G52A-01
Ground Deformation Analysis of Blast-Induced Liquefaction at a Simulated Airport Infrastructure Using High Resolution 3D Laser Scanning
In October 2007, the Port and Airport Research Institute (PARI) of the Japan Ministry of Land, Infrastructure and Transportation conducted a large-scale blast-induced liquefaction experiment in Ishikari, Hokkaido, Japan. Approximately 24,000 m2 of ground was liquefied using controlled blasting techniques to investigate the performance of airport infrastructure. The USGS and Oregon State University participated in the study and measured topographic changes in ground level using 3D laser scanning techniques (terrestrial lidar), as well as changes in shear wave velocity of the between the pre- and post-liquefied soil. This poster focuses on the lidar results. The overall objective of the PARI experiment is to assess the performance of airport infrastructure subjected to liquefaction. Specifically, the performance of pipelines and large concrete utility raceways located beneath runway pavements is of interest, as well as the performance of pavements and embankments with and without soil improvement techniques. At the site, 5-7 m of loose silty sand was placed as hydraulic fill on natural alluvial sand as an expansion of the Ishikari port facility. On a portion of the liquefied site, three 20 m by 50 m test sections were constructed to investigate the performance of improved ground beneath asphalt runways, concrete runway aprons, and open areas. Pipelines and concrete utility conduits were also buried in each section. The three ground improvement techniques investigated were sand-cement mixing, vertical drains, and colloidal silica injection. The PARI experiment provided an excellent opportunity to conduct terrestrial lidar measurements - a revolutionary tool for accurate characterization of fine-scale changes of topography and identification of subtle deformations. Lidar was used for characterizing post-blast deformations both immediately after the charges were used, and subsequently over time at intervals of 2 days, 4 days, and 5 months after blasting. Settlement beneath the tarmac ranged from negligible in the improved areas, to up to 36 cm in the unimproved areas; and over a one-half meter of settlement on the test-embankment. In addition, its use for monitoring construction operations was also explored. The time slices captured development of liquefaction- induced settlement in response to expulsion of pore water. In this poster, we present detailed analysis of the ground deformations and use these to assess the efficacy of specific ground improvement technologies.
G52A-02
Monitoring Growth of the Daisetta, Texas Sinkhole With Terrestrial Laser Scanning, Close Range Digital Photography, and GPS
On 7 May, 2008 a major sinkhole developed in Daisetta, Texas located about 60 miles northeast of Houston. The sinkhole formed by collapse of a salt dome and grew from a minor hole to a diameter of reported in the media of over 200 m and a depth of over 75 m during the course of a single day. The collapse consumed several vehicles, drilling equipment, several oil tanks, and resulted in the destruction of several buildings. Personnel from the Cybermapping Laboratory of the Geosciences Department at the University of Texas at Dallas mobilized and deployed a Riegl LPM 800 HA laser profiler, a TOPCON Hyperlite RTK-GPS system, several camera systems, and a TOPCON IS Imaging Total Station to image the hole to quantitatively assess the size of the collapse on 19 May, 2008. Several overlapping scans with several million points were carried out around the sinkhole with the LPM and numerous digital photographs taken from a variety of locations. The TOPCON IS imaging total station was used to map both control for integrating the scans and for control for integrating the digital photographs. RTK GPS was used define global control points. This was accomplished in one day. The point cloud laser data was then merged with Polyworks and a triangulated mesh was created. The control on the photos were then used to position them with relation to the TIN using UTD software at an accuracy of a pixel. The result was an accurate 3D photorealistic (virtual) model of the entire sinkhole at that time built with days of the data capture. The sinkhole will be reoccupied in October so that a new 3D photorealistic model can be built to allow a comparison using our own software with the original photorealistic model for a quantitative assessment of growth of the hole. It measures the differences taking into account the uncertainties associated with the original and rescanned conversion of point clouds to surfaces. We will attempt to use several different types of laser scanners to compare their strengths and weaknesses so integrated workflows for different scanners could be defined.
G52A-03
Integration of e-GPS,RS,GIS, and Laser Scanning Techniques Applied to the Volcanic Slope Slide Monitoring
Taiwan, located at the Western Pacific, bears the threats from both typhoons and earthquakes. The 921 earthquake resulted in the unstable ground so that typhoons or torrential rain could cause serious disasters. Currently, the hazard mitigation is the target of the authorities. However, using the traditional approaches not only wastes a lot of time but also is ineffectively. Thus, the authorities have employed the techniques of e-GPS, GIS, RS (3S) and laser scanning instead of the traditional approaches. This paper introduces the disasters of volcanic slope slide happening in the northern Taiwan and an application of mobile eGPS measurement system for PDA; moreover, the development and application of the techniques of 3S and laser scanning are also presented in this paper.
