The high‐frequency limit of usable response spectral ordinates from filtered analogue and digital strong‐motion accelerograms

The range of response frequencies for which spectral ordinates obtained from accelerograms may be considered reliable is limited by several factors, primary among them being the effects of filters that are routinely applied to remove noise from the records. Considerable attention has been focused on the low‐frequency limit of the usable spectral ordinates because of various engineering applications requiring long‐period spectral accelerations or displacements but only recently have rational approaches to selecting the high‐frequency limit been proposed. Since there are applications for which the high‐frequency spectral ordinates are important, the approaches to this issue presented in the recent studies are reviewed and their application to the ground‐motion database from Europe and the Middle East is explored. On the basis of the results of these analyses, it is concluded that a large proportion of this dataset can be used to provide reliable estimates of response spectral ordinates at much shorter periods than may have previously been considered feasible. Copyright © 2011 John Wiley & Sons, Ltd.     

中国大陆现代构造应力场与强震活动

依据应力性状和力源特征,中国大陆现代构造应力场可划分为四级应力区.它们分别是2个一级应力区、4个二级应力区、5个三级应力区和26个四级应力区.通过分析中国大陆现代构造应力分区与强震活动之问的关系,初步获得以下结论:①构造应力作用强烈和复杂的地区是强震频发的地区;②应力区边界是强震集中发生的地带;③应力方向、应力结构类型...     

Geochemical Features of the Hubin Spring Gases from the Northern Caldera Lake of the Tianchi Volcano,Changbai Mountains

This paper deals with geochemical features of gas emitted from the Hubin Springs.The Hubin Springs zone,a strong thermal emission zone,is are locatedd at the north edge of the Tianchi caldera lake.Very young deposits with uncertain eruption date are found on the top area of the Tianwenfeng,which might have been formed in one of the recent eruptions or the Millennium Eruption.It is of significance to study the geochemistry features of the emitting gas from the Hubin Springs to understand the activities of the Tianchi Volcano.This paper systematically sampled and analyzed the gases emitted from the Hubin Springs and discussed their geochemistry features.The results show that there is a high content of deep derived gases,such as CO2,He,CH4 and Ar in Hubin Springs zone.The isotopic ratio of He lies between 4.18 and 5.95 Ra.The averaged mantle derived gas content calculated from the 4He/20Ne ratio and He content reaches 67.1%.All these show that the Hubin Springs are located on a special belt of deep gases released in high intensity and large scale.The spatial distribution of Helium isotope is characterized by concavity,showing that this special area may be related to the volcanic edifice.It is highly possible that the released gases represent the residual gas samples of the latest eruptions from the Tianchi Volcano.However more detailed studies are demanded.     

可液化土层隧道围岩的动力响应及液化区发展分析

隧道可液化土层围岩对地震动作用非常敏感,可液化土层动孔压的产生和发展使得地下结构受到上浮作用,从而影响地下结构的稳定性.通过对可液化土层中隧道动力响应计算,研究了不同静应力场隧道围岩动孔压场分布、围岩液化区域分布以及衬砌结构仰拱底与拱顶的动孔压差变化.研究结果表明,不同静应力场对围岩可液化土的动孔压分布、液化区域分布及...     

青海地区各地震带强震活动基本状态探讨

利用青海地区1900年以来5级以上强震目录探讨了省内各地震带地震活动的基本状态,结合累积应变能释放现象讨论了各地震带现今地震活动所处的状态。结果显示,青海地区4个地震带强震活动存在明显的平静与活跃的交替特征,这是普遍的宏观规律,但平静与活跃的特点具有差异性。伴随各地震带地震活动状态的不同,其累积应变能释放呈现加速或减速的特征。     

辽宁省强震动台网运行与管理

本文介绍了台网的运行维护与管理情况,以及海城、伊通4．3级地震强震记录的获取情况,指出了台网现行维护方式的不足,并提出了相应的改进措施。     

陕西一次强沙尘暴过程诊断与分析

2006年陕西共发生沙尘天气13次,其中4月11日的沙尘天气最为严重,危害最大,这也是陕西近10 a来最为严重的一次沙尘暴天气过程。这次沙尘天气带来一系列的天气演变过程,它持续时间虽然只有8~9 h,但覆盖面积大,影响范围广,全省70%~80%左右的区域都受到了影响。运用FY-2卫星红外云图及MICAPS2.0模式中的数值预报进行分析,发现红外云图呈现出异常状态,高低空形势配合较好,气压梯度、温度梯度密集,狂风突起等状况,试图揭示与解读沙尘天气在发生过程中某些气象因子的特征及其对沙尘天气的影响机理,为今后预报沙尘暴强度和发生区域提供一定的理论依据。     

Variations in Frequency and Intensity of Strong Tropical Cyclones Affecting China During

 Based on tropical cyclone track dataset in the western North Pacific from China Meteorological Administration (CMA), variations in frequency and intensity of tropical cyclones (TCs) in the western North Pacific, affecting-China TCs (ACTCs) and landfall TCs (LTCs) achieving a typhoon intensity during 1957-2004 were studied. Frequencies of strong tropical cyclones showed significant decreasing trends from 1957 to 2004 and the linear trend was much greater when the intensity was stronger. There was no linear trend in the portion of strong tropical cyclones achieving a typhoon (TY) intensity, while those reaching a strong typhoon (STY) and a super typhoon (SuperTY) intensity showed decreasing trends during 1957-2004. The maximum intensities of TCs, ACTCs and LTCs all decreased during the period of 1957-2004. The mean intensities of TCs and ACTCs displayed decreasing trends and the mean intensity of LTCs achieving a TY intensity also showed a decreasing trend.     

1998~2003年伽师三次不同类型Ms6级地震震源破裂过程及短期内余震活动特征

利用大量远场观测地震图反演了新疆伽师地区三次不同机制类型M_s6级地震的破裂过程.结果表明,1998年8月2日M_s6.1级地震破裂尺度小,破裂过程简单,最大滑动量为12 cm,主破裂过程持续时间为8 s.1998年8月27日M_s6.5地震破裂过程的空间分布反映出双侧破裂特征,主破裂过程在前13 s基本完成,最大滑动量为63 cm,破裂面上起始破裂点两侧的滑动矢量方向不同.2003年2月24日M_s6.8地震的破裂过程最为复杂,震源时间函数由两次上升时间组成,破裂一共持续了32 s,最大滑动量为32 cm.研究表明,余震主要发生在主震破裂图像中大滑动量区域的外围或滑动量变化梯度较大的区域,主震后短期内发生的余震震源机制解也与破裂面上断层的错动方向一致,表明余震的位置和机制与主震破裂所引起的应力重新分布有关.