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1.
Using a set of synthetic P‐ and S‐wave onsets, computed in a 1D medium model from sources that mimic a distribution of microseismic events induced by hydrofrac treatment to a monitoring geophone array(s), we test the possibility to invert back jointly the model and events location. We use the Neighbourhood algorithm for data inversion to account for non‐linear effects of velocity model and grid search for event location. The velocity model used is composed of homogeneous layers, derived from sonic logging. Results for the case of one and two monitoring wells are compared. These results show that the velocity model can be obtained in the case of two monitoring wells, if they have optimal relative position. The use of one monitoring well fails due to the trade‐off between the velocity model and event locations. 相似文献
2.
O.?NovotnyEmail author J.?Jansky V.?Plicka H.?Lyon-Caen 《Studia Geophysica et Geodaetica》2008,52(1):123-131
The western part of the Gulf of Corinth attracts attention due to its seismically active fault system and considerable seismic
hazard. Detailed studies of the seismic activity of the region have been carried out especially as part of the so-called Corinth
Rift Laboratory (CRL) Project. For standard earthquake locations, the CRL uses the HYPO algorithm and a special structural
model that is composed of homogeneous layers (Rigo et al., 1996). This model was derived from a passive seismic experiment
in a broader area around the western part of the Gulf. A significant part of the seismic activity is concentrated close to
the town of Aigion, which was damaged by a strong earthquake in 1995. A sequence of smaller earthquakes occurred to the south
of this town in the year 2001. In the present paper, we have used this sequence to derive an improved structural model for
the region in the vicinity of the town of Aigion. This new model is based on the minimization of travel-time residuals. In
particular, we used arrival times from a subset of 88 events recorded by at least 5 stations of the southern part of the CRL
network, had magnitudes of over 2.3, and were recorded at the nearest station (station code AIO). A variant of the method
of conjugate gradients has been used for this purpose. In comparison with the model derived by Rigo et al. (1996), the new
model is characterized by a higher νP/νS velocity ratio and by higher velocities to a depth of about 7 km. The new model was derived with the aim to get more accurate
locations of future events in the vicinity of the town of Aigion. 相似文献
3.
基于P波和S波的谱震级特征对汶川地震进行了定量研究,可以看出P波和S波的最大谱震级出现在不同的周期上。对这一现象的构造物理意义进行了讨论,推测相对于P波而言,地震发生期间辐射的S波能量来自异常大的震源体积。选择部分全球地震的谱特征为背景,对汶川地震的体波谱震级特征进行了分析,结论是汶川地震的特征与其所处的周边环境是一致的。 相似文献
4.
Jaromir Demek 《Geoforum》1978,9(1):29-34
The main object of study of geography is the landscape sphere that includes the surface of our planet. The landscape sphere differs from the other geospheres by displaying unusual complexity and consists of structured sets of components which exhibit discernible relationships with one another and operate as a system. The functioning of the landscape sphere is conditioned by the interrelationships of components, as well as by the transfer of mass and energy from one part of the landscape sphere to another in the form of streams of mobile elements. The author is using the name geosystem for determination of this system of planetary dimensions. The landscape sphere may be further divided into subsystems exhibiting characteristic features which facilitate their identification and delimitation.Territorial differentiation of the landscape sphere, on the basis of the law of zonality, produces horizontal, latitudinal and vertical zones called by author geoms. These geoms may be further subdivided into geosystems of smaller dimensions called geochoras. The basic geochora is the landscape. In most landscapes the key elements in these geosystems are controlled by Man and so-called cultural landscapes are developed. The cultural landscapes are parts of the landscape sphere within which natural and socioeconomic geosystems co-exist. The author further distinguishes cultured, disturbed and devastated landscapes. The study of cultural landscape is amongst the most difficult fields of investigation, but such studies are of great significance in terms of predicting future environmental developments. 相似文献
5.
Ocean Dynamics - A three-dimensional, regional coupled ice-ocean model based on the open-source Community Earth System Model has been developed and implemented for the Baltic Sea. The model... 相似文献
6.
