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1.
A local geodetic network of 20 points was established in 1988 around the Seiyal fault for monitoring lateral movements. Two levellinglines, crossing the fault, were prepared for monitoring vertical movements. The initial horizontal geodetic measurements were carried out in March 1989. The measurements were repeated twice a year. The initial vertical geodetic measurements (levelling) were carried out in November 1989 and repeated in November 1990.Four horizontal geodetic measurements and two levelling measurements were analysed. The results revealed remarkable horizontal and vertical changes during the period of measurement. 相似文献
2.
In Turkey, neotectonic activity originated from the collision of the Arabian and Anatolian land masses during the Middle Miocene. As a result of the collision, westward escape of the Anatolian block introduced E-W compression in Western Turkey which began to be relieved by N-S extension. The North Anatolian Fault (NAF) is the major active strike-slip fault that was formed under the neotectonic regime. The rates of the motion along this fault estimated by several authors are in the range of 0.4–2.9 cm/a according to kinematic data. In Turkey, the first studies of crustal movements by geodetic methods were started in the west section of the NAF in 1972. So far, individual activities and studies coordinated by multidisciplinary projects have been realized in this region. The results obtained from available geodetic data indicate the motion of the Anatolian block relative to Eurasia. 相似文献
3.
GPS observations in the Western Bohemia/Vogtland earthquake swarm region revealed indications of horizontal displacements
of low amplitude, and no clear long-term trend in 1993–2007. On the other hand, in 1998–2001 there was relatively significant
active movement along NNE-SSW oriented line that we called the “Cheb-Kraslice GPS Boundary” (ChKB), identical with an important
limitation of earthquake activity. The most impressive were dextral (right-lateral) movements in the 1998–1999 period followed
by reverse sinistral (left-lateral) movements in 1999–2000 that correlate with prevailing motion defined by fault plane solutions
of the Autumn 2000 earthquake swarm. Before the February 2004 micro-swarm, two points located on opposite sides of the Mariánské
Lázně fault showed extension in the order of about 7 mm in the same NNE-SSW direction of ChKB. The new NOKO permanent GPS
station in Novy Kostel showed the peak-to-peak vertical changes up to 10 mm before and during the February 2007 micro-swarm.
Annual precise levelling campaigns in the local network around Novy Kostel revealed regular vertical displacements during
the 1994, 1997 and 2000 earthquake swarms. The points around the Novy Kostel seismological station showed uplift during the
active periods, including the micro-swarm February 2004. However, no such indication was observed on levelling points in the
period of the February 2007 swarm. Long-term vertical displacements depend on the same direction NNE-SSW (ChKB) as the GPS
displacements. Both geodetic techniques have revealed oscillating displacements, GPS horizontal, and levelling vertical, rather
than any long-term trends in the study period 1993–2007. The displacements exhibited significant spatial and temporal relation
to tectonic activity (earthquake swarms) including their coincidence with the seismologically determined sense of motion along
the fault plane during earthquakes. 相似文献
4.
In 1988 two large earthquakes with magnitude of Ms 7.6 and Ms 7.2 occurred in Lancang-Genma area, Southwest China. This paper discusses the determination of the spatial distribution of fault slip caused by the earthquakes using geodetic surveys. The prior information obtained from geological surveys and seismological investigations was used to determine the geometry of the fault plane and the average fault slip. The smooth constraints on the fault slips have been described by a normal distribution with hyperparameters, which are incorporated in the inversion analysis with a Bayesian model. Akaike’s Bayesian Information Criterion (ABIC) is used to get the optimal values of hyperparameters. Once the hyperparameters are determined, the maximum likelihood method is employed to estimate the patterns of a fault slip. Based on the results of inverse analysis monitoring geodetic surveys can be properly designed and conducted to obtain crust deformations and predict potential earthquake sources. 相似文献
5.
青海东部地区新生代构造应力场探讨 总被引：2，自引：0，他引：2
利用地质、地震、测量及地貌资料确定了青海东部地区的新构造应力场的主应力方向,自新第三纪以来,该区地壳构造应力场相对稳定,可能是印度板块与欧亚板块相互作用的结果。 相似文献
6.
7.
