The response of the electromagnetic field to the catastrophic earthquake of March 11, 2011

The electric and magnetic variations observed during the earthquake of March 11, 2011 that occurred in the Pacific close to the northeastern coast of Honshu Island in Japan are analyzed. The variations in the electric voltage were measured at the decommissioned submarine telecommunication cable laid on the bed of the Sea of Japan. The neighboring observatories recorded the anomalous geomagnetic variations during the studied time interval; the sources and spatial location of these anomalies are studied. The seismic signals were identified from the seismograms recorded by the broadband seismometer STS-2 at the nearest seismic station.

     

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.     

Geotechnical engineering aspects of the catastrophic Tohoku (Japan) earthquake of March 11, 2011: the review of first results

Geotechnical engineering aspects of the catastrophic earthquake, which occurred in Japan on March, 11, 2011 and called Tohoku earthquake are discussed. A review is presented of the first results obtained mainly by Japanese scientists based on records of seismic networks of Japan K-NET, Kik-net and on GPS data. The basic concepts of seismic zoning in Japan and the location of the Tohoku-oki earthquake on the seismic zoning maps are described, as well as models of the source process obtained by various authors based on teleseismic data, strong motion data, GPS data, and tsunami observations. The recorded peak accelerations and velocities and their correspondence to the current empirical attenuation curves are discussed. The records of the Tohoku earthquake made by Japanese seismic networks K-NET, Kik-net and some others represent unique seismological material and the most complete seismic database (including vertical array records) in the near-source zone of a strongest earthquake with magnitude M _w = 9. These data will be studied by seismologists all over the world for many years and, probably, they will answer many questions of geotechnical seismic engineering.     

On the GPS-based ionospheric perturbation after the Tohoku earthquake of March 11, 2011

Based on the data from the GPS receiving networks in Japan and America which have a high time resolution (2 min), two-dimensional (2D) distributions of the variations in the ionospheric total electron content (TEC) are constructed both close to and far from of the epicenter of the submarine earthquake of March 11, 2011 in Japan. Above the epicenter, a diverging multi-period disturbance appears after the main shock due to the acoustic gravity waves. Far from the epicenter, the wave trains associated with the tsunamigenic atmospheric internal gravity waves are revealed. These atmospheric waves significantly advance the arrival of the tsunami signal initially on the Hawaiian islands and then on the western coast of North America. The presence of the tsunami precursor in the form of atmospheric gravity waves is supported by the numerical calculations and by the analysis of the dispersion relation for the waves in the atmosphere. The detected ionospheric responses close and far from the epicenter can be used in the early tsunami warning systems.     

On the earthquake of March 11, 2011 near the northeastern coast of Honshu Island

The paper addresses the interpretation of the location, type, and size of the source for the earth-quake of March 11, 2011. The source—a subvertical reverse fault trending in the azimuth of ∼25° along the island arc—is located in the middle part of the Pacific slope of Honshu Island, between 38°–38.5°N and 35.5°N. The length of the source, about 350 km, approximately corresponds to a magnitude ∼8.7 earthquake. In the north, the source is bounded by a sublatitudinal reverse fault, which generated an earthquake with magnitude 7.2–7.5 in 1978. On this segment of the Pacific slope of Honshu Island, there are probably another one or a few other large seismic sources, which are still latent. They are longitudinal reverse faults, which are comparable in scale with the source of the March, 2011 earthquake. The recurrence period of the maximal earthquakes in such sources is more than 1000 years.     

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.     

88小时:美国地质调查局国家地震信息中心对2011年3月11日Mw9.0日本地震的响应

引言 2011年3月11日日本本州岛东海岸附近海域发生的M9．0地震（Tohoku earthquake,以下称“东日本大地震”——译者注）及其引发的海啸造成数以万计的人员死亡,造成的财产损失可能超过1万亿美元,这是有历史记录以来最严重的自然灾害之一。     

Geomagnetic Disturbances Accompanying the Great Japanese Earthquake of March 11, 2011

Geomagnetism and Aeronomy - This work analyzes the geomagnetic field variations recorded at the Magnetic Observatory of Karazin Kharkiv National University (in the period range of 1–1000 s)...     

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.     

