汶川8.0级地震前BSQ型数字垂直摆倾斜仪观测到的地形变异常现象

地倾斜连续观测是地壳形变观测研究中重要内容。汶川8.0级地震前,布设在四川德阳金河测点的新型BSQ型数字垂直摆倾斜仪观测到了明显的地形变异常现象。分析其观测结果可知,汶川8.0级地震前约半月时间内德阳金河测点的地倾斜运动速度较过去的平均运动水平提高了数十倍,且震前地表快速倾斜的方向在N25°W左右。除此之外,德阳金河BSQ型数字垂直摆倾斜仪测点还观测到较为完整的,对应于可以反映地表应力集中、释放过程的震前地表破裂过程。上述现象为今后研究强震孕育机理提供了重要的信息。介绍与分析了布设在龙门山断裂带附近的其它类型地倾斜仪在震前的观测结果。事实证明,BSQ型数字垂直摆倾斜仪在强震前的浅表过程监测中具有重要意义,值得在今后的地震前兆台网工作中进行推广。     

叶蛇纹岩脆性-半脆性破裂研究

利用Paterson气体介质高温高压流变仪对纯叶蛇纹岩在100~400MPa围压、25~700℃温度和10-5~1.5×10-6s-1应变速率下进行了三轴压缩变形实验。实验结果表明叶蛇纹石在低压条件下表现为脆性破裂,高压或脱水条件下表现为半脆性破裂。随着温度的增加,叶蛇纹石的强度显示逐渐降低的趋势;尤其在脱水条件下,温度的增加可导致叶蛇纹石强度大幅度地降低,而且此时预热时间对强度的影响比未发生脱水时更加显著。结合前人的研究并对比发现,围压在室温下的增加导致叶蛇纹岩强度增加;但在高温下围压的增加导致试样强度整体上降低,这很可能是试样内聚力的局部损失与韧性增强引起的。围压和温度的升高,以及断层面上流体的增加很可能会增加破裂面的韧性,从而减小摩擦系数。此外,叶蛇纹石并非以往人们所认为的那样具有极低的强度,其强度要比低温蛇纹石(如利蛇纹石和纤蛇纹石)的大得多,即便在高温(大约600℃)下差应力大于约600MPa和中-低温(≤400℃)下差应力大于约1000MPa时仍没有表现出明显屈服的迹象。在脱水条件下,蛇纹岩并没有发生脱水致脆,相反脱水使得试样的断裂行为变得更加温和些。因此,俯冲带蛇纹岩脱水更可能诱发其周围更加脆性的岩石发生地震而不是脱水的蛇纹岩本身发生地震。     

TESTING OF ENERGY DISSIPATING CLADDING CONNECTIONS

Properly designed precast concrete cladding could potentially provide lateral stiffness, ductility, and energy dissipation for an overall building structure, especially during earthquakes. This paper describes a set of advanced connections that take advantage of the interaction between facade panels and structure (mainly due to horizontal interstorey drift) to dissipate energy, thereby reducing the response of the main structure. The results of an experimental program to characterize the hysteretic behaviour of advanced connections are presented. Design equations for the advanced connections are then calibrated against the test results, and the corresponding design charts are presented. It is anticipated that this research will lead to innovative ways of viewing the entire cladding system of a building.     

基于EMD的中国大陆强震活动特征分析

利用EMD方法对中国大陆年度最大地震时间序列进行逐级分解, 得到5个本征模态函数(IMF)项和1个趋势项, 分析了各个IMF分量不同的周期成分同地球自转速度变化、 太阳黑子活动和潮汐运动等环境因子之间的相关关系, 初步探讨了各个IMF分量的物理机理及其对中国大陆地震活动的影响。     

Historical tsunami in the Makran Subduction Zone off the southern coasts of Iran and Pakistan and results of numerical modeling

Tsunami hazard in the Makran Subduction Zone (MSZ), off the southern coasts of Iran and Pakistan, was studied by numerical modeling of historical tsunami in this region. Although the MSZ triggered the second deadliest tsunami in the Indian Ocean, among those known, the tsunami hazard in this region has yet to be analyzed in detail. This paper reports the results of a risk analysis using five scenario events based on the historic records, and identifies a seismic gap area in western Makran off the southern coast of Iran. This is a possible site for a future large earthquake and tsunami. In addition, we performed numerical modeling to explain some ambiguities in the historical reports. Based on the modeling results, we conclude that either the extreme run-up of 12–15 m assigned for the 1945 Makran tsunami in the historical record was produced by a submarine landslide triggered by the parent earthquake, or that these reports are exaggerated. The other possibility could be the generation of the huge run-up heights by large displacements on splay faults. The results of run-up modeling reveal that a large earthquake and tsunami in the MSZ is capable of producing considerable run-up heights in the far field. Therefore, it is possible that the MSZ was the source of the tsunami encountered by a Portuguese fleet in Dabhul in 1524.     

