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101.
Benedikt Halldorsson Ragnar Sigbjornsson Johannes Schweitzer 《Journal of Seismology》2009,13(1):173-178
A small-aperture, strong-motion array, the ICEARRAY, has been deployed in South Iceland, a region with a history of destructive
earthquakes, some exceeding magnitude 7. The array’s purpose is: (1) monitoring future significant events in the region, (2)
quantifying spatial variability of strong-motion over short distances and (3) shedding light on earthquake source processes.
The number of array stations and their arrangement were based on an optimisation of the shape of the corresponding array transfer
function (ATF). The optimal ICEARRAY configuration comprises 14 stations, has an aperture of ~1.9 km and a minimum interelement
distance of ~50 m and possesses a near-azimuthally independent ATF with a sharp main lobe, negligible sidelobes and a wavenumber
range of 1.5–24 rad/km. Accordingly, the ICEARRAY has the intended capabilities of capturing seismic waves in the frequency
range of 1–20 Hz, which is of main interest to earthquake engineering and engineering seismology applications. 相似文献
102.
The determination of seismic amplitude amplification is a fundamental contribution to seismic hazard assessment. While often
only high-frequency amplitude variations (>1 Hz) are taken into account, we analyse broadband waveforms from 0.14 to 8.6 Hz
using a temporary network of 32 stations in and around the earthquake-prone city of Bucharest. Spectral amplitudes are calculated
with an adaptive multiple-taper approach. Across our network (aperture 25 km × 25 km), we find a systematic northwest/southeast-oriented
structural influence on teleseismic P-wave amplitudes from 0.14 to 0.86 Hz that can be explained by constructive interference
in the dipping Cenozoic sedimentary layers. For higher frequencies (1.4–8.75 Hz), more local site effects prevail and can
be correlated partly among neighbouring stations. The transition between systematic and localised amplitude variations occurs
at about 1 Hz. 相似文献
103.
This study focuses on the southeast Capital area of North China (38.5–39.85° N, 115.5–118.5° E). Shear-wave splitting parameters
at 20 seismic stations are obtained by a systematic analysis method applied to data recorded by the Capital Area Seismograph
Network (CASN) between the years 2002 and 2005. Although some differences in the results are observed, the average fast-wave
polarization is N88.2° W ± 40.7° and the average normalized slow wave time delay is 3.55 ± 2.93 ms/km. The average polarization
is consistent with the regional maximum horizontal compressive stress and also with the maximum principal strain derived from
global positioning system measurements in North China. In spite of the uneven distribution of faults around the array stations
that likely introduce some amount of scatter in the shear-wave splitting measurements, site-dependent polarizations of fast
shear wave are clearly observed: in the northern half of the study area, the polarizations at CASN stations show E–W direction,
whereas in the southern half the polarizations exhibit a variety of possible azimuths, thus suggesting dissimilar stress field
and tectonic frame in both areas. Comparing the splitting results with those previously obtained in the northwest part of
the region, we find a difference in polarization of about 20° between the southeast and northwest parts of the Capital area;
also, in the southeast Capital area the average time delay is smaller than in the northwest Capital area, thus making clear
that the magnitude of crustal seismic anisotropy is not the same in the two zones. Being the shear-wave splitting polarizations
in the southeast Capital area, which lies on the basin, clearly different from the observed polarizations in the northwest
Capital area, where uplifts and basin converge, it is quite evident that the shear-wave splitting results are consequence
of the tectonics and stress field affecting the two regions. 相似文献
104.
