Spectral magnitude and seismic radiated energy computed from CDSN records

We have employed 10 digital records and computed the spectral magnitude and the seismic radiated energy for 18 large earthquakes (M _s≥6) occurred in Eur-asian belt during 1986–1989. The nine digital stations (CD-SN) distribute all over China and one in Germany. The spectral magnitudes of various period have different stability among stations. The stability is better for maximum spectral magnitudemi and seismic radiated energyE, their differences among stations are smaller, especially for the stations where the ray path main penetrates the low mantle. But the stability of corner period is usually not good. The relation between seismic radiated energy and seismic moment magnitudeM _w is lg (E)=1.5Mw+c, wherec is a constant. The maximum spectral magnitudemi=M _w+0.1, it is consistant with theoretical prediction. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 418–426, 1993. This work supported by the Deutsche Forschungsgemeinschaft, Bonn, F. R. Germany. The support is grateful acknowledge.     

Strain segmentation and lateral membrane deformation rate of the subducted Ryukyu slab

Abstract Focal mechanisms of intermediate-depth earthquakes within the subducted Ryukyu slab indicate a systematic pattern of down-dip extension in the northern part under Kyushu. These mechanisms switch rapidly around the Tokara channel to down-dip compression in the southern part toward Taiwan. This intriguing pattern of strain segmentation, together with the differences between the slab geometry of the northern and southern parts, has raised the question of whether stress segmentation, as defined possibly by a tear fault, might exist in the slab. However the Ryukyu trench has a concave oceanward shape in the northern segment while it is convex in the southern oceanward part toward Taiwan. The inflection zone is located around the Tokara channel. The concept of Gaussian curvature of a curved surface suggests that the along-arc variation of the geometric configuration of a subducted slab is related to the shape of the trench. This is in order to accommodate the lateral membrane deformation of the slab as the oceanic lithosphere subducts from a spherical shell to the geometry delineated by the Wadati-Benioff zone. The membrane deformation regime of the subducted Ryukyu slab and its relation with the trench geometry was examined by assuming that the subduction be modelled by the flow field of a thin viscous sheet. A projection operator was utilized to compute the membrane strain-rate tensor of an arbitrary non-Euclidean surface. Numerical experiments indicated that the northern segment of the slab was dominated by lateral compression and down-dip extension and the southern part by lateral extension and down-dip compression. This transition is sharply located near the Tokara channel. These patterns were compatible with what had been observed from studies of focal mechanisms, suggesting that the strain segmentation might be controlled, at least in part, by the lateral membrane deformation within the slab due to the trench shape in this subduction zone. The slab geometry was predicted by minimizing the integrated total dissipation power; this revealed distinct features that were consistent with observations. This implies that the slab geometry may also be affected by the membrane deformation in a systematic fashion.     

攀钢,攀矿场地边坡地震稳定性研究

本文在总结分析攀钢、攀矿昔格达层滑坡基本特征的基础上,对区内滑坡进行了地震稳定性计算,给出了经不同方法治理后的滑坡的地震稳定系数;同时采用“因子迭加”方法对究研区进行边坡稳定性区划,划分出相对的稳定区、欠稳定区和不稳定区,为抗震减灾和土地的开发利用提供了科学依据。     

汾渭地震带Ms≥6级地震的可公度特征初探及中强地震节律分析

汾渭地震带M_s≥6级地震在时间上具有可公度性,可公度值为4.09年。中强地震序次节律存在以3为倍数的韵律特征,据此可建立该带M_s≥6级地震可公度性预测公式。对1989年大同M_s=6.1级地震检验表明,预测公式有较强的稳定性和较高的预测精度,结合节律分析可对汾渭地震带今后的中强地震活动作出一定程度的预测。     

3D高阶抛物Radon变换在不规则地震数据保幅重建中的应用

3D地震数据不规则采样缺失重建是地震勘探数据处理流程中的重要问题.本文提出了一种基于具有保幅特性的非均匀高阶抛物Radon变换（NHOPRT）地震数据重建方法.在最小二乘反演方程中引入Delaunay三角网格剖分来计算空间不规则加权系数,从而获得最接近完整规则数据的高阶抛物Radon变换域系数.在用SVD求解反演方程过程中,利用高阶抛物Radon变换算子在频率域为指数函数,具有线性可分解特性,将二维空间的高阶抛物Radon变换算子分解为两个独立的一维空间变换算子,减小了变换算子的矩阵大小,从而很大程度地提高了计算效率.理论模型和实际地震数据重建测试证明了本文方法的有效性以及实用性.     