Wolfgang Seifert Dieter Rhede Hans-Jürgen Förster Rudolf Naumann Rainer Thomas Jaromir Ulrych 《Mineralogy and Petrology》2014,108(5):645-662
Macrocrysts of corundum, ilmenite, and spinel-group minerals from alluvial deposits of the Eger Rift were studied for composition, texture, and mineral inclusions. All macrocrysts show usually magmatic corrosion textures indicating disequilibrium with the transporting alkali-basalt magma. Corundum grains, exclusively sapphires, were classified by trace-element signatures as magmatic and metamorphic types. Some sapphire grains show erratic compositions that may have resulted from a metasomatic overprint. The inclusion inventory of magmatic corundum suggests crystallization from a differentiated alkaline silicate melt. Corundum itself was never observed as an inclusion mineral. Magnesium- and Fe3+-rich ilmenite, described as typical mantle-derived species, is the dominant heavy mineral in almost all alluvial deposits of the Eger Rift. Most discrete macrocrysts are similar in appearance and composition to kimberlite- and basanite-related ilmenite. Ilmenite included in alluvial corundum and zircon grains differ from the bulk of discrete ilmenite grains by larger concentrations of Nb and Mn. The mantle origin of the Mg–Fe3+-rich ilmenite is confirmed by compositional and thermo-barometric comparison with ilmenite from clinoproxenitic and hornblenditic xenoliths, which probably originated in the Moho region. The Fe–Ti two-oxide geothermometry and oxygen-barometry of coexisting ilmenite–magnetite pairs yield equilibrium temperatures between 900 and 1,080 °C and oxygen fugacities log10fO2 between ?0.1 and 1.1 (relative to the NNO buffer), which indicate that the upper mantle as well as the mantle/crust transition zone below the rift is at least partially oxidized. The ilmenite macrocrysts were transported from the source region to the surface by explosive alkali-basalt magmas, as implied by the presence of basaltic-pipe breccias in close vicinity to some placer deposits. 相似文献
7.
The western part of the Bohemian Massif (West Bohemia/Vogtland region) is characteristic in the relatively frequent recurrence
of intraplate earthquake swarms and in other manifestations of past-to-recent geodynamic activity. In this study we derived
1D anisotropic qP-wave model of the upper crust in the seismogenic West Bohemia/Vogtland region by means of joint inversion
of two independent data sets - travel times from controlled shots and arrival times from local earthquakes extracted from
the WEBNET seismograms. We derived also simple 1-D P-wave and S-wave isotropic models. Reasons for deriving these models were:
(a) only simplified crustal velocity models, homogeneous half-space or 1D isotropic layered models of this region, have been
derived up to now and (b) a significant effective anisotropy of the upper crust in the region which was indicated recently
by S-wave splitting. Both our anisotropic qP-wave and isotropic P-and S-wave velocity models are constrained by four layers
with the constant velocity gradient. Weak anisotropy for P-waves is assumed. The isotropic model is represented by 9 parameters
and the anisotropic one is represented by 24 parameters. A new robust and effective optimization algorithm - isometric algorithm
- was used for the joint inversion. A two-step inversion algorithm was used. During the first step the isotropic P- and S-wave
velocity model was derived. In the second step, it was used as a background model and the parameters of anisotropy were sought.
Our 1D models are adequate for the upper crust in the West Bohemia/Vogtland swarm region up to a depth of 15 km. The qP-wave
velocity model shows 5% anisotropy, the minimum velocity in the horizontal direction corresponds to an azimuth of 170°. The
isotropic model indicates the VP/VS ratio variation with depth. The difference between the hypocentre locations based on the derived isotropic and anisotropic
models was found to be several hundreds of meters. 相似文献
8.
在地球内部的大部分区域地震体波的传播是线弹性过程,仅在震源周围区域由于波的辐射和传播效应可能导致非线性。本研究主要涉及对非线性过程占优势区域的尺度估计。 相似文献
9.
10.
The contribution discusses the problems with modelling design floods for water structures. The statistical extrapolations of observed flood series of, for example, 80 years “only” to the annual exceedance probability AEP = 0.01 is difficult due to the large variability in extreme values. For large dams, however, the AEP = 0.001 or 0.0001 is required. Most of the uncertainties in hydrological modelling are epistemic (uncertainties in model structure, model parameters, inputs, calibration data, and in measurements) and moreover some measurements can be disinformative. With powerful computers, it is now possible to produce very long series (100 to100,000 years in hourly time step) using precipitation and temperatures computed with a weather model. Within the framework of the Generalised Likelihood Uncertainty Estimation (GLUE) many (thousands) of such continuous simulations are produced and compared to the observed historical data. According to Keith Beven's Manifesto for the equifinality thesis the differences between modelled and observed values should not be larger than some limits of acceptability based on what is known about errors in the input and output observations used for model evaluation (e.g., for flow the current metering data are used). The unacceptable realisations are rejected. We have been working with the frequency version of TOPMODEL in various versions according to the unique characteristics of each catchment. Design hydrographs for water structures are then extracted from the acceptable realisations. The continuous simulation with uncertainty estimation seems nowadays the most promising method of computing design hydrographs for important water structures, even if issues associated with epistemic uncertainty of model assumptions remain. 相似文献