Jean F. Schneider 《Journal of Seismology》2009,13(3):387-398
The Pakistan 2005 earthquake, of magnitude 7.6, caused severe damage on landscape and infrastructure, in addition to numerous
casualties. The event reactivated Hattian Slide, creating a rock avalanche in a location where earlier mass movements had
happened already, as indicated by satellite imagery and ground investigation. The slide originated on Dana Hill, in the upper
catchment area of Hattian on Karli Stream, a tributary of Jhelum River, Pakistan, and buried the hamlet Dandbeh and several
farms nearby. A natural dam accumulated, impounding two lakes, the larger one threatening parts of downstream Hattian Village
with flooding. An access road and artificial spillways needed to be constructed in very short time to minimize the flooding
risk. As shown by this example, when pointing out the risk of large-scale damage to population and infrastructure by way of
hazard indication maps of seismically active regions, and preparing for alleviation of that risk, it is advisable to consider
the complete Holocene history of the slopes involved. 相似文献
105.
Seismic response of single-column bent on pile: evidence of beneficial role of pile and soil inelasticity 总被引:2,自引:2,他引:0
While seismic codes do not allow plastic deformation of piles, the Kobe earthquake has shown that limited structural yielding
and cracking of piles may not be always detrimental. As a first attempt to investigate the consequences of pile yielding in
the response of a pile-column supported bridge structure, this paper explores the soil–pile-bridge pier interaction to seismic
loading, with emphasis on structural nonlinearity. The pile–soil interaction is modeled through distributed nonlinear Winkler-type
springs and dashpots. Numerical analysis is performed with a constitutive model (Gerolymos and Gazetas 2005a, Soils Found
45(3):147–159, Gerolymos and Gazetas 2005b, Soils Found 45(4):119–132, Gerolymos and Gazetas 2006a, Soil Dyn Earthq Eng 26(5):363–376)
materialized in the OpenSees finite element code (Mazzoni et al. 2005, OpenSees command language manual, p 375) which can
simulate: the nonlinear behaviour of both pile and soil; the possible separation and gapping between pile and soil; radiation
damping; loss of stiffness and strength in pile and soil. The model is applied to the analysis of pile-column supported bridge
structures, focusing on the influence of soil compliance, intensity of seismic excitation, pile diameter, above-ground height
of the pile, and above or below ground development of plastic hinge, on key performance measures of the pier as is: the displacement
(global) and curvature (local) ductility demands and the maximum drift ratio. It is shown that kinematic expressions for performance
measure parameters may lead to erroneous results when soil-structure interaction is considered. 相似文献
106.
107.
108.
2008年3月21日新疆于田7.3级地震发震构造与震前地震活动特征研究 总被引:6,自引:0,他引:6
2008年3月21日新疆于田发生7.3级地震,打破了中国大陆6年多的7级地震平静,成为我国近期较为显著的一次地震事件.综合分析MS≥4.0余震分布、震区断裂性质以及等震线长轴方向等资料,认为郭扎错断裂是这次地震的发震构造;据Harvard震源机制解分析,这次地震是在近NS向力的作用下,郭扎错断裂发生略带走滑分量的拉张破裂所致.通过地震前震区附近地震活动特征分析发现,于田地震发生在1996年以来新疆南部及邻区7级地震有序分布的空段;震前震区附近有4级地震空区形成,空区持续91个月后发生了2006年9月12日皮山5.8级"信号震",其后1.5年发生于田7.3级地震. 相似文献
109.
110.
科里奥利力对断层作用的统计研究 总被引:2,自引:1,他引:1
首先给出了分解到已知断层面法向和切向上的断层错动科里奥利应力(简称为科里奥利法向应力和切向应力)表达式,然后从哈佛大学矩心矩张量目录中选取主余震资料进行分析,按断层分类研究了科里奥利法向应力和主震震级与其最大余震震级差及主震地震矩与余震地震矩总和之差的折合矩震级间的关系.研究结果显示:地震断层错动过程中虽然产生了使断层两盘相互拉离(或挤压)的科里奥利法向应力,它降低(或增加)了断层错动时断层面上的摩擦阻力,但是应力量值太小(科里奥利法向应力估计最大不到0.1MPa,即不到一个大气压),不足以对断层错动及主震能量释放产生影响,从而影响余震的最大震级和总体水平. 相似文献