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华北地区地震异常前兆信息场演化特征及其与地震关系的研究 总被引:6,自引:1,他引:6
在对地震异常前兆信息量先前研究的基础上,进一步给出了描述各种地震异常前兆信息量的普适性综合数学表达式.从大量震例资料入手,再次研究了地震异常延续有效性的问题,进而建立了地震异常持续有效时间与延续有效时间的数学关系式.收集整理了1980~1997年华北地区水化、形变、地磁、应力、水位、地电等371个观测项目、上百万个前兆观测数据,对每一观测项目逐一计算了它们的地震异常前兆信息量.研究了华北地区近20年的地震异常前兆信息场的演化特征及其与地震的关系,建立了华北地区Ms≥5地震的中短期综合预报指标体系,经R值评分检验,表明该地震综合预报指标体系在中短期地震预测中具有一定效果. 相似文献
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汶川8.0级地震前电磁辐射异常变化特征初步研究 总被引:1,自引:0,他引:1
汶川8.0级地震前,距离震中只有35km的金河电磁波台记录到了宝贵的电磁扰动信息。本文分析了汶川5.12大地震前后该台的电磁波异常变化特征,表明:①强震前确实有电磁辐射异常存在,震前存在丰富的电磁扰动信息;②电磁扰动前兆异常在时间进程上有明显的阶段性变化特征,这可能是地震孕育不同阶段特征的反映。 相似文献
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对唐山地震前后地下水位动态图象的生成方法、时空演化特征及其形成演化模式的研究表明,唐山地震前后地下水位动态图象正负区和异常特征区的时空演化具有明显的规律性和阶段性。负值区的演化具有“收缩—扩展—急速扩展—发震”的特征;异常特征区的演化显示“迁移—扩展—稳定—发震—消失”的特征;滑动变差值显示“增大—减小—发震—急速减小”的变化过程。探讨了地下水位动态图象演化与构造变形、断层运动和上地幔物质上涌的关系,提出了唐山地震地下水位动态图象“场—区—源”的演化模式 相似文献
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利用南北地震带及附近地区20 多年来的大地垂直形变资料, 结合区域地震活动资料, 初步分析归纳了大地形变时空分布与地震群体活动的关系。在此基础上, 进一步对南北地震带中南段之川滇菱形块体形变场中期动态演化图象与b 值等地震活动参数图象进行了综合对比分析, 研究了形变场动态演化所揭示的区域现今构造运动的时空差异与反映地壳介质结构特性的b 值的时空分布变化、强震前后地震非均匀度值分布变化以及地震空区等的关系。结果表明: 强震前区域形变场动态演化与地震活动参数的时空分布均具有一定的非均匀特征, 二者所反映的大区域应力场变化与介质结构的不均匀导致的强烈差异运动产生的应变能积累是强震孕育的主要原因。得出了一些利用大地形变场动态演化与地震活动参数图象相结合进行强震中期预测的有益结果。 相似文献
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<正>在地壳内部存在大量的地震断裂带,地震的发生是断裂带上应力不断积累的结果,而地震发生的地点和时间取决于断裂带之间的应力传递。地震矩张量分析是研究断裂活动应力性质的重要手段。2008年5月12日汶川8.0级地震极大地改变了区域应力场,在附近多个断 相似文献
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Using the digital telemetric seismic waveform data of Chengdu and Kunming, this article studies the focal mechanism solutions and the apparent stress values of a large number of small earthquakes, and then analyzes the dynamic variation of regional stress fields and the spatio-temporal distribution of apparent stress values. The annual variation values of the azimuth of average principal stress field before the May 12, 2008 M_S8.0 Wenchuan earthquake in the Sichuan-Yunnan region were 58° from 2003 to 2004, 85° from 2003 to 2005,61° from 2006 to 2007 and 90° from 2006 to April 2008 respectively. In recent years, deflection or disturbances occurred in the azimuth of the average principal stress field in the Sichuan-Yunnan region. Analysis shows that this may be related to the change of stress field states of crustal blocks before and after the December 26, 2004 M_S9.0 Sumatra earthquake and the 2008 M_S8.0 Wenchuan earthquake. The ratio of thrust-type earthquakes in the Sichuan-Qinghai block was on the higher side in the period from 2006 to 2007, and the source faulting type of the regional moderate and small earthquakes had changed before the M_S8.0 Wenchuan earthquake. The change of state of the stress field is consistent with the changes in block displacement fields revealed by GPS data and the crustal shortening velocity vertical to the Longmenshan fault zone. Based on the radiation energy calculated from all bands of the seismic waveform, the value of apparent stress σ_app is obtained. The fluctuation shape of the fitting trend of the apparent stress is related to the intensity of regional seismicity. It reveals that the micro-dynamic fluctuation process of the regional stress value is similar to the azimuth transition of the regional principal compressive stress field, which can be used to probe for pregnant physical processes. Areas with a higher value of apparent stress σ_app are possible areas of potential seismic risk. It can be seen from the spatial distribution of the medium and short-term apparent stress σ_app before the M_S8.0 Wenchuan earthquake, the Longmenshan fault zone is in a low stress distribution area, and the relatively high apparent stress is in the peripheral area. These images may show medium and short-term locking phenomena near the seismogenic tectonics of the M_S8.0 Wenchuan earthquake. For example, changes with time of the focal parameter consistency of the sub-blocks in Sichuan and Yunnan Provinces, continual increase of thrust-type earthquakes in the Sichuan-Qinghai block and the appearance of spatial distribution areas of high apparent σ_app stress. The work on this aspect was continued after the M_S8.0 Wenchuan earthquake, and the results seem to be shown a clearer relationship between these phenomena and future great earthquakes. 相似文献
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Li Zhiqiang Yuan Yifan Li Xiaoli Zhang Qin Dai Boyang Ye Youqing Ge Peifeng Zeng Jie 《中国地震研究》2009,23(3):278-298
