Global Positioning System Geodesy Research Articles

Climate‐driven vertical acceleration of Icelandic crust measured by continuous GPS geodesy

AbstractEarth's present‐day response to enhanced glacial melting resulting from climate change can be measured using Global Positioning System (GPS) technology. We present data from 62 continuously operating GPS instruments in Iceland. Statistically significant upward velocity and accelerations are recorded at 27 GPS stations, predominantly located in the Central Highlands region of Iceland, where present‐day thinning of the Iceland ice caps results in velocities of more than 30 mm/yr and uplift accelerations of 1–2 mm/yr2. We use our acceleration estimates to back calculate to a time of zero velocity, which coincides with the initiation of ice loss in Iceland from ice mass balance calculations and Arctic warming trends. We show, through a simple inversion, a direct relationship between ice mass balance measurements and vertical position and show that accelerated unloading is required to reproduce uplift observations for a simple elastic layer over viscoelastic half‐space model.

A Comprehensive Study of the Seismicity of the Kenai Peninsula-Cook Inlet Region, South-Central Alaska

Abstract We compare 30 yr of background seismicity of the Kenai Peninsula–Cook Inlet region (extending from eastern Prince William Sound–Kayak Island to west of the Cook Inlet volcanic arc) to potential field (gravity, magnetics), tomographic, Global Positioning System–geodesy, and geologic information to better determine factors controlling seismicity. We also compare the occurrence of M w >5 events over the past 80–100 yr to background seismicity in an effort to determine how reflective background seismicity is of the regional seismic hazard. Our results indicate that contrasts in upper plate rheology leading to changes in density, magnetic susceptibility, and velocity of the upper plate serve to concentrate seismicity. The southwestern edge of the subducting Yakutat microplate has a strong influence on both upper and lower plate seismicity. Density and velocity contrasts also indicate changes in lower plate rheology that influence the location of deeper (>30 km) seismicity and the occurrence of a double seismic zone within the subducting Pacific plate.

Bounds on the width of mantle lithosphere flow derived from surface geodetic measurements: application to the central Southern Alps, New Zealand

SUMMARY We show that the strain rate pattern measured at the surface of an oblique collision zone, the New Zealand Southern Alps, can be used to impose bounds on the width of present-day deformation in underlying mantle lithosphere. Geological and geophysical evidence supporting localized shearing along the downdip extension of the Alpine Fault, is used to constrain the upper slipping patch. Using finite-element models, we investigate the effect of different boundary conditions in the lower lithosphere on the predicted interseismic velocity profile at the surface. For a homogeneous elastic rheology, distributed lower lithosphere shear over widths greater than about 100 km causes the fit with interseismic velocities derived from Global Positioning System (GPS) measurements to significantly degrade. In comparison, either localized shear along a slipping patch or distributed shear over a width less than 100 km can fit the data. The strike-parallel velocity component is most diagnostic between the differing models. Finite-element models incorporating variations in elastic strength and non-linear viscous creep in the crust and mantle lithosphere, while indicating that some decoupling can occur between crust and mantle lithosphere, also support the conclusion that mantle lithosphere cannot be deforming over a width greater than about 100 km. In contrast, shear-wave splitting studies have been interpreted to show a wide, 200–400-km deforming zone beneath the Southern Alps. The discrepancy highlights the different timescales measured by GPS geodesy compared to estimates of finite strain that has accumulated over millions of years.

Late Quaternary slip rates across the central Tien Shan, Kyrgyzstan, central Asia

