Movement
Data collection at the Woodway landslide ceased on October 19, 2006
WARNING: Provisional Data, subject to revision
Summary of Uncorrected Movement Data 1997-2003
Summary of long-term movement record at extensometers (median daily values for each sensor). Continuous monitoring of extensometers ended August 2003. No significant displacement occurred at extensometers E-1 and E-3. Apparent displacement at E-1 is due to sensor malfunction and apparent displacement at E-3 resulted from a change in the type of instrument being used. Abrupt displacement occurred at E-2 in February 1998 as described below and creeping movements occurred at E-4 in 1998-'99.
Interpreting Movement Data
Interpreting extensometer graphs requires several kinds of information. Knowledge of an instrument's installation, maintenance history, sensitivity, accuracy, and range enter into the interpretation as illustrated by data from E-2 (below). Other measurements or direct observations usually verify movement.
The only real movement indicated on the graph of E-2 occurred about January 9, 1998, when a block of soil fell from the scarp. However, the actual amount of movement was much greater than indicated on the graph. E-2 was repaired on February 2, 1998. Since then, mechanical and electrical noise has caused alternating changes of about 2 cm as illustrated in the graph above. Extensometer E-4 shows no movement, only noise prior to February 1998, its sensor was replaced on February 3, 1998 to eliminate the noise. The offset in the graph of E-3 resulted from deflection of the extensometer cable. The cable was straightened Feb 2, 1998.
Data from extensometer E-2 at the Woodway landslide showing changes caused by abrupt movement, repairs, and noise.
Steady change in the extensometer output (vertical axis) indicates downslope movement. The data graphed above show steady movement amounting to several centimeters per day for the period from April 23, 1985, through June 5, 1985. (Baum, R.L., Fleming, R.W., and Johnson, A.M., 1993, Kinematics of the Aspen Grove landslide: U.S. Geological Survey Bulletin 1842-F)
Data from three extensometers on the Aspen Grove landslide, Sanpete County, Utah that show steady movement