基于形变观测分析2011年日本9.0级地震与断层运动间关系

2011年3月11日日本发生9.0级地震,本文以此次地震的震间、同震和震后形变观测为约束,依据不同时段断层运动空间分布特征分析日本海沟地区强震与断层运动间关系.震间日本海沟地区,断层运动闭锁线深度约为60km,闭锁线以上从深到浅依次为断层运动强闭锁段、无震滑移段和弱闭锁段.由同震位错反演结果,2011年日本9.0级地震同震存在深浅两个滑移极值区,同震较浅的滑移极值区(同震位错量10~50m,深度小于30km)震间为断层弱闭锁段;同震较深的滑移极值区(同震位错量10~20m,深度在40km左右)震间为断层强闭锁段;而在两者之间的过渡带同震位错相对较小,震间断层运动表现为无震滑移.震后初期断层运动主要分布在在闭锁线以上的同震较深滑移极值区,而同震较浅的滑移极值区能量释放比较彻底,断层震后余滑量相对较小.依据本文同震和震间断层运动反演结果,震间强闭锁段积累10m同震位错需要100多年时间,与该区域历史上7级地震活动复发周期相当;震间弱闭锁段积累30~50m同震位错约需要300~600年时间,与相关研究给出的日本海沟9级左右地震复发周期比较一致.在实际孕震能力判定的工作中,由于不同性质的断层段在同震过程中会表现更多的组合形式,断层发震能力判定结果存在更多的不确定性,但利用区域形变观测等资料给出震间断层运动特征的研究工作对于断层强震发震能力的判定具有非常重要的实际意义.     

汶川8.0级地震前后电磁场的变化特征

2008年5月12日汶川Ms8.0地震前后,距震中320 km甘肃陇南汉王地震台的地电阻率、大地电场、ELF电磁等多种观测手段捕捉到这次地震前后的异常信息.本文采用解析方法,着重探讨汶川8.0级地震前后观测到的电磁场变化特征,从电磁现象来探讨汶川Ms8.0地震发生前后,电磁场长、中、短、临期的异常特征和变化规律.自2003年以来甘东南地区及甘川交界发生4次5.0级以上地震,从空间上看,有从南北地震带中段的西北向西南方向移动的特点,强度逐渐增强,其中,文县5.0和两次岷县5.0级以上地震可以视为汶川8.0级地震的前震;从时间上分析,震前陇南汉王地震台观测到电磁场出现了长趋势变化和短临异常变化,其特征：①2003～2008年,ZD8B地电仪观测的N54°W、N85°E和N73°W测道地电阻率均显示出长趋势变化和短期变化;②视电阻率各向异性度‘S′’年变化率在有震年（异常年）是无震年（正常年）的两倍;③ELF电磁仪观测到了（0.5～39 Hz）频率段的电场、磁场在汶川8.0级地震及余震序列中异常变化分别比正常月份大1～5个数量级,并记录到电磁同震现象;④大地电场仪（ZD9A-Ⅱ）在汶川震前17个小时也记录到高频临震变化信息.     

Relocation of the 10 March 2011 Yingjiang,China, earthquake sequence and its tectonic implications

An earthquake with M_S5.8 occurred on 10 March 2011 in Yingjiang county, western Yunnan, China. This earthquake caused 25 deaths and over 250 injuries. In order to better understand the seismotectonics in the region, we collected the arrival time data from the Yunnan seismic observational bulletins during 1 January to 25 March 2011, and precisely hand-picked the arrival times from high-quality seismograms that were recorded by the temporary seismic stations deployed by our Institute of Crustal Dynamics, China Earthquake Administration. Using these arrival times, we relocated all the earthquakes including the Yingjiang mainshock and its aftershocks using the double-difference relocation algorithm. Our results show that the relocated earthquakes dominantly occurred along the ENE direction and formed an upside-down bow-shaped structure in depth. It is also observed that after the Yingjiang mainshock, some aftershocks extended toward the SSE over about 10 km. These results may indicate that the Yingjiang mainshock ruptured a conjugate fault system consisting of the ENE trending Da Yingjiang fault and a SSE trending blind fault. Such structural features could contribute to severely seismic hazards during the moderate-size Yingjiang earthquake.     

