2011年日本东北大地震特低频地磁信号的分形标度特征研究

本文选择2011年3月11日M9.0日本东北大地震震中附近三个地磁台站16个月(2010/01/01—2011/04/30)的特低频地磁观测资料,采用去倾扰动分析方法,得到了这三个台站地磁记录的非均匀标度特征随时间的变化,提出了一种能反映地磁三分量非均匀标度特征同步变化的指标,并据此探讨了特低频地磁信号分形标度特征变化与日本东北大地震之间的可能关联性,初步结果表明,这三个台站的特低频地磁信号分形标度特征指标在日本东北大地震前25~50天左右呈现出同步的异常增加,基于磁静日观测资料的随机合成地磁数据的统计检验结果可知前述异常并非随机异常,而是一种具有统计显著性的异常,可能反映了日本东北大地震对周边地磁信号内在的非线性系统特征产生了有统计意义的影响.     

Spatio-temporal characteristics of aftershocks and seismogenic structure of the 2011 MW9.0 Tohoku earthquake,Japan

The Tohoku megathrust earthquake, which occurred on March 11, 2011 and had an epicenter that was 70 km east of Tohoku, Japan, resulted in an estimated ten's of billions of dollars in damage and a death toll of more than 15 thousand lives, yet few studies have documented key spatio-temporal seismogenic characteristics. Specifically, the temporal decay of aftershock activity, the number of strong aftershocks (with magnitudes greater than or equal to 7.0), the magnitude of the greatest aftershock, and area of possible aftershocks. Forecasted results from this study are based on Gutenberg-Richter's relation, Bath's law, Omori's law, and Well's relation of rupture scale utilizing the magnitude and statistical parameters of earthquakes in USA and China (Landers, Northridge, Hector Mine, San Simeon and Wenchuan earthquakes). The number of strong aftershocks, the parameters of Gutenberg-Richter's relation, and the modified form of Omori's law are confirmed based on the aftershock sequence data from the M_W9.0 Tohoku earthquake. Moreover, for a large earthquake, the seismogenic structure could be a fault, a fault system, or an intersection of several faults. The seismogenic structure of the earthquake suggests that the event occurred on a thrust fault near the Japan trench within the overriding plate that subsequently triggered three or more active faults producing large aftershocks.     

基于移动窗解卷积法的2011年日本东北 MW9.0大地震场地非线性时变识别

利用模拟记录和2011年日本东北M_W9.0大地震观测记录分析了基于移动窗解卷积法识别场地非线性时变特征的可行性,并与移动窗谱比法的结果进行了对比分析。研究表明:基于移动窗解卷积法可以较好地揭示场地非线性随地震动水平的变化过程,识别非线性发生的阈值、非线性变化程度及强震动后的恢复程度;与移动窗谱比法相比,移动窗解卷积法更容易获得较为稳定的土体非线性时变过程,但对于存在强阻抗比的浅表层土体,移动窗谱比法可以获得更准确的非线性程度。对2011年日本东北M_W9.0大地震中8个KiK-net台站进行了非线性时变分析,结果表明;两种方法识别的非线性阈值较接近,约在40—100 cm/s2之间,且与场地v_S30没有明显的相关性;在峰值加速度PGA较低的IBRH20台站,非线性引起的波速下降较小（3%）且震后几乎完全恢复;PGA 处于386—822 cm/s2之间的其余7个台站,场地等效剪切波速下降13%—37%,产生了显著的场地非线性,且震后未完全恢复;PGA大于380 cm/s2时,非线性所导致的场地波速下降、恢复与PGA无明显相关性。      

Catastrophic Tohoku earthquake of March 11, 2011, in Japan

The results of the comparative analysis of parameters of the Tohoku earthquake (Honshu Island, Japan) of March 11, 2011, 05:46 UTC and its aftershocks are presented.     

利用GPS和InSAR数据反演2011年日本东北MW9.0地震断层的同震滑动分布

本文首先对Envisat/ASAR数据进行干涉处理, 获取2011年日本东北M_W9.0地震的地表InSAR同震形变场; 然后通过对InSAR同震形变数据重采样方法的深入分析, 选择条纹率法结合干涉图的空间相干性对InSAR同震形变数据进行重采样; 最后基于弹性半空间位错模型, 联合InSAR与GPS形变数据, 采用最小二乘法反演发震断层的滑动分布. 研究结果表明: 考虑相干性的条纹率重采样方法, 更适用于形变场中存在除断层外的有限边界、 且形变场范围较大的InSAR数据重采样处理; 断层滑动主要发生在地表以下50 km范围内, 最大滑动量为49.9 m, 矩张量为4.89×1022 N·m, 所对应的矩震级为M_W9.1, 与地震学反演的结果比较吻合.      

