Detailed ground-based Tripod LiDAR (T-LiDAR) scans at two sites spanning the San Andreas fault (t... more Detailed ground-based Tripod LiDAR (T-LiDAR) scans at two sites spanning the San Andreas fault (the bridge entering into Parkfield and the USGS video camera array on Carr Hill) show spatially and temporally complex nearfield postseismic deformation fields in the 10 months following the 29-September-2004 mainshock, as imaged through the positional changes of concrete pillars, bridge supports, fence posts, tree trunks, and other natural and artificial features. The Parkfield bridge was scanned the day following the mainshock with high- resolution (~3 mm spot spacing) from two vantage points. Additional scans of the bridge and at Carr Hill were made from the same vantage points 10, 23.5, and 41 weeks [Dec. 7, 2004; March 10, 2005; and July 15, 2005] following the mainshock. Structural supports for the Parkfield bridge closest to the San Andreas fault have 7.1 cm of right-lateral displacement in the 10 weeks following the mainshock with an additional 2.6 cm of right-lateral displacement in March. The LiDAR imagery at Carr Hill shows both fault parallel and fault normal nearfield displacement patterns within 30-meters of the fault zone. The fault parallel motion is similar to what was seen at the bridge, with 9.5 cm of right-lateral motion in the 10 weeks following the mainshock and decreased with time to 12.6 cm of slip in March. Unlike the bridge, Carr Hill had about 4 cm of fault normal extension between Sept. and Dec. which changed to contraction in the Dec.-Mar. epoch with the final July position consistent with pure right-lateral slip with little to no net fault normal motion. One interpretation of this fault normal transient, only observed at Carr Hill, is that the minor restraining bend along the San Andreas fault at Carr Hill produced very localized poroelastic response, similar to what was seen in large scale following the 1992 Landers earthquake using InSAR (Peltzer et al, 1998).
Geodesy in the 21st century is embracing two distinct areas of research: “Geodetic Science” — the... more Geodesy in the 21st century is embracing two distinct areas of research: “Geodetic Science” — the scientific discipline that deals with the measurement and representation of the kinematics and dynamics of the Earth’s size, shape, orientation, and gravity field; and “Geodetic Applications”— the wide range of applied geodetic techniques contributing to research not only within the geodetic community, but also across the broad natural science spectrum including, hazards, hydrology, ecosystems, geomorphology, and climate change. Ground-based LiDAR, known as Tripod/Terrestrial LiDAR (T-LiDAR) and Terrestrial Laser Scanning, is a rapidly evolving emergent ‘geodetic science’ technology that is also a forefront ‘geodetic application’ tool that will allow researchers from multiple disciplines to address questions that were unanswerable only 5 years ago. T-LiDAR has unsurpassed ability to collect ultra-high resolution detailed (cm to sub-centimeter) 3D and 4D point cloud measurements that are on scales ranging from individual tree branches and small outcrops to landscapes and glaciers upwards of a few square kilometers in extent. T-LiDAR is ushering in a new era of geodetically driven mesoscopic scale science with true 3D site characterization and 4D change detection. T-LiDAR has made it possible to image 4D postseismic surface change through tracking how elements on the land surface move over time; fence post, bridges, buildings, trees, and the unique land surface morphology elements are now becoming tractable benchmark-like objects whose 3D positions change. Similar approaches have been applied to a wide range of applications including landslides, rock falls, glacial motion, fissure growth, breakwater/structural stability, and mine collapses. T-LiDAR can image how basins respond to aeolian and fluvial processes following major fires through detailed 4D time-series that show how sediment and material move through a denuded landscape via dry ravel, fluvial, slumping, and debris flow processes. It is now possible to track material volume as a function of basin slope, rainfall intensity and transport mode through detailed geomorphologic analysis and repeat laser surveys. Similar approaches also are being used to track the ice mass-balance during glacier retreat, and spatially variable snow mass balance as a function of solar radiation on north vs. south facing slopes. Furthermore, T-LiDAR is making it possible to accurately and non-destructively measure biomass using a methodology that preserves the target while providing a wealth of information about the target in its surrounding ecosystem. Detailed laser scans of excavated tree root systems are providing detailed biomorphic information that relates surface slope, solar angle, and water source with root growth as a function of depth below the land surface and distance from the tree. The analysis of dense point cloud data has necessitated the development of new 3D workspace environments such that data quality can be assess and the science/applications objectives can be achieved. This presentation will discuss geodetic science applications of ground based T-LiDAR spanning the broad range of earth science. A stereo 3D projection system will be used to visualize specific science elements and 3D glasses will be provided.
