Analysis of foreshock sequence of the 1975 Haicheng earthquake of Ms 7.3

Ａｎａｌｙｓｉｓｏｆｆｏｒｅｓｈｏｃｋｓｅｑｕｅｎｃｅｏｆｔｈｅ１９７５ＨａｉｃｈｅｎｇｅａｒｔｈｑｕａｋｅｏｆＭｓ７．３Ｚｈａｏ－ＲｏｎｇＺＵＯ（左兆荣）；Ｊｉａｎ－ＰｉｎｇＷＵ（吴建平）ａｎｄＺｈｉ－ＬｉｎｇＷＵ（巫志玲）（Ｉｎｓｔｉｔｕｔｅｏｆ...     

Analysis of foreshock sequence of the 1975 Haicheng earthquake of M S 7.3

The “earthquake nucleation” is discussed in this paper. The acceleration is a property of the nucleation phase and is a necessary condition of earthquake instability too. If the acceleration property of this nucleating process is described by the equation dΘ/dt=C/(t _f−t) ⁿ , the process can be summarized briefly that the rate of cumulative seismic release is proportional to the inverse power of the remaining time to failure. Based on this principle, the foreshock sequence of the 1975 Haicheng earthquake withM _S7.3, was analysed backward. It is stated clearly that the time-to-failure and magnitude of the mainshock can be predicted successfully if the coefficientr ² attains to the maximum. In the estimation of mainshock time, the error can generally be less than, or far less than, one-half the remaining time between the time of the last used data point and the mainshock. Contribution No. 95A0024, Institute of Geophysics, SSB, China. This study is the "Eighth-Five" contract project ofSSB.     

Damage of 1975 Haicheng Ms7.3 earthquake in the Korean Peninsula and its effect on Kyushu, Japan

The 1975 Haicheng MS7.3 earthquake affected whole Korean Peninsula and even Kyushu,Japan.In this paperisoseismal map of this earthquake was drawn for these areas by sorting out and analyzing data systematically col-lected,furthermore,the characteristics of the earthquake damage were discussed.In the northern Korean Peninsula,the intensity is V in great majority of this area except local area with intensity VI,and the damage is basically inaccordance with typical characteristics of corresponding intensity grade.In the southern Korean Peninsula,theintensity is IV in large part of the area,however,in some big cities such as Seoul etc.,not only high buildingsshook strongly,but also some people appeared perceptions such as feeling dizzy and so on,and electrical servicewas interrupted on one or two districts because of transformer tripping.These phenomena could be caused by theeffect of long-period wave generated from a large earthquake on far-field.     

Variations of gravity before and after the Haicheng earthquake, 1975, and the Tangshan earthquake, 1976

Before and after the Haicheng earthquake of magnitude 7.3 which occurred on February 4, 1975, five repeated gravimeter surveys were carried out, three before and two after the earthquake, along a northwest-southeast profile of about 250 km in length not far on the west of the epicenter. The mean-square error of the measurements of the gravity differences between two consecutive points on the profile is less than 40 μGal. From June, 1972 to May, 1973, within a period of about one year, the results of three surveys indicated a clear decrease of the gravity values at points on the southeastern portion of the profile, amounting to about 352 μGal. After the earthquake, the fourth survey, which was carried out in March, 1975, revealed that the gravity values had recovered to the levels of the first survey and continued to increase as was shown by a fifth survey carried out in July of the same year.Variations of gravity were also observed before and after the Tangshan earthquake of magnitude 7.8 which occurred on July 28, 1976, but in this case, gravity was increasing instead of decreasing before the earthquake. Along an east-west profile of about 270 km in length and not far on the north of the epicenter, two gravity surveys were made before and two after the earthquake. The results showed that after the main shock, the gravity values of the whole profile, especially at those points closer to Tangshan, tended to return gradually to their values of the first survey before the earthquake.From these results, there seems to be a close relationship between these gravity variations and the occurrences of earthquakes. Based on results of repeated levelling work done in these regions, the estimated amount of gravity change caused by the change of elevation of the ground surface is far too small to account for the observed value. Therefore we speculate that some large earthquakes might be associated with some sort of mass transfer under ground, within the crust or in the upper mantle. This transfer would cause a large part of the gravity variation observed. We have made a theoretical analysis of this effect and attempted to obtain some estimate of the magnitude of this mass transfer, even though we are not yet clear about the physics of it.     

