This chapter contains sections titled:
Introduction
Data and GPS Data Analysis
Observed Site Velocities
Seismic Cycle and Tectonic Models
Alaska‐Scale Deformation Models
Block Models
Conclusions
A new and efficient algorithm using the geometry conditions between satellite and tracking receivers is proposed to determine the receiver differential code bias (DCB) using permanent reference ...stations. This method does not require a traditional single-layer ionosphere model and can be used for estimating DCBs of receivers in a regional network as long as one of the receiver DCBs is already known. The main underlying rationale for this algorithm is that the magnitude of the signal delay caused by the ionosphere is, under normal conditions, highly dependent on the geometric range between the satellite and the receiver. The proposed algorithm was tested with the Ohio Continuously Operating Reference Stations (CORS) sub-network data. The results show that quality comparable to the traditional DCB estimation method is obtainable by implementing this simple algorithm.
Global Navigation Satellite Systems (GNSS) are space based positioning techniques and widely used in geodetic applications. Geodetic networking accomplished by engineering surveys constitutes one of ...these tasks. Geodetic networks are used as the base of all kinds of geodetic implementations, Co from the cadastral plans to the relevant surveying processes during the realization of engineering applications. Geodetic networks consist of control points positioned in a defined reference frame. In fact, such positional information could be useful for other studies as well. One of such fields is geodynamic studies that use the changes of positions of control stations within a network in a certain time period to understand the characteristics of tectonic movements. In Turkey, which is located in tectonically active zones and struck by major earthquakes quite frequently, the positional information obtained in engineering surveys could be very useful for earthquake related studies. For this purpose, a GPS (Global Positioning System) network of 650 stations distributed over Istanbul (Istanbul GPS Triangulation Network; abbreviated IGNA) covering the northern part of the North Anatolian Fault Zone (NAFZ) was established in 1997 and measured in 1999. From 1998 to 2004, the IGNA network was extended to 1888 stations covering an area of about 6000 km2, the whole administration area of Istanbul. All 1888 stations within the IGNA network were remeasured in 2005. In these two campaigns there existed 452 common points, and between these two campaigns two major earthquakes took place, on 17 August and 12 November 1999 with a Richter scale magnitude of 7.4 and 7.2, respectively. Several studies conducted for estimating the horizontal and vertical displacements as a result of these earthquakes on NAFZ are discussed in this paper. In geodynamic projects carried out before the earthquakes in 1999, an annual average velocity of 2–2.5 cm for the stations along the NAFZ were estimated. Studies carried out using GPS observations in the same area after these earthquakes indicated that point displacements vary depending on their distance to the epicentres of the earthquakes. But the directions of point displacements are similar. The results obtained through the analysis of the IGNA network also show that there is a common trend in the directions of point displacements in the study area. In this paper, the past studies about the tectonics of Marmara region are summarised and the results of the displacement analysis on the IGNA network are discussed.
Global Positioning System (GPS) and geodetic control networks are used today for analyzing and monitoring time-dependent crustal deformations, providing a series of accurate positional measurements ...to deliver information on positional changes and deformations that have occurred. Still, such networks present a low-resolution dispersal of positional measures, and do not take into account various physical constraints that affect the terrain’s seismic behavior. An alternative form of spatio-temporal infrastructure that is feasible and practical to establish might involve the use of Digital Terrain Model (DTM) databases. These databases use higher positional resolutions, and are exhibiting an increasing level of positional and height accuracy. Still, when comparing temporal DTMs, the separation of actual physical phenomena from data-related ambiguities is essential in the framework of spatio-temporal analysis. This paper proposes the use of a hierarchical co-modeling of different DTM databases for the task of landform monitoring. Analyses showed promising results, pointing to the feasibility of the proposed methodology in monitoring and quantifying topographic-related spatio-temporal phenomena, such as landslides and change detection, thus facilitating a reliable and precise landform monitoring and warning framework for geomorphodynamic analyses.
