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In this paper, the precursor response characteristics of digital fluid caused by the Wenchuan M8.0 and Yushu M7.1 earthquakes are studied, and the response difference of the observations of Wuliying well to the two strong earthquakes is compared. The result shows that the abnormal fluid response has a certain relationship with earthquake size and epicenter distance. The greater the earthquake, and the closer it is to the epicenter from the observatory, the more sensitive the response will be to fluid anomalies. Abnormal Helium release was first observed before both strong earthquakes in the fluid precursor observation. The release intensity is related to earthquake magnitude; the larger the magnitude, the stronger the abnormal changes. The large change in He release in a short period after the Wenchuan earthquake may be related to the continuous activity of strong aftershocks and the structural adjustment after the earthquake. Helium release increased significantly after both earthquakes, as contributed by the abnormal deep-sited Helium release. However, this process may be connected to the annual change from July to September or the hot-reservoir type gas release in the Wuliying well. In the earthquake preparation process, a large number of deep-derived Helium is released into the geothermal system and the entire composition is changed. Temporally, this gas release appears later than fault-type gas release, and the disappearance time of this anomaly is also much later. The response difference of the fluid precursor to the two strong earthquakes may be related to differences of deep structural setting and dynamic mechanism. It also shows there is a stronger correlation between Wenchuan M8.0 earthquake in the North-South Seismic Belt and North China region than the Yushu M7.1 earthquake in the internal Qinghai-Tibetan plateau. Helium gas can be a sensitive indicator for monitoring abnormal deep-gas activity of the region where the observation station is located. Hence, observation and research should be strengthened in the future. 相似文献
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By scanning modulated or un-modulated earthquakes spatio-temporally in the region of Sichuan-Yunnan,short-term non-stationary seismic precursory patterns were extracted with significant difference and the characteristic of non-stationary short-term seismic anomalies were analyzed as well as prediction efficiency of modulated small earthquakes before a strong earthquake. Besides,small earthquake modulation ratios near the region of the epicenter were calculated and sorted by time. The results indicated that there were significant effects using the modulated earthquake method to predict earthquakes greater than MS6. 0 in a short time. Before the MS8. 0 Wenchuan earthquake,there were obvious short-term precursory seismicity gap patterns of modulated small earthquakes. 相似文献
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The contrast research results show that the number of items and stations with imminent, short and medium term precursor anomalies for the Wenchuan M_S 8. 0 earthquake is less than that of the Menglian earthquake. The number of anomalies and stations associated with the Wenchuan earthquake increased in the early stage of the short-term range,as opposed to the later period for the Menglian and Lijiang earthquakes. Most of the medium term anomalies occurred two to three years before the Wenchuan earthquake,when the number of anomaly stations and items was eleven,and a great change appeared in the observation values in about half of the stations ( items ) . However,for the Menglian earthquake,medium term anomalies happened one to two years before the earthquake, the number of abnormal stations and items reached 20,and a sharp change appeared in the observation values six months to one year before the earthquake in about 30 percent of the stations or items. In the epicenter and the nearby area,the macroscopic abnormalities started 3 years before the Wenchuan earthquake and lasted intermittently until 1 month before the earthquake. Within 2 percent of the total area of the province,the macroscopic abnormalities accounted for 30 to 50 percent of the total number of anomalies of the Province. For the Xingtai,Tangshan,Haicheng,Songpan earthquakes,the macroscopic anomalies started two to three months before,or on the very day of the earthquakes. The common feature of the precursors between the Wenchuan and other strong earthquakes is the appearance of tremendous changes in a certain number of observation values of anomalies in the mid and short terms before all these earthquakes. 相似文献