2011年日本9.0级及7.5级地震震源破裂反投影初步结果

2011年3月日本仙台东部太平洋海域接连发生了Mw7.5和Mw9.0级地震.地震及引发的海啸给日本造成了严重的破坏.本文运用近年来国际上流行的研究大地震震源破裂过程的非反演方法,反投影远震P波,研究了这两次地震的震源破裂特征,得到了他们各自的破裂区域和破裂持续时间.     

Low frequency seismic noise before a magnitude 9.0 Tohoku earthquake on March 11, 2011

The dynamics of seismic noise before the catastrophic earthquake of March 11, 2011 in Japan is studied in a minute period range using the records of broadband IRIS stations. It is found that the dispersion of the noise and the number of asymmetric pulses recorded within 500 km from the epicenter of the earthquake have drastically increased 1.5 months before the event. This is the highest enhancement ever recorded by these stations during the same interval of the year for the past 15 years since the IRIS network started stably operating. No increase is revealed in the noise recorded beyond 1200 km from the epicenter. The pattern of decay in amplitudes of the anomalous noise with increasing distance from the epicenter to the corresponding stations likely indicates that the sources of the noise were located close to the source of the earthquake. The noise contains both regular and chaotic components.     

Schumann resonance observation in China and anomalous disturbance possibly associated with Tohoku M9.0 earthquake

Schumann resonance (SR) is an electromagnetic resonance phenomenon in the Earth–ionosphere cavity exited by global lightning activities when the wavelength matches the circumference of the Earth, and the lowest four peak frequencies of SR are about 8, 14, 20, and 26 Hz. This article presents the new observational data of SR in China. The observations of two horizontal magnetic components (B _NS and B _EW) in the frequency band range of 3–29 Hz at Yongsheng observatory (26.7°N, 100.8°E) in southwestern China were mainly analyzed. It is found that the SR amplitudes at peak frequencies in B _NS and B _EW components all showed diurnal and seasonal variations, and that the SR amplitude in B _NS component is always higher than that in B _EW component. Diurnal variation of SR amplitude around equinoxes and solstices in B _NS component is related to active intervals of three global thunderstorm centers, while SR amplitude in B _EW component is the most significant at around 16 LT, corresponding to Asian center. SR amplitudes both in B _NS and B _EW components increase in the rainy season from May to September. In addition, the SR anomalies in association with the 2011 Japan earthquake are exhibited. The anomalous effect was characterized by an increase in amplitude at the lowest four SR modes beginning at 4 days before this earthquake. Upon analyzing the wave interference between the direct wave and disturbed wave scattered by localized modification of lower ionosphere over the epicenter, Asian and African thunderstorm centers are found to contribute to anomalous effect observed at Yongsheng station. Modeling results of SR regular and disturbed spectra at different local times led to the similar conclusion.     

GPS资料反映的日本东北MW9.0地震的孕震特征

在对海洋板块俯冲型地震孕震模式的分阶段变形特征进行分析的基础上,结合同震位错反演结果分析了M_W9.0级地震的同震变形特征,分析过程中通过精度检验讨论了该反演结果的可靠性.通过对震前和同震GPS结果的对比分析,讨论了二者的差异性.GPS应变(率)结果表明,震前日本岛应变积累主要反映了太平洋板块和菲律宾板块的俯冲作用,同震结果表现为指向震源方向拉张应变的释放,对日本岛的主要影响区域介于35°N和43°N之间.震前和同震GPS剖面结果反映的变形特征具有互补性,但量值相差上百倍.震前的GPS速度、应变率剖面和时间序列结果表明靠近日本岛东海岸一侧可能存在变形趋于极限现象.通过对此次地震可能前兆的分析表明,中长期预测方面、震前GPS时间序列的趋势性偏离、前震活动、震源区b值降低等现象在一定程度上反映了此次地震的孕震特征.     

