地震震中实时动态定位的方法研究

在地震早期预警系统中具破坏性地震震中的确定速度十分重要.本文提出了地震发生后根据1个、2个、3个台站P波到时记录进行动态、近实时确定地震发生区域、线区间和震中位置的方法.方法充分考虑了地震触发台站和非触发台站分布与地震波传播规律的一致性和差异性特征,提高了震中定位结果的精度.对由79个台站组成的山东虚拟测震台网2009-2010年期间记录的425次网内地震进行了快速定位,结果表明对发生在网内的地震可在要求时间内给出比较准确的震中位置,可满足预警地震速报时效性和精度的双重要求.     

周至井数字化资料映震效能分析与研究

地震台站观测人员清理自己的观测资料对促进地震观测资料在地震预报实践中的应用具有十分重要的意义。我们对周至井十多年的地下流体数字化观测资料进行了系统的整理,从固体潮特征、降雨特征、气压效应、同震变化与震前异常等方面进行了分析,初步结果认为周至井是一口很好的地震地下流体观测井孔,只要能对其观测数据出现的各种不正常现象加以分析,就有可能对未来将要发生的中强地震做出有一定价值的预报意见。     

基于克里金方法的区域震相走时标定技术研究div.

在台网比较稀疏的情况下,台站走时标定是提高低震级事件定位、识别能力的重要手段．为了提高稀疏台网的定位精度,首先利用标定事件和IASPEI1991走时表以及中国大陆走时表,计算了初至P波和Lg波到AAK,MAKZ,NIL,TLG以及WMQ等5个台站的走时残差;接着,采用非平稳贝叶斯克里金方法和走时残差数据构造上述台站的走时校正曲面;最后,通过加入和不加入走时校正定位一系列位置准确的发生在新疆地区的地震事件评估克里金走时校正的有效性．结果表明,克里金走时校正能够较大地提高稀疏台网的定位精度,同时有效地缩小误差椭圆的面积．      

Surface Deformation and Seismic Rebound: Implications and Applications

An earthquake process includes pre-seismic stress accumulation, co-seismic rock rupture and post-seismic elastic and/or viscoelastic rebound. Although co-seismic and post-seismic deformations have been readily observed using the global positioning system (GPS), detecting pre-seismic stress accumulation hidden in time-series data remains challenging. This study applies the Hilbert–Huang transform to extract non-linear and non-stationary pre-earthquake deformation data from GPS records for central Taiwan. By converting the derived surface deformation into horizontal azimuths, the randomly oriented GPS-azimuths are reoriented in a similar direction several days before and after earthquakes due to loading and rebound stress, respectively. Analytical results demonstrate that the stress accumulation and release along the entire course of an earthquake process provide significant evidence supporting the seismic rebound theory. This finding would be applicable to areas with dense GPS networks and active plate interactions. Surface deformations detected by the proposed analytical technique have encouraging potential for mitigating future seismic hazards.     

用近场强震动记录快速估计同震位移并反演震源滑动分布

利用自动经验基线校正方法,分析日本2008年岩手-宫城内陆M_w6.9地震震中周围密集强震动观测台网资料,快速解算出了同震位移场分布,并据此反演了震源滑动模型.经与GPS结果比较,两种不同方法给出的同震位移幅值、方向和总体分布特征较为接近.基于相同断层面参数反演的震源模型空间展布形态、主要滑动范围、平均和最大滑动量、滑动方向以及由模型计算的矩震级等均吻合较好,从而验证了方法的可行性.讨论了自动经验基线校正方法尚存在的问题和不足,为今后利用强震资料快速解算M_w6-7级及以上地震的同震位移场并反演震源滑动分布提供参考.     

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.     

