2017年3月27日漾濞5.1级地震前后气枪震源观测走时数据的变化

以2017年3月27日漾濞5.1级地震为例,根据区域特性和信噪比要求,选取数据较为完整的6个台站记录的2017年1月1日～6月6日期间的宾川地震信号发射台气枪震源波形资料,采用互相关检测技术提取6个台站各自稳定震相的走时数据,并对漾濞5.1级地震前后走时数据的变化情况进行分析。结果表明,漾濞5.1级地震前后6个台站各自稳定震相存在较为明显的走时变化,且短期内走时变化具有较好的同步性,相关台站异常幅度大小和异常出现时间存在细小差异。地震发生前,6个台站走时低值异常过程明显,以YUL台最为显著。地震发生前后走时变化形态特征为双“V”型,漾濞5.1级地震发生在第1个“V”型末端。地震发生后,不同方位相关台站受地震的影响程度不同,走时波动大小存在差异。     

基于GNSS资料分析漾濞MS6.4地震前应变时空演变特征

基于云南省内及邻区2009—2020年GNSS观测数据解算结果,在各个测点时间序列和速度场的基础上,采用克里金插值方法估计区域应变率场;以连续基准站时间序列为约束,获取漾濞M_S6.4地震近场区域的块体应变时间序列。分析发现:漾濞地震发生在前期最大剪应变高值区以及面应变高梯度带的张压转换区,发震的时间处于区域应变积累速率逐渐降低的过程之后。震中近场区域均以NW向断层的右旋走滑应变积累为主,且大多呈现持续增强趋势,与漾濞地震的发震断层走向及其破裂特征一致。震前震区东部块体出现了短期应变趋势转折及反向加速的异常现象,反映了应力-应变积累在接近临界破裂状态时的非线性调整。     

2021年云南漾濞MS6.4地震前后主动源观测走时数据的变化

基于2021年5月21日漾濞M_S6.4地震震中附近50 km范围内15个地震观测台站记录的2020年11月1日—2021年5月30日的气枪震源信号,采用互相关时延检测技术提取这15个台站各自稳定震相(Sg震相)的走时变化时间序列,并对漾濞M_S6.4地震前后各台站的走时变化特征进行分析。结果表明:(1)漾濞M_S6.4地震前10天左右,有4个台站走时开始出现异常,其中,Ey211和Ey213台走时呈"V"型变化结构,Ey210和CHT台走时呈上升趋势。(2)漾濞M_S6.4地震后短期内,大部分台站走时出现了明显的趋势性变化,以维西—乔后—巍山断裂为界,断裂带两侧台站走时变化趋势存在明显差异,断裂以东的EYA、HDQ、YSW09台走时呈上升趋势,变化最为显著的为HDQ台,走时差变化量为0.067 s;而断裂带以西的所有台站在漾濞M_S6.4地震当天(或震后1～2天)开始出现明显趋势性下降,走时下降持续时间在4～9天间,走时差变化量在-0.053～-0.201 s间,其中走时差下降量最大为53 285台,最小为CHT台。     

利用祁连山主动源资料研究2016年门源6.4级地震前后波速变化

采用叠加、互相关、插值拟合等方法对祁连山气枪主动源台网数据进行处理,针对2016年1月21日青海门源6.4级地震前后气枪激发地震P波、S波震相的走时变化特征进行了分析,结果表明,地震前约6个月时,震中附近3个台站的相对走时出现下降变化（走时减少）,至震前约3个月时低值异常恢复正常,之后再次出现走时下降变化,地震即发生于走时变化恢复过程中。S波走时变化最大下降幅度达18ms,震后走时变化逐渐恢复正常,且3个台站变化趋势较为一致,其中,距震中最近的台站的S波走时变化最明显（ZDY38台）,较远台站的走时变化幅度较小,其变化特征与震源区位置有关。走时缩短意味着速度增加,可能与区域应力积累间存在一定的关系。     

Spatial Correlation Anomalies of the Diurnal Variation of the Geomagnetic Vertical Component before the Yingjiang MS6.1 and Ludian MS6.5 Earthquakes

Significant anomalies were observed at the geomagnetic stations in the southwest region of China before the Yingjiang M_S6.1 earthquake and the Ludian M_S6.5 earthquake in 2014. We processed the geomagnetic vertical component diurnal variation data by the spatial correlation method. The results show that during the period from April 1 to May 20, 2014,there existed quasi-synchronous decrease changes in the coefficient curves between the five geomagnetic stations of Guiyang,Hechi,Nanshan,Muli,Yongning and Xinyi and Hongshan stations.Furthermore,there was a high gradient zone in the normalized correlation coefficient contour map with background values removed. The epicenters of the Yingjiang M_S6.1 earthquake and the Ludian M_S6.5 earthquake are located in the gradient zone or near the gradient zone.     