新疆于田M_S7.3地震余震序列重定位研究

截至2014年3月18日00时,新疆地震台网共记录于田MS 7.3地震M≥3余震57次,2—3级余震147次。主震位置较为精确,可以采用基于初至波视速度的主事件定位技术,对余震序列进行重新定位。通过对震源区附近进行网格搜索,对序列地震中具有6个以上P波初至的M≥2事件重新定位,获得182个高精度结果,为研究此次地震的发震构造提供参考。     

Numerical simulation for 1975 Haicheng and 1999 Xiuyan earthquake processes by DDA+FEM

Introduction The Xiuyan earthquake(MS=5.4)on Nov.29,1999,occurred between Hushan town and Pi-anling town at the southeast end of the aftershocks of Haicheng earthquake(MS=7.3).These two earthquakes′sequences are highly similar in the way that the foreshocks are very frequent,focal mechanisms of the main shocks are about the same and fault strikes are approximately in the same direction.It is important to study these earthquakes for further research on seismogenesis to fore-cast earthquake…     

辽宁海城7.3级地震死亡人数-年龄分布的分析

2004年2月，我们在辽宁省海城市档案馆发现了《海城市县委关于全县干部人员受地震伤亡统计表名单》。通过对地震时死亡以及震后冻死、烧死、捂死和病死者年龄段的分析，得出不同的原因致死者所集中的年龄段不同。这个结论对于中国北方冬季的防震减灾有相当的参考价值，对今后的防震减灾工作有一定的指导意义。     

Seismic imaging of the middle and upper crust by double-difference tomography: the Haicheng earthquake (Ms 7.3) in Liaoning Province

The Haicheng earthquake (Ms 7.3) occurred in Liaoning Province (39°N–43°N, 120°E–126°E ), China on February 4, 1975. The mortality rate was only 0.02% owing to the first timely and accurate prediction, although the area affected by the earthquake was 9200 km² and covered cities with a population density of 1000 p/km². In this study, the doubledifference (DD) tomography method was used to obtain high-resolution three-dimensional (3D) P- and S-wave velocity (Vp and Vs) structures and Vp/Vs as well as the earthquake locations. Tomography results suggest that velocity structure at shallow depth coincides well with topography and sediment thickness. The earthquake locations form a northwest-striking zone associated with the Jinzhou(JZ) Fault and a northeast-striking zone associated with the Haichenghe-Dayanghe (HD) Fault, and suggest that the JZ Fault consists of three faults and the Ms 7.3 Haicheng earthquake originated at the intersection of the JZ and the Faults. Lowvelocity zones (LVZs) with low Vp/Vs are observed at 15–20 km depth beneath the Haicheng (HC) region. We interpret the LVZs in the middle crust as regions of fluids, suggesting rock dehydration at high temperatures. The LVZs and low Vp/Vs in the upper crust are attributed to groundwater-filled cracks and pores. We believe that large crustal earthquakes in this area are caused by the combination of faulting and fluid movement in the middle crust.     

岫岩MS5.4与海城MS7.3地震的共性和个性研究

1999年海城-岫岩交界地区的Ms5．4地震和1975年海城Ms7．3地震在许多方面有相似之处,如具有大量的前震和前兆异常。但由于两者震级不同,所以前兆异常既有共性,又有其特殊性。通过对这两次地震前地震活动特点及前兆异常的对比分析,利用数值模拟方法模拟了两次地震共性和个性可能的形成机制。     

Promoting effects of 1975 Haicheng foreshocks on theoccurrence of the mainshock

Ｐｒｏｍｏｔｉｎｇｅｆｆｅｃｔｓｏｆ１９７５ＨａｉｃｈｅｎｇｆｏｒｅｓｈｏｃｋｓｏｎｔｈｅｏｃｃｕｒｒｅｎｃｅｏｆｔｈｅｍａｉｎｓｈｏｃｋＸｉｎｇ－ＣａｉＬＩ（李兴才）（ＩｎｓｔｉｔｕｔｅｏｆＧｅｏｐｈｙｓｉｃｓ，ＳｔａｔｅＳｅｔｉｓｍｏｌｏｇｉｃａ...     

