Shallow-landslide hazard map of Seattle, Washington

Harp, Edwin L.; Michael, John A.; Laprade, W. T.

doi:10.3133/ofr20061139

Cited by 21 publications

(24 citation statements)

References 6 publications

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“…Table S2B. Published data (Harp et al, 2008) from Seattle area used to estimate angle of internal friction (φ) of faulted sediments in Aplodontia and Springboard trenches. If you are viewing the PDF of this paper or reading it offl ine, please visit http:// dx .doi .org /10 .1130 /GES01067 .S10 or the full-text article on www .gsapubs .org to view Supplemental Table S2. on December 9, 2014 geosphere.gsapubs.org Downloaded from ference (90° -φ/2) from the main shear direction (Riedel, 1929;Tchalenko, 1968Tchalenko, , 1970.…”

Section: Fault Geometry and Sense Of Slipmentioning

confidence: 99%

Holocene earthquakes and right-lateral slip on the left-lateral Darrington–Devils Mountain fault zone, northern Puget Sound, Washington

et al. 2014

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Sources of seismic hazard in the PugetSound region of northwestern Washington include deep earthquakes associated with the Cascadia subduction zone, and shallow earthquakes associated with some of the numerous crustal (upper-plate) faults that crisscross the region. Our paleoseismic investigations on one of the more prominent crustal faults, the Darrington-Devils Mountain fault zone, included trenching of fault scarps developed on latest Pleistocene glacial sediments and analysis of cores from an adjacent wetland near Lake Creek, 14 km southeast of Mount Vernon, Washington. Trench excavations revealed evidence of a single earthquake, radiocarbon dated to ca. 2 ka, but extensive burrowing and root mixing of sediments within 50-100 cm of the ground surface may have destroyed evidence of other earthquakes. Cores in a small wetland adjacent to our trench site provided stratigraphic evidence (formation of a laterally extensive, prograding wedge of hillslope colluvium) of an earthquake ca. 2 ka, which we interpret to be the same earthquake documented in the trenches. A similar colluvial wedge lower in the wetland section provides possible evidence for a second earthquake dated to ca. 8 ka. Three-dimensional trenching techniques revealed evidence for 2.2 ± 1.1 m of right-lateral offset of a glacial outwash channel margin, and 45-70 cm of north-side-up vertical separation across the fault zone. These offsets indicate a net slip vector of 2.3 ± 1.1 m, plunging 14° west on a 286°-striking, 90°-dipping fault plane. The dominant right-lateral sense of slip is supported by the presence of numerous Riedel R shears preserved in two of our trenches, and probable right-lateral offset of a distinctive bedrock fault zone in a third trench. Holocene northside-up, right-lateral oblique slip is opposite the south-side-up, left-lateral oblique sense of slip inferred from geologic mapping of Eocene and older rocks along the fault zone. The cause of this slip reversal is unknown but may be related to clockwise rotation of the Darrington-Devils Mountain fault zone into a position more favorable to right-lateral slip in the modern N-S compressional stress fi eld.

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Section: Fault Geometry and Sense Of Slipmentioning

confidence: 99%

Holocene earthquakes and right-lateral slip on the left-lateral Darrington–Devils Mountain fault zone, northern Puget Sound, Washington

et al. 2014

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“…This 5 year project focused on development of standardized methods of procedure based on recent research at the USGS-LP, North Carolina Geologic Survey, California Geologic Survey, and others (Schulz, 2004;Harp et al, 2006). The goal was to have the standardized methods in place, so that future projects could focus on performing the mapping, modeling, and risk analysis at an accelerated rate.…”

Section: Implementation Of Loss Reduction Measuresmentioning

confidence: 99%

Landslide Risk Reduction in the United States—Signs of Progress

Graff¹,

Burns²,

McConnell³

2016

Environmental & Engineering Geoscience

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Scientific literature is replete with papers describing advances in applying new technologies to the study of landslides and advances in our understanding of factors affecting landslide occurrence, distribution, and movement. Far fewer papers look at how this knowledge is implemented to achieve landslide risk reduction. State and local governments exercise the greatest control on how landslide risk reduction is accomplished. Data generated from a questionnaire to state geological surveys, review of their agency Web sites, and two case studies demonstrate that progress has been made during the last 20 years in implementing actionable policy changes and programs to achieve a reduction is landslide risk in the United States. Progress is evident from the pivotal role played by state and local government in the areas of: (1) developing guidelines and training, (2) increasing public awareness and education, (3) implementing loss reduction measures, and (4) conducting emergency preparedness, response, and recovery. The number of states requiring registration for practicing geologists has nearly doubled during the last 20 years. This increase was accompanied by a shift from individual state tests as part of determining competency to a uniform national test. During this period, state geological surveys established Web sites as a primary means for promoting public awareness and education about landslide hazards. Measures reducing the impact of landslides have included providing information specific to residents and landowners, as well as supporting land-use planning efforts by local governments. Many state geological surveys are involved with emergency management of landslide hazards.

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“…. In the following analyses, we draw on extensive shear-strength databases from the Los Angeles area of southern California, San Francisco Bay area of California, and Seattle, Washington (Jibson et al, 2000;Harp et al, 2006) to help estimate reasonable geotechnical parameters.…”

Section: Geotechnical Datamentioning

confidence: 99%

“…where α, and γ w , are slope inclination and unit weight of water respectively, γ is the unit weight of slope material, c′ is the cohesion of the slope material, and ϕ′ is the friction angle of the slope material, both in terms of effective stress, t is the slope-normal thickness of the potential landslide block, and m is the proportion of the slope thickness that is saturated (Jibson et al, 2000;Harp et al, , 2004Harp et al, , 2006. Slope-normal thickness is used to avoid model instability at steep slope angles.…”

Section: Infinite Slope Analysismentioning

confidence: 99%

“…Spatially distributed modeling approaches, using a 1-D infinite-slope analysis for each grid cell, have been employed in a wide variety of models and landslide hazard assessments in industrialized countries (e.g., Hammond et al, 1992;Montgomery and Dietrich, 1994;Wu and Sidle, 1995;Pack et al, 1999, Baum et al, 2003, Casadei et al, 2003, Crosta and Frattini, 2003Frattini et al, 2004, Haneberg, 2004. These assessment methods have been applied to a few developing countries in Central and South America and Africa (van Westen and Terlien, 1996;Zaitchik et al, 2003;Harp et al, 2004Harp et al, , 2006Claessens et al, 2007). The comparison and calibration of model results with an actual landslide distribution is the critical step that transforms the model from susceptibility to a spatially probabilistic hazard analysis that may have implications for populations living in landslide-affected areas.…”

Section: Introductionmentioning

confidence: 99%

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