A Study on the Seismic Velocity Changes before and after the 2016 MS6.4 Menyuan Earthquake Using the Active Source Data in the Qilian Mountain

The Qilian Mountain active source network data was processed using the methods of stacking, cross-correlation and interpolation, and the airgun travel time variation characteristics of P and S waves around the January 21, 2016 M_S6.4 Menyua, Qinghai earthquake. The results show that about 6 months before the earthquake, the relative travel time of three stations near the epicenter showed a declined change (travel time decrease), and such a change of low value anomaly was recovered about 3 months before the earthquake. The travel time decrease then appeared again, and the earthquake occurred during the recovery process. The maximum decrease of the S-wave travel time was 18ms, and the change in travel time returned to normal after the earthquake. The variation trend of the 3 stations is consistent, including the S-wave travel time change of station ZDY38, which is nearest to the epicenter and changed obviously, and the variation range of the travel time is smaller at the stations afar. This variation pattern is related to the position of the seismic source. The shorter travel time means the velocity increase, which may be related to the regional stress accumulation.     

2018年9月4日新疆伽师MS5.5地震序列及发震构造讨论

2018年9月4日新疆伽师发生M_S5.5地震,震中处于塔里木地块西北缘,位于1997~1998年伽师强震群震区内。此次伽师地震前发生了M_S4.7前震,截至9月30日最大余震震级为M_S4.6（M_L5.0）,初步判定为前-主-余型地震序列。序列精定位结果显示,余震沿近NE向展布,主震震源深度与1997~1998年伽师强震主震基本一致,发震断层陡立。本文从区域的构造环境、地震震源机制解和余震分布特征等方面分析认为,地震发生在伽师隐伏断裂东南端部,为1997~1998年伽师强震群震区的一次新的构造活动。序列参数、视应力等计算结果显示,伽师M_S5.5地震的预测最大余震震级与最大余震震级M_S4.6接近,表明序列最大余震已经发生。     

Analysis on the Characteristics of the Kalpin MS5.3 Earthquake Sequence of December 1, 2013 and Anomalies before the Earthquake

This paper introduces the basic parameters, focal mechanism solutions and earthquake sequence characteristics of the Kalpin M_S5.3 earthquake sequence of December 1, 2013, and analyzed seismic activity before the earthquake, the adjacent tectonic features and the precursory anomaly at fixed points within a range of 200km. Research indicates:(1) The earthquake occurred on Kalpin fault, the source rupture type is thrust faulting with sinistral strike-slip component. (2) The earthquake sequence is mainshock-aftershock type, with the aftershock distribution attenuating quickly and trending NE. (3) Abnormal seismic activity before the earthquake was characterized by seismically nesting quiescence of M_S2.0-4.0 earthquakes, seismic quiescence of M_S4.0 earthquakes and seismic belts of M_S3.0 earthquakes in the Kalpin block, abnormal enhancement zone of moderate earthquakes on Puchang fault and seismological parameters. (4) Anomalies of precursory observation data at fixed stations are mainly characterized by mutation. Apart from the borehole tiltmeter in Halajun, the spatial distribution of other abnormal precursors showed a phenomenon of migration from the near field to far field and from the epicenter to the peripheries.     

2021年青海玛多MS7.4地震前地下流体异常特征分析

地震地下流体在地震预测研究与震情跟踪方面发挥着重要作用,本文对2021年5月22日青海玛多MS7.4地震前震中附近地下流体观测资料及异常特征进行系统分析,并结合震前预测过程进行了回顾性总结。结果表明,玛多MS7.4地震震中距500km范围内存在5项异常,其中4项为短期异常,主要出现在震前2～3个月。异常在空间上分布不均匀,主要位于玛多MS7.4地震震中的东北部和西南部,整体呈现出由外围向震中收缩的迁移特征,且玛多MS7.4地震和2010年青海玉树MS7.1地震在异常特征和应力加载作用方面具有较好的相似性。研究结果为地震监测能力较低地区积累了震例资料,对于提升强震地下流体前兆异常认识及未来震情趋势判定水平具有一定的参考意义。     

