SOURCE PARAMETERS OF THE CANGWU MS5.4 EARTHQUAKE, 31 JULY, 2016

On July 31^st, 2016, an earthquake of M_S5.4 occurred in Cangwu County, Guangxi Zhuang Autonomous Region, which is the first M_S ≥ 5.0 earthquake in coastal areas of southern China in the past 17a. The moderate earthquake activities have come into a comparatively quiet period in coastal areas of southern China for decades, so the study about the Cangwu M_S5.4 earthquake is very important. However, differernt research institutions and scholars have got different results for the focal depth of the Cangwu M_S5.4 earthquake. For this reason, we further measured the focal depth by using CAP method and sPL phase method. sPL phase was first put forward by Chong in 2010. It is often observed between P and S wave of continental earthquakes with epicentral distance of about 30km to 50km. The energy of sPL phase is mainly concentrated on the radial component. Arrival time difference between sPL phase and direct P wave is insensitive to epicentral distancs, but increases almost linearly with the increase of focal depth. Based on these characteristics and advantages, sPL phase method is chosen to measure the focal depth of Cangwu M_S5.4 earthquake in the paper. First of all, we selected the broadband waveform data through seismic stations distributed mainly in Guangxi and adjacent provinces from Data Management Centre of China National Seismic Network and Guangxi Earthquake Networks Center. And an appropriate velocity model of Cangwu area was constructed by the teleseismic receiver function method. Then, the focal mechanism and focal depth of Cangwu M_S5.4 earthquake were determined by using the CAP(Cut and Paste)method. Next, we compared the synthetic waveforms simulated by F-K forward method of different focal depth models with the actual observed waveforms. According to the difference of arrival times between sPL and Pg phases, we finally obtained the focal depth of Cangwu earthquake. The results show that the focal depth is 11km measured by CAP method and 9km by sPL phase method. Based on the focal mechanism solution, isoseismal shapes, aftershocks distributions and investigation on spot, we conclude that the Cangwu M_S5.4 earthquake is a left-lateral strike-slip earthquake which occurred in the upper crust. Our preliminary analysis considers that the seismogenic structure of Cangwu earthquake is a north-northwest branch fault, and the control fault of this earthquake is the Hejie-Xiaying Fault.     

多维多点激励下考虑支座摩擦滑移及结构碰撞的非规则桥梁抗震性能研究

以一座典型山区非规则梁桥为研究对象,建立了该桥梁多维多点激励下的多自由度动力计算模型,研究了该桥梁在多维多点激励下考虑支座摩擦滑移及结构碰撞等非线性因素时的抗震性能。研究结果表明:相比一维地震输入,多维地震可使结构的动力响应增加,桥墩底部弯矩需求增大;相比一致激励,多点激励可使得支座的位移需求增大,且地震波最后到达的桥墩上方支座位移最大;同时考虑多点激励和碰撞效应可使桥墩的弯矩需求增加;水平地震作用下,矮墩上部的支座容易滑动,且双向地震较单向地震更明显,三向地震输入较双向有所增强。因此,对山区非规则梁桥进行抗震设计时应有针对性地进行多维多点地震输入计算,找出结构的最大地震需求,以期指导设计。     

五台地震科技中心水平摆倾斜仪对应强远震前兆异常特征分析

通过对数字石英水平摆倾斜仪最近几年积累数据的分析,发现在大多数中强远震发生前数小时,倾斜仪东西分量观测数据锯齿状异常、固体潮曲线出现畸变并伴有明显的抖动,这对异常识别和地震预测具有一定的参考价值。     

双向地震作用下锯末混合土场地动力特性分析

在北京工业大学振动台台阵系统上开展了一系列锯末混合土地基自由场振动台模型试验,试验中模型箱采用装配式连续体刚性模型箱,试验中输入地震动时程采用El Centro地震动记录、Taft地震动记录和天津地震动记录,地震动输入方向分为水平单向和水平双向。文中,重点考察了双向地震动输入下锯末混合土模型场地的动力特性及其变化规律,主要指标包括模型场地地震动反应的峰值加速度及其动力放大系数、加速度时程及其傅氏谱。试验结果表明:随着输入地震动强度的增大,同一测点反应的峰值加速度总体上在增大,而其加速度动力放大系数总体上呈现减小的趋势,反应的频谱组成从较高频率向较低频率移动;双向地震作用下锯末混合土模型场地的动力变化规律与单向地震作用下较为一致。     

Application of Avaatech X-ray fluorescence core-scanning in Sr/Ca analysis of speleothems

Application of X-ray fluorescence core-scanning(XRF-CS) on both marine and lake sediments has achieved remarkable results. However, its application has not been widely extended to the research on speleothems. In this study, we measure the Sr abundance and the Sr/Ca ratios of three stalagmites(two aragonite stalagmites, one calcite stalagmite) using the state-of-the-art fourth-generation Avaatech high-resolution XRF core scanner. Through comparisons among different scan paths and among different scan resolutions, as well as comparisons with inductively coupled plasma optical emission spectrometer(ICP-OES), Itrax XRF, and Artax XRF results, we confirm that the Avaatech XRF core scanner could precisely, quickly, and nondestructively analyze the high-resolution Sr abundance of speleothems. Furthermore, we combine the stalagmite δ~(18)O records to explore the paleoclimatic significance of the measured stalagmite Sr/Ca.     