Slip rates across active faults and folds show that late Quaternary faulting is distributed across the central Tien Shan, not concentrated at its margins. Nearly every intermontane basin contains Neogene and Quaternary syntectonic strata deformed by Holocene north‐south shortening on thrust or reverse faults. In a region that spans two thirds of the north‐south width of the central Tien Shan, slip rates on eight faults in five basins range from ∼0.1 to ∼3 mm/yr. Fault slip rates are derived from faulted and folded river terraces and from trenches. Radiocarbon, optically stimulated luminescence, and thermoluminescence ages limit ages of terraces and aid in their regional correlation. Monte Carlo simulations that sample from normally distributed and discrete probability distributions for each variable in the slip rate calculations generate most likely slip rate values and 95% confidence limits. Faults in basins appear to merge at relatively shallow depths with crustal‐scale ramps that underlie mountain ranges composed of pre‐Cenozoic rocks. The sum and overall pattern of late Quaternary rates of shortening are similar to current rates of north‐south shortening measured using Global Positioning System geodesy. This similarity suggests that deformation is concentrated along major fault zones near range‐basin margins. Such faults, separated by rigid blocks, accommodate most of the shortening in the upper crust.

Velocity field across the Southern Caribbean Plate Boundary and estimates of Caribbean/South‐American Plate Motion using GPS Geodesy 1994–2000

Global Positioning System (GPS) observations between 1994 and 2000 at twenty‐two sites in the Lesser Antilles and northern South‐America indicate that the Caribbean plate, along its southern boundary, slips at a rate of 20.5±2 mm/a with an azimuth of N 84°±2°E at 65°W, relative to the South‐American plate. East of 68° W, 80% of the dextral slip is contained within a 80‐km wide shear zone centered on the El Pilar‐San Sebastián fault system. West of 68° W the plate boundary broadens to more than 300 km with dextral shear shared between the northeast trending Boconó fault (9–11 mm/a) in western Venezuelan, and an offshore system near the northern coast.

Active displacement partitioning and arc-parallel extension of the Aleutian volcanic arc based on Global Positioning System geodesy and kinematic analysis

Active displacement partitioning and arc-parallel extension of the Aleutian volcanic arc based on Global Positioning System geodesy and kinematic analysis

Active displacement partitioning and arc-parallel extension of the Aleutian volcanic arc based on Global Positioning System geodesy and kinematic analysis

Research Article| August 01, 2000 Active displacement partitioning and arc-parallel extension of the Aleutian volcanic arc based on Global Positioning System geodesy and kinematic analysis Hans G. Avé Lallemant; Hans G. Avé Lallemant 1Department of Geology and Geophysics, Rice University, Houston, Texas 77251-1892, USA Search for other works by this author on: GSW Google Scholar John S. Oldow John S. Oldow 2Department of Geological Sciences, University of Idaho, Moscow, Idaho 83844-3022, USA Search for other works by this author on: GSW Google Scholar Geology (2000) 28 (8): 739–742. https://doi.org/10.1130/0091-7613(2000)28<739:ADPAAE>2.0.CO;2 Article history received: 10 Jan 2000 rev-recd: 18 May 2000 accepted: 26 May 2000 first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Hans G. Avé Lallemant, John S. Oldow; Active displacement partitioning and arc-parallel extension of the Aleutian volcanic arc based on Global Positioning System geodesy and kinematic analysis. Geology 2000;; 28 (8): 739–742. doi: https://doi.org/10.1130/0091-7613(2000)28<739:ADPAAE>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu nav search search input Search input auto suggest search filter All ContentBy SocietyGeology Search Advanced Search Abstract Global Positioning System geodesy and structural analysis of parts of the Aleutian island chain support the interpretation of forearc migration westward along right-lateral transcurrent faults. Measured displacements are essentially arc parallel in the eastern (Unalaska Island) and western (Attu Island) parts of the arc and vary from 3.1 mm/yr to 31.4 mm/yr, respectively. At the center of the arc (Adak) subduction of the Amlia fracture zone disrupts the pattern of arc-parallel displacement and records an upper plate velocity of 9.6 mm/yr parallel to plate motion. Where active, displacement partitioning accommodates 30%–50% of the strike-slip component of plate convergence. In the area of impeded subduction partitioning ceases, suggesting that the process is sensitive to the degree of coupling across the plate-boundary megathrust. The differential arc-parallel displacements observed at the ends of the arc together with structural relations indicate substantial arc-parallel extension, which may play an important role in exhumation of high-pressure–low-temperature metamorphic rocks in ancient arc systems. You do not currently have access to this article.

