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61.
62.
Manfred Baer Nicolas Deichmann Jochen Braunmiller John Clinton Stephan Husen Donat Fäh Domenico Giardini Philipp Kästli Urs Kradolfer Stefan Wiemer 《Swiss Journal of Geoscience》2007,100(3):517-528
This report of the Swiss Seismological Service summarizes the seismic activity in Switzerland and surrounding regions during
2006. During this period, 572 earthquakes and 91 quarry blasts were detected and located in the region under consideration.
Of these earthquakes, two occurred in conjunction with the construction of the new Gotthard railway tunnel and 165 were induced
artificially by the stimulation of a proposed geothermal reservoir beneath the city of Basel. With 20 events with M
L
≥ 2.5, five of which were artificially induced, the seismic activity in the year 2006 was far below the average over the
previous 31 years. Nevertheless, six events were felt by the public, most prominently the strongest of the induced Basel events
(M
L
3.4), which caused some non-structural building damage. Noteworthy are also the two earthquakes near Cortaillod (M
L
3.2), on the shore of Lake Neuchatel, and in Val Mora (M
L
3.5), between the Engadin and Val Müstair, as well as the 42 aftershocks of the M
L
4.9 Vallorcine earthquake, between Martigny and Chamonix, of September 2005.
Editorial handling: Stefan Bucher 相似文献
63.
A structural model for the seismicity of the Arudy (1980) epicentral area (Western Pyrenees, France)
Noalwenn Dubos-Sallée Bertrand Nivière Pierre Lacan Yves Hervouët 《Geophysical Journal International》2007,171(1):259-270
The Western Pyrenees presents a diffuse and moderate ( M ≤ 5.7) instrumental seismicity. It nevertheless historically suffered from strong earthquakes (I = IX MSK). The seismic sources of these events are not yet clearly identified. We focus on the Arudy (1980) epicentral area ( M = 5.1) and propose here the reactivation of early Cretaceous normal faults of the Iberian margin as a potential source. The late Cretaceous inversion of this basin, first in a left-lateral strike-slip mode and then in a more frontal convergence, resulted in a pop-up geometry. This flower structure attests of the presence of a deep crustal discontinuity.
The present-day geodynamic arrangement suggests that this accident is reactivated in a right lateral mode. This reactivation leads to a strain partitioning between the deep discontinuity that accommodates the lateral component of the motion and shallow thrusts, rooted on this discontinuity. These thrusts accommodate the shortening component of the strain. The distribution of the instrumental seismicity fits well the structural model of the Arudy basin. Whatever the compressive regional context, the structural behaviour of the system explains too the extensive stress tensor determined for the Arudy crisis if we interpret it in terms of strain ellipsoid. Indeed numerical modelling has shown that this concomitant activity of strike-slip and thrust faulting results in an extensive component that can rise 50 per cent of the finite strain.
We identify too a 25–30 km long potential seismic source for the Arudy area. The size of the structure and its potential reactivation in a strike-slip mode suggest that a maximum earthquake magnitude of ∼6.5 could be expected. The extrapolation of this model at the scale of the Western Pyrenees allows to propose other potential sources for major regional historical earthquakes. 相似文献
The present-day geodynamic arrangement suggests that this accident is reactivated in a right lateral mode. This reactivation leads to a strain partitioning between the deep discontinuity that accommodates the lateral component of the motion and shallow thrusts, rooted on this discontinuity. These thrusts accommodate the shortening component of the strain. The distribution of the instrumental seismicity fits well the structural model of the Arudy basin. Whatever the compressive regional context, the structural behaviour of the system explains too the extensive stress tensor determined for the Arudy crisis if we interpret it in terms of strain ellipsoid. Indeed numerical modelling has shown that this concomitant activity of strike-slip and thrust faulting results in an extensive component that can rise 50 per cent of the finite strain.
We identify too a 25–30 km long potential seismic source for the Arudy area. The size of the structure and its potential reactivation in a strike-slip mode suggest that a maximum earthquake magnitude of ∼6.5 could be expected. The extrapolation of this model at the scale of the Western Pyrenees allows to propose other potential sources for major regional historical earthquakes. 相似文献
64.
65.
On the basis of our predecessors' research,we study the distribution and the space-time evolution characteristics of the seismic apparent strain field in Yunnan since the 1970's using the seismic data of Yunnan and its surrounding areas.The result shows that there is a rather strong corresponding relationship between the anomaly region of seismic apparent strain and strong earthquakes.In the nine earthquakes studied,anomaly areas of seismic apparent strain had appeared before eight earthquakes,including five occurring in the anomaly region and three on the edge.Finally,the investigative result is demonstrated primarily. 相似文献
66.
67.
Prantik Mandal R. K. Chadha N. Kumar I. P. Raju C. Satyamurty 《Pure and Applied Geophysics》2007,164(10):1963-1983
During the last six years, National Geophysical Research Institute, Hyderabad has established a semi-permanent seismological
network of 5–8 broadband seismographs and 10–20 accelerographs in the Kachchh seismic zone, Gujarat with a prime objective
to monitor the continued aftershock activity of the 2001 Mw 7.7 Bhuj mainshock. The reliable and accurate broadband data for the 8 October Mw 7.6 2005 Kashmir earthquake and its aftershocks from this network as well as Hyderabad Geoscope station enabled us to estimate
the group velocity dispersion characteristics and one-dimensional regional shear velocity structure of the Peninsular India.