Simultaneous infrasonic,seismic, magnetic and ionospheric observations in an earthquake epicentre

Various pre-seismic and co-seismic effects have been reported in the literature in the solid Earth, hydrosphere, atmosphere, electric/magnetic field and in the ionosphere. Some of the effects observed above the surface, particularly some of the pre-seismic effects, are still a matter of debate. Here we analyze the co-seismic effects of a relatively weak earthquake of 28 October 2008, which was a part of an earthquake swarm in the westernmost region of the Czech Republic. Special attention is paid to unique measurements of infrasonic phenomena. As far as we know, these have been the first infrasonic measurements during earthquake in the epicentre zone. Infrasonic oscillations (～1–12 Hz) in the epicentre region appear to be excited essentially by the vertical seismic oscillations. The observed oscillations are real epicentral infrasound not caused by seismic shaking of the instruments or by meteorological phenomena. Seismo-infrasonic oscillations observed 155 km apart from the epicentre were excited in situ by seismic waves. No earthquake-related infrasonic effects have been observed in the ionosphere. Necessity to make vibration tests of instruments is pointed out in order to be sure that observed effects are not effects of mechanical shaking of the instrument.     

晋冀蒙交界地区地壳三维P波速度结构及地震活动性研究

2014年9月晋冀蒙临时地震台网正式运行,为晋冀蒙交界地区的地震研究提供了丰富的资料。结合临时台与固定台记录的P波走时资料,采用双差层析成像方法对该区进行地震重定位和三维P波速度结构联合反演,分析该区3个典型盆地的速度扰动结果,结果表明,地震重定位残差显著降低,震源深度分布更加合理;P波速度浅层基本符合平原地区低速、山区高速的特点,深层则有相反表现,典型盆地P波速度在浅层较为复杂,高低速相间,深层表现为低速;研究时段内忻定盆地和延怀盆地地震活动密集,大同盆地地震活动较弱,低速体及边缘地震活动强度高于高速体及边缘。     

天山-准噶尔地区地震层析成像与壳幔结构

通过对东西天山两条天然地震剖面的远震P波与近震P波走时资料以及2001-2007年新疆地方台网的近震走时资料分析,获得了天山-准噶尔地区的三维地震层析图像.层析反演使用的台站数140个,地震事件1132个,P波走时数24904条.检测板试验结果指出,东西天山剖面、天山轴部和东准噶尔地区P波速度扰动恢复能力相对高.纵波波...     

GPS观测结果反映的尼泊尔M_w7.8地震孕震特征

针对2015年4月25日尼泊尔Mw7.8地震的孕震特征,本文首先对覆盖尼泊尔及周边地区的5套GPS水平速度场结果进行了融合,得到了近似统一参考框架下的速度场结果;在此基础上通过对此次地震震源区及周边地区的速度场、应变率场、基线时间序列分析,识别了震前变形特征.GPS应变率场结果显示,喜马拉雅主边界断裂存在大范围挤压应变积累,震源区处于近南北向应变积累高值过渡区.跨喜马拉雅构造带的GPS基线时间序列结果表现为持续缩短现象,表明印度板块与欧亚板块之间的持续挤压变形特征,2012年以来的缩短增强现象反映了印度板块对青藏块体的推挤增强作用明显.距离震中较近的西藏南部GPS同震位移结果以南向运动为主且指向震中,反映了青藏高原存在逆冲应变释放现象.综合此次尼泊尔地震前变形和同震应变释放特征,认为此次地震的孕震区域和同震应变释放区域均较大,将会对青藏高原的地壳变形与强震孕育产生深远影响.     

云南垂直摆映震能力研究

利用震例分析方法,通过对云龙、云县、永胜、通海等10个观测点垂直摆监测数据在云南省内及周边最近10年发生的51次中强地震中的同震响应、震前情况的研究,总结出了云南垂直摆的映震能力特征,可为未来地震前兆监测仪器选型、地震预测提供参考。      

河北易县M_L3.8、3.3地震同震形变响应及其震源机制

2010年7月30日河北省易县相继发生ML3.8、3.3地震,震中距离易县地震台仅7 km,震中附近主要以形变观测台站为主.虽然地震震级相对较小,但是12个形变测项均有不同程度的同震响应,这在中小地震的同震响应分析中是较为突出的震例.根据河北台网的地震波形资料对地震进行了重新定位.根据速报震中和重新定位震中分别计算两次地震的震源机制,震源断层初步断定为NEE向断层,断层表现为正断兼右旋走滑.     