The production of ground water in confined aquifer systems often results in a land- surface motio... more The production of ground water in confined aquifer systems often results in a land- surface motion that is in a gradient between two end-member models--elastic deformation and inelastic deformation--that is directly measurable by satellite-based geodetic techniques. Elastic deformation is manifested by seasonal motion associated with the pumping, but with no permanent deformation; inelastic deformation results from permanent compaction of the fine-grained units and unrecoverable subsidence of the land surface. The combination of InSAR imagery, GPS measurements, and water-levels for Salt Lake City, UT, Chino Basin, CA and the metropolitan Los Angeles-Santa Ana region, CA, are used to characterize the end-member models and a hybrid model to show how aquifers respond to ground-water pumping stresses. In Salt Lake City, ground-water pumping results in a strong seasonal motion of as much as 85 mm that is not associated with any measurable long-term subsidence signal. Conversely the Chino Basin is subsiding at a rate of 34 mm/yr from ground-water pumping, with little seasonal motion. In the Los Angeles-Santa Ana region there is both elastic and inelastic motion, with greater than 60 mm of seasonal motion associated with 20 mm/year of subsidence. The inelastic subsidence began in 1995 and has been associated with a change in ground-water pumping policy. Improved characterization of these aquifer systems, and associated subsidence, may result in more effective approaches to ground-water resource management.
The design and development of the next generation of continuous GPS arrays can be optimized to me... more The design and development of the next generation of continuous GPS arrays can be optimized to measure both tectonic and ground water-induced surface deformation, by minimizing the number of GPS sites located on the margins of pumped aquifers. Ground water pumping and hydrocarbon production throughout southern California cause vertical and horizontal deformation that are evident in Interferometric Synthetic Aperture Radar (InSAR) imagery and continuous GPS measurements. For instance, multi-year InSAR imagery show that portions of metropolitan Los Angeles are subsiding at rates of more than 20 mm/yr and seasonal InSAR imagery show vertical oscillations of as much as 110 mm, from late summer to early fall. GPS sites located on the margins of these basins have as much as 15 mm of seasonal horizontal motion in their time-series and are pulled towards the basins with annual subsidence. Establishing GPS arrays that attempt to avoid anthropogenic deformation signals altogether will leave significant gaps in the network that would be ineffective for resolving slip on targeted faults. In addition, changes in ground water pumping patterns may encroach on the tectonic geodetic network. However, since most tectonic studies heavily rely on horizontal GPS components to model fault slip at depth and most ground water subsidence modeling studies use only vertical elevation changes, then locating GPS sites in regions with small InSAR gradients will satisfy both modeling needs. Therefore, GPS sites located well within or outside of ground water basins will have significantly smaller horizontal motion than sites located on basin margins and can be utilized by both science communities.
High resolution (centimeter level) three-dimensional point-cloud imagery of offset glacial outwas... more High resolution (centimeter level) three-dimensional point-cloud imagery of offset glacial outwash deposits were collected by using ground based tripod LiDAR (T-LiDAR) to characterize the cumulative fault slip across the recently identified Polaris fault (Hunter et al., 2009) near Truckee, California. The type-section site for the Polaris fault is located 6.5 km east of Truckee where progressive right-lateral displacement of middle to late Pleistocene deposits is evident. Glacial outwash deposits, aggraded during the Tioga glaciation, form a flat lying `fill' terrace on both the north and south sides of the modern Truckee River. During the Tioga deglaciation melt water incised into the terrace producing fluvial scarps or terrace risers (Birkeland, 1964). Subsequently, the terrace risers on both banks have been right-laterally offset by the Polaris fault. By using T-LiDAR on an elevated tripod (4.25 m high), we collected 3D high-resolution (thousands of points per square meter; ± 4 mm) point-cloud imagery of the offset terrace risers. Vegetation was removed from the data using commercial software, and large protruding boulders were manually deleted to generate a bare-earth point-cloud dataset with an average data density of over 240 points per square meter. From the bare-earth point cloud we mathematically reconstructed a pristine terrace/scarp morphology on both sides of the fault, defined coupled sets of piercing points, and extracted a corresponding displacement vector. First, the Polaris fault was approximated as a vertical plane that bisects the offset terrace risers, as well as bisecting linear swales and tectonic depressions in the outwash terrace. Then, piercing points to the vertical fault plane were constructed from the geometry of the geomorphic elements on either side of the fault. On each side of the fault, the best-fit modeled outwash plane is projected laterally and the best-fit modeled terrace riser projected