首都圈数字地震台网的微震定位实验

新建成的首都圈数字地震台网由 10 7个数字地震台站组成 ,其地震监测和定位能力需要检验。此文主要目的是为评估首都圈数字地震台网的地震活动监测能力提供参考依据。在地震定位中 ,应充分发挥数字地震记录的优势 ,采用相应的数字地震记录处理技术 ,提高地震定位的可靠性和精度。采用滤波、偏振及台站扫描、震相追踪等数字技术 ,提高了震相识别的可靠性和精度 ,并用Geiger方法对 2 0 0 1年首都圈数字地震台网记录到的 7个网内及网缘微震 (ML<2 .0 )进行了精确定位 ,还通过对爆破的定位来检验程序和方法的可靠性和精度。结果表明 ,震中定位误差估计小于2km ,震源深度误差估计小于 3km     

神经网络方法在爆炸地震震中定位方面的应用

地震定位过程中,由于地球介质的不均一性以及台站局部地质条件的复杂性,使震中距和地震波走时呈非线性关系。利用通常地震定位方法所确定的爆炸地震震中位置和实际震中存在２０～３０ｋｍ偏差。人工神经网络具有高度非线性映射功能,可应用于地震震中定位。应用ＢＰ（反向传播）神经网络确定远场爆破地震震中的实例表明,所确定的震中位置和实际震中位置偏差在８ｋｍ以内,外延预测确定的震中位置和实际震中位置偏差小于１８ｋｍ     

用余震确定2008年汶川M_w7.9地震的震源位置与发震时刻

利用同一地点的2个地震在相同台站记录的P波到时差是一个常数这一原理,找到了与汶川主震位置相近的余震,并利用台站距震中近,且记录波形清晰、完整的优势,对余震进行了定位,依此确定了汶川主震的位置和发震时刻.结果是震中位于31°1.26′N、103°22.50′E;震源深度7.9km;发震时刻(北京时间)为2008年5月12日14时27分58.80秒.     

用于地震预警的三维实时定位方法

为了尽快定位地震,在“着未着”定位算法基础上,尝试引入三维地壳模型,构建具有三维空间格点分布的走时表.根据已触发台站的到时和未触发台站的位置信息设计概率分布函数,通过八叉树搜索方法,快速给出震源在三维空间的可能位置.使用波前追踪算法,计算中国几个地区三维地壳模型的走时网格,利用中国地震台网资料,对区域内发生的地震进行定位分析.结果显示,在一定的台网密度条件下,三维实时定位方法能在震后数秒给出震源位置,可满足地震预警要求.     

2020年7月12日唐山MS5.1地震预警处理能力分析

2020年7月12日,河北唐山发生M_S5.1地震,河北省地震预警系统成功地处理并产出了这次地震预警各种结果数据,本文借助此次地震对河北地震预警网内震中距200km范围内台站产出质量以及地震预警前5次处理结果进行详细分析。此次地震发生在河北地震预警网内,平均台间距为10km,首台触发后3s、震后6s发布首次处理结果,与编目结果相比,震级偏差为-1.3,震中位置偏差为2.6km,盲区半径为18km。随着参与定位台站数量增多,震级与位置偏差越来越小,但震级仍整体偏小。河北地震预警网台站产出质量整体较高,其中烈度台作为地震预警最重要的组成部分,是决定预警效果的关键因素。本次地震震中距200km范围内,烈度台平均信噪比为48,震中距50km范围内平均信噪比为112,符合预警系统对信噪比的要求。本次地震预警结果表明,河北地震预警网内台站布局基本合理,波形质量较高,地震预警系统处理软件在本次地震中预警产出效果较好,已经具备了一定的地震预警能力。     

