甘肃岷县漳县M_S6.6地震序列波速比变化特征研究

收集了甘肃岷县漳县MS6.6地震序列固定台站和震后6个流动台站震相观测报告,提取了P波、S波走时信息,采用多台和达法计算该地震序列波速比,发现震后较强余震发生前波速比趋势性下降的特征。这对后续震情跟踪和趋势判定过程中强余震预测有一定的参考价值和指示意义。     

岷县-漳县MS6.6地震前后甘肃前兆异常及响应特征

分析总结了2013年7月22日甘肃岷县—漳县MS6.6地震前后甘肃前兆台网观测资料变化情况,发现该地震前有7个台站、4种观测手段、14个测项出现了明显的异常,既有长期、中长期异常,也有短期和短临异常,说明对资料的分析既要看短期变化,还要看中期和长期变化。出现异常测点的震中距多数在200 km范围之内。另外部分水位、流量和水温测点的资料记录到不同程度的同震效应;形变观测多数测点记录到比较明显的同震响应,记录同震响应的测点与震中位置、方向、距离无明显关系。     

2017年九寨沟7.0级地震前应力状态及b值异常特征研究

2017年8月8日青藏高原东缘四川九寨沟地区发生7.0级强震,依据前人研究结果分析九寨沟7.0级地震发震构造,并计算震前应力状态。结果显示:本次地震受到构造和历史强震的影响,是发生在历史强震引起的应力加载区域。另外,采用中国地震台网1990年以来的地震目录,在评估目录完整性的基础上,利用最大似然法计算得到2017年8月8日九寨沟7.0级地震前震源区及邻区地震b值空间图像。结果显示,九寨沟7.0级地震发生在四川北部地区显著低b值高应力异常区域内部(0.82b0.75)。所以,研究区域内外历史强震可能促进了九寨沟7.0级地震的发生。     

岷县、漳县6.6级地震的预测过程回顾

After the Ms6.6 earthquake occurred in the border region between Min and Zhang counties of Gansu Province on July 22, 2013, we preliminarily estimated the earthquake sequence to be a main shock-aftershock type based on the history of moderate-strong earthquake sequences in this area. As time went on, there were more aftershock events. These could be used for further analysis, and then for further decision on the earthquake sequence type. Finally, we determined the Ms6.6 earthquake sequence that occurred in the border region between Min and Zhang counties, Gansu Province as having been a main shock-aftershock type, with the largest Ms5.6 aftershock having occurred on the same day as the main Ms6.6 shock, from a comprehensive analysis of the historical characteristics of moderatety strong earthquakes of the earthquake zone, and the space-time evolution characteristics and parameters of the earthquake sequence. These provided a correct basis for anti- earthquake relief work and played an important role in mitigating the earthquake disaster and stabilizing the disturbed soci- ety after the earthquake in the earthquake zone and its neighboring areas. Reviewing the forecasting process and the re- sults, we found that we had successfully predicted the Ms6.6 earthquake that occurred in the border region between Min and Zhang counties on July 22, 2013 several years before it occurred. The magnitude and location of the earthquake had been predicted accurately, and the accuracy of the prediction was much higher than any other example in Chinese earth- quake prediction history. Forecasting on a monthly scale, we had indicated at the monthly meeting on earthquake prediction at the end of February, 2013 that there would be a risk of a moderately strong earthquake in Gansu Province from the change in moderately strong earthquake activity on the Chinese mainland. Even for short and impending earthquake prediction from several days to several dozens of days, we had proposed the likelihood of a moderate-strong earthquake happening in Gansu Province and the adjacent areas from the results of previous studies and the cases of earthquakes with MI ≥ 4.0 from the time before the Ms6.6 earthquake occurred. In a meeting about earthquake prediction held several days before the occurrence of the Ms6.6 event, we made the prediction that there would be an earthquake of M≥ 5.0 happening somewhere in Gansu Province and the surrounding area within dozens of days. The fact we had successfully predicted the Ms6.6 earth-quake on a several-year scale, as well as over a short time period to some extent, reinforces our belief that earthquakes can be forecast. Even with our present level of understanding, we can still capture some information on the gestation and occurrence of earthquakes before the arrival of a disaster. However, in order to achieve the goal of earthquake prediction in China, earthquake scientists still need to make arduous efforts. As long as earthquake scientists use the correct approach, and government supplies the necessary manpower and material resources to predict earthquakes, we believe that there will be a hope to achieve the aim of earthquake prediction with a relief effect. It is promising that we have achieved at least one or two earthquake forecasts.     

前震或广义前震识别的频谱偏移法及其应用研究

在前期研究工作的基础上,本文提出了一种前震或广义前震识别的频谱偏移法。其判定指标为,正常背景的中等地震事件频谱较宽,而具有前震或广义前震性质的中等地震具有频带变窄且向低频端偏移集中的特征。究其根源可能与强震前震源区或主震相关区域亚稳态扩展破裂或区域介质破碎损伤、裂隙扩展成核等过程有关。对2010年4月14日青海玉树7.1级、2014年2月12日新疆于田7.3级等地震前震的计算结果显示,2次前震的频谱都发生了偏移,与非前震性同等震级地震频谱差异明显。     

祁连山地震带强震前M_L4.0地震活动特征研究

正祁连山地震带总体上呈北西西向展布,东端与南北地震带相接,西与阿尔金山地震带毗邻,北界在金塔、龙首山,南界进入青海境内。带内活动断裂发育,地震活跃,有利于开展地震活动性和地震预测研究工作。本文通过对祁连山地震带1970年以来M_L4.0地震和祁连山地震带西段2010年以来的M_L4.0地震的M-t图、频度图、震中分布图的细致分析以及相关地震的统计分析,结果显示,祁连山地震带1970—2018年M_L4.0地震存在弱活动现象,共出现过7次地     

高压直流输电对甘肃地电场观测影响分析

以甘肃河西地区瓜州、嘉峪关、高台地电场观测受酒泉一湖南±800 kV高压直流输电工程影响为例,分析了甘肃地电场观测受干扰的异常变化形态和特征,并结合高压直流输电基本原理,对异常机理进行了探讨,定量的计算了不同距离、不同电导率和高压直流输电入地电流等对地电场观测的可能影响。结果表明,在理想状态下,高压直流输电对地电场观测的影响与入地电流成正比,与地电场观测场地距换流站接地极的距离的平方和影响区域的电导率成反比。并采用最小二乘拟合法对干扰进行消除,效果理想。