upward to a virtual intersection in space, creating a vector. These constructed vectors were projected to intersection with the fault plane, defining statistically significant piercing points. The distance between the coupled set of piercing points, within the plane of the fault, is the cumulative displacement vector. To assess the variability of the modeled geomorphic surfaces, including surface roughness and nonlinearity, we generated a suite of displacement models by systematically incorporating larger areas of the model domain symmetrically about the fault. Preliminary results of 10 models yield an average cumulative displacement of 5.6 m (1 Std Dev = 0.31 m). As previously described, Tioga deglaciation melt water incised into the outwash terrace leaving terrace risers that were subsequently offset by the Polaris fault. Therefore, the age of the Tioga outwash terrace represents a maximum limiting age of the tectonic displacement. Using regional age constraints of 15 to 13 kya for the Tioga outwash terrace (Benson et al., 1990; Clark and Gillespie, 1997; James et al., 2002) and the above model results, we estimate a preliminary minimum fault slip rate of 0.40 ± 0.05 mm/yr for the Polaris type-section site.
Studies involving the modeling of snow pack and snowmelt distribution under current conditions an... more Studies involving the modeling of snow pack and snowmelt distribution under current conditions and potential climate change conditions often use MODIS snow cover maps for the snow cover extent (satellite imagery product with 500 m pixel postings), point data from snow pillows that provide snow water equivalent (SWE), and snow course data that provide estimates of SWE from composite measurements
ABSTRACT The design and development of the next generation of continuous GPS arrays can be optimi... more ABSTRACT The design and development of the next generation of continuous GPS arrays can be optimized to measure both tectonic and ground water-induced surface deformation, by minimizing the number of GPS sites located on the margins of pumped aquifers. Ground water pumping and hydrocarbon production throughout southern California cause vertical and horizontal deformation that are evident in Interferometric Synthetic Aperture Radar (InSAR) imagery and continuous GPS measurements. For instance, multi-year InSAR imagery show that portions of metropolitan Los Angeles are subsiding at rates of more than 20 mm/yr and seasonal InSAR imagery show vertical oscillations of as much as 110 mm, from late summer to early fall. GPS sites located on the margins of these basins have as much as 15 mm of seasonal horizontal motion in their time-series and are pulled towards the basins with annual subsidence. Establishing GPS arrays that attempt to avoid anthropogenic deformation signals altogether will leave significant gaps in the network that would be ineffective for resolving slip on targeted faults. In addition, changes in ground water pumping patterns may encroach on the tectonic geodetic network. However, since most tectonic studies heavily rely on horizontal GPS components to model fault slip at depth and most ground water subsidence modeling studies use only vertical elevation changes, then locating GPS sites in regions with small InSAR gradients will satisfy both modeling needs. Therefore, GPS sites located well within or outside of ground water basins will have significantly smaller horizontal motion than sites located on basin margins and can be utilized by both science communities.
Detailed ground-based Tripod LiDAR (T-LiDAR) scans at two sites spanning the San Andreas fault (t... more Detailed ground-based Tripod LiDAR (T-LiDAR) scans at two sites spanning the San Andreas fault (the bridge entering into Parkfield and the USGS video camera array on Carr Hill) show spatially and temporally complex nearfield postseismic deformation fields in the 10 months following the 29-September-2004 mainshock, as imaged through the positional changes of concrete pillars, bridge supports, fence posts, tree trunks,
ABSTRACT Coseismic leveling and triangulation observations are used to determine the faulting geo... more ABSTRACT Coseismic leveling and triangulation observations are used to determine the faulting geometry and slip distribution of the July 21, 1952, Mw 7.3 Kern County earthquake on the White Wolf fault. A singular value decomposition inversion is used to assess the ability of the geodetic network to resolve slip along a multisegment fault and shows that the network is sufficient to resolve slip along the surface rupture to a depth of 10 km. Below 10 km, the network can only resolve dip slip near the fault ends. The preferred source model is a two-segment right-stepping fault with a strike of 51° and a dip of 75°SW. The epicentral patch has deep (6-27 km) left-lateral oblique slip, while the northeastern patch has shallow (1-12.5 km) reverse slip. There is nearly uniform reverse slip (epicentral, 1.6 m; northeast, 1.9 m), with 3.6 m of left-lateral strike slip limited to the epicentral patch. The seismic moment is Mo=9.2+/-0.5×1019Nm (Mw=7.2). The signal-to-noise ratio of the leveling and triangulation data is reduced by 96% and 49%, respectively. The slip distribution from the preferred model matches regional geomorphic features and may provide a driving mechanism for regional shortening across the Comanche thrust and structural continuity with the Scodie seismic lineament to the northeast.