新疆于田7.3级地震前异常特征

分析2014年2月12日新疆于田7.3级地震前山西地区倾斜仪、应变仪资料,发现侯马地震台水管仪、伸缩仪及临汾、太原、离石地震台水平摆不同程度地发生转向、速率变化。经对同时段观测资料差分分析得知,震前1—9天日均值差分值超出2倍中误差;谱分析表明,震前10天,在0.000 37—0.000 43 Hz、0.000 76—0.000 87 Hz频段,观测到大幅值异常信息;小波细节分析说明,多种形变仪器在64—128小时时段内观测到长周期低频率异常信号;震前20天体应变加卸载响应比大幅偏离正常值现象,恢复正常后发震。各测向在异常的起始时间有较好的准同步性。     

海城地震预报过程的回顾及地震预报发展的思考

通过1975年海城地震预报过程的回顾,结合国内外地震监测预报研究的进展,提出了发展我国地震预报研究的建议。     

Damage of 1975 Haicheng <Emphasis Type="Italic">M</Emphasis><Subscript>S</Subscript>7.3 earthquake in the Korean Peninsula and its effect on Kyushu,Japan

The 1975 Haicheng M _S7.3 earthquake affected whole Korean Peninsula and even Kyushu, Japan. In this paper isoseismal map of this earthquake was drawn for these areas by sorting out and analyzing data systematically collected, furthermore, the characteristics of the earthquake damage were discussed. In the northern Korean Peninsula, the intensity is V in great majority of this area except local area with intensity VI, and the damage is basically in accordance with typical characteristics of corresponding intensity grade. In the southern Korean Peninsula, the intensity is IV in large part of the area, however, in some big cities such as Seoul etc., not only high buildings shook strongly, but also some people appeared perceptions such as feeling dizzy and so on, and electrical service was interrupted on one or two districts because of transformer tripping. These phenomena could be caused by the effect of long-period wave generated from a large earthquake on far-field.     

1994年台湾海峡7.3级地震发震断层的地震学证据

通过地震学观测资料的分析和研究,并综合其他作者的研究成果,论证了台湾海峡１９９４年７．３级地震发震断层的主破裂面走向应为北西向,地震的发生是由分布于该区域的巴士系构造活动所致。     

辽宁海城M4.3地震强震记录分析

2008年辽宁海城M 4.3地震,辽宁省强震动台网12个强震台站记录到地面运动,是辽宁省自开展强震动观测以来同时获取强震记录最多的一次,记录的最大加速度为167.5 cm·s-2,初步展现了辽宁省强震动台网建设的成效.     

The source rupture feature of the southern Taiwan Straits earthquake of September 16, 1994 (M S7.3) & the analysis of earthquake circumstance in southeastern coast of China

According to the source mechanism of the main shock and the distribution feature of the aftershocks occurring in the southern Taiwan Straits on Sept. 16, 1994, in this paper the authors analysed the source rupture feature of the major earthquake, demonstrated that this seismic sequence possessed the characteristics of a large intraplate earthquake. And according to the seismotectonic background and the historical seismicity in the area, the authors clarified the active characteristics of the seismically active belts along northwestern direction and analysed preliminarily the earthquake circumstance in the southeastern coast of China.     

日本福岛7.3级地震灾害损失总结与讨论

2021年2月13日,日本本州东岸近海发生7.3级地震,没有造成人员死亡,仅150余人受伤,导致建筑物和基础设施发生不同程度的破坏和功能中断。此次强震并未造成大量的人员伤亡和工程结构本体破坏,但出现非结构构件破坏较为普遍以及基础设施功能中断的情况。介绍了各机构的震后灾害损失快速评估工作,总结了工程结构破坏和功能影响、人员伤亡和经济损失情况。对此次地震的灾害特征进行了总结和思考,认为随着各地区抗震能力的提高,非结构构件破坏、地震灾害链、基础设施功能中断与恢复、抗震韧性将成为今后研究的重点。     

2011年3月9日日本本州东海岸近海发生7.3级地震

中国地震台网中心和美国地质调查局(USGS)公布的该地震的参数如下:1中国地震台网中心发震时间:北京时间2011年3月9日10时45分;震中位置:日本本州东海岸近海(38.5°     

2014年2月12日新疆于田M_S7.3级地震的回顾性预测讨论

静中动判据、异年倍九律、三性法、高山峰指标是郭增建研究组提出的中期与短期的预测指标。用这几个指标回顾性地讨论了2014年2月12日新疆于田南MS7.3级地震的中期和短临预测。     

Relocation of the 1998 Zhangbei-Shangyi earthquake sequence using the double difference earthquake location algorithm

Introduction On January 10, 1998, at 11h50min Beijing Time (03h50min UTC), an earthquake of ML=6.2 occurred in the border region between the Zhangbei County and Shangyi County of Hebei Province. In total 87 events with ML3.0 were recorded by Beijing Telemetry Seismic Network (BTSN) before March of 1999. Before relocation the preliminary hypocenters determined by BTSN showed an epicentral distribution of 25 km long and 25 km wide without any predominate orientation. The epicentral a…