G52A-04 INVITED
Topographic Change Detection Monitoring Using Terrestrial Lidar at Archaeological Sites in the Colorado River Corridor of Grand Canyon National Park, Arizona
Erosion of archaeological sites within the Colorado River corridor of Grand Canyon National Park (GCNP) is a subject of continuing interest to the National Park Service, and currently supports an ongoing debate about whether and to what degree controlled releases from Glen Canyon Dam, located immediately upstream of GCNP and completed in 1963, are affecting the physical integrity of archaeological sites. Long-term topographic change due to a variety of natural sources is typical in the Grand Canyon region. However, continuing erosion of archaeological sites, which may be related in-part to anthropogenic factors, threatens both the future preservation of archaeological sites and as well as our future ability to study evidence of past human habitation along the Colorado River. As a part of the directive to the U.S. Geological Survey, Grand Canyon Monitoring and Research Center, through participation in the Glen Canyon Dam Adaptive Management Program, studies have been initiated to quantitatively identify changes to archaeological sites in the Colorado River corridor with an ultimate goal of ascertaining cause and effect relationships. Here we present the results of one component of this ongoing research project: an analysis of terrestrial-lidar-derived topographic datasets collected at nine archaeological sites in this region over two summer monsoon seasons (2006 and 2007). The data are used to identify high- resolution vertical change (with lower bound detection limits of 8 cm) over large-scale (hundreds to thousands of square meters) landscapes. The results show that areas of both deposition and erosion have occurred at many of the sites and that their cause can be positively linked in most cases to one or more geomorphologic factors (aeolian deposition, overland flow erosion, concentrated gullying, etc.). In addition, we show that care must be taken with the filtering of the processed data point clouds, with determining the proper error budget for both data collection and processing methodologies, and with the statistical significance of the result interpretation. This study provides insight into both the potential utility of terrestrial LiDAR for archaeological site topographic monitoring and the use of terrestrial lidar as a low-impact high resolution survey technique for moderate sized landscape-scale geomorphologic studies.
G52A-05
Natural and Anthropogenic Controls on Beach Morphology from Analysis of Terrestrial Scanning Laser Time Series Data, Waimea Bay, Oahu.
To determine the environmental conditions and timing leading to long time scale (O(years)) and specific event (O(days-hours)) changes in beach morphology we collected terrestrial scanning laser (TLS) topographic time series, offshore wave data, and high resolution digital photographs of the entire beach at Waimea Bay, Oahu from January through June 2007. Each survey had better than 1cm range-resolution, average spot-spacing of 10 cm, and had tilts removed using GPS-based geocoding. The TLS surveys on monthly time-scales quantify the seasonal transition in beach morphology and volume forced by high waves (winter) to small waves (summer). The surveys over daily to hourly time scales quantify the evolution of discrete morphological features. For instance, two surveys taken three hours apart on 27 April 2007 when significant wave height was roughly 0.7m document an order 0.1 m increase in sand elevation occurring along the foreshore indicating active sand accretion following an erosion event on 24 April 2007 when significant wave height was roughly 2.5m. Well-defined fore-beach and back-beach cuspate features were present during the surveys. The elevation difference map shows that the main area of accretion occurred in the fore-beach cusp embayments, i.e., the beach cusps appear to be filling in with sand. We further use the TLS time series data to quantify the subaerial morphologic signal and volumetric beach change budget of foot-traffic on the beach. Our initial observations indicate that the upper portions of the beach, rarely affected by waves but receiving hundreds to thousands of visitors per day, exhibits convex upward character typical of diffusive forcing. We assess whether a diffusive landscape evolution model based on linear or non-linear flux laws describes the temporal and spatial evolution of the upper parts of beaches where wave forcing rarely occurs.
G52A-06 INVITED
Evolution of fault-surface roughness with slip from ground-based LIDAR
Principal slip surfaces in fault zones accommodate most of the displacement during earthquakes. The topography of these surfaces is integral to earthquake and fault mechanics, but is poorly constrained at the scale of earthquake slip. We use ground-based LiDAR to map exposed fault surfaces over scales of 0.5 m to 120 m and then combine the data with laboratory measurements to extend the range to a minimum wavelength of 10 microns. For each sample, we average >500 profiles to provide a robust estimate of the power spectrum of the topography in both the slip parallel and slip perpendicular directions. We find that fault-surface roughness evolves with increasing slip. Small-slip faults (slip <1 m) are rougher than large-slip faults (slip >10 m) on profiles parallel to the slip direction. Surfaces of small-slip faults have asperities over the entire range of observed scales, while large-slip fault surfaces are polished, with RMS values of <3 mm on profiles as long as 1-2 m. Both fault populations are identical in the slip perpendicular direction. The power spectra in the slip perpendicular direction are also the same as an arbitrary natural cliff. Furthermore, the slip perpendicular roughness is also identical to that of the small-slip faults in the slip parallel direction. We interpret the spectra to indicate that faults start with a primordial roughness similar to that of an arbitrary natural surface. Continued slip wears down the roughness in the slip parallel direction so that mature faults are distinctly smoother.
