Expressions are obtained for the ray-theoretical spectral amplitudes of body waves induced by a shear dislocation of arbitrary orientation and depth situated in a radially heterogeneous model of the earth. Account is taken of the azimuthal and colatitudinal radiation patterns of the source, the geometrical spreading, and the reflections and refractions at the free surface and at the mantle-core boundary.In this work spectral amplitudes are calculated for PKP, PKS, SKP and SKS. The results are presented in the form of tables for a source of strength U0dS = 1015 cm3, where U0 is the amount of the dislocation and dS is the fault area. Given the slip and dip angles of the source, the amplitudes of the four core phases can be obtained from these tables for all azimuths, for most of the epicentral distances at which a particular phase is observable, and for all the fourteen focal depths included in the Jeffreys-Bullen tables. It is found that the depth of the source has a strong effect on the amplitudes of the body-wave signals. 相似文献
Expressions are obtained for the ray-theoretical spectral amplitudes of body waves induced by a shear dislocation of arbitrary orientation and depth situated in a radially heterogeneous model of the earth. Account is taken of the azimuthal and colatitudinal radiation patterns of the source, the geometrical spreading, and the reflections and refractions at the free surface and at the mantle-core boundary.In this work spectral amplitudes are calculated for P, SH, SV, PP, PPP, PS, PSS, SP, SPP, SSH, SSSH, SSV, and SSSV. The results are presented in the form of tables for a source of strength U0dS = 1015cm3, where U0 is the amount of the dislocation and dS is the fault area. Given the slip and dip angles of the source, the amplitudes of these surface reflections and direct phases can be obtained from these tables for all azimuths, for most of the epicentral distances at which a particular phase is observable, and for all the fourteen focal depths included in the Jeffreys-Bullen tables. It is found that the depth of the source has a strong effect on the amplitudes of the body wave signals. 相似文献
This paper is a second follow-up discussion concerning the role, economic viability and operational characteristics of the Negev Continental Bridge in the fluid geo-political atmosphere of the Middle East. The two previous papers (Geoforum8, 29–32 and 311–318) discussed the viability of the Israeli Continental Bridge as an alternative to the Suez Canal. Now, two years after the Canal was re-opened for use by Israeli vessels, the annual amount of cargo movement across the Israeli land bridge is still growing, although it is less economical than the Suez Canal. It is thus suggested that there is a need to view the continental bridge as one part of a chain in an intermodal transport system. 相似文献
We present a model for earthquake failure at intermediate scales (space: 100 m–100 km, time: 100 m/vshear- 1000’s of years). The model consists of a segmented strike–slip fault embedded in a 3-D elastic solid as in the framework of Ben-Zion and Rice (1993). The model dynamics is governed by realistic boundary conditions consisting of constant velocity motion of the regions around the fault, static/kinetic friction laws with possible gradual healing, and stress transfer based on the solution of Chinnery (1963) for static dislocations in an elastic half-space. As a new ingredient, we approximate the dynamic rupture on a continuous time scale using a finite stress propagation velocity (quasi–dynamic model) instead of instantaneous stress transfer (quasi–static model). We compare the quasi–dynamic model with the quasi–static version and its mean field approximation, and discuss the conditions for the occurrence of frequency-size statistics of the Gutenberg–Richter type, the characteristic earthquake type, and the possibility of a spontaneous mode switching from one distribution to the other. We find that the ability of the system to undergo a spontaneous mode switching depends on the range of stress transfer interaction, the cell size, and the level of strength heterogeneities. We also introduce time-dependent log (t) healing and show that the results can be interpreted in the phase diagram framework. To have a flexible computational environment, we have implemented the model in a modular C++ class library. 相似文献
A unified computational scheme is presented for sequential least-squares processing ofGPS dual-band carrier-beat-phase observations in network-mode positioning with orbit relaxation, and in orbit determination applications.
This scheme is applicable to any spatial and temporal distribution of stations and satellites during a particularGPS experiment. Full covariance matrices can be specified for carrier-beat-phases and for weighted constraints on the ionosphere
in order to improve phase ambiguity resolution. Physically meaningful choices for these covariance matrices are developed. 相似文献
By interferometric analysis ofGPS phase observations made at Owens Valley, Mojave, and Mammoth Lakes, California, we determined the coordinate components of the71–245–313 km triangle of baselines connecting these sites. A separate determination was made on each of four days, April 1–4, 1985. The satellite ephemerides used in these determinations had been derived from observations on other baselines. Therms scatters of the four daily determinations of baseline vector components about their respective means ranged from a minimum of6 mm for the north component of the71-km baseline to a maximum of34 mm for the vertical component of the245-km baseline. To test accuracy, we compared the mean of ourGPS determinations of the245-km baseline between Owens Valley and Mojave with independent determinations by others using very-long-baseline interferometry(VLBI) and satellite laser ranging(SLR). TheGPS-VLBI difference was within 2 parts in107 for every vector component. TheGPS-SLR difference was within6 parts in108 in the horizontal coordinates, but83 mm in height. 相似文献
We use modern and novel techniques to study the problems associated with detection and analysis of multitudinous seismic events, which form the background for isolated great earthquakes. This new approach involves multivariate analysis of low and large magnitude events recorded in space over a couple of centuries in time. We propose here the deployment of the clustering scheme both for extracting small local structures and large-scale trends in synthetic data obtained from four numerically simulated models with: uniform properties (U), a Parkfield-type asperity (A), fractal brittle properties (F), and multi-size-heterogeneity fault zone (M). The mutual nearest neighbor (mnn) clustering scheme allows for extraction of multi-resolutional seismic anomalies in both the spatio-temporal and multi-dimensional feature space. We demonstrate that the large earthquakes are correlated with a certain pathway of smaller events. Visualization of the anomalies by using a recently introduced visualization package Amira reveals clearly the spatio-temporal relationships between clusters of small, medium and large earthquakes, indicating significant stress relaxation across the entire fault region. We demonstrate that this mnn scheme can extract distinct clusters of the smallest events, which precede and follow a singularly large magnitude earthquake. These clusters form larger spatio-temporal structures comprising a series of large earthquakes. The link between the large and medium magnitude events is not so clearly understood. Short-ranged correlations are dominated by strong spatio-temporal anomalies, thus reflecting the global seismic properties of the entire fault zone.Electronic Supplementary Material Supplementary material is available for this article if you access the article at . A link in the frame on the left on that page takes you directly to the supplementary material. 相似文献
A typical fresh–saline water interface in a coastal aquifer is characterized by saline-water circulation below the interface and freshwater flow above. Both flows are perpendicular to the shoreline. The flow pattern near two separated saline lakes is more complicated. For example, in the Middle East, the Dead Sea northern basin and the evaporation ponds of the Dead Sea Works are adjacent to each other but separated. The northern basin level is dropping by 1.1 m/year and the evaporation ponds’ levels are increasing by 0.2 m/year. The fresh–saline water interface in such situation is numerically simulated. Streamlines parallel or semiparallel to the shoreline are significant. Moreover, the fresh–saline water interface intrudes landward adjacent to the higher saline lake and is pushed lakeward adjacent to the lower saline lake. The simulation results support field observations showing that the interface migrates vertically at a faster rate relative to the changes in the water table and the lake levels.