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1.
Jack E. Staples 《Tectonophysics》1986,130(1-4):171-177
Whether monitoring crustal movements in localized volcanic areas along known fault lines, or over large crustal-movement areas, the geodesist has been restricted by the measurement accuracy of the instruments used, the accumulation of errors, the lack of reliable air refraction information and the problem of finding proper measurement procedures and mathematical solutions to assure that the inherent errors of the measurement-mathematical procedures do not exceed any conceivable ground movement.
Recent technological advances have placed new instruments and systems at the disposal of the geodesist, so that is now feasible to measure and analyze these micro and macro crustal movements within the accuracies required.
The paper describes three such systems:
1. (1) The Wild Electronic Theodolite T-2000 with a highly precise distance-measurement instrument, the DI-4S, together with a data collector, the GRE-3, which are connected to a computer and a plotter to measure and analyze both micro and macro crustal movements.
2. (2) The Wild NAK-2 level with an antimagnetic compensator which increases the accuracy in the height/velocity monitoring of vertical crustal movements by virtual elimination of the influence of natural or man-made magnetic fields on the automatic level.
3. (3) The use of analytical photogrammetry employing both terrestrial and aerial photography to monitor crustal movements.
By taking advantage of these new instruments and systems, the scientists capability to provide crustal movement data for use in the analysis and prediction of micro or macro crustal movement is greatly enhanced. 相似文献
2.
The determination of rates of land uplift in Norway 总被引：1，自引：0，他引：1
Sivert Bakkelid 《Tectonophysics》1986,130(1-4):307-326
It is the task and the responsibility of the Geodetic Section within the Geographical Survey of Norway to establish and maintain the national horizontal and vertical geodetic primary control networks of that country.
Provided that relative crustal movements take place within Norway, they will cause deformations to these networks. There is no geodetic proof that any horizontal deformations of the surface layer of the crust take place in continental Norway and there is no established geological evidence of such movements either. In 1984, a small geodetic control network was established and measured for the first time across a possibly active fault. It is not expected that horizontal movements will cause any serious problems in the maintenance of the horizontal network. Vertical movements of the ground, however, are causing us problems both in the establishment and in the maintenance of a national height system. 相似文献
3.
I. Jo 《Tectonophysics》1986,130(1-4):271-279
The author, as coordinator of the investigation of recent vertical crustal movements in the Carpatho-Balkan Region, reports on the purpose, conditions and method of recent (starting in 1980) investigations, as well as on the results obtained so far. He presents the geodetic and oceanographic data applied, together with their reliability and the standard error of deduced velocities and absolute height data, in tabular form. Deduced height-value differences between the mean sea levels of the three seas considered (Baltic, Black and Adriatic seas) are also shown. Up to now, the joint adjustment and compilation of national maps of movements have been completed. At present compilation of the overall map at a scale of 1: 1,000,000 is under way, for publication in 1985, and its presentation was scheduled for the Budapest International Symposium in October, 1985.
As far as further investigations are concerned, the derivation of movement velocity gradients and their cartographic presentation are discussed. 相似文献
4.
J. Van Mierlo 《Tectonophysics》1979,52(1-4)
Geodetic networks are designed to obtain data that can be used to monitor crustal movements. The relative position on the earth's surface is determined from these networks by means of coordinates. The coordinates of stations and its variance—covariance matrix are based on the computational model. In spatial networks at least three points, the base points, should be chosen to define the coordinate system “fixed” to the earth. In monitoring crustal movements these base points are considered to be stationary over the time span of the motion involved. A procedure for testing the stability of the base points, together with other stable points, is described.The coordinate differences between two time epochs, t0 and t1 are considered to investigate crustal movements. A statistical test is introduced to determine whether crustal movements have actually occurred.The reliability, i.e., the influence, of nondetected errors in the observations or computations, should be considered. Two types of decisions can be made which may lead to incorrect conclusions. These conclusions are as follows:
- 1. (1) That no movement has taken place, although a nondetected error leads to the opposite conclusion.
- 2. (2) That a movement has occurred, although a nondetected error in the observations leads to the opposite conclusion.
5.
Besides systematic instrumental and environmental effects in high-precision levellings and gravimetry, some theoretical problems are decisive in the evaluation and interpretation of recent vertical crustal movements. In view of the increased accuracy of recently developed portable instruments for absolute gravity measurements, some global effects on gravity may no longer be neglected, necessitating additional time-dependent reductions for polar motion effects. Another problem concerns the evaluation of recent vertical crustal movements from repeated geodetic measurements: a rigorous treatment of the problem demands both repeated levellings and gravity measurements; only under additional hypotheses can these limitating prerequisites be eliminated. 相似文献
6.