Aswan Lake is the second largest man-made lake in the world. Its filling started 1964 and reached the maximum water level in 1978. An earthquake of magnitude 5.5 took place in 1981 along the most active fault near the lake (Kalabsha fault). This earthquake was follwed by a tremendous number of smaller events that continue till now.Seismicity and the underground water table around the lake are monitored continuously through a radio-telemetered network. A local geodetic network was established around parts of the active faults in the northwestern part of the High Dam Lake, for monitoring vertical and lateral movements. The Kalabsha local geodetic network (the first one) was established around an active part of the Kalabsha fault in 1983. Precise geodetic measurements have benn carried out twice a year since 1984.On the basis of the repeated geodetic measurements, seismicity of the area and geophysical as well as geological data, the present state of the geodynamical properties of the Kalabsha area is studied.Remarkable horizontal movements were detected; they are correlated with the seismicity of the area and are attributed to the differential loading by the lake. The Kalabsha fault is a right-lateral strike-slip motion on an E-W plane. The magnitude of the movements detected along the fault is variable for the different epochs of measurements and is correlated with both seismicity and water loading in the lake. 相似文献
8.
Raffaello Cioni Alessandro Sbrana Raffaella Vecci 《Journal of Volcanology and Geothermal Research》1992,51(1-2)
Three eruptive sequences of historical and recent activity of Vesuvius were carefully studied using scanning electron microscopy analysis techniques. The aim of this study was to characterize and distinguish deposits from magmatic and phreatomagmatic eruption phases.The sample pretreatment methods from previous authors were reviewed and a washing technique was checked, making it possible to obtain easily examinable samples without modifying their morphologic features.In each stratigraphic sequence the single samples were examined and their shape, type of vesiculation, and state of glass (edge modification by abrasion, alteration, presence of aggregates, secondary minerals and coatings) were analyzed and described.Characteristic features were recognized for deposits from different eruptive phases. Samples from phreatomagmatic deposits show the following features:
- • - glass alteration;
- • - presence of secondary minerals on the external surfaces or inside the cavities;
- • - coatings;
- • - presence of aggregate formed by juvenile and lithic particles.
9.
The comparison of seismological materials with the front boundary of the latest continental glaciation has shown that all
revealed really tectonic earthquakes occur exclusively in the occurrence area of a thick cover of this glaciation. The thickness
of the glacier at a distance of about 50–100 km from its front could have reached 1 km, and the amplitude of glacioisostatic
lowering and subsequent uplifts could have reached 0.3 km. The total amplitude of these movements, which were taking place
during 20 thousand years, is comparable with the amplitudes of vertical neotectonic movements, which were taking place during
35–37 million years and on the average were three orders of magnitude more intense than neotectonic movements. With such amplitudes
and speeds of vertical glacioisostatic movements, it looks quite plausible that the buried rupture zones could be revived
recently (including in Holocene) with block movements of crystalline basement with an amplitude of a few tens of meters. This
explains the localization of modern seismicity, which is a hazard to construction, within the occurrence domain of the latest
glacial shield. 相似文献
10.
E. Mantovani N. Cenni D. Albarello M. Viti D. Babbucci C. Tamburelli F. D'Onza 《Journal of Geodynamics》2001,31(5):190
The highly heterogeneous strain field indicated by neotectonic and seismological data in the central-eastern Mediterranean region has been reproduced, at a first approximation, by finite element modelling, of a 2D elastic thin plate. The zone considered is modelled as a mosaic of poorly deformable zones decoupled by highly deformable belts, simulating the major tectonic structures indicated by geological and geophysical evidence. The deformation of the model is obtained by imposing kinematic boundary conditions, representative of the motion of Africa and eastern Anatolia relative to Eurasia. Experiments carried out with different boundary conditions and model parameterisations have provided information on the sensitivity of the model and some insights into the geodynamic behavior of the study area. The deformation pattern of the central Mediterranean area is strongly conditioned by the mechanical properties assumed in the border zones between the Aegean and Adriatic systems. The match of the complex strain pattern observed in the western Anatolian–Aegean–Balkan zones is significantly favoured if high rigidity is assigned to the inner part of this structural system. A motion of Africa with respect to Eurasia compatible with an Eulerian pole located offshore Portugal best accounts for the observed strains in the central Mediterranean region. The match of the strongly heterogeneous strain field observed in the study area can hardly be achieved by simplified models not including major tectonic features and lateral heterogeneity of mechanical properties. The kinematic field resulting from the model configuration which best simulates the observed strain field presents some differences with respect to geodetic measurements in the Aegean–Western Anatolian area, where the computed velocities are systematically lower than the geodetic ones. It is suggested that the most plausible explanation of such differences is related to the fact that the present deformation pattern, inferred from geodetic data, may be different from the middle–long term one, inferred from seismological and geological data. 相似文献
11.
