排序方式： 共有35条查询结果，搜索用时 15 毫秒
1.
通过对北京遥测地震台网近年来记录到的北京及邻区地震的震中分布,地震活动频度及能量释放强度的分析,得到本区地震活动在时间分布上具有“聚堆性”。在年发震频度,地震强度和能释放方面均具有双峰值特征,并且具有较好的一致性和同步性,在空间分布上具有条带特征,且形成北东～南西和北西～南东的两条相互交汇的条带。又通过统计分析得到本区发震概率最大的时间段是每年的１０月前后,而地震主要发生在北西～南东带上。 相似文献
2.
By deploying a 30 3-component digital seismic array in the Messiniakos gulf and the surrounding region, we recorded for a period of 45 days the microseismic activity. With a minimum of six records per event, we located 1121 earthquakes corresponding to an average of 20 events per day. For the hypocenter location we used a local velocity model adopted to two controlled source seismic experiments. Within the array, traveltime residuals were within ± 0.2 s and the epicentral accuracy in the order of ± 2 km, while the hypocentral one is twice this value. Correlation of the seismicity with the tectonic elements indicated that most of the NW-SE oriented faults are active with strike-slip movement along this orientation and extension perpendicular to it. The neogene basins of Messini, Meligalas and Megalopolis are seismically very active and their eastern flanks are delineated by higher seismic activity than their western ones. This indicates that the basins are asymmetric with master faults defining their eastern-northeastern flanks. This hypothesis is supported by the asymmetric structure mapped at the offshore Messiniakos basin as densely spaced high resolution reflection seismic profiles have revealed. The western margins of the basins are less deformed and the seismic activity is dispersed over several minor NW-SE faults. Since the NW-SE striking faults onshore are truncated by major NE-SW oriented ones, their overall length is shortened, reducing their seismic potential and capacity to store large stresses that could produce events above Ms6.1. Offshore western Messinia, in the Ionian Sea, the size and activity of the faults is significantly larger and prone to develop events of larger magnitudes. Subcrustal seismicity indicates a deepening of the foci to the east-northeast.Part of this work was presented at the CIESM Conference, Monaco, 2001, and in the EGS General Assembly, Nice, 2001. 相似文献
3.
4.
5.
6.
Denis Hatzfeld Vassilis Karakostas Maria Ziazia Iannis Kassaras Elephteria Papadimitriou Kostas Makropoulos Nikos Voulgaris and Christos Papaioannou 《Geophysical Journal International》2000,141(2):438-456
During the summer of 1993, a network of seismological stations was installed over a period of 7 weeks around the eastern Gulf of Corinth where a sequence of strong earthquakes occurred during 1981. Seismicity lies between the Alepohori fault dipping north and the Kaparelli fault dipping south and is related to both of these antithetic faults. Focal mechanisms show normal faulting with the active fault plane dipping at about 45° for both faults. The aftershocks of the 1981 earthquake sequence recorded by King et al . (1985 ) were processed again and show similar results. In contrast, the observations collected near the western end of the Gulf of Corinth during an experiment conducted in 1991 ( Rigo et al . 1996 ), and during the aftershock studies of the 1992 Galaxidi and the 1995 Aigion earthquakes ( Hatzfeld et al . 1996 ; Bernard et al . 1997 ) show seismicity dipping at a very low angle (about 15°) northwards and normal faulting mechanisms with the active fault plane dipping northwards at about 30°. We suggest that the 8–12 km deep seismicity in the west is probably related to the seismic–aseismic transition and not to a possible almost horizontal active fault dipping north as previously proposed. The difference in the seismicity and focal mechanisms between east and west of the Gulf could be related to the difference in the recent extension rate between the western Gulf of Corinth and the eastern Gulf of Corinth, which rotated the faults dipping originally at 45° (as in the east of the Gulf) to 30° (as in the west of the Gulf). 相似文献
7.
8.
Seismogenic zone structure beneath the Nicoya Peninsula, Costa Rica, from three-dimensional local earthquake P- and S-wave tomography 总被引：3，自引：0，他引：3
9.
T. Bardainne P. Gaillot N. Dubos-Sallée J. Blanco G. Sénéchal 《Geophysical Journal International》2006,166(2):699-718
10.
S. D. McKinnon 《Rock Mechanics and Rock Engineering》2006,39(3):255-279
Summary. Observations of seismicity and ground control problems in the Sudbury mining camp have shown that late-stage (young) sub-vertical
strike-slip faults are sensitive to small mining-induced stress changes. The strength-limited nature of stress measurements
made in the region indicates that these structures are in a state of marginal stability. Numerical continuum models are developed
to analyze the behavior of such structures. In the models, shear strain localizations (faults) evolve such that there is close
interaction between the fault system, stresses, and boundary deformation. Fault slip activity in these systems is naturally
sporadic and reproduces the commonly observed Gutenberg-Richter magnitude frequency relation. It is shown that a relatively
minor disturbance to such a system can trigger significant seismicity remote from the source of the disturbance, a behavior
which cannot be explained by conventional numerical stress analysis methodologies. The initially uniform orientation of the
stress field in these systems evolves with increasing disorder, which explains much of the scatter commonly observed in data
sets of stress measurements. Based on these results, implications for stress measurement programs and numerical stability
analysis of faults in mines are discussed. 相似文献