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随着地下流体观测技术的提高,尤其是地下流体观测数字化改造以后,观测资料的采样频率明显提高,这些高频采样的观测资料中蕴含着丰富的构造信息,如何从分钟值甚至更高频率采样的观测资料中提取有用的异常信息,是目前从事地震地下流体资料分析人员最为关注的科学问题之一.本文引入概率密度分布法,分析了2008年汶川8.0级地震前南北地震带及其附近区域72个测点的数字化水位和水温分钟值采样高频观测资料,结果显示:汶川8.0级地震前有16个测点水位和14个测点水温出现高频异常信息,出现高频信息异常的观测点多集中在滇西南构造带,异常出现的时间呈现出由南向北推移的特征.据此认为概率密度分布法在流体资料的高频异常信息提取方面具有一定的可靠性与适用性,可为数字化高频观测资料异常提取提供借鉴. 相似文献
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共和7.0级地震前地下流体前兆的动态演化特征 总被引：3，自引：0，他引：3
使用４０个地下流体观测点的资料,对１９９０年４月２６日青海省共和ＭＳ７．０地震的前兆动态特征进行了系统研究．结果表明：（１）地震带内观测点的水氡趋势异常及水化、水位群体异常及频次异常与断层平均形变速率呈同步变化．地下流体群体异常频次的累加值曲线在地震前表现为指数加速变化图形．（２）震源外围２４０ｋｍ范围内的水氡中短期趋势上升异常,表现为由震源逐渐向外围扩散的特点．在短临阶段各测点水氡的异常变化基本同步．（３）流体短临前兆出现明显的起伏加剧和层次现象,突出的表现是流量、断层气日变化在临震阶段出现３次加剧,且异常幅度一次高于一次 相似文献
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为了进一步提高地下流体台网的运行效能,为合理划分国家级和省级台站提供依据,以地下流体学科技术协调组制定的《地下流体观测站（点）质量与效能评估方案》为依据,从7个方面对山西省地下流体3个固定观测网4大测项的观测质量、效能以及各观测网存在的问题进行了评估和分析,并提出改进措施及建议。 相似文献
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系统收集广东地区地下流体观测网水位和水温资料,归纳汶川8.0级地震引起的同震响应,研究其响应特征、响应时间过程、响应空间分布等。结果表明:不同区域的水位测点出现同震响应的比例存在差异;水位同震阶跃变化以下降为主,其阶升、阶降的测井在空间分布上存在分区性;响应灵敏性方面,水位明显高于水温;震级越大、距离测点越近的强震,水位出现同震阶跃响应的比例越高;水位同震阶跃响应的方向能在一定程度上反映测点区域所受的构造应力状态,汶川8.0级地震对广东地区的影响以张应力为主。 相似文献
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在地震的孕育、发生到发展的过程中，可能会出现多项地下流体观测量不同程度的前兆异常变化，这些异常变化是复杂多样、模糊不清的。引入模糊识别法对一定区域和一定时间段的地下流体观测数据进行了分析和处理，表明模糊识别法可较好地识别和分辨出地下流体前兆的地震异常。 相似文献
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Observation
network of ground fluid in northwestern China is comprehensively evaluated as three
stages,that is,establishment,adjustment and development.The observation network of ground
fluid has already tended to ripe and makes a certain effect in seismologic surveillance
and earthquake prediction.But because it is restricted by some conditions,the network
action is still limited.Efficacy of seismologic surveillance of the network is
synthetically evaluated.The result shows that medium-short term anomalies are observed at
sensitive sites in distant field and short-impending anomalies are observed at sensitive
sites in close field. 相似文献
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Effects of hanging wall and forward directivity in the 1999 Chi-Chi earthquake on inelastic displacement response of structures 总被引：1，自引：0，他引：1
The characteristics of the inelastic response of structures affected by hanging wall and forward directivity in the 1999 Chi-Chi earthquake are investigated. Inelastic displacement ratios (IDRs) for ground motions impacted by these near- field effects are evaluated and comprehensively compared to far-field ground motions. In addition, the inelastic displacement responses to hanging wall and footwall ground motions are compared. It is concluded that the inelastic displacement response is significantly affected in the short period range by hanging wall and in the long period range by footwall. Although high peak ground acceleration was observed at hanging wall stations, the IDRs for structures on hanging wall sites are only larger than footwall sites in the very long period range. Forward directivity effects result in larger IDRs for periods longer than about 0.5s. Adopting statistical relationships for IDRs established using far-field ground motions may lead to either overestimation or underestimation in the seismic evaluation of existing structures located in near-field regions, depending on their fundamental vibration periods. 相似文献
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Human activities, such as fluid injection as part of the stimulation of an enhanced geothermal system (EGS) for heat and power production, can cause damaging earthquake ground motions. A difficulty in quickly settling or rejecting insurance claims to the policy of the EGS operator is the lack of ground truth on the observed shaking at sites of reported damage. To overcome this problem a local seismic network could be installed prior to injection to constrain the ground-motion field at points of potential damage. Since the installation and maintenance of seismometers are costly there is an incentive to keep the number of instruments to a minimum. In this short communication, ground-motion fields are simulated and receiver operating characteristic analysis is conducted to guide decisions on the number of sensors required to obtain a certain confidence in the rate of false alarms and missed detections. For densities of 10–20 instruments per km2 the ability to estimate potentially damaging ground motions is reasonable but associated with a significant chance of missed detections and false alarms. If an EGS operator or regulatory authority does not want to accept such chances then network densities of 50–100 instruments per km2 are required and even in this case the exceedance/non-exceedance of a certain ground-motion threshold cannot be completely constrained. 相似文献
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跨省市交界区地震监测预报的组织工作薄弱是我同地震竹理体制的一个缺陷。地震监测预报区的地理范围与地震行政竹辖区范围的不一致是造成这种缺陷的基本原因。实行相邻省市地震协防制,建立协防领导小组是改善和强化跨省市交界区地震监测预报工作的可行和有效的途径和管理方式。 相似文献
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地下流体的源兆,场兆,远兆及其在地震预报中的意义 总被引：33，自引：8，他引：33
我国地震地下流体监测网中，发现强震前有３种不同的前兆异常，即来自震源的源兆异常、与地震有关的区域活动关联的场兆异常及远距离强震前出现的远兆异常，它们在成因、特征与地震预报实践中的意义不同。从数量上看，场兆是大量的，源兆是少量的，而远兆也是不可忽略的。因此，地震预报实践中，必须正确地区别这３种前兆，全力寻找源兆，积极地开发场兆的预报功能，承认远兆并揭示其科学意义。 相似文献