The ``Station'' fire, the largest fire in the history of Los Ange... more The ``Station'' fire, the largest fire in the history of Los Angeles County in southern California, began on August 26, 2009 and as of the abstract deadline had burned over 150,000 acres of the Angeles National Forest. This fire creates both a demand and an opportunity for hazards science to be used by the communities directly hit by the fire,
After the 1987 Whittier Narrows and 1994 Northridge earthquakes revealed that blind thrust faults... more After the 1987 Whittier Narrows and 1994 Northridge earthquakes revealed that blind thrust faults represent a significant threat to metropolitan Los Angeles, a network of 250 continuously recording global positioning system (GPS) stations was deployed to monitor displacements associated with deep slip on both blind and surface faults. Here we augment this GPS data with interferometric synthetic aperture radar imagery
... Author: Brooks, Benjamin A, School of Ocean and Earth Sciences and Technology, University of ... more ... Author: Brooks, Benjamin A, School of Ocean and Earth Sciences and Technology, University of Hawaii at Manoa Bawden, Gerald, Southwest Area Sciences Division US Geological SurveyManjunath, Deepak, School of Ocean and Earth Sciences and Technology ... SJ CR SN ...
Http Dx Doi Org 10 1162 Leon 2010 43 2 204, Apr 1, 2010
Abstract Understanding the collapse of natural and social systems is a key artistic and scientifi... more Abstract Understanding the collapse of natural and social systems is a key artistic and scientific endeavor. By collaborating on a multimedia dance-theatre production, we contributed individual approaches, techniques, and insights to a performance that captured both cultural and scientific aspects of collapse in an aesthetically meaningful way.
Detailed ground-based Tripod LiDAR (T-LiDAR) scans at two sites spanning the San Andreas fault (t... more Detailed ground-based Tripod LiDAR (T-LiDAR) scans at two sites spanning the San Andreas fault (the bridge entering into Parkfield and the USGS video camera array on Carr Hill) show spatially and temporally complex nearfield postseismic deformation fields in the 10 months following the 29-September-2004 mainshock, as imaged through the positional changes of concrete pillars, bridge supports, fence posts, tree trunks, and other natural and artificial features. The Parkfield bridge was scanned the day following the mainshock with high- resolution (~3 mm spot spacing) from two vantage points. Additional scans of the bridge and at Carr Hill were made from the same vantage points 10, 23.5, and 41 weeks [Dec. 7, 2004; March 10, 2005; and July 15, 2005] following the mainshock. Structural supports for the Parkfield bridge closest to the San Andreas fault have 7.1 cm of right-lateral displacement in the 10 weeks following the mainshock with an additional 2.6 cm of right-lateral displacement in March. The LiDAR imagery at Carr Hill shows both fault parallel and fault normal nearfield displacement patterns within 30-meters of the fault zone. The fault parallel motion is similar to what was seen at the bridge, with 9.5 cm of right-lateral motion in the 10 weeks following the mainshock and decreased with time to 12.6 cm of slip in March. Unlike the bridge, Carr Hill had about 4 cm of fault normal extension between Sept. and Dec. which changed to contraction in the Dec.-Mar. epoch with the final July position consistent with pure right-lateral slip with little to no net fault normal motion. One interpretation of this fault normal transient, only observed at Carr Hill, is that the minor restraining bend along the San Andreas fault at Carr Hill produced very localized poroelastic response, similar to what was seen in large scale following the 1992 Landers earthquake using InSAR (Peltzer et al, 1998).