Rotations in the actively colliding Finisterre Arc Terrane: paleomagnetic constraints on Plio-Pleistocene evolution of the South Bismarck microplate, northeastern Papua New Guinea

We report paleomagnetic results from 12 Plio-Pleistocene localities in the actively colliding Finisterre Arc Terrane of northeastern Papua New Guinea (PNG). Calcareous, hemipelagic cover rocks possess a stable, syn-collisional remagnetization indicating a clockwise rotation of the colliding terrane through about 40° in post-Miocene time. A decrease in paleomagnetic declination anomalies as a function of along-strike distance in the Finisterre Arc Terrane, analyzed by our preferred model of a linear remagnetization and a migrating Euler pole, suggests an average rotation rate of 8° Ma −1, in good agreement with the instantaneous rate from global positioning system geodesy. Thus, we propose that this rotation results from a coherent, rigid-body rotation of the Finisterre Terrane rather than from sequential docking of independently colliding blocks of the terrane. Moreover, we conclude that these paleomagnetic declinations result mainly from South Bismarck Plate motion, and not decoupled rotation of the crustal terrane independent of the underlying lithosphere. We examine models of a syn-collisional remagnetization with both fixed and migrating Euler poles of South Bismarck/Australia plate relative motion, and suggest that the Euler pole describing South Bismarck Plate motion has migrated southwestward to its present location on the collision suture in response to the propagating collision. This plate kinematic model agrees with the variability in depth of the seismogenic slab beneath the collision zone. Our best-fit model of pole migration describes South Bismarck/Australia relative motion producing a highly oblique collision in its early stages, with the Finisterre Arc Terrane converging along a left-lateral Ramu-Markham suture, gradually changing to the nearly orthogonal convergence observed today.

GPS measurement of surface deformation around Soufriere Hills Volcano, Montserrat from October 1995 to July 1996

Global Positioning System geodesy was used to measure surface deformation on Soufriere Hills volcano, Montserrat from October 6, 1995 to July 1, 1997 during initial dome growth and gravitational collapse. Our data from this period show non‐axially symmetric horizontal displacements, and decreasing subsidence as a function of radial distance from the former topographic high of the volcanic edifice. Forward modeling suggests that surface deformation is caused by a shallow vertical dike (&lt; 3 km), which expanded approximately 1 m, coupled with a deflating Mogi source at about 6 km depth. These inferred source parameters are in good agreement with independent observations of regional dike widths and preemption magma storage depth.

GPS APPLICATIONS FOR GEODYNAMICS AND EARTHQUAKE STUDIES

▪ Abstract Geodetic measurements obtained with the Global Positioning System (GPS) are increasingly more widely applied in geophysical studies. In this paper, we review the changes to the technology of GPS geodesy over the last five years that are responsible for this increased applicability. We survey geophysical investigations employing GPS to measure coseismic, postseismic, and interseismic deformation; plate motion and crustal deformation at plate boundaries; volcano deformation; and the deformation associated with glacial isostatic adjustment and its application to sea-level studies. We emphasize the use of GPS determinations for the modeling of this wide variety of geophysical phenomena. We also discuss the recent advent of permanent GPS networks for regional geophysical studies, as well as the possible future of GPS surveying in light of the recent advances.

Blending old and new approaches to regional GPS geodesy

High precision Global Positioning System (GPS) geodesy has emerged as a powerful new tool for the Earth sciences. Over the last decade it has revolutionized global and regional geodesy and research into crustal motion and deformation, and it shows great promise in other areas such as remote sensing of atmospheric water vapor and the ionosphere. Increasingly, geodesists and geophysicists constructing regional GPS networks are interacting with meteorologists, space physicists, seismologists, control surveyors, and others seeking a multiple‐use infrastructure.

