DISPLACEMENT VECTORS OF THE CERCA DEL CIELO, PONCE, PUERTO RICO LANDSLIDE MEASURED BY HIGH-PRECISION GPS

Global Positioning System (GPS) technologies have been increasingly employed to monitor ground deformations related to earthquakes, volcanos, landslides, and subsidence. GPS has been justified as a very precise displacementmeter. Funded by a NSF-REU project, we are monitoring a landslide within the Cerca Del Cielo community, Ponce, Puerto Rico. This landslide had been identified about 30 years ago. It creeps significantly recently, particularly during rainy season. About 60 families live on the landslide block. Currently the creeping has damaged more than 30 houses. To study displacement vectors of the landslide, a campaign GPS surveying network had been set up around the landslide area. It includes a reference station outside the landslide area and 21 rover stations (benchmarks) within the landslide area. The maximum distance between the reference station and rover stations is less than 1 km. One Trimble NetRS GPS receiver with Zerphyr antenna is used as our reference station. Two sets of Topcon GB1000 receiver with PG-A1 geodetic antenna are used as our rover stations. We repeat the campaign surveying once per week since March 2008. Our measurements have clearly identified the displacement vectors (magnitude, direction) and kinematics of the landslide. They are critical for local engineers to choose effective landslide control methods. The GPS surveying methods and technologies developed through this study are applicable to other landslides in Puerto Rico and transferable elsewhere. We also studied the relationship between rainfall and landslide slipping rate. There are three USGS weather stations in this region and rainfall data are available. Our results show that the landslide was significantly affected by rainfall.