Geodesy in the 21st century is embracing two distinct areas of research: “Geodetic Science” — the... more Geodesy in the 21st century is embracing two distinct areas of research: “Geodetic Science” — the scientific discipline that deals with the measurement and representation of the kinematics and dynamics of the Earth’s size, shape, orientation, and gravity field; and “Geodetic Applications”— the wide range of applied geodetic techniques contributing to research not only within the geodetic community, but also across the broad natural science spectrum including, hazards, hydrology, ecosystems, geomorphology, and climate change. Ground-based LiDAR, known as Tripod/Terrestrial LiDAR (T-LiDAR) and Terrestrial Laser Scanning, is a rapidly evolving emergent ‘geodetic science’ technology that is also a forefront ‘geodetic application’ tool that will allow researchers from multiple disciplines to address questions that were unanswerable only 5 years ago. T-LiDAR has unsurpassed ability to collect ultra-high resolution detailed (cm to sub-centimeter) 3D and 4D point cloud measurements that are on scales ranging from individual tree branches and small outcrops to landscapes and glaciers upwards of a few square kilometers in extent. T-LiDAR is ushering in a new era of geodetically driven mesoscopic scale science with true 3D site characterization and 4D change detection. T-LiDAR has made it possible to image 4D postseismic surface change through tracking how elements on the land surface move over time; fence post, bridges, buildings, trees, and the unique land surface morphology elements are now becoming tractable benchmark-like objects whose 3D positions change. Similar approaches have been applied to a wide range of applications including landslides, rock falls, glacial motion, fissure growth, breakwater/structural stability, and mine collapses. T-LiDAR can image how basins respond to aeolian and fluvial processes following major fires through detailed 4D time-series that show how sediment and material move through a denuded landscape via dry ravel, fluvial, slumping, and debris flow processes. It is now possible to track material volume as a function of basin slope, rainfall intensity and transport mode through detailed geomorphologic analysis and repeat laser surveys. Similar approaches also are being used to track the ice mass-balance during glacier retreat, and spatially variable snow mass balance as a function of solar radiation on north vs. south facing slopes. Furthermore, T-LiDAR is making it possible to accurately and non-destructively measure biomass using a methodology that preserves the target while providing a wealth of information about the target in its surrounding ecosystem. Detailed laser scans of excavated tree root systems are providing detailed biomorphic information that relates surface slope, solar angle, and water source with root growth as a function of depth below the land surface and distance from the tree. The analysis of dense point cloud data has necessitated the development of new 3D workspace environments such that data quality can be assess and the science/applications objectives can be achieved. This presentation will discuss geodetic science applications of ground based T-LiDAR spanning the broad range of earth science. A stereo 3D projection system will be used to visualize specific science elements and 3D glasses will be provided.
The production of ground water in confined aquifer systems often results in a land- surface motio... more The production of ground water in confined aquifer systems often results in a land- surface motion that is in a gradient between two end-member models--elastic deformation and inelastic deformation--that is directly measurable by satellite-based geodetic techniques. Elastic deformation is manifested by seasonal motion associated with the pumping, but with no permanent deformation; inelastic deformation results from permanent compaction of the fine-grained units and unrecoverable subsidence of the land surface. The combination of InSAR imagery, GPS measurements, and water-levels for Salt Lake City, UT, Chino Basin, CA and the metropolitan Los Angeles-Santa Ana region, CA, are used to characterize the end-member models and a hybrid model to show how aquifers respond to ground-water pumping stresses. In Salt Lake City, ground-water pumping results in a strong seasonal motion of as much as 85 mm that is not associated with any measurable long-term subsidence signal. Conversely the Chino Basin is subsiding at a rate of 34 mm/yr from ground-water pumping, with little seasonal motion. In the Los Angeles-Santa Ana region there is both elastic and inelastic motion, with greater than 60 mm of seasonal motion associated with 20 mm/year of subsidence. The inelastic subsidence began in 1995 and has been associated with a change in ground-water pumping policy. Improved characterization of these aquifer systems, and associated subsidence, may result in more effective approaches to ground-water resource management.