PNG Transect 1998–2001

We report paleomagnetic results from 12 Plio-Pleistocene localities in the actively colliding Finisterre Arc Terrane of northeastern Papua New Guinea (PNG). Calcareous, hemipelagic cover rocks possess a stable, syn-collisional remagnetization indicating a clockwise rotation of the colliding terrane through about 40° in post-Miocene time. A decrease in paleomagnetic declination anomalies as a function of along-strike distance in the Finisterre Arc Terrane, analyzed by our preferred model of a linear remagnetization and a migrating Euler pole, suggests an average rotation rate of 8° Ma−1, in good agreement with the instantaneous rate from global positioning system geodesy. Thus, we propose that this rotation results from a coherent, rigid-body rotation of the Finisterre Terrane rather than from sequential docking of independently colliding blocks of the terrane. Moreover, we conclude that these paleomagnetic declinations result mainly from South Bismarck Plate motion, and not decoupled rotation of the crustal terrane independent of the underlying lithosphere. We examine models of a syn-collisional remagnetization with both fixed and migrating Euler poles of South Bismarck/Australia plate relative motion, and suggest that the Euler pole describing South Bismarck Plate motion has migrated southwestward to its present location on the collision suture in response to the propagating collision. This plate kinematic model agrees with the variability in depth of the seismogenic slab beneath the collision zone. Our best-fit model of pole migration describes South Bismarck/Australia relative motion producing a highly oblique collision in its early stages, with the Finisterre Arc Terrane converging along a left-lateral Ramu-Markham suture, gradually changing to the nearly orthogonal convergence observed today.

GPS data, acquisition, environmental effects

Precise geodesy with the Global Positioning System (GPS) emerged in the early 1990s from a decade‐long incubation to find vigorous application worldwide. Today we enjoy a full 24‐satellite constellation, a new generation of high‐precision receivers at about one‐third the 1991 cost, a growing permanent global network, and a vital International GPS Service to support GPS geodesy worldwide. In addition, dedicated regional GPS networks are springing up on every continent. The period has been marked less by conceptual advance than by disciplined application and refinement. Here we review the key developments in receivers and networks, and in understanding the environmental factors that limit GPS geodetic performance.

UNAVCO to support DOSE regional geodesy

The Earth science programs at NASA and the National Science Foundation are joining forces to support regional Global Positioning System (GPS) geodesy experiments. The combined field project support functions will be conducted by the University Navstar Consortium (UNAVCO) facility.NASA's Solid Earth Science Branch initiated the Dynamics of the Solid Earth (DOSE) program in 1992. DOSE supports a variety of investigations, including studies of crustal deformation due to tectonic plate motion, earthquakes, post‐glacial rebound, and volcanic activity. Many of these investigations require high‐precision geodetic measurements utilizing the space‐based GPS technology. NSF's Earth Sciences Division established UNAVCO in 1984 to provide equipment, technical, and related support to university investigators applying GPS technology to geosciences research. UNAVCO has since supported investigators in more than 100 regional GPS geodesy projects. The UNAVCO facility operates in Boulder, Colo., as a program of the University Corporation for Atmospheric Research.

Measurement of Crustal Deformation Using the Global Positioning System

During the past several years, there has been a tremendous surge of interest in geodesy among geophysicists interested in the kinematics and dynamics of crustal deformation. I n 1 980, there were � 30 talks concerning geodesy applied to tectonics given at the Spring and Fall meetings of the American Geophysical Union (AGU). Of these, over half were authored by scientists at government agencies charged with geodetic missions. Fewer than five were by academic scientists who had collected the data that they discussed. In contrast, in 1990, almost three times as many papers were given at AGU, almost halfby academic scientists addressing data that they themselves had participated in collecting. The total number of authors increased even more dramatically-from �75 in 1980 to �325 in 1 990. This remarkable increase in geodetic activity in the past decade, par­ ticularly by academics, has largely resulted from the opportunities pro­ vided by the development of a new geodetic tool-high-accuracy relative vector positioning made possible by analyzing radio signals broadcast by the Global Positioning System (GPS) satellites operated by the United States Department of Defense. The development of GPS geodesy was greatly facilitated by advances in the space geodetic techniques of very long baseline interferometry (VLBI) and satellite laser ranging (SLR).