Firstly, we measure Rayleigh-and Love-wave group velocity dispersion curves in the period range of 8 to 35 sec and invert
these curves to estimate the crustal and upper mantle structure below the western part of Peninsular India. Our best model
suggests a two-layered crust: The upper crust is 13.8 km thick with a shear velocity (Vs) of 3.2 km/s; the corresponding values
for the lower crust are 24.9 km and 3.7 km/sec. The shear velocity for the upper mantle is found to be 4.65 km/sec. Based
on this structure, we perform a moment tensor (MT) inversion of the bandpass (0.05–0.02 Hz) filtered seismograms of the Kashmir
earthquake. The best fit is obtained for a source located at a depth of 30 km, with a seismic moment, Mo, of 1.6 × 1027 dyne-cm, and a focal mechanism with strike 19.5°, dip 42°, and rake 167°. The long-period magnitude (MA ~ Mw) of this earthquake is estimated to be 7.31. An analysis of well-developed sPn and sSn regional crustal phases from the bandpassed
(0.02–0.25 Hz) seismograms of this earthquake at four stations in Kachchh suggests a focal depth of 30.8 km. 相似文献
68.
A statistical analysis of the peak acceleration demands for nonstructural components (NSCs) supported on a variety of stiff and flexible inelastic regular moment‐resisting frame structures with periods from 0.3 to 3.0 s exposed to 40 far‐field ground motions is presented. Peak component acceleration (PCA) demands were quantified based on the floor response spectrum (FRS) method without considering dynamic interaction effects. This study evaluated the main factors that influence the amplification or decrease of FRS values caused by inelasticity in the primary structure in three distinct spectral regions namely long‐period, fundamental‐period, and short‐period region. The amplification or decrease of peak elastic acceleration demands depends on the location of the NSC in the supporting structure, periods of the component and building, damping ratio of the component, and level of inelasticity of the supporting structure. While FRS values at the initial modal periods of the supporting structure are reduced due to inelastic action in the primary structure, the region between the modal periods experiences an increase in PCA demands. A parameter denoted as acceleration response modification factor (Racc) was proposed to quantify this reduction/increase in PCA demands. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
69.
Fault network of the Upper Silesian Coal Basin (USCB) is built of sets of strike-slip, oblique-slip and dip-slip faults. It is a typical product of force couple which acts evenly with the parallel of latitude, causing horizontal and anti-clockwise movement of rock-mass. Earlier research of focal mechanisms of mine tremors, using a standard fault plane solution, has shown that some events are related to tectonic directions in main structural units of the USCB. An attempt was undertaken to analyze the records of mine tremors from the period 1992–1994 in the selected coal fields. The digital records of about 200 mine tremors with energy larger than 1×104 J (M
L
>1.23) were analyzed with SMT software for seismic moment tensor inversion. The decomposition of seismic moment tensor of mine tremors was segmented into isotropic (I) part, compensated linear vector dipole (CLVD) part and double-couple (DC) part. The DC part is prevalent (up to 70%) in the majority of quakes from the central region of the USCB. A group of mine tremors with large I element (up to 50%) can also be observed. The spatial orientation of the fault and auxiliary planes were obtained from the computations for the seismic moment DC part. Study of the DC part of the seismic moment tensor made it possible for us to separate the group of events which might be acknowledged to have their origin in unstable energy release on surfaces of faults forming a regional structural pattern. The possible influence of the Cainozoic tectonic history of the USCB on the recent shape of stress field is discussed. 相似文献
70.
Jiangchuan Ni Yuntai Chen Ming Wang Mingxi Wu Jiayu Zhou Peide Wang Francis T. Wu 《地震学报(英文版)》1992,5(3):459-467
Based on the three component accelerograms, recorded at near-field distance by a temporary seismic network consisting of digital
cassette tape recording accelerographs, the focal mechanisms of three aftershocks of the April 18, 1985, Luquan, Yunnan Province,
China, earthquake ofM
S=6.1, are calculated using seismic moment tensor inversion technique. The phases of direct P, S and converted SP waves in
the displacement seismograms, produced by twice integrations of the observed accelerograms, are identified via forward calculation
using Green’s functions for homogeneous semi-infinite elastic medium, and used in the inversion. The results of inversion
show that a better fit of synthetic to the observed seismograms of direct as well as converted phases can be achieved if appropriate
weighting functions are used in solving the over definite linear equations. While these aftershocks are of different magnitudes
(M
L=4.8, 3.2 and 3.5, respectively) and hypocentral locations, their focal mechanisms are very similar and consistent with that
of the main shock. This feature demonstrates the intrinsic correlation between the occurrence of aftershocks and the seismogenic
fault of main shock. Our experimentations show that using the near field accelerogram obtained from the digital seismic network
with appropriate azimuthal coverage on the focal sphere, with the aid of even simple medium model, not only the shear dislocation
source, but also the isotropic part and CLVD (compensated linear vector dipole) can be retrieved by the technique of moment
tensor inversion.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 412–419, 1991.
This work is supported by the Chinese Joint Seismological Sciences Foundation and the Western Yunnan Earthquake Prediction
Test Site (WYEPTS), State Seismological Bureau. 相似文献