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Precipitation, Pore-pressure, and Extensometer Measurements from area above the 1997 Woodway landslide, Snohomish County, Washington


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U.S. Geological Survey, Landslide Hazards Program, 2006, Precipitation, Pore-pressure, and Extensometer Measurements from area above the 1997 Woodway landslide, Snohomish County, Washington: U.S. Geological Survey,


On January 15, 1997, a landslide of approximately 100,000-m3 from a coastal bluff swept five cars of a freight train into Puget Sound at Woodway, Washington, USA, 25 km north of downtown Seattle. The landslide resulted from failure of a sequence of dense sands and hard silts of glacial and non-glacial origin, including hard, jointed clayey silt that rarely fails in natural slopes. Joints controlled ground-water seepage through the silt and break-up of the landslide mass. During September of 1997, the U.S. Geological Survey began measuring rainfall, ground-water pressures, and ground movement at the bluff where the landslide occurred. The original sensor array comprised a tipping-bucket rain gauge, four extensometers (cable-extension [...]


Point of Contact :
Rex Baum
Originator :
U.S. Geological Survey, Landslide Hazards Program
Metadata Contact :
GHSC Data Steward
Publisher :
U.S. Geological Survey
Distributor :
USGS Mission Area :
Natural Hazards
SDC Data Owner :
Landslide Hazards Program

Attached Files

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Original FGDC Metadata

9.67 KB
“Paper describing monitoring methods”
953.18 KB
README.txt 7.07 KB
“Unprocessed data and calibration constants”
9.7 MB


Geotechnical engineers who investigated the January 15, 1997 Woodway landslide attributed the slide to unusually high pore-water pressures, based on observations of water seeping from vertical fractures in the dense glaciolacustrine clay deposits exposed near the base of the landslide head scarp. The precipitation and pore pressure measurements in this data set were collected to help understand hydrologic factors, such as groundwater response to precipitation that might have contributed to occurrence of the Woodway landslide and other similar large, deep landslides that occur from time to time on the coastal bluffs surrounding Puget Sound. The extensometer data were collected to monitor for possible opening of cracks behind the main scarp of the landslide that might be premonitory to retreat of the bluff. The data may be useful for studying relationships between precipitation and subsurface water pressures. Users should be aware that the pressures recorded from the sealed pressure transducers are affected by changes in barometric pressure and short-term oscillations of unknown origin (probably instrument noise). Data from all sealed pressure transducers when corrected for barometric pressure display an annual cycle in phase with the seasonal barometric pressure changes recorded by the National Weather Service. Short-term (periods of minutes to hours) low-amplitude oscillations in the pore pressure measurements appear to be instrumental noise but the exact cause and nature of these oscillations cannot be discerned due to the 15-minute sampling rate. Additional issues with these data are described in the file "README.txt."

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