2014年云南盈江两次中强震发生前后震源区P波速度变化

基于云南地震台网的地震记录,利用基于双差层析成像的时移层析成像方法,开展了2014年5月24日盈江MS5.6和5月30日MS6.1地震前后震源区地下P波速度变化的时空特征研究.结果表明:在盈江MS5.6地震后,震源区的P波速度轻微下降,在MS6.1地震后,相对于MS5.6地震,P波速度继续下降,并下降至最低,下降幅度约...     

地幔上涌对鄂尔多斯西缘岩石圈的改造:来自远震多尺度层析成像的证据

本文利用喜马拉雅二期科学探测台阵的678个地震台站及26个固定台站记录到的9,641个地震共约160000条远震P波走时数据,采用基于稀疏约束的多尺度层析成像方法,获得了鄂尔多斯西缘及邻区上地幔800 km深度范围内P波速度结构.结果显示,在东经104°附近阿拉善地块与鄂尔多斯盆地间存在岩石圈深度的构造边界,这表明阿拉善地块与鄂尔多斯可能分别从属于不同的大地构造单元.以北纬38°线为界,鄂尔多斯地块西缘在岩石圈范围内南北存在明显的速度差异,鄂尔多斯南部上地幔200~300 km深度范围显示为高速异常,而鄂尔多斯北部上地幔显示大面积的低速异常.这一现象表明,鄂尔多斯地块南北两部分经历了不同的构造演化过程.根据本文的结果可以进一步推断,由于青藏高原、阿拉善地块向东北方向推挤以及岩石圈的拆离引起的上地幔扰动导致了地幔上涌,上涌的热物质改造了鄂尔多斯西北缘地区的岩石圈,并使该区的岩石圈减薄.地幔上涌也可能是东经104°边界带和北纬38°构造带形成的深部动力学因素.     

印尼8.7级大震前后GPS观测站的地壳水平与垂直位移时间序列结果

利用IGS及中国地壳运动观测网络GPS连续观测站6年多时间的观测结果, 以中国大陆东部的稳定点组作为水平位移与垂直位移解的参考基准, 得到了2004年12月26日印尼苏门答腊8.7级与2005年3月28日8.5级大震前后GPS观测站的地壳水平及垂直位移时间序列的结果。 尽管所采用的GPS站点少, 且分布范围大, 但仍可看到在如此大的地震震前、 同震与震后地壳运动的特征, 为今后观测研究提供了十分有意义的结果。 文中所采用稳定点组基准有效消除水平位移场的平移与旋转, 而局部椭球面的不平性对计算区域地壳运动结果, 特别是对垂直位移的影响很小, 说明了位移解所描述的大范围区域位移场是合理的。 这两次地震的同震水平位移及震后的垂直位移影响量级达数厘米, 范围达远离8.7级地震震中4500 km之外, 甚至更远。     

地震波到时与视出射角联合定位方法研究

提出了利用地震波到时和P波初动视出射角联合定位的新方法.经过理论计算和实际地震资料处理结果分析,显示该方法对震源深度分辨有较好的改善,从而提高了地震的定位精度.该方法适合于现代数字化地震观测定位,其地震定位结果对研究地震断层性质和断层的空间展布有重要意义.     

Physico-chemical evolution of groundwater in tectonically active areas. Application to the Leana hot spring (Murcia Region,SE Spain)

Seismic events can affect the physico-chemical characteristics of groundwater. These anomalies are of a pre-seismic, co-seismic and post-seismic nature and correspond to pulse variations, sudden increases and decreases without return to initial values and upward or downward changes in trend. Continuous and in situ conductivity and temperature monitoring and periodic water sampling at a hot spring associated with neotectonic activity are of great interest for establishing predictive methods. This method is limited to the seismic activity affecting the fracturing system with which the hot spring is associated. The Region of Murcia and surroundings (southeast Spain) was selected as the study area for exploring the nature of these influences on groundwater. A hot spring in the Leana spa (Murcia) was equipped and monitored during the period 2006–2008, allowing for the in situ determination of conductivity and temperature as well as of major and minor constituents at the laboratory. Due to its proximity and related with fault network, we suggest that 86 % of earthquakes located between 0 and 10 km may affect in situ parameters of groundwater, and 75 % may affect laboratory determinations. This percentage drops in more distant zones. Of all earthquakes that seem to influence groundwater, 55 % of the in situ parameter anomalies and 53 % of laboratory were of a pre-seismic nature.     