Recent crustal movements are components and the direct continuation of some neotectonic movements i.e. the Neogene-Quaternary stage of the earth's development. According to geodetic and oceanographic data these crustal movements are constantly taking place everywhere on the continents and probably on the ocean floor. Their velocity and velocity gradients are certainly different on platforms from that in orogenic regions. Orogenic regions are characterized by higher velocity, varying from several mm to several cm per year, and to an even greater degree by the different character of the movement. The velocity gradient in these regions reaches values of 10?6–10?5/year.A peculiar indication of recent movements is their irregularity in time. Periodic movements are typical for platforms; orogenic regions are characterized by sharp increases in velocity by 1–2 orders of magnitude and their gradients by 2–3 orders, close to the time occurrence of earthquakes.The deep processes generating the measured recent crustal movements are manifested also in earthquakes, the state of stress of rocks and anomalies of gravitational and other fields. Thus estimations of recent tectonic activity should be based on the whole complex of quantitative data, such as the velocity and velocity gradients of recent movements, values of stress in mines, and seismicity.To study the deep processes causing the present tectonic activity, it is necessary to determine the types of crustal deformation occurring in different geotectonic regions. The relationships between recent movements and the distribution of earthquakes in the regions with a high degree of crustal activity allow to identify four types of movement: pleistoseismic, hyposeismic, kryptoseismic and teleseismic. 相似文献
7.
G. Gerstbach 《Tectonophysics》1986,130(1-4):427-436
In mountainous regions, the effect of vertical deflections vastly exceeds the accuracy of most geodetic measurements and causes systematic errors of some cm per km at steep sightings. Therefore, crustal movements may be veiled by the enlarged error ellipses.
This paper shows how to compute local vertical deflections to ± 1–2″ within 5 minutes per point, using a parabolic formula and a raw topographical map. For very asymmetrical peaks, by-valleys and irregular slopes, a simple correction is given. No astronomical observations or digital height models are necessary. 相似文献
8.
《International Geology Review》2012,54(8):40-51
Increased accuracy and volume of geodetic investigation, particularly precise repeated leveling, has made possible the study of secular land movements, the slow uplift and subsidence of the lithosphere. Many nations have engaged in level-measuring surveys which have resulted in the compilation of maps of contemporary crustal movements. Although many geodesists and geologists maintain that only certain parts of the earth's crust are mobile, there is not a single area of any consequence in which secular movements are absent. Contemporary movements, varying in direction and intensity, occur in mountainous regions, plains, and sea bottoms. These movements influence river patterns, shoreline configurations, and landscape forms in general. With increased precision and number of engineering projects, the consideration of secular movements becomes a necessary element in longterm planning of complex construction such as ports, pipelines, canals, irrigation systems, and hydroelectric stations. -- G. E. Denegar. 相似文献
9.
Wolfgang Torge 《Tectonophysics》1986,130(1-4):385-393
Through recent developments in absolute and relative techniques, gravimetry has reached an accuracy of a few hundredths to a few tenths of μm s−2 *in small or large-scale networks, respectively. Consequently, gravimetric techniques can now be employed as one efficient tool for detecting vertical crustal movements. Gravity data are necessary for converting the results of geometric levelling to heights defined in the gravity field, and—by repeated surveys—to control time variations of the height-reference surface. More important is the use of repeated gravity surveys for strengthening and partly replacing levelling, being a time-consuming procedure with unfavourable error propagation over larger distances. The successful application of observed gravity variations with time in the detection of vertical crustal movements depends on the reliability of the conversion factor between gravity and height changes, and on the accuracy of the gravity measurements. The conversion factor should be determined through simultaneous levelling and gravimetry, in representative parts of the survey region. Strategies for establishing gravimetric control are changing now with the availability of transportable absolute gravity meters, and the possibility of accurately calibrating relative instruments and observing small gravity differences with feed-back-systems. Consequently, more attention has to be given now to disturbing effects of environmental character, such as microseismics, atmospheric pressure and groundwater table variations, and to periodic effects such as gravimetric earth tides and polar motion. 相似文献
10.
11.