Tsunami damage to coastal defences and buildings in the March 11th 2011 M w 9.0 Great East Japan earthquake and tsunami

On March 11th 2011 a M _w 9.0 mega-thrust interface subduction earthquake, the Great East Japan Earthquake, occurred 130 km off the northeast coast of Japan in the Pacific Ocean at the Japan Trench, triggering tsunami which caused damage along 600 km of coastline. Observations of damage to buildings (including vertical evacuation facilities) and coastal defences in Tōhoku are presented following investigation by the Earthquake Engineering Field Investigation Team (EEFIT) at 10 locations in Iwate and Miyagi Prefectures. Observations are presented in the context of the coastal setting and tsunami characteristics experienced at each location. Damage surveys were carried out in Kamaishi City and Kesennuma City using a damage scale for reinforced concrete (RC), timber and steel frame buildings adapted from an earlier EEFIT tsunami damage scale. Observations show that many sea walls and breakwaters were overtopped, overturned, or broken up, but provided some degree of protection. We show the extreme variability of damage in a local area due to inundation depth, flow direction, velocity variations and sheltering. Survival of many RC shear wall structures shows their high potential to withstand local earthquake and significant tsunami inundation but further research is required into mitigation of scour, liquefaction, debris impact, and the prevention of overturning failure. Damage to steel and timber buildings are also discussed. These observations are intended to contribute to mitigation of future earthquake and tsunami damage by highlighting the key features which influence damage level and local variability of damage sustained by urban coastal infrastructure when subjected to extreme tsunami inundation depths.     

Anomalous variations in the foF2 critical frequency above Japan prior to the earthquake of March 9, 2011

Based on data from the Japanese Kokubunji and Wakkanai stations of vertical sounding of the ionosphere, the variations in the foF2 critical frequency prior to the strong earthquakes of March 9 and 11, 2011 (M 7.2 and 9.0, respectively), are analyzed. It is found that significant positive disturbances of foF2 had been recorded approximately one day before the first earthquake. Notably, at the Irkutsk reference station, which is located about 3300 km from the earthquake epicenters, there were no significant disturbances of foF2. This suggests that the effects of increased foF2, observed at the Kokubunji and Wakkanai stations, were probably caused by the earthquake preparation processes. The seismo-ionospheric manifestations of the stronger earthquake on March 11, 2011, even if they took place, were hidden by the geomagnetic storm’s effects.     

利用海啸数值模拟结果进行海底地震有限断层模型验证

基于地震有限断层模型进行海啸的数值模拟通常被用来估计海啸的到时、 波高等, 另一方面, 海啸数值模拟的结果也可以作为限定条件用来考察同一地震的不同断层模型之间的相对合理性。 采用国际上各地震研究机构在震后各自得出的不同的有限断层模型作为海啸源, 使用基于二维浅水波方程的海啸传播模型对2011年日本东北地震海啸的传播过程进行模拟, 以海啸模拟所得到的沿岸浪高分布、 平均波高、 最大波高等与实际观测值相比较, 进而判断由各有限断层模型所计算得到的海啸中哪个结果与实际的海啸情况更为符合, 由此推断断层模型的相对合理性。     

Effects of the Tohoku tsunami of March 11, 2011 on the Pacific coast of Russia

The records of the Tohoku tsunami of March 11, 2011, obtained at the nearest Deep-Ocean Assessment and Reporting of Tsunamis (DART) stations and the coastal telemetric recorders of the Russian Tsunami Warning System, are analyzed. Such parameters as tsunami arrival times, heights of the first and maximal waves, and predominant periods are presented. The eyewitness accounts and photographs of tsunami effects are presented. The tsunami height distribution along the coast of Kuril Islands is discussed.     

地球磁场对太阳风的加卸载响应与地震

将磁暴过程作为地球磁场对太阳风的加卸响应，计算分析了北京地磁台１９６５．１－１９７９．１２和１９８９．１－１９９１．１２共１８年垂直分量Ｚ的暴时场Ｄｓｔ加卸载响应比值ｆＤ（Ｚ）的变化。     

Anomalous increase in the foF2 critical frequency prior to the Spanish earthquake of May 11, 2011

A study of variations in the critical frequency of the F2 layer (foF2) prior to a shallow-focus eartquake with a magnitude M = 5.1 which occurred in Spain on May 11, 2011, is carried out. The obtained results show that a positive disturbance in the foF2 value was observed at the ionospheric Del’ebre station, which is the closest to the earthquake epicenter. At the same time, no disturbances in foF2 are revealed at ionospheric stations located at a greater distance from the epicenter. This fact makes it possible to conclude that the positive disturbance in the F2 layer observed at the Del’ebre station could have a sesmogenic nature.