G52A-07 INVITED
Dense Temporal and Spatial Measurement of Surface Deformation using Real-Aperture Ground-Based Radar Interferometry
In 2007 Gamma developed a high resolution 17.2 GHz real-aperture interferometric radar capable of measuring sub-millimeter scale deformation at distances up to 8 km. This instrument can be rapidly deployed and used to perform in-situ measurements of deformation associated with landslides, glaciers, and infrastructure. The instrument utilizes a real-aperture antenna to form a narrow azimuth beam. The azimuth beam width of 0.4 degrees determines the azimuth resolution that is proportional to the distance from the radar. The elevation antenna beamwidth is 45 degrees. The radar scans the area of interest by rotation about the vertical axis at intervals of 0.1 degrees. Ranging information is obtained by 200 MHz bandwidth chirp modulation of the transmit pulse. Radar resolution is 7m in azimuth at 1 km slant range and 0.75 meters in range. These data are first processed to images in radar coordinates and subsequently transformed to terrain-geocoded map products using an auxiliary DEM. A local terrain model can also be created from interferometric analysis of images acquired from the dual receiving antennas of our instrument. These antennas are separated by 25 cm creating a spatial interferometer. We report radar observations made during the rapid draining of the Gornersee glacial lake at the confluence of the Gorner and Grenz glaciers in Switzerland. These measurements, made in cooperation with ETHZ, cover the period of 21-24 June, 2008. We observe glacier deformation correlated with the drainage event. The nearly continuous radar data exhibit diurnal variations of the influence of water vapor, and decorrelation due to melting on the glacier surface caused by solar heating. A map of LOS velocity of the glaciers visible from the Gornergrat has been produced showing velocities exceeding 300m/year. We also show observations acquired in Triesenberg, Liechtenstein of a large slope landslide moving up to 4 cm/year. Interferograms made from data acquired during January 2007 and May 2008 show deformation of up to 1 cm in the region of the landslide. Time series of measurements show atmospheric related phase variations on the scale of minutes demonstrating the advantage of ground-based measurements for acquisition of multiple images for atmospheric noise suppression.
G52A-08
Comparison of Coincident Terrestrial and Airborne Lidar Datasets with Respect to Detection of Ground Metrics and Topographic Change
The Multidisciplinary Center for Earthquake Engineering Research and National Science Foundation, in collaboration with the City of Los Angeles Department of Water and Power (LADWP), coordinated a controlled study of the use of pulse-based terrestrial lidar and phase-based airborne lidar systems to detect topographic changes and ground deformations in areas of buried pipelines subject to earthquakes and storm-induced landslides. Terrestrial and airborne lidar scans were performed at three LADWP sites in the Los Angeles region and their accuracy was evaluated using coincident high-precision total station survey measurements as a control. Horizontal accuracy was evaluated through the measurement of latitude Northing and longitude Easting (standardized to WGS84) residuals for distances separating well defined objects in the lidar scans, such as buildings and tanks. The bias and dispersion of lidar elevation measurements (standardized to NGVD88) was assessed at a flat un-vegetated site near the Los Angeles Reservoir before and after carefully measured trenching, and at a heavily vegetated and steeply sloping site at Power Plant 2 in San Francisquito Canyon. At the trench site, airborne lidar showed minimal bias and standard deviation (6-20 cm), whereas terrestrial lidar was nearly unbiased with very low dispersion (4-6 cm). Pre- and post-trench bias-adjusted normalized residuals are essentially randomly scattered, but elevation change was affected by relative bias within epochs. At the PP2 site, airborne lidar showed minimal elevation bias and a standard deviation of approximately 50 cm, whereas terrestrial lidar demonstrated large bias and dispersion (on order of meters) due the inability of side-looking ground-based lidar to penetrate heavy vegetation. With careful calibration, both terrestrial and airborne lidar are capable of measuring centimeter-to decimeter level ground displacements for large features in areas of minimal vegetation, whereas their application is more limited in areas of dense vegetation where line-of-site access to the ground is hampered.