采用双台子台阵方法的实时地震预警

地震定位是地震学最基本的问题之一。在速度作为确定系统成功水平关键因素的实时地震预警系统中，快速对具有潜在毁坏性大地震的定位能力具有特别重要的意义。我们开发了一种简单的、仅采用台阵中两个最先到达的P波到时的方法。假设一个简单的速度模型，这两个P波波至可用于绘制一条期待包含有近似地震震中的双曲线。根据台阵中其他台站的初波至不是最先到达的P波初至的事实，可将双曲线上的震中位置进一步加以约束。当应用到加州赫克托矿地震以及美国中部一个较小的地震事件时，模型结果表明与实际地震震中位置符合。虽然子台阵对大地震定位的方法存在固有的不确定性，但对早期预警系统而言这是可以接受的折衷，因为这可节省几秒至十几秒的时间，而不用等待其他台站的P波波至。尽管本文的主要目的是提出一种定位方法，但本文还表明：最靠近赫克托矿地震震中的台站，在P波到达的2s和3s内，分别记录到0．3mm和1mm的地面运动，这表示一个大的地震事件已经发生。     

上海电信传输地震台网监测能力及其定位精度

上海电信传输地震台网现有地面和深井观测点13处。本文根据现有的台站布局导出了估算震中定位误差的统计模型。计算了它的最大监测能力及其定位精度。结果表明上海台网至少有4个台站可同时记录到上海市内M_L≥1.5和网内M_L≥2.0的地震,并且网内的震中定位水平误差大约为2km。     

石家庄台网的台站布局与地震处理精度分析

本文描述了石家庄台网的台站布局,分析了地震数据处理精度与网内台站的记录质量、台站仪器的放大倍数、地震发生部位及地震震级的关系。     

2015年河北滦县震群发震机理分析

震群发震机理研究是近年来地震学研究的热点之一,其中基于观测现象对不同发震机理模型的分析和讨论是研究焦点.本文以2015年河北滦县震群为研究对象,首先通过模板匹配方法检测震群活动期间目录遗漏地震事件,得到更为完整的地震目录.再通过波形互相关震相检测技术标定地震事件在记录台站的震相到时,依据标定的震相到时,利用双差定位方法对震群进行精定位,基于地震精定位结果分析震群的震中扩展特征.最后通过波形互相关系数和破裂面重合程度检测震群中是否存在重复地震活动.通过计算共检测到目录遗漏地震事件103个.地震精定位结果显示发震构造为北东向断层,震中扩展表现出迁移速率先快后慢的两阶段线性扩展特征.震群活动期间共检测到两组重复地震活动,其中第一组发生在震中扩展的第一阶段,第二组发生在震中扩展的第二阶段.在三种常见的震群发震机理模型——级联触发模型、断层慢滑动模型和流体侵入模型中,断层慢滑动模型能够解释我们观测到的重复地震活动和震中线性扩展现象,因此认为此次滦县震群活动可能伴随断层的慢滑动,断层慢滑动可能对滦县震群的触发和持续活动起到一定作用.     

Voronoi图和双曲线联合方法在地震快速定位中的应用

基于Voronoi图和地震震中近似满足双曲线分布,提出了一种联合应用V图和双曲线的地震预警快速定位方法.并对青海地震台网记录的地震进行了重新定位处理.研究结果发现,该地震定位方法能满足地震速报的精度要求,在时效性上也可满足地震预警的需要.该方法在地震预警方面有应用前景.     

A generalized zero-lag cross-correlation approach for Rapid Earthquake Localization (REL): the example of the Istanbul Megacity Rapid Response System

A seismic antenna approach based on the generalized zero-lag cross-correlation method for rapid earthquake localization is proposed. This method is intended to be applied primarily for early warning, whenever the epicentre-to-target distances guarantee enough lead-time, rapid response purposes, and for those circumstances when a seismogenic area is not directly accessible with seismic stations or/and a network of instruments is concentrated within the area to be warned. The procedure we propose aims to provide useful information for magnitude determination and shake-maps generation. Indeed, it relies only on the first P-wave triggered arrivals from seismic stations, and is designed to work in real-time for the localization of events occurring outside of the network, that is, under conditions that might be detrimental to standard localization approaches. The procedure can by summarized by a few preliminary pre-seismic and real-time co-seismic steps. In the pre-seismic time-frame, for the cases where a large and dense network exists, waiting for all stations to trigger could dramatically reduce the available lead-time for the warning. Therefore, in such cases, the network could profitably be divided into sub-arrays, while also taking advantage of available earthquake recordings or simulated data sets. During the co-seismic time-frame, the main operations are: (1) individual on-site triggering by the P-wave of the seismic stations (e.g. by a STA/LTA algorithm); (2) real-time communication of key parameters (e.g. P-wave arrival time, and signal quality) to a main centre by SMS/WLAN; (3) setup of a pseudo data set, composed by a Gaussian function centred at the P-time, and with a bell width that can be set up proportional to the trigger signal-to-noise ratio (SNR); (4) calculation of a coherency map for the sub-array with triggered stations (preliminary sub-array location); and (5) stacking of coherency maps from the different sub-arrays (final location). By the stack of coherency maps estimated by the different sub-arrays in the last step of the procedure, the epicentral area’s location may be better constrained. This innovative approach for rapid localization was applied to both synthetic data, and real observations of two small earthquakes that occurred in the Marmara Sea, Turkey, which were recorded by the Istanbul Earthquake Rapid Response System.     

