: https://doi.org/10.2113/gseegeosci.17.4.315 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyEnvironmental & Engineering Geoscience Search Advanced Search Abstract The Johnson Creek Landslide is a translational slide in seaward-dipping Miocene siltstone and sandstone (Astoria Formation) and an overlying Quaternary marine terrace deposit. The basal slide plane slopes sub-parallel to the dip of the Miocene rocks, except beneath the back-tilted toe block, where it slopes inland. Rainfall events raise pore-water pressure in the basal shear zone in the form of pulses of water pressure traveling laterally from the headwall graben down the axis of the slide at rates of 1–6 m/hr. Infiltration of meteoric water and vertical pressure transmission through the unsaturated zone has been measured at ∼50 mm/hr. Infiltration and vertical pressure transmission were too slow to directly raise head at the basal shear zone prior to landslide movement. Only at the headwall graben was the saturated zone shallow enough for rainfall events to trigger lateral pulses of water pressure through the saturated zone. When pressure levels in the basal shear zone exceeded thresholds defined in this paper, the slide began slow, creeping movement as an intact block. As pressures exceeded thresholds for movement in more of the slide mass, movement accelerated, and differential displacement between internal slide blocks became more pronounced. Rainfall-induced pore-pressure waves are probably a common landslide trigger wherever effective hydraulic conductivity is high and the saturated zone is located near the surface in some part of a slide. An ancillary finding is apparently greater accuracy of grouted piezometers relative to those in sand packs for measurement of pore pressures at the installed depth. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Research Article| September 01, 1995 Tectonic setting of the Portland-Vancouver area, Oregon and Washington: Constraints from low-altitude aeromagnetic data Richard J. Blakely; Richard J. Blakely 1U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025 Search for other works by this author on: GSW Google Scholar Ray E. Wells; Ray E. Wells 1U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025 Search for other works by this author on: GSW Google Scholar Thomas S. Yelin; Thomas S. Yelin 2U.S. Geological Survey, Geophysics Program AK50, University of Washington, Seattle, Washington 98195 Search for other works by this author on: GSW Google Scholar Ian P. Madin; Ian P. Madin 3Oregon Department of Geology and Mineral Industries, Portland, Oregon 97230 Search for other works by this author on: GSW Google Scholar Marvin H. Beeson Marvin H. Beeson 4Department of Geology, Portland State University, Portland, Oregon 97207 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1995) 107 (9): 1051–1062. https://doi.org/10.1130/0016-7606(1995)107<1051:TSOTPV>2.3.CO;2 Article history first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Richard J. Blakely, Ray E. Wells, Thomas S. Yelin, Ian P. Madin, Marvin H. Beeson; Tectonic setting of the Portland-Vancouver area, Oregon and Washington: Constraints from low-altitude aeromagnetic data. GSA Bulletin 1995;; 107 (9): 1051–1062. doi: https://doi.org/10.1130/0016-7606(1995)107<1051:TSOTPV>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Seismic activity in the Portland-Vancouver metropolitan area may be associated with various mapped faults that locally offset volcanic basement of Eocene age and younger. This volcanic basement is concealed in most places by young deposits, vegetation, and urban development. The U.S. Geological Survey conducted an aeromagnetic survey in September 1992 to investigate the extent of these mapped faults and possibly to help identify other seismic and volcanic hazards in the area. The survey was flown approximately 240 m above terrain, along flight lines spaced 460 m apart, and over an area about 50 × 50 km. These magnetic data indicate a pronounced northwest-striking magnetic lineation east of the Willamette River in downtown Portland associated with a fault concealed beneath Quaternary sedimentary deposits and previously inferred from shallow well data. The magnetic lineation confirms the existence of the fault and suggests that it has had a prolonged history: (1) Although well data indicate <200 m of vertical offset of underlying volcanic basement, models based on the aeromagnetic data from downtown Portland suggest reverse faulting with up to 1 km of offset deeper in the section. (2) The magnetic lineation associated with this fault extends southeast to the Clackamas River drainage, a distance of 50 km and considerably beyond the mapped extent of the fault. A northwest-striking magnetic anomaly located southwest of the Tualatin Mountains corresponds closely with another mapped fault and with mixed reverse and strike-slip faulting during a seismic swarm (M ≤ 3) in 1991. We believe these and other anomalies in the aeromagnetic data reflect the Portland Hills fault zone, believed to be the southwestern boundary of a structural basin now occupied by Portland and Vancouver. The postulated northeastern boundary of the basin, the Frontal fault zone, is also evident, although less well represented in the aeromagnetic data. Aeromagnetic anomalies, geologic mapping, and earthquake focal-plane solutions demonstrate a complex deformational history in the Portland-Vancouver area since middle Miocene time that includes elements of compression, extension, and dextral slip. These complexities reflect Portland-Vancouver's unique position within a north-south transition in tectonic styles along the Cascadia margin, from compressional in the north to extensional in the south. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.