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Research on the Characteristics and Repeatability of Strong Earthquake Activity in Sichuan-Yunnan 总被引：1，自引：0，他引：1
According to the method for predicting strong earthquakes using seismicity patterns, this paper summarizes the seismicity anomalies, generally called anomalous seismicity patterns, as the basis for prediction based on some historical data in the Sichuan-Yunnan seismic zone. Using our results, it can be confirmed that these anomaly patterns, which reflect the features of the late stage of strong earthquake preparation process and stress release in the main shock rupture zone, did exist before many earthquake cases. This paper also introduced the characteristics of seismic repeatability and its validation result, and discussed the mechanism of repeatability, which will have an application value for strong earthquake tendency prediction. 相似文献
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On the basis of previous study results about the seismic anomaly precursor information quantity, universal and synthetic mathematical expressions that describe the precursor information quantity of various seismic anomalies are further given. Starting from large amounts of data of earthquake cases, the problem of the sustained effective time of seismic anomaly was studied again and the mathematical relationship between the sustained effective time of seismic anomaly and continuing effective time of seismic anomaly was further established. About one million pieces of precursor observation data belonging to 371 items of hydrochemistry, deformation, geomagnetism, stress, water level, geoelectricity, etc. In North China region in the period of 1980～ 1997 were collected and sorted out, and the seismic anomaly precursor information quantity of these items was calculated item by item. The evolutionary characteristics of seismic anomaly precursor information field in North China region in about 20 years and their relation to earthquakes were studied; an index system for medium- and short-term predictions of earthquakes with Ms ≥ 5.0 in North China region was established. After having checked by the R-value scoring method, the index system for synthetic earthquake prediction was proved to be of certain efficacy in medium- and short-term earthquake prediction. 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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After the Yushu M S 7.1 earthquake on April 14,2010,a large number of aftershocks were recorded by the surrounding permanent network and temporary seismic stations.Due to the distribution of stations,knowledge about velocity structure,the reliability of seismic phases,and so on,the location result from conventional method is usually of low precision,from which it is difficult to recognize the spatial and temporal distribution and the trends of aftershock activity.In this paper,by using teleseismic waveforms recorded by permanent station,the seismic velocity structure beneath the vicinity is obtained from receiver function stacking and inversion methods.And the Yushu earthquake sequences are relocated from seismic phase data by HypoDD.The results show that the Yushu M S 7.1 earthquake occurred at 13 km depth;the aftershock sequences were distributed mainly in the NWW along the Garzê-Yushu fault,and most aftershocks were concentrated in a 100 km length and 5-20 km depth.Combined with the velocity structure,it can be inferred that the earthquake mainly destroys the high-velocity layer of the upper crust.In the west of the seismic fault near(33.3°N,96.2°E),the aftershock sequences were distributed like a straight column,suggesting there was a comminuted break from 25km depth to the ground. 相似文献
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Source spectra,corner frequency and zero frequency amplitudes in near-source conditions were measured using waveform data from 989 earthquakes with magnitudes larger than ML2.0 observed by the Beijing Digital Telemetry Seismic Network in the Capital Circle Region of China and its surrounding areas from January 2002 to June 2006 by the Brune model.Relevant formulas that were used for the calculation of dynamic source parameters include rupture radius,seismic moment,seismic energy,stress drop,and apparent stress.Scaling relations and characteristics of temporal-spatial variations of these dynamic parameters before the MS5.1 Wenan earthquake in Hebei Province that occurred on July 20,2006 were analyzed.Results show that apparent stress,stress drop,and the ratio of seismic energy to the rupture radius had relatively high values in some areas before the Wenan earthquake.These high-value concentration areas were mainly distributed in the North China Plain seismic zone.As is seen from the time curves,parameters,such as apparent stress,stress drop,and ratio of seismic energy to rupture radius underwent significant ascending processes before the Wenan earthquake,but the variation in the corner frequency showed a descending trend.This result might be related to the enhancement of stress in the North China Plain seismic zone before the earthquake. 相似文献
