基于钻孔应变地震波记录确定地震面波应变震级

近年发展的高采样率的钻孔应变仪可以记录到地震波造成的水平应变,是动态库仑应力研究的重要手段.利用钻孔应变仪记录的应变地震波确定地震震级,是一个重要的科学课题.本文收集了我国10个应变台站四分量钻孔应变仪2020年1—3月记录的10 Hz采样应变地震波资料,共选出震级M≥4.0的浅源地震68个,用最小二乘法求得应变震级公式为Mε=lg E max+1.65 lg(Δ)+1.43.对于6.5级以下的地震,计算得到的应变震级ε与中国地震台网中心公布的震级M CENC基本一致:M CENC=1.03ε-0.23,但本研究中的两个7级地震,应变震级出现了震级饱和现象.本文的基本结论是:应变定震级是可行的,但对于两个7级地震的饱和现象需要进一步深入研究,因为它们不但涉及震级确定,而且涉及远震动态库仑应力触发地震的研究.今后要对更多的大震钻孔应变波形记录进行分析.     

朝鲜核爆的Rayleigh波震级测量

利用1995年至2009年中国东北及邻近地区11个宽频带台站记录到的77个地震事件、3个化学爆炸和2次朝鲜核爆的区域地震资料,标定该区域台网的Rayleigh波震级.通过对8~25 s 周期的垂直分量Rayleigh波形进行分析,获取基于最大振幅的面波震级.计算82个区域事件不同周期的台基响应,经过台基校正后取最大振幅的面波震级为事件震级.2006年和2009年两次朝鲜核爆的面波震级分别为2.93±0.19和3.62±0.21.将地震和核爆事件的面波震级M_s与体波震级m_b(Lg)进行比较,发现根据该区域台网的数据利用M_s-m_b识别方法无法鉴别朝鲜地区的核爆与地震.朝鲜核爆的面波震级相对较大,使M_s-m_b识别方法失效,其原因可能是源区介质的不均匀性、由核爆炸冲击引发的深部的拉伸破坏被抑制,或者是近爆源区存在张性的构造预应力.假定核爆可能的埋藏深度范围是0.01~1.0 km,用Rayleigh波震级估计朝鲜核爆的当量,对2006年和2009年核爆当量的估值范围分别为0.42~3.17 kt和2.06~15.53 kt.     

Calculation of Calibration Functions and Explosive Aftershock Magnitudes in the Near Field

The current calibration function used in calculating the magnitude of natural earthquakes within 5km is a constant; a fact that causes several serious difficulties for the calculation of the magnitude of small and shallow-focus earthquakes. According to the attenuation law of explosions and the propagation theory of elastic waves, the calibration function is calculated for near field quakes from 0kin to 5kin. Magnitudes of two aftershock sequences are calculated. The magnitudes of most explosion earthquakes are small, ranging mainly from magnitude -0.5 to 1.0. The M-t chart of the explosive aftershocks is completely different from that of strong earthquake aftershocks. It not only shows positive columnar lines indieatJng large magnitudes but also short negative columnar lines indicating small magnitudes.     

金州断裂降震效应初探

利用位于金州断裂两侧地震台所记录的地震震级的差异,研究金州断裂的降震效应。统计表明,当地震波通过断裂时存在明显的衰减现象,震级相差近０．４级。     

新疆测震台网与中国地震台网测定的地震震级对比分析

选用2010～2012年间新疆境内和边邻地区MS≥4.0地震41个,以中国地震台网给出的震级为标准震级,对新疆台网记录的数字记录波形使用不同仪器分析、仿真处理。用速度量记录直接计算,将速度量记录仿真为短周期WA位移记录、中长周期SK仪记录的勒夫波和长周期763仪记录的瑞利波位移记录计算震级,分别进行了震级偏差统计分析,初步得出震级偏差值的震级校正值,有利于提高新疆地震台网速报地震震级的准确性。     

库尔勒地震台地震监测能力初探

主要选用库尔勒地震台测点单台地震目录,运用单台小震优势分布法、logN-M法和b值计算法然后采用M-△法对结果进行验证。对库尔勒台监测点300km范围内的地震监测能力进行了初步分析和讨论,确定库尔勒台监测点300km以内的控震能力;再依此方法确定了库尔勒附近的库米什台300km以内的地震监测能力。     

新疆境内各相邻区域地震活动相关性分析

新疆地震活动分布区域广,主要分布在南北天山、西昆仑、阿尔泰、阿尔金山与塔里木盆地和准噶尔盆地的衔接地带。各地震带地震活动水平不尽相同,其中南天山与北天山地震带以及帕米尔一西昆仑地震带的地震活动水平较高,地震活动呈西强东弱的特点。自2011年以来新疆境内地震活动呈现出5级地震连发,6级地震活动频繁,且各地震带均有分布的特点。利用新疆历史地震目录,分析新疆境内各片区发生地震活动是否具有相关性,并从中获得各片区地震活动相关性的量度,以此可以将这些量度作为新疆境内各片区地震中长期预报的辅助性分析方法。     

Prediction of cyclic resistance ratio for silty sands and its applications in the simplified liquefaction analysis

Liquefaction resistance of granular soils is commonly characterized by the cyclic resistance ratio (CRR) in the simplified shear stress procedure of liquefaction potential assessment. This parameter is commonly estimated by cyclic tests on reconstituted samples or empirical correlations between liquefied/non-liquefied case histories. The current study employs results of cyclic triaxial tests on reconstituted soil specimens and presents a predictive equation for cyclic resistance ratio (CRR) of clean and silty sands. The CRR equation is a function of relative density, effective mean confining pressure, non-plastic fines content, number of harmonic cycles for liquefaction onset, and some other basic soil properties. It is demonstrated that the developed relationship obtains reasonable accuracy in the prediction of laboratory-based CRR. Based on the developed CRR model, new relationships are then presented for the coefficient of effective overburden pressure (K_σ) and magnitude scaling factor (MSF), two important modification factors in the simplified shear stress procedure. These new modification factors are then compared with those recommended by previous researchers. Finally, the possible application of the proposed CRR model in field condition is shown for a specific case. This study provides a preliminary insight into the liquefaction resistance of silty sands prior to the complementary laboratory studies.     

现今地震预警技术及其在国内发展状况的探讨

本文首先从地震预警的概念、系统构成和技术方法等方面入手,对目前国际上地震预警技术的最新研究进展和热点问题进行了全面的论述。继而通过对国内发展现状的系统分析,认为地震预警系统的开展在政府、社会、台网建设和研究基础等方面都已经具备了基本的条件。结合当前国内的实际情况,对地震预警系统在实施过程中可能遇到的技术问题和非技术性挑战进行了估计,并建议加强法律措施、公众教育、震害防御等方面的配套工作,最大限度地发挥地震预警系统在防震减灾工作中的作用。     

Estimated Visual Magnitudes of the EISCAT UHF Meteors

We have investigated the conditions for simultaneous meteor observations with the EISCAT UHF radar system and telescopic optical devices. The observed characteristics of 410 meteors detected by all three UHF receivers are compared with model simulations and their luminosity is calculated as a part of a meteoroid ablation model using a fifth order Runge–Kutta numerical integration technique. The estimated absolute visual magnitudes are in the range of +9 to +5. The meteors should therefore be observable using intensified CCD or EMCCD (Electron Multiplying CCD) cameras with telephoto lenses. A possible setup of a coordinated radar and optical campaign is suggested.