苏皖地区2次中强地震前地下流体异常及其形成机理分析

归纳总结了安庆M_S4.8地震、高邮-宝应M_S4.9地震前出现的地下流体异常,并对其形成机理作了初步讨论。结果显示,这2次地震前地下流体异常特征比较相似。在时间进程上,都表现出中期趋势背景异常与短临异常的配套性特征。在空间分布上,中期趋势背景阶段,水位异常均表现为震中附近流体井水位呈趋势性转折上升,而震中外围流体井水位呈趋势性转折下降的特点。且转折上升的流体井在空间上的分布方位与地震的发震断层走向一致。在短临阶段,异常均表现为先向外迁移继而向震中靠拢的特点。水位在空间上的规律性分布可能受区域应力场作用以及区域构造格局所控制。     

九寨沟M_S7.0地震震源机制解及构造应力场研究

2017年8月8日四川九寨沟县发生M_S7.0地震。根据中国地震台网固定台站的记录波形,利用gCAP方法和P波初动符号反演方法求解了主震的震源机制解,其结果与哈佛CMT震源机制解、美国地质勘探局发布的震源机制以及中国地震局发布的各震源机制解有很好的一致性。此外,还求解了九寨沟地震震中附近2010—2016年间28次小震的震源机制解,利用得到的小震震源机制解反演了该区域的构造应力场。结果表明,这一区域构造应力场的最大应力轴与最小应力轴均为水平方向,其中最大应力轴方向为NWW方向,最小应力轴方向为SSW方向。     

2022年门源MS6.9和2016年门源MS6.4地震序列比较分析

2022年1月8日青海省海北州门源县发生M_S6.9地震,震中距离2016年1月21日门源M_S6.4地震震中约33km,两次门源地震均发生在冷龙岭断裂附近,但在震源机制、主发震断层破裂过程及地震序列余震活动等方面显著不同。针对两次门源地震序列的比较分析,对研究冷龙岭断裂及其附近区域强震序列和余震衰减特征等具有重要研究意义。通过对比分析2022年门源M_S6.9地震和2016年门源M_S6.4地震余震的时空演化特征,发现二者在震源过程和断层破裂尺度上存在明显差异,前者发震断层破裂充分,震后能量释放充分,余震丰富且震级偏高;而后者发震断层未破裂至地表,余震震级水平偏低。综合分析两次门源地震序列表现出来的差异性,认为其可能与地震发震断层的破裂过程密切相关,且同时受到区域构造环境的影响。     

新10井水位对九寨沟M_S7.0、精河M_S6.6地震同震响应

基于新10井水位对九寨沟M_S7.0、精河M_S6.6地震的同震响应特征,分别利用水震波和潮汐分析法,反演得到了新10井水位在地震波作用期间和地震波作用前后含水层参数特征,探讨了2次地震引起的新10井同震响应变化机理。结果表明,新10井水位对九寨沟地震和精河地震具有不同的同震响应形态,利用水平流模型反演所得的新10井含水层渗透系数,在九寨沟地震时为61m/d,而在精河地震时为147m/d,表明地震波作用导致水平向的渗透性增强;利用垂向流模型反演得到的新10井含水层渗透系数,在2次地震之前约为49×10~(-5)m/d,而在地震之后约为18×10~(-5)m/d,表明地震波作用导致垂直向的渗透性减弱。因此,新10井水位的同震响应变化与地震波引起的含水层渗透率的改变有关。     

A Preliminary Analysis of the Seismogenic Structure of the Akto MS6.7 Earthquake Sequence on November 25, 2016

In this study,data from the Xinjiang regional network and IRIS shared global stations are used to relocate the Akto M_S6. 7 earthquake sequence on November 25,2016 by using double difference location method. Three earthquakes of M_S4. 8,M_S6. 7 and M_S5. 0 are inverted by using the g CAP method,and the focal mechanism solutions are obtained.According to the results of relocating,the location of the main shock is 39. 22°N,73. 98°E,the distribution of the earthquake sequence is about 70 km in length,and the focal depth is mainly within the range of 5-20 km. The plane and depth profiles of the earthquake sequence show that aftershocks extended in SEE direction after the main shock and the dip angle of fault plane is steep. Focal mechanism results show that the three earthquakes are characterized by strike-slip movement. Based on the results of field geological investigation,it is inferred that the seismogenic fault of the Akto earthquake is Muji fault,which is located at the northernmost end of the Kongur extensional system.The possible cause of this earthquake is that the Indian Plate continues to push northward,and during this compression process,the Indian Plate is affected by the clockwise rotation of the Tarim basin,which causes the accumulation of right-lateral action of the Muji fault,resulting in this earthquake.     