哈尔滨地铁环境振动噪声测试与降噪处理

考虑地铁环境振动噪声对未来城市地铁地震警报系统中地震信号识别的影响,以包含Ⅱ类和Ⅲ类2种场地土类型的哈尔滨市4个地铁站的上行线首部和尾部作为观测点,展开地铁环境振动噪声的测试、分析以及降噪处理研究。首先,对采集的列车振动数据进行统计分析;其次,基于滑动平均法,提出确定帕曾窗带宽b值的经验方法,并利用其对采集的地脉动数据进行平滑滤波处理;最后,采用本方法确定哈尔滨地铁地震P波预警的滤波频带,并与日本气象厅仪器地震烈度以及新干线地震预警系统的滤波频带进行对比。结果表明:①三轴向地铁列车振动信号中,竖向振动比水平向振动要大,切向振动比径向振动要大。②帕曾窗带宽b值为0.4 Hz时,平滑滤波处理后的频谱能较好地反映地脉动信号的频谱主频,且滤波后的地脉动信号的卓越频率和场地土类型有明显的对应关系,即水平向卓越频率和场地土类型的相关性较好,而竖向卓越频率的误差较大。③哈尔滨地铁地震P波预警的滤波频带为0.3~10 Hz时,能较好地滤除地震动信号中的地铁环境振动噪声,满足地震警报系统对地震记录信噪比的要求。     

利用宽频带地震数据资料研究辽宁地区的地壳结构

通过收集辽宁省地震局数字地震台网34个地震台站记录的2008—2009年的60个震中距为30°~90°之间,震级6,信噪比较高的远震记录数据,采用频率域反褶积方法计算获得各台站的远震P波接收函数,并用H-Kappa叠加方法对获得的接收函数进行叠加处理获得各台站下方的地壳厚度以及泊松比。通过研究表明,辽宁地区的地壳泊松比在0.24~0.29之间,地壳厚度介于30~36km之间。     

Continuous estimates on the earthquake early warning magnitude by use of the near-field acceleration records

In this article, the seismic records of Japan’s Kik-net are selected to measure the acceleration, displacement, and effective peak acceleration of each seismic record within a certain time after P wave, then a continuous estimation is given on earthquake early warning magnitude through statistical analysis method, and Wenchuan earthquake record is utilized to check the method. The results show that the reliability of earthquake early warning magnitude continuously increases with the increase of the seismic information, the biggest residual happens if the acceleration is adopted to fit earthquake magnitude, which may be caused by rich high-frequency components and large dispersion of peak value in acceleration record, the influence caused by the high-frequency components can be effectively reduced if the effective peak acceleration and peak displacement is adopted, it is estimated that the dispersion of earthquake magnitude obviously reduces, but it is easy for peak displacement to be affected by long-period drifting. In various components, the residual enlargement phenomenon at vertical direction is almost unobvious, thus it is recommended in this article that the effective peak acceleration at vertical direction is preferred to estimate earthquake early warning magnitude. Through adopting Wenchuan strong earthquake record to check the method mentioned in this article, it is found that this method can be used to quickly, stably, and accurately estimate the early warning magnitude of this earthquake, which shows that this method is completely applicable for earthquake early warning.     