2021年青海玛多MS7.4地震同震应力场与形变台站同震阶变分布关系探讨

利用基于升、降轨InSAR形变场及余震精定位结果反演得到的同震滑动模型,通过PSGRN/PSCMP程序获得同震水平形变场及应力场分布特征,结合玛多M_S7.4地震周边形变同震阶变台站分布特征,探讨同震应力场变化与同震阶变台站分布间的关系。模拟得到的水平形变场结果显示,此次玛多地震为左旋走滑运动特征,水平形变量主要集中在巴颜喀拉块体内,其次是北部的柴达木块体;羌塘块体以及祁连块体同震水平位移量较小;昆仑山口-江错断裂作为一条NE倾向的走滑型断裂,断层上盘区域滑动量明显大于下盘,模拟得到的最大水平形变量达1380mm;形变同震阶变的台站主要集中分布在祁连山断裂带中东段以及西秦岭等地区,祁连山断裂带中东段位于此次玛多地震同震正应力变化正值区域,而西秦岭等地区则处于玛多地震同震剪切应力变化的正值区域,即出现同震阶变的台站与同震应力场变化的正值区域具有较好的一致性。     

Nemuro-Oki earthquake of June 17, 1973: A lithospheric rebound at the upper half of the interface

P-wave first motions, radiation patterns and amplitudes of long-period surface waves, relocated aftershock distributions, leveling and tsunami data indicate that the 1973 Nemuro-Oki earthquake is caused by a low-angle thrust-faulting, representing a rebound at the upper 50 km of the interface between the continental and oceanic lithospheres. Rebound, most likely aseismic, at depths below 50 km, is suggested to take place in the near future from a comparison of recent geologic crustal deformation with pre-seismic and co-seismic data. The estimated seismic moment is about $\text{1}\text{3}\text{–}\text{1}\text{4}$ of that for the neighboring great earthquakes. The macro-seismic data suggest that the 1973 earthquake is smaller than the 1894 Nemuro-Oki earthquake, the last great earthquake in this region.The 1973 earthquake had been predicted on the basis of a seismic gap. Although the prediction was successful as to the location and nature of the faulting and partly as to the occurrence time, it is smaller than the predicted one. A part of the seismic gap may still remain. The difference between the observed seismic slip (1.6 m) and that predicted on the basis of the pre-seismic crustal deformation (3.0 m) indicates either (1) the 1973 earthquake relieved only a part of the strain accumulated in the upper 50 km, or (2) a significant amount of aseismic slip took place on the seismic fault and completely relieved the accumulated strain in the focal region of the 1973 earthquake. If the former is the case, the remaining strain, not only in the focal region, but also in the remaining seismic gap adjoining it, may be relieved in a larger earthquake in the future.The source parameters obtained are as follows: fault plane, dip direction = N40°W, dip angle = 27°; seismic moment = 6.7 · 10²⁷ dyn cm; average slip dislocation, 1.6 m in N63°W direction; stress drop = 35 bars. In these calculations, the fault dimension and the rigidity are assumed to be 100 · 60 km² and 7.0 · 10¹¹ dyn/cm², respectively.     

Locating Seismic Events in the CTBT Context

—?The verification of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) requires the determination of accurate location of seismic events from a fixed network of seismic stations across the globe. The requirements of possible on-site inspections mean that the goal is to place the location estimate in a zone smaller than 1000 km² that includes the true location. Because a defined set of stations will be used, corrections can be refined to represent the influence of departures from the global reference model IASPEI91. The primary stations in the International Monitoring Scheme (IMS) are mostly seismic arrays and therefore the present location scheme is based on minimisation of a misfit function built from arrival time, azimuth and array slowness residuals. The effective network will change markedly with the magnitude of the event and as a result regional information has to be integrated into the location process.