强烈地震前阿拉木图试验场地震平静期研究

对强震孕育和发震期阿拉木图预报试验场弱震活动性进行了动力学分析,发现弱震活动性变化明显地表现出时空平静异常。研讨了北天山地震平静异常表现的形态和幅度特性。     

从震例总结角度分析玉树7.1级地震前地震活动性异常特征

利用1970年以来青海省完成的震例总结工作结果,对震例中明确提出的地震活动性异常进行了统计,结合玉树7.1级地震前出现的空区、前震等异常进行了分析。结果显示玉树地震前提出的多震级档空区异常是震例中有较高映震能力的指标。2010年4月14日玉树的4.7级地震被认为是当日7.1级地震的前震,这在以往震例中是少有的,也进一步说明震例总结和典型震例的深入研究对推动地震预报的发展具有重要的作用。     

震前电磁波异常特征探讨

介绍了电磁波观测的原理与方法,归纳出震前电磁波的几种异常特征,对近年来几次典型的震前电磁波异常进行了分析,探讨了异常的规律。     

宁蒗5.5级地震短临异常特征分析

本文在此次地震前短临预报的基础上,对震前的地震活动性,微观和宏观前兆的短临异常特征进行了研究。指出地震活动在该区最典型的短临异常特征是平静,分析了震前地震活动图象和各类异常的时空特征所显示的“膨胀—扩散模式”的孕震机制。     

苍山5.2级地震异常群体时空演化特征

在对 1 995年山东省苍山 5 2级地震异常筛选的基础上 ,分析了异常群体阶段性演化过程。结果表明 ,震前 1 0a左右震中周围出现小震小区域综合断层面解主压应力P轴偏转 (约 3 0°) ,震前 7a左右震中附近 3～ 4级地震增强集中及应变释放加速 ;震前 4a左右转为异常平静 ;震前 1a左右震中外围开始出现形变类前兆异常 ,前兆异常台站比和异常台项比约达 6%及 4%左右 ,异常比例偏少 ;震前约半年起 ,以震中附近地震波速比异常出现为起点 ,相继出现各类前兆异常 6条 ,短期前兆异常台站比和异常台项比分别约达 2 5 %和 1 7%左右 ,显示孕震进入短期阶段 ,但临震异常不明显。对由此获得的 5级地震预测启示进行了讨论。     

大气电场异常作为地震短临预报标志研究进展

通过对华北地地区进行震前大气电场异常观测研究的较为全面分析和总结,验证和论述了震前大气电场异常的基本特征,用大量的震例证实了在每次较大的近场地震发生前都能观测到该类异常现象,以及当较长一段时间内观测不到该类异常时,近场近期也不会有较大地震发生的可能。     

新疆地倾斜地震短期异常特征研究

利用常规分析方法研究了新疆部分4级和5级以上地震前地倾斜资料所出现的短期和临震异常变化,统计了异常开始至发震时间、异常持续时间、异常结束至发震时间、异常量级及异常形态等,通过对典型震例的剖析得出了中强地震和远场强地震前的地倾斜短期异常特征。在地震前的短临阶段,异常的项数和异常量级急剧增加;震级不同,异常起始时间和发震的优势时段也有所不同。     

丰满地震台水氡对M≥5.0级东北深震的映震分析

在对丰满地震台水氡井的基本情况和水氡的动态影响因素分析的基础上,列举并分析了该测点自1987年1月1日到2011年12月31日期间M≥5.0级东北深震前后水氡资料的异常形态,得出水氡具有一定的深震效应。结合深震震源机制和水氡井所处特殊区域地质构造,对深震前后异常形态问题进行了初步解释,为今后利用水氡异常形态判别深震发生提供依据。     

香河短水准异常与唐山地震的关系

本文对唐山地震前后香河短水准资料进行了剖析,肯定了香河短水准在唐山震前的中短期异常和震时观测到的同震变化。通过计算在水平应力作用下的线源倾斜场理论值,验证了唐山震前香河短水准前兆异常的可靠性;同时,用弹性位错理论模式计算香河台及周围的震时倾斜场,进一步证明香河台震时观测到的同震变化的可能性。对计算结果中理沦值和实测值存在的差异作了理论上的解释。     