This study simulates water resources in the Tien Shan alpine basins to forecast how global and regional climate changes would affect river runoff. The model employed annual mean values for the major ...characteristics of the water cycle: annual air temperature, precipitation, evapotranspiration and river runoff. The simulation was based on 304 hydro-meteorological stations, 23 precipitation sites, 328 high altitudinal points with glaciological measurements, 123 stream-gauges, and 54 evaporation sites, and it took into account topography. The findings were simulated over Tien Shan relief using a 1:500,000 scale 100 m grid resolution Digital Elevation Model. An applicable GIS-based distributed River Runoff Model was implemented in regional conditions and tested in the Tien Shan basins. The annual evapotranspiration exceeds the river runoff in the Tien Shan watersheds particularly up to 3700 m. Hypothetical climate-change scenarios in the Tien Shan predict that by 2100 river runoff will increase by 1.047 times with an increase in air temperature averaging 3 °C and an increase in precipitation averaging 1.2 times the current levels. Change in precipitation, rather than temperature, is the main parameter determining river runoff in the Tien Shan. The maximum ratio for predicted river runoff could reach up to 2.2 and the minimum is predicted to be 0.55 times current levels. This possibly dramatic change in river runoff indicates on non-linear system response caused mainly by the non-linear response of evapotranspiration from air temperature and precipitation changes. In the frame of forecasted possible climate change scenarios the probability of river runoff growth amounts 83–87% and probability of this decline is 17–13% by 2100 in the Tien Shan River basins.
In countries where on the tectonic plate movements, one of the distorting effects due to plate movements occurs on national geodetic networks. As a result of distorting effects geodetic networks lose ...their homogenous characteristics, and discrepancies increase particularly around active fault lines. Furthermore, these fault lines form distinctive borders on the network, and two sides of fault line become apart from each other in line with the plate movements.
These distortions on geodetic networks make geodetic transformation processes much more difficult and complex. In addition to this, transformations between global and national or regional datum are still needed in much case.
However, it does not seem possible to achieve satisfactory results with conventional transformation methods especially in places on tectonic plate movements and/or places with distortions on geodetic basic network such as Turkey. In this article, there are studies particularly towards solution of the problem of continuity for a transformation based on finite element method. Results verified that finite element based methods are enable to ensure continuity.
Over the last few decades, the use of space-borne radar altimetry has dramatically improved our knowledge and understanding of the oceans. During this same period, sea-level observation with tide ...gauges has also undergone spectacular changes, both from a technological point of view and in the applicative fields. This article gives a brief history of tidal observation and then explains how this discipline is closely linked both to geodesy and to oceanography. The renewed interest in tide gauges is illustrated using three case studies; these reflect how the discipline is complementary to space geodesy.Original Abstract: Alors que l'altimetrie radar embarquee sur satellite revolutionne notre connaissance des oceans, la maregraphie connait un essor sans precedent depuis deux decennies, aussi bien dans ses technologies que dans ses applications. Cet article remonte brievement aux origines de la maregraphie. Il s'attache ensuite a montrer combien cette discipline reste liee a la geodesie autant qu'a l'oceanographie. Le regain d'interet pour les maregraphes est illustre par trois etudes de cas qui refletent la complementarite de la maregraphie et de la geodesie spatiale.
The southern California Permanent GPS Geodetic Array (PGGA) was established in 1990 across the Pacific‐North America plate boundary to continuously monitor crustal deformation. We describe the ...development of the array and the time series of daily positions estimated for its first 10 sites in the 19‐month period between the June 28, 1992 (Mw=7.3), Landers and January 17, 1994 (Mw=6.7), Northridge earthquakes. We compare displacement rates at four site locations with those reported by Feigl et al. 1993, which were derived from an independent set of Global Positioning System (GPS) and very long baseline interferometry (VLBI) measurements collected over nearly a decade prior to the Landers earthquake. The velocity differences for three sites 65–100 km from the earthquake's epicenter are of order of 3–5 mm/yr and are systematically coupled with the corresponding directions of coseismic displacement. The fourth site, 300 km from the epicenter, shows no significant velocity difference. These observations suggest large‐scale postseismic deformation with a relaxation time of at least 800 days. The statistical significance of our observations is complicated by our incomplete knowledge of the noise properties of the two data sets; two possible noise models fit the PGGA data equally well as described in the companion paper by Zhang et al. this issue; the pre‐Landers data are too sparse and heterogeneous to derive a reliable noise model. Under a fractal white noise model for the PGGA data we find that the velocity differences for all three sites are statistically different at the 99% significance level. A white noise plus flicker noise model results in significance levels of only 94%, 43%, and 88%. Additional investigations of the pre‐Landers data, and analysis of longer spans of PGGA data, could have an important effect on the significance of these results and will be addressed in future work.
Despite the fact that the pattern and deep structure of the Baikal rift system is well understood, there is no general agreement as to the model of its formation. Consistently suggested were ...mechanisms of passive and active rifting, a model combining both mechanisms, and then again a model with predominating active rifting under the effect of a local mantle source or gravitational instability of sediments. This work offers additional arguments for substantiating the passive mechanism of extension in the Baikal rift at the present stage of evolution, which were adduced on the basis of the analysis of long-term measurements by the method of GPS geodesy.
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