Stochastic coupled simulation of strong motion and tsunami for the 2011 Tohoku,Japan earthquake

This study conducts coupled simulation of strong motion and tsunami using stochastically generated earthquake source models. It is focused upon the 2011 Tohoku, Japan earthquake. The ground motion time-histories are simulated using the multiple-event stochastic finite-fault method, which takes into account multiple local rupture processes in strong motion generation areas. For tsunami simulation, multiple realizations of wave profiles are generated by evaluating nonlinear shallow water equations with run-up. Key objectives of this research are: (i) to investigate the sensitivity of strong motion and tsunami hazard parameters to asperities and strong motion generation areas, and (ii) to quantify the spatial variability and dependency of strong motion and tsunami predictions due to common earthquake sources. The investigations provide valuable insights in understanding the temporal and spatial impact of cascading earthquake hazards. Importantly, the study also develops an integrated strong motion and tsunami simulator, which is capable of capturing earthquake source uncertainty. Such an advanced numerical tool is necessary for assessing the performance of buildings and infrastructure that are subjected to cascading earthquake–tsunami hazards.     

日本M9.0级巨震对山东地区地壳活动的影响研究

以山东地壳运动GPS观测网为基础,结合周边IGS提供的全球GPS观测资料,计算了2011年3月11日发生的日本9.0级巨震对山东所处地块产生的影响,并给出了该地区站点的真实运动轨迹和运动方式.结果显示:山东各GPS基准站受地震波影响产生的震时最大振幅超过0.2 m,持续时间约160 s;同震位移方向为东东南向,位移量最大超过10 mm.日本9.0级地震对山东所在地块的影响主要是在水平方向,对垂直方向影响不大,它对山东主要断裂带-沂沭断裂带起到了拉张的作用,且N段幅度明显大于S段.根据地震前后站点时间序列的发展趋势来看,近期山东所处地块处于向西回调运动状态,推测震后3～5个月左右将恢复到震前的轨迹,为本地区的震情判定提供了可靠依据.     

2011年日本东北大地震（M_W=9.0）震间与震前变形场特征及其对强震预测的启示

强震震前(preseismic)动力学过程的研究对于地震预测具有十分重要的意义,但由于观测资料的限制,目前对强震前孕震区力学状态及其演化过程的认识还非常有限.2011年日本东北9.0特大地震(Tohoku-Oki)发生在GPS观测台站最为密集的地区,为研究特大地震震间(interseismic)与震前的变形状态提供了难得的机会.文中将利用日本东北大地震之前连续的GPS观测资料,分别计算震间与震前的速度场与变形场.通过对比分析发现,日本东北地区(Tohoku)震前的应变状态与震间的有很大的不同,震间的变形主要受到太平洋板块向日本海沟北西西向的俯冲挤压作用所控制,其主压应变以近东西向压缩为主,日本东北地区的运动方向与太平洋板块的运动方向大体一致.但是,临近地震前(震前)日本东北地区的运动方向发生了很大变化,震前30天的连续GPS观测结果显示,速度场的优势方向经常变换,间歇性地出现与太平洋板块运动方向相反的情况.这意味着震前孕震区的力学状态发生了很大的改变.这种变化可能与震前破裂成核或慢滑移及慢地震等过程有关,这些过程将加速或促进大地震的发生,从而为大地震的发生准备了力学条件.值得特别强调的是,这些现象都是可以通过直接观测能够发现的大地震之前的异常现象.由此可见,加密GPS站点进行连续观测,寻找震前变形异常区以及探索异常的物理机制对于地震预测预报有重要的科学意义.     

Ground motion characteristics and shaking damage of the 11th March 2011 M w9.0 Great East Japan earthquake

A catastrophic M _w9.0 earthquake and subsequent giant tsunami struck the Tōhoku and Kanto regions of Japan on 11th March 2011, causing tremendous casualties, massive damage to structures and infrastructure, and huge economic loss. This event has revealed weakness and vulnerability of urban cities and modern society in Japan, which were thought to be one of the most earthquake-prepared nations in the world. Nevertheless, recorded ground motion data from this event offer invaluable information and opportunity; their unique features include very strong short-period spectral content, long duration, and effects due to local asperities as well as direction of rupture/wave propagation. Aiming at gaining useful experience from this tragic event, Earthquake Engineering Field Investigation Team (EEFIT) organised and dispatched a team to the Tōhoku region of Japan. During the EEFIT mission, ground shaking damage surveys were conducted in Sendai, Shirakawa, and Sukagawa, where the Japan Meteorological Agency intensity of 6+ was observed and instrumentally recorded ground motion data were available. The damage survey results identify the key factors for severe shaking damage, such as insufficient lateral reinforcement and detailing in structural columns from structural capacity viewpoint and rich spectral content of ground shaking in the intermediate vibration period range from seismic demand viewpoint. Importantly, inclusion of several ground motion parameters, such as nonlinear structural response, in shaking damage surveys, can improve the correlation of observed ground motion with shaking damage and therefore enhance existing indicators of potential damage.     