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This paper introduces the geological structure background around the 2014 Yutian Ms7. 3 earthquake area, investigates and analyzes the regime of small earthquake activity and the characteristics of regional seismicity pattern in Xinjiang before the earthquake, and compares the characteristics of the regional seismic activity with the 2008 Yutian Ms7.3 earthquake. The results show： ① 2 ~ 3 years before the 2014 Yutian Ms7. 3 earthquake, Xinjiang was in a seismic active state with strong earthquake occurring successively, and before the 2008 Ms 7. 3 earthquake, Xinjiang was in the quiet state of moderate-small earthquakes with M3. 0 ~ 4. 0. ② Before this Yutian Ms7. 3 earthquake, the regional seismic activity showed a short-term anomaly feature, that is, seismicity of M ≥ 5. 0 earthquakes significantly increased on the Altun seismic zone and in the source area three years before the Ms7.3 earthquake, while a five year long quiescence of seismicity of M ≥4. 0 earthquakes appeared on the east of the source area in a range of about 440kin. Six months before this M7. 3 earthquake, there existed seismic gap of M3. 0 ~ 4. 0 earthquakes and near-conjugate seismic belt magnitude 3. 0 and 4. 0 in the source area. ③ The state of strong earthquake activity and the seismicity pattern of small earthquakes before this Yutian Ms7. 3 earthquake were significantly different to that before the 2008 Yutian Ms7. 3 earthquake, and this may be related to the different seismogenic environments of the two Ms7. 3 earthquakes. 相似文献
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The Yutian earthquake with Ms7. 3 happened on February 12, 2014. The precursor monitoring ability is weak in that area. We found tendency anomalies and middle- and short-term anomalies from metal pendulum tilt measurements in Hotan seismic station before the earthquake. And we also compared the anomalies with that of the Ms7. 3 Yutian earthquake on March 21, 2008. The tendency anomalies measured by the metal pendulum tiltmeter appeared since 2012 as tilting eastward. While the middle- and short-term anomalies were characterized by acceleration, pause and rapid change of tilt rate in two directions. The tendency anomalies of metal pendulum tilt records are the same before the two earthquakes. They both happened in the east direction. However, there are differences in duration, characteristic and earthquake intervals for the middle- and short-term anomalies. 相似文献
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研究2001年昆仑山口西地震和2008年汶川地震前的中源地震活动特征,与唐山地震前的特征进行比较,发现:3次大地震前曾发生6或7次h≥60 km的中源地震,且"大震前中源地震活跃的时间跨度T"约5年或5年多。这是大震前中源地震活动最主要的两个特征,包含了孕育大地震的一些重要信息。其他特征还有:中源地震的活动—平静交替、临近大地震前的地震平静、呈条带分布和(或)地震空区等特征,这与大震前壳内地震活动性的一些特征类似。 相似文献
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分析了“十五”期间社会，政府对防震减灾工作的需求，联系工作实际进行了全面论述和分析，并对推进防震减灾提出了一些有益的政策建议。 相似文献
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地震序列是对地震现象的回顾性描述,只有在地震序列结束后它才有可能被确切无疑地判定.鉴于龙门山断裂带或地震带的整体性、统一性和系统性,不可否认在其西南段发生的芦山地震是与汶川地震一样的同属于龙门山断裂带的事件.鉴于芦山地震的震源位置、震源机制、震级大小和破裂区覆盖的范围,目前可认为它是汶川地震迄今最大的余震.鉴于地震序列的判定是对地震现象的唯象的描述,有相当的任意性,对芦山地震究竟是"新的主震"还是"汶川余震"的"讨论"实质上是在根据经验判定地震的类型,即使目前看"主震说"提出的4条"论据"明显缺乏说服力,"余震说"比较有说服力,但最后都需要等到地震序列结束之后才有可能"定论".作者认为,相对于需要等到地震序列结束之后才能"定论"、甚而在地震序列结束之后未必能"定论"的芦山地震究竟是"新的主震"还是"汶川余震"问题,应当更为关注芦山地震的发生引出的一些重要的亟待研究的科学问题与防震减灾问题. 相似文献
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牛智 《地震地磁观测与研究》1996,17(5):56-60
用地震电磁波法作临震预报，发现地震的发震时间是有规律性的，仪器到的辽南发生的地方震和有些大地震，就是在预测的“发震时段”里发生的。 相似文献
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基于GDP宏观易损性分析方法,是从全球尺度地震灾害损失过程中发展起来的,本文在真实震例的基础上,运用宏观易损性分析方法,分别计算科考影响场与经验影响场的震后经济损失,与实际震害评估结果进行对比,初步验证该方法在省级区域震后经济损失快速评估中的可用性. 相似文献
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以物理模型为指导开展中尺度地震预测试验场研究 总被引：1，自引：1，他引：0
震源物理的研究进展表明：地震预测工程不仅是高科技问题,更重要的是需要以正确的物理模型作为指导。地震预测试验场的研究可以从气象学、地球物理、地球化学、矿山地震和瓦斯突出的研究中获得许多启示。在今后的十年中,要注意流体,特别是超临界流体在地震成因中的作用。地震试验场应有明确物理思路,形成多种物理方法的实质性格局,改变自由进出、过于分散的情况。建议除在京津、川滇等建立构造地震预测研究试验场外,还可以利用矿山、火山作为中尺度地震试验场。 相似文献
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