Monitoring data from the Aleppo rockslide, Allegheny County, Pennsylvania, November 2013 - December 2018
Upon reactivation, movement of deep-seated landslides in the Greater Pittsburgh region may persist for long periods of time. Monitoring equipment was located at two sites on a deep-seated rockslide in Aleppo Township, Pennsylvania to establish relationships between precipitation and changes in the state of activity and velocity. Precipitation, snow depth, and air temperature are monitored at a weather station (ARS_WS) located in a relatively flat, open area in the northern part of the rockslide. Displacement and soil moisture are monitored at a second site located in the southern part of a graben (ARS_GR) in the head of the rockslide. At ARS_WS, instrumentation includes a tipping bucket rain gauge, temperature probe, and a sonic ranging sensor, and at ARS_GR instrumentation includes two cable extension transducers and a soil moisture probe. This data release presents the time series data from this instrumentation for an initial monitoring period starting on November 6, 2013 and ending on December 31, 2018. The data release generally presents the output for each sensor type as recorded on the datalogger, except in one case, for which the output requires conversion to engineering units and the factor necessary to make this conversion is provided. ARS_WS instrumentation Rain gauge: The rain gauge at ARS_WS has a resolution of 0.01 inch (in.) and an accuracy of 1 percent for rainfall intensities up to 2 in/hr. Initially, rainfall was recorded by a Hobo event datalogger and each event was equal to 0.01 in. Beginning on November 18, 2016, 15-minute (min) rainfall totals were recorded by a Campbell Scientific CR1000 datalogger. The rain gauge collector is subject to periodic clogging due to vegetative debris and insect activity. This type of rain gauge is not designed to accurately measure the snow water equivalent of snow fall and likely underestimates precipitation during the winter. Maintenance of the rain gauge is only performed periodically during site visits to retrieve data, install or maintain equipment, or perform other work. No field calibration was performed on the rain gauge. Snow depth sensor: Snow depth is measured using a sonic ranging sensor that has a resolution of 0.25 millimeters (mm) (0.01 in.) and a stated accuracy of 1 centimeter (cm) based on the height of the sensor, which was installed 1.68 meters (m) above the ground. Measurements are recorded on an hourly interval. Quality numbers (Q) provide additional information about snow depth measurement certainty. An explanation of the quality number ranges is included as a separate text file (QualityNos_SnowDepth_ReadMe.txt). In May 2015, a square meter (m2), flat measurement area covered with locally derived claystone fragments was constructed beneath the sensor. Periodic maintenance of the site entails removing vegetation from this and the surrounding area in the fall prior to the initial snow fall. Air temperature probe: Air temperature is measured using a temperature probe housed in 6-plate solar radiation shield. The probe consists of a thermistor in an epoxy-filled aluminum housing. The probe has a stated measurement range of -30oC to +50oC with no more than 0.01oC error over this range. Average air temperature is recorded at 15-min intervals. ARS_WS_DATA.xlsx contains three worksheets labeled EVENT, 15MIN, and 1HR. The EVENT worksheet contains the following fields: TIMESTAMP_EST - records the timestamp in the format mm/dd/yyyy hh:mm, Eastern Standard Time; and EVENT – records precipitation, where each event equals 0.01 in. The 15MIN worksheet contains the following fields: TIMESTAMP_EST - records the timestamp in the format mm/dd/yyyy hh:mm, Eastern Standard Time; AT_Avg – records the average air temperature in degrees Celsius; PRCP_Tot – records the total precipitation in inches; and BV_Avg – records the average battery voltage in volts. The 1HR worksheet contains the following fields: TIMESTAMP_EST - records the timestamp in the format mm/dd/yyyy hh:mm, Eastern Standard Time; AT_Avg – records the average air temperature in degrees Celsius; DT_Avg – records the average distance to target in meters; Q_Avg -records the quality number; TCDT_Avg – records the average temperature corrected distance to target in meters; and SD_Avg – records the snow depth (when snow is present) in meters. ARS_GR Instrumentation Cable Extension Transducers: Displacement and ground surface rotation is monitored at two locations near the margins of the graben using cable extension transducers (CETs) that have a 152-cm (60-in.) range and an accuracy of 0.1 percent of full stroke (potential deviations may range up to 1.5 mm). Both CETs are mounted above the ground surface on a 5.1-cm (2-in.) diameter stainless steel pole that is grouted approximately 90 cm deep into the slope colluvium and uppermost weathered/fractured claystone. An Invar wire attached to the factory-installed cable on each CET provides the required additional length to reach the anchor point. At the first location (CET01_MS), the anchor point consists of a stainless-steel eyebolt grouted into the sandstone exposed in the main scarp free face. At the second location on the western margin of the graben (CET02_AS), the cable is anchored to a stainless-steel pole grouted into the antithetic (upslope-facing) scarp slope. The CET data may be affected by falling tree limbs throughout the year and cable icing in winter. The average eyelet position (or amount of cable extension), measured in cm, is recorded at 15-min intervals. Soil moisture probe: The volumetric water content (VWC) of the shallow colluvial deposit is measured using water content reflectometer. The probe derives VWC from its sensitivity to dielectric permittivity and has an accuracy of approximately ±3 percent. The probe was inserted into the upslope wall of shallow hand-excavated test pit using an insertion guide tool to create two parallel holes for the probe rods. The probe was installed at a depth of 20 cm, a depth approximately half the total thickness of the colluvium at that location. The pit is located approximately 4 m downslope from the stress relief joint that is the main scarp free face. The average slope of the ground surface is about 18 percent (10 degrees). Average volumetric water content in meters3/meters3 (m3/m3), electrical conductivity in deciSiemens/meter (dS/m), and soil temperature (°C) are recorded at either 15-min or hourly intervals. ARS_GR_DATA.xlsx contains two worksheets labeled 15MIN and 1HR. The 15MIN worksheet contains the following fields: TIMESTAMP_EST - records the timestamp in the format mm/dd/yyyy hh:mm, Eastern Standard Time; CET01_MS_Avg – records the average extension at cable extension transducer CET01_MS in cm; CET02_AS_Avg – records the average extension at cable extension transducer CET02_AS in cm; VWC_20_Avg – records the average volumetric water content at a depth of 20 cm in m3/m3; EC_20_Avg – records the average electrical conductivity at a depth of 20 cm in dS/m; ST_20_Avg – records average soil temperature at a depth of 20 cm in °C; and BV_Avg – records the average battery voltage in volts. The 1HR worksheet contains the following fields: TIMESTAMP_EST - records the timestamp in the format mm/dd/yyyy hh:mm, Eastern Standard Time; VWC_20_Avg – records the average volumetric water content at a depth of 20 cm in m3/m3; EC_20_Avg – records the average electrical conductivity at a depth of 20 cm in dS/m; and ST_20_Avg – records average soil temperature at a depth of 20 cm in °C. Details of this study are described in the journal article: Ashland, F. X., and Delano, H. L., 2015, Continuous monitoring of meteorological conditions and movement of a deep-seated, persistently moving rockslide along Interstate Route 79 near Pittsburgh: Pennsylvania Geology, v. 45, no. 2, p. 22–26.