Liquefaction of soil in the Tokyo Bay area from the 2011 Tohoku (Japan) earthquake

Immediately following the 11th March 2011 M_w 9.0 Tohoku (Japan) earthquake, a field investigation was carried out around the Tokyo Bay area. This paper provides first-hand observations (before or just at the onset of repair) of widespread liquefaction and the associated effects. Observations related to uplift of manholes, settlement of ground, performance of buildings and bridges and the effects of ground improvements are also presented. Recorded ground motions near the Tokyo Bay area were analysed to understand their key characteristics (large amplitude and long duration). Lessons learnt are also presented.     

2011年日本MW9.0地震对沂沭断裂带及其两侧地区地壳运动的同震影响研究

2011年日本M_W9.0地震（简称日本地震）后沂沭断裂带及其两侧地区地震活动显著增强,研究日本地震对该地区地壳运动及地震潜势的影响十分必要.为此,本文通过112个连续GPS观测站获取了研究区高空间分辨率的日本地震同震形变场并得到如下认识：（1）8个定点地球物理观测的同震响应验证了本文同震形变场的可靠性;日本地震的东向拉张使研究区整体上处于张性同震应变状态,但存在局部挤压区域,其中莱州湾至海州湾的挤压条带穿过沂沭断裂带并对断裂带南北两段产生了不同的同震作用,对南段具有拉张作用,对北段产生挤压作用;（2）同震形变场在鲁东隆起和鲁西断块产生了显著的剪应变,地震b值显示上述区域的构造应力在日本地震后增强,因此同震形变场可能改变了这些区域的应力特征;（3）地震矩张量叠加分析显示,同震形变场短期内对鲁西断块、鲁东隆起区和沂沭断裂带南段累积了地震矩,可能有助于上述区域在日本地震以后的地震活动增强;日本地震对沂沭断裂带北段的地震矩具有释放作用,或许是该区域地震活动减弱的原因.     

M_W9 Tohoku earthquake in 2011 in Japan: precursors uncovered by natural time analysis

This paper reviews the precursory phenomena of the 2011 MW9 Tohoku earthquake in Japan that emerge solely when we analyze the seismicity data in a new time domain termed natural time. If we do not consider this analysis, important precursory changes cannot be identified and hence are missed. Natural time analysis has the privilege that enables the introduction of an order parameter of seismicity. In this frame, we find that the fluctuations of this parameter exhibit an unprecedented characteristic change, i.e., an evident minimum, approximately two months before Tohoku earthquake, which strikingly is almost simultaneous with unique anomalous geomagnetic field variations recorded mainly on the z component. This is consistent with our finding that such a characteristic change in seismicity appears when a seismic electric signal(SES) activity of the VAN method(from the initials of Varotsos, Alexopoulos, Nomicos) initiates, and provides a direct confirmation of the physical interconnection between SES and seismicity.     

Erratum to:Schumann resonance observation in China and anomalous disturbance possibly associated with Tohoku M9.0 earthquake

正Erratum to:Earthq Sci(2013)26(2):137–145DOI 10.1007/s11589-013-0009-0In the published article,first author’s name was misspelt.The correct name appears in this erratum.     

2011年日本MW9.0地震引发的海啸对地震背景噪声的影响

基于北美沿岸和内陆地震台站的连续地震波形记录,并结合沿岸台站附近布设的DART系统记录的海底压力数据以及预测潮汐数据,利用时频分析和极化分析方法对2011年3月11日日本东北部海域MW9.0大地震所激发的海啸对地震背景噪声所产生的影响予以深入分析.结果显示:海啸对高频噪声(1.3—1.5 Hz)以及短周期双频微地动噪声...