珠江口洪季最大浑浊带的大小潮变化与机制分析*

基于ROMS三维模型, 模拟了珠江口洪季最大浑浊带的轴、侧向分布和大、小潮变化。模拟结果表明, 珠江口伶仃洋最大浑浊带的轴向位置在22.3°—22.45°N之间, 并随着潮流变化而周期性上下游迁移。控制最大浑浊带形成的主要因素是余流作用下的底层泥沙辐聚, 决定最大浑浊带位置的主要因素是水平对流输沙, 泥沙来源主要是上游浅滩沉积物的再悬浮。小潮期间堆积在浅滩的细颗粒沉积物在大潮期间被悬浮, 搬运到下游的滞流点位置, 在中滩南部和西滩外缘落淤。“潮泵”作用在大潮期间将泥沙向下游输运, 在小潮期间向上游输运; 垂向剪切作用则有利于悬浮泥沙的陆向输运; 二者共同作用产生泥沙辐聚, 形成最大浑浊带。大、小潮期间余流结构差异不大, 主要由密度差和潮汐混合不对称共同导致, 其中前者贡献更大。     

大黄鱼病原副溶血弧菌单克隆抗体制备及其应用

用甲醛灭活副溶血弧菌(Vibrio parahaemolyticus)和溶藻弧菌(V.alginolyticus)制成免疫原免疫BALB/c小鼠,利用淋巴细胞杂交瘤技术,获得1株特异的针对副溶血弧菌的单克隆抗体,命名为D6F3H5。腹水及培养上清液抗体的ELISA效价分别为:1∶5 120和1∶1 280,该单克隆抗体与其它细菌没有明显的交叉反应。利用该单克隆抗体和兔抗副溶血弧菌多克隆抗体,建立了检测副溶血弧菌的双抗体夹心ELISA方法。该方法对副溶血弧菌的最小检出量为5×104个/mL。用双抗体夹心ELISA检测大黄鱼(Pseudosciaena crocea)样品,14尾患病大黄鱼中有11尾检出副溶血弧菌,而10尾健康大黄鱼都没有检出副溶血弧菌。由此可见,本试验制备的高特异性的抗副溶血弧菌单克隆抗体,可以用于患病大黄鱼副溶血弧菌的快速诊断。     

用单纯形法和PTD法对2016年新疆阿克陶M_S6.7地震序列的震源深度测定分析

用单纯形法计算了阿克陶M_S6.7主震的震源深度,结果为7.5 km,但单纯形法对设定的初始深度依赖值过高,震源深度值不一定可靠。用PTD法计算了阿克陶M_S6.7主震的震源深度,结果为9.4 km,且用了44个台站的震相数据共组成99个有效样本数参与了计算,不仅样本数多,而且震源深度样本数的集中度也比较符合高斯分布的特征,所以震源深度值可信度高,也非常接近国内和国外地震研究机构给出的此次地震的震源深度。当主震的震源深度已知且适合单纯形法设定的初值时,用单纯形法来计算地震序列的震源深度,不仅残差小,而且软件实现简单,确保了地震序列的按时提交。再用PTD法来检验该地震序列震源深度的准确性,结果显示,2种方法得到的震源深度差值不超过10 km,符合中国地震台网对震源深度误差的要求。     

利用自洽方程计算法分析天山中段分量钻孔应变资料可靠性

根据天山中段8套四分量钻孔应变仪观测资料,利用自洽方程计算应变观测的信度,用信度指标检验数据的可靠性,从而进一步用自洽方程计算实际各元件灵敏度的相对大小,并用相对标定的结果,对观测数据进行校正。结果表明:①石场、巴仑台、巴音沟、雀儿沟、榆树沟和库米什台经过校正后,数据观测信度有了明显提升,其中石场和雀儿沟台的数据信度最高;②库米什台校正前数据观测信度较高,因个别“坏点”影响,校正后,观测信度反而下降;③小泉沟和新源台数据信度较低,存在从自洽到失洽的情况,分析认为这可能与系统自身存在问题有关,也有可能是前兆异常,有待进一步研究。     

高烈度区公路隧道横通道地震响应分析

双洞隧道主隧道与横通道交接部位是隧道抗震中的薄弱位置,以穿越高烈度区隧道为背景,采用MIDAS GTS-NX有限元分析软件,对在汶川地震动作用下的公路隧道横通道进行地震响应分析。在X方向和Y方向地震动荷载的共同作用下,通过对围岩和衬砌的计算结果研究,得出以下结论:隧道整体的最大相对位移主要发生在主隧道与横通道拱顶和连接处;衬砌相对位移随埋深增加而减小;隧道产生的横向变形更大;横通道边墙位置更容易受到剪切破坏,主隧道与横通道连接处拱脚的弯矩、剪力、最大主应力和最大剪应力最大,应重点采取设防措施。