Due to the importance of Aswan area, Egypt, it has been selected for the present study. Since 1982, after the main shock of November 14, 1981 with M?=?5.6, several study programmes were initiated for monitoring seismicity and crustal movements at Aswan area (Tealeb 1996). Starting from 1997, GPS geodetic networks were established and observed many times in different campaigns. The observations are repeated twice a year. At the beginning of 2012, a moderate earthquake has occurred in the Aswan region with magnitude of 4.2 located at the southwest of the High Dam along Kalabsha fault. Before and after this event, these local geodetic networks were measured using GPS. Regional, Kalabsha-Sayal and Kalabsha networks were used in the present work. GPS data were processed using Bernese 5.0. The collected data before and after this event have shown that the area southwest of the High Dam and Kalabsha area suffered from stress and strain. The behaviour of the areas has changed after earthquake for pre-earthquake. 相似文献
12.
Short-term vertical velocity field in the Apennines (Italy) revealed by geodetic levelling data 总被引：2，自引：0，他引：2
E. D'Anastasio P.M. De Martini G. Selvaggi D. Pantosti A. Marchioni R. Maseroli 《Tectonophysics》2006,418(3-4):219-234
We estimate current vertical movements along the Apennines (Italy) through repeatedly measured high precision levelling routes. In order to highlight regional crustal deformation the analysis of a geodetic database, with a minimum benchmark density of 0.7 bm/km (1943–2003 time period), is carried out. We evaluate systematic and random error and their propagation along the levelling routes. Tests on original raw height data have been carried out to define error propagation. The computed relative vertical rates stand significantly above error propagation. A series of traverses along and across the Apennines and a map of relative vertical velocities reveal a geodetic signal characterised by values up to 2.5–3.0 mm/a and by wavelengths up to 100 km. 相似文献
13.
Four-dimensional modeling of recent vertical movements in the area of the southern california uplift
This paper describes an analytical technique that utilizes scattered geodetic relevelings and tide-gauge records to portray Recent vertical crustal movements that may have been characterized by spasmodic changes in velocity. The technique is based on the fitting of a time-varying algebraic surface of prescribed degree to the geodetic data treated as tilt elements and to tide-gauge readings treated as point movements. Desired variations in time can be selected as any combination of powers of vertical movement velocity and episodic events. The state of the modeled vertical displacement can be shown for any number of dates for visual display. Statistical confidence limits of the modeled displacements, derived from the density of measurements in both space and time, line length, and accuracy of input data, are also provided. The capabilities of the technique are demonstrated on selected data from the region of the southern California uplift. 相似文献
14.
Dieter Fritsch 《Tectonophysics》1986,130(1-4):407-420
Progress in model building and in advanced exposure and evaluation methods is leading photogrammetry up into the field of precise point determination, up to now solved by classical geodetic triangulation and/or trilateration. In combination with the statistical test theory, photogrammetry can be used as a tool to detect recent crustal movements or deformations of man-made constructions, such as in coal mining or oil and gas exploitation.
For these reasons, this paper deals with model building for modern aerial triangulation with respect to hypothesis tests to detect point displacements greater than the measurement noise. An example from brown-coal mining demonstrates accuracies and the application of some statistical tests shows the efficiency of advanced aerial photogrammetry. 相似文献
15.
Larry D. Brown 《Tectonophysics》1978,44(1-4)
The first detailed profile of apparent vertical crustal movement along the east coast of the United States, extending from Calais, Maine to Key West, Florida, has been produced from the results of precise leveling by the National Geodetic Survey. Comparison of this profile with one obtained from secular trends in sea level reveals a serious systematic disagreement between the two methods, as large as 19 mm/year. Estimates of normal measurement error can account for some, but not all, of the misclosures indicated. Thus at least one of the methods must be seriously affected by some systematic non-tectonic influence. The cause of the discrepancy is presently unknown, but the comparisons presented here make possible an estimate of its magnitude, an important step toward identification of the cause and elimination of its effect. The two data sets have been adjusted using different assumptions as to the source of their disagreement to produce several possible versions of a crustal movement profile along the east coast. Comparison of these profiles with topography, gravity and seismicity indicate some weak correlations. However, there are several striking correspondences between apparent movements and tectonic and geomorphic features on a regional scale; in particular, the Connecticut Valley graben, the Chesapeake embayment, the Cape Fear arch and the Cape Canaveral prominence correspond to marked changes in the crustal movement profile. These correlations persist in all of the adjustments and it is unlikely that they can be attributed to chance. The implication is, therefore, that these four features are active elements in the contemporary tectonic fabric of the eastern United States. 相似文献
16.