四川长宁地区地震震源参数的时空分布特征

使用谱比法计算得到四川长宁地区2018年12月至2019年7月期间442个地震的震源参数,并进一步分析了震源参数之间的相互关系及应力降的时空分布特征。研究区的地震活动主要集中在长宁背斜核部和南部建武向斜页岩气开采区。研究结果显示,该地区M_L1.3~4.7地震的应力降位于0.02~7.26MPa范围内,超过90%的地震应力降小于2MPa,应力降总体呈现随震级增大而增大的趋势,但与震源深度的关系并不明显。长宁M_S6.0地震发生之前,震源区地震的应力降总体处于较低水平,主震发生之后,短期内余震的应力降较高,随后快速衰减。这些高应力降地震空间上主要集中在长宁余震区的西北段,也是余震强度较大、发生了几次M_S>5.0强余震的位置。建武向斜页岩气开采区地震的应力降总体略低于长宁背斜地区,但差异并不显著。     

川东南长宁地区地震活动及b值演化特征

利用全国统一目录和流动台站目录,研究了四川盆地东南部长宁地区的地震活动特征和b值的空间分布特征。研究结果显示,长宁地区的地震活动在时间上呈现明显的分段特征,地震活动在2015年后明显增强;在空间上,长宁地区的地震活动主要集中在以28.3°N为界限的南、北2个地区,对于这2个区域的b值演化,计算结果显示出不同的分段特征。此外,研究了不同震中距下,长宁地区2018年兴文5.7级、2019年珙县5.3级和2019年长宁6.0级3次主要地震事件震前与震后的b值演化,结果表明统计范围会显著影响b值的变化特征,当计算范围为20km时,3次主震震前短期内均出现了低于背景b值90%的低b值异常,这表明在地震目录相对完备的情况下,利用低b值异常分析区域地震危险性,应采用较小范围的地震数据。     

2017年九寨沟7.0级地震前应力状态及b值异常特征研究

2017年8月8日青藏高原东缘四川九寨沟地区发生7.0级强震,依据前人研究结果分析九寨沟7.0级地震发震构造,并计算震前应力状态。结果显示:本次地震受到构造和历史强震的影响,是发生在历史强震引起的应力加载区域。另外,采用中国地震台网1990年以来的地震目录,在评估目录完整性的基础上,利用最大似然法计算得到2017年8月8日九寨沟7.0级地震前震源区及邻区地震b值空间图像。结果显示,九寨沟7.0级地震发生在四川北部地区显著低b值高应力异常区域内部(0.82b0.75)。所以,研究区域内外历史强震可能促进了九寨沟7.0级地震的发生。     

Effects of the Nepal MS8.1 Earthquake in 2015 on Seismic Activity in the Qinghai-Tibetan Plateau

We obtained the displacement and deformation caused by the 2015 Nepal M_S8.1 earthquake adopting the finite element method, and analyzed the displacement and deformation characteristics and effect of three large earthquakes on seismic activity in the Qinghai-Tibetan block. Our primary results suggest southward movement of the Qinghai-Tibetan block is caused by a large earthquake occurring on thrust fault in the Himalayan zone, the displacement direction is reverse to the background displacement. The occurrence of these large earthquakes will result in stress unloading and earthquake activity will be weakened in stress unloading areas. Through the simulation results, we can detect the distribution area of stress loading and unloading caused by large earthquakes. Simultaneously, it provides a fundamental evidence for determination of earthquake activity trend.     

Analysis of Anomalous Characteristics of Regional Crustal Deformation before the September 16th, 2019 Zhangye MS5.0 Earthquake, Gansu, China

To study the crustal movement in the vicinity of the epicenter before the Zhangye M_S5.0 earthquake in 2019, the characteristics of crustal deformation before the earthquake are discussed through the GPS velocity field analysis based on the CMONOC data observed from GPS. The baseline time series between two continuous GPS stations and the strain time series of an area among several stations are analyzed in the epicenter area. The resulting time series of baseline azimuth around the epicenter reflects that the energy of the fault in the northern margin of Qilian Mountain is accumulated continuously before 2017. Besides, the movement trend of azimuth slows down after 2017, indicating the stress accumulation on both sides of the seismogenic fault zone has reached a certain degree. The first shear strain and EW-direction linear strain in the epicentral area of the Zhangye M_S5.0 earthquake remain steady after 2017, and the surface strain rate decreases gradually after 2016. It is illustrated that there is an obvious deformation loss at the epicentral region three years before the earthquake, indicating that a certain degree of strain energy is accumulated in this area before the earthquake.     

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。