The design and development of the next generation of continuous GPS arrays can be optimized to me... more The design and development of the next generation of continuous GPS arrays can be optimized to measure both tectonic and ground water-induced surface deformation, by minimizing the number of GPS sites located on the margins of pumped aquifers. Ground water pumping and hydrocarbon production throughout southern California cause vertical and horizontal deformation that are evident in Interferometric Synthetic Aperture Radar (InSAR) imagery and continuous GPS measurements. For instance, multi-year InSAR imagery show that portions of metropolitan Los Angeles are subsiding at rates of more than 20 mm/yr and seasonal InSAR imagery show vertical oscillations of as much as 110 mm, from late summer to early fall. GPS sites located on the margins of these basins have as much as 15 mm of seasonal horizontal motion in their time-series and are pulled towards the basins with annual subsidence. Establishing GPS arrays that attempt to avoid anthropogenic deformation signals altogether will leave significant gaps in the network that would be ineffective for resolving slip on targeted faults. In addition, changes in ground water pumping patterns may encroach on the tectonic geodetic network. However, since most tectonic studies heavily rely on horizontal GPS components to model fault slip at depth and most ground water subsidence modeling studies use only vertical elevation changes, then locating GPS sites in regions with small InSAR gradients will satisfy both modeling needs. Therefore, GPS sites located well within or outside of ground water basins will have significantly smaller horizontal motion than sites located on basin margins and can be utilized by both science communities.
High resolution (centimeter level) three-dimensional point-cloud imagery of offset glacial outwas... more High resolution (centimeter level) three-dimensional point-cloud imagery of offset glacial outwash deposits were collected by using ground based tripod LiDAR (T-LiDAR) to characterize the cumulative fault slip across the recently identified Polaris fault (Hunter et al., 2009) near Truckee, California. The type-section site for the Polaris fault is located 6.5 km east of Truckee where progressive right-lateral displacement of middle to late Pleistocene deposits is evident. Glacial outwash deposits, aggraded during the Tioga glaciation, form a flat lying `fill' terrace on both the north and south sides of the modern Truckee River. During the Tioga deglaciation melt water incised into the terrace producing fluvial scarps or terrace risers (Birkeland, 1964). Subsequently, the terrace risers on both banks have been right-laterally offset by the Polaris fault. By using T-LiDAR on an elevated tripod (4.25 m high), we collected 3D high-resolution (thousands of points per square meter; ± 4 mm) point-cloud imagery of the offset terrace risers. Vegetation was removed from the data using commercial software, and large protruding boulders were manually deleted to generate a bare-earth point-cloud dataset with an average data density of over 240 points per square meter. From the bare-earth point cloud we mathematically reconstructed a pristine terrace/scarp morphology on both sides of the fault, defined coupled sets of piercing points, and extracted a corresponding displacement vector. First, the Polaris fault was approximated as a vertical plane that bisects the offset terrace risers, as well as bisecting linear swales and tectonic depressions in the outwash terrace. Then, piercing points to the vertical fault plane were constructed from the geometry of the geomorphic elements on either side of the fault. On each side of the fault, the best-fit modeled outwash plane is projected laterally and the best-fit modeled terrace riser projected upward to a virtual intersection in space, creating a vector. These constructed vectors were projected to intersection with the fault plane, defining statistically significant piercing points. The distance between the coupled set of piercing points, within the plane of the fault, is the cumulative displacement vector. To assess the variability of the modeled geomorphic surfaces, including surface roughness and nonlinearity, we generated a suite of displacement models by systematically incorporating larger areas of the model domain symmetrically about the fault. Preliminary results of 10 models yield an average cumulative displacement of 5.6 m (1 Std Dev = 0.31 m). As previously described, Tioga deglaciation melt water incised into the outwash terrace leaving terrace risers that were subsequently offset by the Polaris fault. Therefore, the age of the Tioga outwash terrace represents a maximum limiting age of the tectonic displacement. Using regional age constraints of 15 to 13 kya for the Tioga outwash terrace (Benson et al., 1990; Clark and Gillespie, 1997; James et al., 2002) and the above model results, we estimate a preliminary minimum fault slip rate of 0.40 ± 0.05 mm/yr for the Polaris type-section site.