南北地震带中南段典型强震震前跨断层形变特征分析

基于南北地震带中南段18个不同震级的典型震例震前跨断层形变观测异常特征, 结合《中国震例》已有研究结果, 定性分析了各地震震前跨断层形变观测异常的类型和时、 空变化特征。 结果表明, 对于8.0级以下地震, 震前2~3年异常数量明显增多、 震前1~1年半左右异常达到峰值、 震前部分场地异常恢复的特征对区域强震预测在时间上具有一定的中期或短期前兆意义; 震前跨断层场地异常震中距和异常类型对强震震级具有一定的预测意义; 无论是跨断层异常类型、 空间分布, 还是异常的时间进程特征均与区域强震发生地点没有显著的统计关系。 汶川M_S8.0地震前出现趋势异常多、 中短期异常较少、 外围异常多和中心异常少的特征; 异常最早出现在7~8年前, 震前3年左右明显增加, 震前部分异常恢复; 异常以趋势异常和速度变化为主, 没有破年变异常。     

Three-dimensional characteristics of focal fault of 1995 M S=6.5 Wuding earthquake occurring in Yunnan Province

By means of the hypocenter distribution and focal mechanism of Wuding MS=6.5 earthquake sequence occurred in 1995, the space orientation and activity characteristics of focal fault of Wuding earthquake have been studied from the three-dimensional space-time process. The results indicate that the focal fault of Wuding earthquake is a subsurface, NWW-trending, upright and right-lateral strike slip fault which is consistent with the intensity distribution in the meizoseismal region. Although the large-scale NS-trending Tanglang-Yimen active fault passes through the earthquake region, it is irrelevant to the MS=6.5 Wuding main earthquake. Since the relationship between the strong earthquake and the shallow geological active fault can not be determined, the crustal deep structure should be studied. The method proposed in the paper can be used to distinguish the focal fault in the deep crust.     

Correlation between abnormal trends in the spontaneous fields of tectonic plates and strong seismicities

Tectonic activities, electrical structures, and electromagnetic environments are major factors that affect the stability of spontaneous fields. The method of correlating regional synchronization contrasts(CRSC) can determine the reliability of multi-site data trends or shortimpending anomalies. From 2008 to 2013, there were three strong earthquake cluster periods in the North–South seismic belt that lasted for 8–12 months. By applying the CRSC method to analyze the spontaneous field E_(SP) at 25 sites of the region in the past 6 years, it was discovered that for each strong earthquake cluster period, the E_(SP) strength of credible anomalous trends was present at minimum 30%of the stations. In the southern section of the Tan-Lu fault zone, the E_(SP) at four main geoelectric field stations showed significant anomalous trends after June 2015, which could be associated with the major earthquakes of the East China Sea waters(MS7.2) in November 2015 and Japan's Kyushu island(MS7.3) in April 2016.     

广州地区活动断裂的特征及其与工程抗震的关系

根据第四纪地质、地球化学、地壳形变和地震活动资料,论述了晚第四纪广州地区主要断裂的活动特征。认晚更新世以来,广从断裂、清泉街断裂、瘦狗岭断裂和文冲断裂发生过拉张式活动,但活动较弱,对工程地震未构成较严重危害,但在这些断裂所通过的地了在砂土液化、淤泥塌陷等潜在地质灾害。     

中国大陆强震前兆时空分布的大尺度特征初探

依据对中国大陆一些强震(M_s≥7.0)震例前兆异常的分析,初步阐述了中国大陆强震前兆时空分布的大尺度特征:①强震的前兆场及震后的影响场是广阔的;②有些前兆异常的时间较长,可能与几个强震有关,持续十几年。     

暗条爆发与日冕物质抛射

本文对太阳活动区ＡＲ６８９１ 中两个暗条爆发的磁场环境、及爆发所引起的日地物理效应进行了比较和分析结果表明, 出现在靠近大尺度单极区的活动区暗条爆发, 可能导致较强烈的日冕物质抛射     

Moment tensor inversion of the November 6, 1988 M S=7.6, Lancang-Gengma, China, earthquake using long-period body-waves data

Moment tensor inversion was carried out to invert the source mechanism and source time function of the MS=7.6 November 6, 1988, Lancang-Gengma, Yunnan Province, China, earthquake. Waveforms of long-period body-waves recorded by China Digital Seismograph Network (CDSN) were used in the inversion. The inverted result shows one nodal plane of right-lateralstrike-slip faulting and another of left-lateral strike-slip faulting and a simple source time function of a duration of about 15 s and scalar seismic moment of 6.4(1020 N(m. From the geological dataand tectonic settings and also from field observations and epicentral distribution of aftershocks, the nodal plane striking in the azimuth of 313( is preferred as the fault plane. The pressure axis lies almosthorizontally in north-south direction.     