The M_S8.0 Wenchuan earthquake on May 12, 2008 caused heavy casualties and economic loss. According to the field investigations, the characteristics can be described as follows: The meizoseismal region with an intensity of XI shows an obviously zonal distribution and suffered serious destruction from the earthquake, and the destruction perpendicular to the earthquake surface rupture decreased sharply. At the same time, the intensity X and IX regions perpendicular to the rupture are narrow and therefore their coverage area is small. The intensity on both sides of the rupture attenuates rapidly, but intensity VII and the VI regions are wide, the latter covering about 240,000 km~2. In intensity VI region, the damage area perpendicular to the rupture in the southern part is much larger than that of the northern part. Also, much new understanding about destruction types and destructive modes for all kinds of buildings, landforms and terrain is achieved in this paper. 相似文献
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In this paper, we analyze the crustal movements, strain field changes and large scale dynamic characteristics of horizontal deformation before the Wenchuan earthquake (M_S=8.0) using GPS data obtained from the Crustal Movement Observation Network of China. The following issues are discussed. First, the strain fields of the Longmenshan fault zone located at the epicenter show slow accumulation, because of the tectonic dynamics process subjected to the eastward movement of the Bayan Har block. Second, the different movements between the Longmenshan fault and South China block are smaller than the errors of GPS observation. Third, the high value of compressive strain (2004~2007) is located at the epicenter, which shows that the local squeezing action is stronger than before. Fourth, the data from GPS reference stations in the Chinese Mainland show that crustal shortening is faster than before in the north-eastern direction, which is part of the background of the local tectonic dynamics increase in the Longmenshan fault zone. 相似文献
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The reason for the failure to forecast the Wenchuan M_S8.0 earthquake is under study, based on the systematically collection of the seismicity anomalies and their analysis results from annual earthquake tendency forecasts between the 2001 Western Kunlun Mountains Pass M_S8.1 earthquake and the 2008 Wenchuan M_S8.0 earthquake. The results show that the earthquake tendency estimation of Chinese Mainland is for strong earthquakes to occur in the active stage, and that there is still potential for the occurrence of a M_S8.0 large earthquake in Chinese Mainland after the 2001 Western Kunlun Mountains Pass earthquake. However the phenomena that many large earthquakes occurred around Chinese Mainland, and the 6-year long quietude of M_S7.0 earthquake and an obvious quietude of M_S5.0 and M_S6.0 earthquakes during 2002~2007 led to the distinctly lower forecast estimation of earthquake tendency in Chinese Mainland after 2006. The middle part in the north-south seismic belt has been designated a seismic risk area of strong earthquake in recent years, but, the estimation of the risk degree in Southwestern China is insufficient after the Ning’er M_S6.4 earthquake in Yunnan in 2007. There are no records of earthquakes with M_S≥7.0 in the Longmenshan fault, which is one of reasons that this fault was not considered a seismic risk area of strong earthquakes in recent years. 相似文献
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Based on seismic wave records of the Chengdu digital seismic network and Zipingpu reservoir digital seismic network from August 16,2004 to May 12,2008 when the Wenchuan MS8.0 earthquake occurred,the parameters of focal mechanisms of 486 earthquakes with magnitude larger than M1.6 in the Zipingpu reservoir area were calculated using amplitude ratio method,meanwhile the temporal-spatial variation characteristics of mechanisms and stress field were analyzed based on these parameters.Results show a low ratio of thrust earthquakes and an increased number of strike-slip earthquakes in the reservoir water area in the period from 2006 to 2008.While in the areas far from the reservoir waterfront,the thrust earthquakes took up a high proportion and the strike-slip ones did not increase.The direction of mean principal compressive stress field was deflected and disturbed differently in each area before the Wenchuan MS8.0 earthquake. 相似文献
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对汶川8.0级地震震中周围800km范围内73个井孔的表层水温资料进行了分析。根据设定的异常与不确定性异常判定依据,发现有9个井孔出现了前兆异常;有5个井孔的异常不能确定是否为前兆异常;有3个井孔出现了典型非前兆异常变化;其余未出现任何异常变化。分析认为异常存在早期、中期和晚期三个阶段,表现为缓变、突变和向下的阶梯状变化。对9个异常井孔的同井水位、气氡等其它流体测项以及同台或邻近台站形变仪器(钻孔应变、钻孔倾斜、洞体应变等)在表层水温异常变化时段内的动态变化特征进行了对比,发现地壳形变与表层水温在异常的晚期阶段具有一定的相关关系;而同井水位与表层水温异常的关系不大。 相似文献
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对汶川8级地震后群众咨询信息的分析及探讨 总被引:3,自引:0,他引:3
“5.12”四川汶川8.0级地震发生后,很多人打电话咨询有关情况,对5月12日至6月12日电话中的咨询信息进行了分析.就群众关心的地震问题、解答的效果以及暴露出的工作问题进行总结与分析,并提出一些建议。 相似文献