在四川鲜水河断裂带上的炉霍和道孚两地,分别于1973年和1981年发生了7.9级和6.9级地震,本文根据该断裂带上六处跨地震主破裂面和跨断层短水准、短基线场的多年形变测量资料,分析了断层活动特征与地震孕育和发生的关系,并对运用跨断层形变测最手段与地震预报作了粗浅的探讨. 相似文献
12.
1976年唐山发生了7.8级地震,相继又发生了两次大余震——滦县7.1级地震和宁河6.9级地震.地震发生在观测条件比较好的地区,水准测量和三角测量测得了地震的同震位移场.本研究采用原始水准测量数据,而不是采用根据水准数据处理的地面沉降图像,和三角测量数据反演了该地震序列的破裂分布.模型构建中考虑了滦县地震和宁河地震的断层形态和大小.结果表明,唐山地震主震断层有明显的右旋走滑性质,最大走向滑动错距>6 m,位于断层南段,北段的走滑分量明显小于南段.主震总地震矩达2.58×1020N·m,与地震波反演得到的地震矩的量级相当;滦县地震断层总体表现为左旋正断层,释放地震矩达4.95×1019N·m;宁河地震断层总体表现为右旋正断层,释放地震矩达3.94×1019N·m,比地震波反演的地震矩大一个量级.据此可以推测唐山地震的无震滑移主要发生在宁河地震断层的西部上,滑动性质以正断层为主.该结果对于唐山地震序列后的动力学演变过程及余震发生机理有一定参考. 相似文献
13.
The purpose of the geoscientific Observatory at Schiltach in the Black Forest in SW-Germany is to measure and monitor motions and deformations of the earth in a frequency band as broad as possible. The spectrum of geodynamic signal contains
- • - the short period waves (up to 40 Hz) of near earthquakes,
- • - the longer period body and surface waves from teleseismic events,
- • - the free oscillations of the earth excited by giant earthquakes,
- • - the earth tide deformations caused by the gravitational forces of the moon and the sun having periods of 12 h and longer,
- • - deformations of the earth in a wide period range from other sources (e.g. atmosphere).
14.
Estimation of the 2001 Kunlun earthquake fault slip from GPS coseismic data using Hori's inverse method 
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下载免费PDF全文 The Horios inverse method based on spectral decomposition was applied to estimate coseismic slip distribution on the rupture plane of the 14 November 2001 <i<M</i<<sub<S</sub<8.1 Kunlun earthquake based on GPS survey results. The inversion result shows that the six sliding models can be constrained by the coseismic GPS data. The established slips mainly concentrated along the eastern segment of the fault rupture, and the maximum magnitude is about 7 m. Slip on the eastern segment of the fault rupture represents as purely left-lateral strike-slip. Slip on the western segment of the seismic rupture represents as mainly dip-slip with the maximum dip-slip about 1 m. Total predicted scalar seismic moment is 5.196?×10<sup<20</sup<N·m. Our results constrained by geodetic data are consistent with seismological results. 相似文献
15.
Tadeusz Wyrzykowski 《Journal of Geodynamics》1987,8(2-4)
A new determination of recent vertical movements of the Earth's crust in Poland is described in this paper. It resulted from the joint adjustment of the network of repeated levelling in 7 countries of Eastern and Central Europe. The author presents the characteristics of the levelling data sets used (measurements made in 1953–1957 and 1974–1979), results of the repeated levelling, the method of determination of the recent crustal movements and of the preparation of the map at a scale of 1:2.500.000 presenting these movements for the area of the whole country. The results of the determination of the Earth's crustal movements are discussed, and causes of the prevailing appearance of sinking movements are suggested. Differences between the values of vertical movements of the Earth's crust obtained during various determinations are presented, as well as the maximum mean error of the difference between new and old determinations. The conformity of these determinations is assessed. 相似文献
16.
We show that geodetic data from the Bay Area Regional Deformation (BARD) network indicate asymmetric motion across the San Andreas fault in the San Francisco Bay Area (SFBA), resulting from a strong contrast in rigidity across the fault, as determined previously from seismological data. Assuming asymmetric motion across the fault, we determine the location and size of the maximum strain rate in the region. We find that, compared to the determination using a symmetric model of deformation, it is shifted eastward and its value increases from ～0.4 μstrain/yr to ～0.65 μstrain/yr. Such strain rate amplitudes are consistent with previous geodetic slip rate estimates. We confirm that the geological units located east of SAF are entrained by the motion of the Pacific Plate and that the San Andreas fault (SAF) is the real rheological limit between the Pacific and North-American Plates. The asymmetry of rheology constrained in this study implies the strain rate maximum in SFBA is likely located between SAF and the Hayward fault system. This also has implications for hazards in the northern SFBA, in particular on the Rodgers creek fault. 相似文献
17.