Earthquake-related Electric Field Changes Observed in the Ionosphere and Ground

The changes of the ionospheric electric field before and after four huge earthquakes, which include the Ms 8.7 earthquake of 2004 and the Ms 8.5 earthquake of 2005 in Sumatra of Indonesia, the Ms 8.0 Wenchuan earthquake of 2008 in China, the Ms 8.8 earthquake of 2010 in Chile, and their strong aftershocks are studied in this paper. The significant results revealed that the power spectral density of low-frequency electric field below 20 Hz in the ionosphere, a kind of electromagnetic radiation phenomena, increased abnormally before and after the earthquakes and partially corresponded to the increased power spectral density of the low-frequency geoelectric field in time. This research preliminarily indicates that the low-frequency electromagnetic radiation during the imminent stages before such earthquakes could be detected by the observation of the ionospheric electric field. However, the spatial, temporal, and intensive complexities of the electric field anomalies in the ionosphere before earthquakes have come in sight also.     

孟连7.3级强震短临预报研究--应用"层次法"的模拟预测

孟连7.3 级大震前有中强地震发生,这对大震的地点预报十分有利,但中、强震发生后是否一定有大震发生,这仍然是预报难题.其次,中、强震发生后,究竟相隔多长时间后发生大震,这是另一个预报难题.以孟连地震作为震例,用"层次法"对上述二个问题作出回答.最后由"层次法"得到孟连地震的预报参数为:震中22°N,99°E;MX 7 .3;时间1995年7月12日.预测参数与实际地震参数一致.     

包头西6.4级地震前地球物理场特征的研究

通过对包头６．４级地震前较大范围前兆资料的研究,认为一个强烈地震在发生之前,围绕震中区不同区域内,将出现具有不同特点的前兆场异常群。其近场（Δ≤１００ｋｍ）的主要特征是具有较长时间尺度的趋势性异常;中场（１００ｋｍ〈Δ≤２００ｋｍ）的主要特征是趋势和突发性异常并重;而远场（Δ〉２００ｋｍ）则一般无趋势性异常,只有急剧变化的短临异常。     

Focal Mechanism Solutions of the 2008 Wenchuan earthquake sequence from P-wave polarities and SH/P amplitude ratios: new results and implications

The 2008 Wenchuan earthquake, a major intraplate earthquake with M _w 7.9, occurred on the slowly deforming Longmenshan fault. To better understand the causes of this devastating earthquake, we need knowledge of the regional stress field and the underlying geodynamic processes. Here, we determine focal mechanism solutions (FMSs) of the 2008 Wenchuan earthquake sequence (WES) using both P-wave first-motion polarity data and SH/P amplitude ratio (AR) data. As P-wave polarities are more reliable information, they are given priority over SH/P AR, the latter of which are used only when the former has loose constraint on the FMSs. We collect data from three categories: (1) permanent stations deployed by the China Earthquake Administration (CEA); (2) the Western Sichuan Passive Seismic Array (WSPSA) deployed by Institute of Geology, CEA; (3) global stations from Incorporated Research Institutions for Seismology. Finally, 129 events with magnitude over M _s 4.0 in the 2008 WES are identified to have well-constrained FMSs. Among them, 83 are well constrained by P-wave polarities only as shown by Cai et al. (Earthq Sci 24(1):115–125, 2011), and the rest of which are newly constrained by incorporating SH/P AR. Based on the spatial distribution and FMSs of the WES, we draw following conclusions: (1) the principle compressional directions of most FMSs of the WES are subhorizontal, generally in agreement with the conclusion given by Cai et al. (2011) but with a few modifications that the compressional directions are WNW–ESE around Wenchuan and ENE–WSW around Qingchuan, respectively. The subhorizontal compressional direction along the Longmenshan fault from SW to NE seems to have a left-lateral rotation, which agrees well with regional stress field inverted by former researchers (e.g., Xu et al., Acta Seismol Sin 30(5), 1987; Acta Geophys Sin 32(6), 1989; Cui et al., Seismol Geol 27(2):234–242, 2005); (2) the FMSs of the events not only reflected the regional stress state of the Longmenshan region, but also were obviously controlled by the faults to some extent, which was pointed out by Cai et al. (2011) and Yi et al. (Chin J Geophys 55(4):1213–1227, 2012); (3) while the 2008 Wenchuan earthquake and some of its strong aftershocks released most of the elastic energy accumulated on the Longmenshan fault, some other aftershocks seem to occur just for releasing the elastic energy promptly created by the 2008 Wenchuan earthquake and some of its strong aftershocks. (4) Our results further suggest that the Longmenshan fault from Wenchuan to Beichuan was nearly fully destroyed by the 2008 Wenchuan earthquake and accordingly propose that there is less probability for great earthquakes in the middle part of the Longmenshan fault in the near future, although there might be a barrier to the southwest of Wenchuan and it is needed to pay some attention on it in the near future.