云南地区中强地震连发及其调制比的时空展布特征

剖析并定义了云南地区1970～2001年中强地震连发,发现中强地震连发的时空展布具有空间分布按一定方向有规律迁移,时间分布集中于5～11个月的特点。利用小震调制比分析云南地区中强地震连发的孕震演变,结果发现小震调制比的异常特性：空间上中强震连发前2～0．5a的时段内小震调制比出现8个平方度以上的异常面积元,异常面积元集中的地区为未来中强震连发的主体区域,时间上中强震连发前1～3a出现小震调制比R。的高值异常。并用花岗岩块体受压实验结果初步探讨了中强地震连发及其调制比时空展布特征的构造活动。     

民国时期滇西南地区三次强震补充调查

本文通过对民国时期发生在滇西南地区的1938年5月14日澜沧MS6.0级、1941年5月16日耿马MS7.0级和1941年12月26日澜沧MS7.0级3次地震历史资料的系统收集和整理,并在前人已有研究的基础上,通过现场采访和补充调查获得的新资料,修改和完善了这3次地震的等震线图和极震区范围,并结合该区地形地貌特征和断裂最新活动性研究结果,综合分析评述了其发震构造特征。结果表明,这3次强震发生在腾冲-澜沧新生地震带附近,分别与黑河断裂、南汀河断裂西支及澜沧断裂勐遮段的新活动密切相关。     

邢台地震区大地电磁观测与研究

在邢台地震区进行了大地电磁观测,并对该地区电性结构与地震的关系进行了研究.该地区地下电性结构较复杂,电性在纵向及横向都存在着显著的变化.一维结果表明,该地区电性纵向分布可分五层,第三层为高导层,埋深约10—20 km.在地震震源集中区,高导层深度有较大变化.电性横向分布也有明显变化.总体上看,地震区内电阻较高,可是地震并不发生在电阻率最高的地点,而多发生在电性变化较大地段.     

Surface air temperature changes over the Tibetan Plateau: Historical evaluation and future projection based on CMIP6 models

With its amplification simultaneously emerging in cryospheric regions, especially in the Tibetan Plateau, global warming is undoubtedly occurring. In this study, we utilized 28 global climate models to assess model performance regarding surface air temperature over the Tibetan Plateau from 1961 to 2014, reported spatiotemporal variability in surface air temperature in the future under four scenarios (SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5), and further quantified the timing of warming levels (1.5, 2, and 3 °C) in the region. The results show that the multimodel ensemble means depicted the spatiotemporal patterns of surface air temperature for the past decades well, although with differences across individual models. The projected surface air temperature, by 2099, would warm by 1.9, 3.2, 5.2, and 6.3 °C relative to the reference period (1981–2010), with increasing rates of 0.11, 0.31, 0.53, and 0.70 °C/decade under the SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5 scenarios for the period 2015–2099, respectively. Compared with the preindustrial periods (1850–1900), the mean annual surface air temperature over the Tibetan Plateau has hit the 1.5 °C threshold and will break 2 °C in the next decade, but there is still a chance to limit the temperature below 3 °C in this century. Our study provides a new understanding of climate warming in high mountain areas and implies the urgent need to achieve carbon neutrality.     

Earthquakes in Switzerland and surrounding regions during 2006

This report of the Swiss Seismological Service summarizes the seismic activity in Switzerland and surrounding regions during 2006. During this period, 572 earthquakes and 91 quarry blasts were detected and located in the region under consideration. Of these earthquakes, two occurred in conjunction with the construction of the new Gotthard railway tunnel and 165 were induced artificially by the stimulation of a proposed geothermal reservoir beneath the city of Basel. With 20 events with M _L ≥ 2.5, five of which were artificially induced, the seismic activity in the year 2006 was far below the average over the previous 31 years. Nevertheless, six events were felt by the public, most prominently the strongest of the induced Basel events (M _L 3.4), which caused some non-structural building damage. Noteworthy are also the two earthquakes near Cortaillod (M _L 3.2), on the shore of Lake Neuchatel, and in Val Mora (M _L 3.5), between the Engadin and Val Müstair, as well as the 42 aftershocks of the M _L 4.9 Vallorcine earthquake, between Martigny and Chamonix, of September 2005. Editorial handling: Stefan Bucher