Imaging 3-D crustal P-wave velocity structure of western Yunnan with bulletin data

Western Yunnan is a region with intensive tectonic activity and serious earthquake risk. It is of significant importance to study three dimensional crustal structure of this region to understand the tectonic setting and disaster mechanism. Densification and digitalization of seismic networks in this region provides an opportunity to study the velocity structure with bulletin data. In this study, we collect P-wave data of 10 403 regional earthquakes recorded by 79 seismic stations from January 2008 to December 2010. In addition to first arrivals data (Pg with epicentral distance less than 200 km and Pn), the Pg (or P) data with epicentral distance more than 200 km are also considered as later direct arrivals in the tomographic inversion. We also compare the quantity and the quality of the seismic data before 2010 and after 2010. The test results show that adding the follow-up Pg phase can effectively improve the inversion ability of crustal imaging, and quantity and the data quality are significantly improved since 2010. The tomographic results show that: (1) The Honghe fault zone, which is the major fault systems in this region, may cut through the entire crust, and the velocity contrasts between two sides at lower crust beneath the Honghe fault are estimated at higher than 10%, while the velocity difference below Nujiang fault zone extends only in the upper crust; (2) Most of the earthquakes in the region occurred at the interface of high-velocity media and low-velocity media, i.e., the areas with high velocity gradient, which has been validated in other areas.     

面向地震烈度仪的现地地震动预测模型的构建与验证

利用初期P波预警参数构建现地地震动预测模型,使其在达到设定阈值时快速发出报警信息,是现地地震预警系统面临的一个关键问题,直接关系到发布信息的准确性和及时性。针对地震烈度仪基于微机电系统传感器记录到的数据质量较差,通过两次积分获取的位移存在较大偏差,会引起更多的误报和漏报,本文采用不同阶数（1—4阶）的巴特沃斯滤波器,分别构建了基于P波3 s和全P波段数据的位移幅值PD、速度幅值PV和加速度幅值PA与地震动峰值速度PGV和峰值加速度PGA的现地地震动预测模型,然后利用收集到的川滇示范预警网地震事件记录进行验证。结果表明,对于地震烈度仪微机电系统传感器的记录,采用1阶巴特沃斯滤波器处理、基于全P波段波形拟合获取到的PV与PGV的相关性和PA与PGA的相关性为两种最优现地地震动预测模型。具体应用时,应同时利用两种或两种以上的统计关系进行现地地震动预测,并将实际地震动观测值作为额外的判定条件,以降低误报率和漏报率。      

模拟PLUM方法在2021年日本福岛县近海M7.3级地震中的表现

2021年2月13日晚,日本福岛县近海发生M7.3级地震,产生强烈振动,此次地震被认为是"3.11"地震的余震。首先介绍了PLUM方法的原理及日本气象厅地震预警系统对于PLUM方法的应用,评述了JMA地震预警结果。通过模拟PLUM方法在此次地震中的表现,由预测精度和有效预警时间两个指标来评估该方法的性能,并与日本气象厅发布的预警信息对比。模拟结果显示:受限于地震数据以及PLUM方法本身的原理,在震后第24 s发出第一次警报,不及使用P波预警与PLUM相结合的JMA地震预警系统及时。在地震前期0~40 s处于烈度剧烈上升阶段,预测精度较差;40 s之后的预测结果较为准确,预测精度高达100%。PLUM方法可以有效克服点-源模型中的弊端,特别是在多个地震同时发生的情况下预警效果良好,将PLUM方法纳入我国地震预警系统可以有效提高预警能力。     

Comparison of two earthquake early warning location methods

According to earthquake catalog records of Fujian Seismic Network, the T _now method and the four-station continuous location method put forward by Jin Xing are inspected by using P-wave arrival information of the first four stations in each earthquake. It shows that the four-station continuous location method can locate more seismic events than the T _now method. By analyzing the results, it is concluded that the reason for this is that the T _now method makes use of information from stations without being triggered, while some stations failed to be reflected in earthquake catalog because of discontinuous records or unclear records of seismic phases. For seismic events whose location results can be given, there is no obvious difference in location results of the two methods and positioning deviation of most seismic events is also not significant. For earthquakes outside the network, the positioning deviation may amplify as the epicentral distance enlarges, which may relate to the situation that the seismic stations are centered on one side of epicenter and the opening angle between seismic stations used for location and epicenter is small.