《地震研究进展（英文）》2023,3(1):100177
The long-term earthquake prediction from 2021 to 2030 is carried out by researching the active tectonic block boundary zones in the Chinese mainland. Based on the strong earthquake recurrence model, the cumulative probability of each target fault in the next 10 years is given by the recurrence period and elapsed time of each fault, which are adopted from relevant studies such as seismological geology, geodesy, and historical earthquake records. Based on the long-term predictions of large earthquakes throughout the world, this paper proposes a comprehensive judgment scheme based on the fault segments with the seismic gap, motion strongly locked, sparse small-moderate earthquakes, and apparent Coulomb stress increase. This paper presents a comprehensive analysis of the relative risk for strong earthquakes that may occur in the coming 10 years on the major faults in the active tectonic block boundary zones in the Chinese mainland. The present loading rate of each fault is first constrained by geodetic observations; the cumulative displacement of each fault is then estimated by the elapsed time since the most recent strong earthquake. 相似文献
18.
Jordi Giménez Maria J. Borque Antonio J. Gil Pedro Alfaro Antonio Estévez Emma Suriñach 《Studia Geophysica et Geodaetica》2009,53(1):81-98
The seismic activity of the Guardamar-Torrevieja zone (Eastern Betic Cordillera, SE Spain) can be associated with the Bajo
Segura fault zone, an E-W reverse blind fault with secondary NW-SE dextral faults. A high-precision levelling profile 30 kilometers
long was set up and levelled in 1997 to monitor the vertical displacement of this active fault zone. This profile runs parallel
to an older high-precision levelling line included in the Spanish first order levelling network measured by the Instituto
Geográfico Nacional (IGN) in two different campaigns (1934 and 1976). The 1997 line was relevelled in 2003 and 10 new benchmarks
were set up, both to increase benchmark density and to restore some of the 1997 benchmarks that had been destroyed. We have
used the 1976 IGN and the 2003 measurement to construct a recent vertical movements profile with a significant time difference
(27 years). This recent vertical movements profile shows that the vertical movements are very small, nearly equal to the error
bars, with a 0.2 mm/year rise in the town of Guardamar, and a 0.2 mm/year subsidence of the southern part of the profile (Punta
Prima) respect to the town of Torrevieja. These movements could be related to the activity of the Bajo Segura and the San
Miguel faults respectively. Using geological markers we have deduced uplift rates of 0.1 mm/year during the last 3 million
years. Therefore, these preliminary results indicate that geodetically (short-term deformation) determined uplift rates are
similar to those estimated from geological markers (long term deformation). 相似文献
19.
研究了直接用多期重复大地测量观测资料求剪切应变速率的相关平差方法,简单地讨论了判断计算结果中反映形变信息的可靠性的标准,并对相关平差法与一般方法计算结果的差别进行了比较。通过几个地区的实际计算,认为在地震工作中,为探测大范围的地壳水平运动,迫切需要大幅度提高目前的大地测量精度。 相似文献
20.
J. Mrlina A. H. Radwan R. M. Hassan S. M. Mahmoud A. A. Tealeb E. A. Issawy 《Journal of Geodynamics》2003,35(4-5):499-509
The Kalabsha region at the northwest side of Lake Aswan has been a subject of seismological and geodetic investigations since 1981, after the 5.5 M earthquake on 14 November. The subsequent seismic activity was related to the effect of water-level oscillations in the Lake. Geodetic measurements provided indications of regional stress and of the local character of vertical movements. As crustal dynamics represents a potential hazard with respect to the size of the lake, other techniques have been applied to the monitoring system. Repeated gravity test measurements were already made in the late 1980s and in 1994, but only in 1997 was a new epoch of long-term investigation initiated. The measured data showed sufficient accuracy of approx. 5 μGal. Already the first difference of the two campaigns of the years 1997 and 2000 showed a few important features. First of all, the temporal non-tidal changes of gravity exceed the level of confidence significantly. The changes were compared with older available geodetic data, and it was concluded, that the gravity changes were not related directly to the vertical movements of the surface. On the contrary, a water loading effect may be expected on the eastern side of the network, especially in the Kalabsha local net. The development of the stress field is considered to be the main source of observed gravity changes. In both the Kalabsha and Seiyal nets the changes differ according to the relative positions of the particular measuring points with respect to the faults. 相似文献