A comparative analysis of repeated geodetic leveling data was made along nine subparallel, E—NE-trending leveling lines located in the central to northern Sierra Nevada and the eastern Central Valley. The analysis was made to identify relative changes of elevation and evaluate these changes with respect to the regional geology and tectonics. The analysis used National Geodetic Survey first- and second-order, unadjusted, observed elevations.The relative changes in elevation indicate that crustal deformation is continuing to occur in the Sierra Nevada along pre-existing zones of crustal weakness and that this deformation is localized along some strands of Late Cenozoic faulting within the Mesozoic Foothills fault system. This deformation is characterized by variable and nonunifor westward tilt of the Sierran block west of the Melones fault zone, and relatively consistent eastward tilt of the Sierran block east of the Melones fault zone. Variable elevation changes occur within the Foothills fault system and are often associated with prominent geological or structural contacts. In addition, subsidence in the Central Valley appears to be of small magnitude and localized in extent, indicating nontectonic changes in elevation problably due to compaction of unconsolidated sediments. 相似文献
17.
Digital national land information 总被引：1，自引：0，他引：1
H. Matsuda 《GeoJournal》1980,4(4):313-318
The digital land data maintained in the Geographic Survey Institute are listed in Tab 1. They are computerized for the digital national land information to establish a geographical data bank of land information.The digital national land information contains many kinds of land data, which have been maintained mainly as maps, aerial photos and statistics, and is stored as magnetic tape.The smallest geographical unit is either the standard mesh, geodetic coordinate or dots, according to accuracy of the original data.The digital national land information can be used in the various fields of geographical researches and in national or local land planning.In this paper, as an example of application, the housing land selection method is introduced, using the natural land data and the land use data. 相似文献
18.
We present the previous work done in order to establish a geodetic control network at the Caldera of Teide (Canary Islands) for the purpose of detecting crustal movements in volcanic areas, as well as a procedure for solving the configuration problem, taking into account the features of the terrain. 相似文献
19.
F. Riguzzi S. Atzori F. Obrizzo G. Pietrantonio F. Pingue 《International Journal of Earth Sciences》2012,101(6):1661-1671
The Colli Albani volcanic complex (Rome, Italy) has been dominated by episodic eruptions commencing around 561?ka and ending with the most recent activity of the Albano maar phase (<70?ka). Earthquakes of moderate intensity, gas emissions and significant ground deformations are the recent evidences of a residual activity. Former geodetic data from leveling surveys, GPS stations and InSAR observations tracked ongoing significant uplift of the order of few mm/year near the Colli Albani western flank. Different uplift rates were detected by each technique in different time spans, suggesting also the possibility of sporadic recharge of the hydrothermal system. The renewed high precision leveling data from IGMI survey carried out in 1997/1999 and the last leveling survey carried out in 2006 show that the uplift along the route is currently significant at an average rate of ~3?mm/year. Radar interferograms from ALOS satellite show uplift rate of ~6?mm/year, southwest of the central sector of the leveling route. We have undertaken a joint inversion of the various geodetic data (vertical rates from leveling surveys, GPS site velocities and InSAR observations acquired by ALOS satellite) using a nonlinear inversion technique to estimate the parameters of a point-pressure source, possibly capable of explaining the ongoing deformation at Colli Albani volcano. 相似文献
20.
Yao Yevenyo Ziggah Hu Youjian Alfonso Tierra Ahmed Amara Konaté Zhenyang Hui 《Arabian Journal of Geosciences》2016,9(17):698
Two national horizontal geodetic datums, namely, the Accra and Leigon datum, have been the only available datum used in Ghana. These two datums are non-geocentric and were established based on astro-geodetic observations. Relating these different geodetic datums mostly involves the use of conformal transformation techniques which could produce results that are not very often satisfactory for certain geodetic, surveying and mapping purposes. This has been ascribed to the incapability of the conformal models to absorb more of the heterogeneous and local character of deformations existing within the local geodetic networks. Presently, application of new approaches such as artificial neural network (ANN) is highly recommended. Whereas the ANN has been gaining much popularity to solving coordinate transformation-related problems in recent times, the existing researches carried out in Ghana have shown that only three-dimensional conformal transformation methods have been utilized. To the best of our knowledge, plane coordinate transformation between the two local geodetic datums in Ghana has not been investigated. In this paper, an attempt has been made to explore the plane coordinate transformation performance of two different ANN approaches (backpropagation neural network (BPNN) and radial basis function neural network (RBFNN)) compared with two different traditional techniques (six- and four-parameter models) in the Ghana national geodetic reference network. The results revealed that transforming plane coordinates from Leigon to Accra datum, the RBFNN was better than the BPNN and traditional techniques. Transforming from Accra to Leigon datum, both the BPNN and RBFNN produced closely related results and were better than the traditional methods. Therefore, this study will create the opportunity for Ghana to recognize the significance and strength of the ANN technology in solving coordinate transformation problems. 相似文献