Studies involving the modeling of snow pack and snowmelt distribution under current conditions an... more Studies involving the modeling of snow pack and snowmelt distribution under current conditions and potential climate change conditions often use MODIS snow cover maps for the snow cover extent (satellite imagery product with 500 m pixel postings), point data from snow pillows that provide snow water equivalent (SWE), and snow course data that provide estimates of SWE from composite measurements
ABSTRACT The design and development of the next generation of continuous GPS arrays can be optimi... more ABSTRACT The design and development of the next generation of continuous GPS arrays can be optimized to measure both tectonic and ground water-induced surface deformation, by minimizing the number of GPS sites located on the margins of pumped aquifers. Ground water pumping and hydrocarbon production throughout southern California cause vertical and horizontal deformation that are evident in Interferometric Synthetic Aperture Radar (InSAR) imagery and continuous GPS measurements. For instance, multi-year InSAR imagery show that portions of metropolitan Los Angeles are subsiding at rates of more than 20 mm/yr and seasonal InSAR imagery show vertical oscillations of as much as 110 mm, from late summer to early fall. GPS sites located on the margins of these basins have as much as 15 mm of seasonal horizontal motion in their time-series and are pulled towards the basins with annual subsidence. Establishing GPS arrays that attempt to avoid anthropogenic deformation signals altogether will leave significant gaps in the network that would be ineffective for resolving slip on targeted faults. In addition, changes in ground water pumping patterns may encroach on the tectonic geodetic network. However, since most tectonic studies heavily rely on horizontal GPS components to model fault slip at depth and most ground water subsidence modeling studies use only vertical elevation changes, then locating GPS sites in regions with small InSAR gradients will satisfy both modeling needs. Therefore, GPS sites located well within or outside of ground water basins will have significantly smaller horizontal motion than sites located on basin margins and can be utilized by both science communities.
Detailed ground-based Tripod LiDAR (T-LiDAR) scans at two sites spanning the San Andreas fault (t... more Detailed ground-based Tripod LiDAR (T-LiDAR) scans at two sites spanning the San Andreas fault (the bridge entering into Parkfield and the USGS video camera array on Carr Hill) show spatially and temporally complex nearfield postseismic deformation fields in the 10 months following the 29-September-2004 mainshock, as imaged through the positional changes of concrete pillars, bridge supports, fence posts, tree trunks,
ABSTRACT Coseismic leveling and triangulation observations are used to determine the faulting geo... more ABSTRACT Coseismic leveling and triangulation observations are used to determine the faulting geometry and slip distribution of the July 21, 1952, Mw 7.3 Kern County earthquake on the White Wolf fault. A singular value decomposition inversion is used to assess the ability of the geodetic network to resolve slip along a multisegment fault and shows that the network is sufficient to resolve slip along the surface rupture to a depth of 10 km. Below 10 km, the network can only resolve dip slip near the fault ends. The preferred source model is a two-segment right-stepping fault with a strike of 51° and a dip of 75°SW. The epicentral patch has deep (6-27 km) left-lateral oblique slip, while the northeastern patch has shallow (1-12.5 km) reverse slip. There is nearly uniform reverse slip (epicentral, 1.6 m; northeast, 1.9 m), with 3.6 m of left-lateral strike slip limited to the epicentral patch. The seismic moment is Mo=9.2+/-0.5×1019Nm (Mw=7.2). The signal-to-noise ratio of the leveling and triangulation data is reduced by 96% and 49%, respectively. The slip distribution from the preferred model matches regional geomorphic features and may provide a driving mechanism for regional shortening across the Comanche thrust and structural continuity with the Scodie seismic lineament to the northeast.
The ``Station'' fire, the largest fire in the history of Los Ange... more The ``Station'' fire, the largest fire in the history of Los Angeles County in southern California, began on August 26, 2009 and as of the abstract deadline had burned over 150,000 acres of the Angeles National Forest. This fire creates both a demand and an opportunity for hazards science to be used by the communities directly hit by the fire,
After the 1987 Whittier Narrows and 1994 Northridge earthquakes revealed that blind thrust faults... more After the 1987 Whittier Narrows and 1994 Northridge earthquakes revealed that blind thrust faults represent a significant threat to metropolitan Los Angeles, a network of 250 continuously recording global positioning system (GPS) stations was deployed to monitor displacements associated with deep slip on both blind and surface faults. Here we augment this GPS data with interferometric synthetic aperture radar imagery
... Author: Brooks, Benjamin A, School of Ocean and Earth Sciences and Technology, University of ... more ... Author: Brooks, Benjamin A, School of Ocean and Earth Sciences and Technology, University of Hawaii at Manoa Bawden, Gerald, Southwest Area Sciences Division US Geological SurveyManjunath, Deepak, School of Ocean and Earth Sciences and Technology ... SJ CR SN ...
Http Dx Doi Org 10 1162 Leon 2010 43 2 204, Apr 1, 2010
Abstract Understanding the collapse of natural and social systems is a key artistic and scientifi... more Abstract Understanding the collapse of natural and social systems is a key artistic and scientific endeavor. By collaborating on a multimedia dance-theatre production, we contributed individual approaches, techniques, and insights to a performance that captured both cultural and scientific aspects of collapse in an aesthetically meaningful way.
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