松辽盆地东缘域地壳结构及其地质意义:深反射地震

松辽盆地东缘域位于松嫩—张广才岭微板块东部.自晚古生代以来该域经历了西拉木伦河缝合带闭合产生的北向挤压作用、蒙古—鄂霍茨克洋自西向东剪刀叉式闭合对其东侧东南侧产生的挤压作用以及西太平洋板块西向变向俯冲产生的挤压作用等区域构造应力场影响,从而产生了复杂的地壳变动.该东缘域的地壳结构与松辽盆地地壳是否具有相近的结构特点,这是至今未被研究的内容.在Songliao Drep研究中已经用深反射地震手段得到松辽盆地地壳结构的一组新认识.这些认识在其东缘域是否还成立,也需要用同样精度的手段予以研究.另外,莫霍界面的宏观特征与微观（内部）特征,从松辽盆地到其东缘域有什么样的变化,其形成机理是什么,也需要进一步研究.为了回答这些科学问题,从哈尔滨西至尚志市附近实施了一条东西向约150 km长的深反射地震剖面.通过研究发现东缘域与松辽盆地基底地壳具有明显的差别,即由松辽盆地地壳的三分性变到东缘域盆地外地壳的二分性,在剖面近东端得到近26 km深的莫霍界面深度,并用均衡理论分析莫霍界面形态特征的形成机理;上部地壳存在双向大型推覆断裂,推测其被推覆体主体是古亚洲洋沉积地层即C-P系海相地层.这些认识为中国东北地区探查晚古生代海相地层、研究东北亚地壳结构特征提供了理论依据.     

深地震反射剖面揭示的天津地区张渤带地壳精细结构

穿过天津地区张渤带的长86 km、NE向深地震反射剖面揭示了该区清晰的地壳精细结构图像和断裂的深浅构造特征,为研究张渤地震构造带的深部孕震环境和构造模式提供了地震学证据,对探讨晚中生代以来华北裂陷盆地的深部动力学过程及演化具有重要意义.结果表明,天津地区张渤带地壳以结晶基底反射T_G为界,分为上下两部分;上地壳反射波组丰富,分层特征明显,界面起伏形态清楚,清晰地刻画出冀中坳陷新生代沉积分层、箕状沉积凹陷的底界、潮白河断裂、蓟运河断裂及丰台—野鸡坨断裂的几何结构;地壳内部结晶基底（T_G）至Moho之间,显示出近于"反射透明"的地震波场特征,无明显震相,这与华北其他地区的深地震反射剖面结果明显不同;地壳厚度为30.0~34.5 km,总体变化趋势为中段地壳厚而南北端相对较薄,Moho在横向上显示出明显的不均匀和横向间断特征,在Moho被错断处存在两个明显的反射事件R_A和R_C,R_A可能是软流圈热物质上涌的侧向残留物,叠层状反射震相R_C则表现出壳幔过渡带特征;剖面揭示了2条错断Moho的超壳深大断裂（F_D1和F_D2）和9条上地壳断裂,深大断裂应是软流圈热物质上涌,造成上地幔隆起而形成的,上地壳断裂与地壳垂直运动及侧向引张力有关;超壳深断裂（F_D1和F_D2）为本区深部热物质的上涌与能量交换提供了通道,而与之对应的地壳浅部断裂（F₃和F₉）,则为能量调整提供了可能的条件,断裂邻近区域可能是未来发生强震的地区,值得注意.     

Amplitude Response of a LCR Gravimeter with Feedback at Periods of Microseisms and Earthquake Waves

The amplitude response of a LCR gravimeter with the SRW-E feedback was determined on a vertical vibrating platform. The ink-pen recorder was connected parallel with the digital voltmeter input to obtain an analog response of the gravimeter to the harmonic motion of the base with a peak-to-peak amplitude of 10 m and periods excited in an interval of 4 - 10 s as by the ground motion of meteorological microseisms, and in the interval 10 -100 s as by surface waves of distant strong earthquakes. In the first interval, an unexpected maximum of the amplitude response was observed with the double amplitude of apparent 6,5 Gal (6.5 × 10 _–8 m/s ² ) at a period of 4.8 s, and a baseline shift with the amplitude of–64Gal was observed at the same period. The value of this direct component cannot be separated from the effect of the Earth's gravity field. In the second interval, the amplitude response of the gravimeter displayed one expected maximum at a period of 40 s with the double amplitude of 8.1Gal. At the usual level of microseisms with a peak-to-peak amplitude of up to 2 m the fluctuation of the gravimeter on the direct baseline shifted by –4.9 Gal was estimated at 1 Gal. With typical Rayleigh surface waves with periods of 20 s and double amplitudes of up to 100 m, the fluctuation reached 67 Gal.     

On seismic strengthening area before strong and great shocks and its mechanism

IntroductionI.thasbeenpayingattentiontotheanomalousphenomenonbyseismologiststhattheearthquakeactivityoftenstrengthensinacertainspaceandduringacertaintimearoundthesourceareabeforeastrongearthquake.Mogi(1969)pointedoutthataringdistributiveareaofthestrengthenedearthquakeactivityoftenappearsaroundthesourcearea10to20yearsbeforegreatshock,whichcalledaringphenomenon(or"doughnut").Afterthat,otherscholarsreportedinsuccessionthatringdistributionofearthquakeactivityoccurredbeforeastrongertquakeorevenbefo…     

Applications of seismic moment tensor inversion in fast response to earthquakes

IntroductionAfteramoderateorstronger(Ms25.0)earthquake,themosturgentworkofthedivisionforearthquakemonitoringandpredictionistodetermineitstimeoforigin,hypocentrallocation(longitude,latitudeanddepth)andmagnitudeandtojudgethetrendofseismicregimedevelopmentassoonaspossible.Ingeneralcases,whenanearthquakewithMS25.0insideChinaoraonewithMS26.0inneighboringareasofChinahasoccurred,theEarthquakeBulletinofChineseSeismologicalNetworkcanprovidedeterminationoftheorigintime,hypocentrallocation(longitude,…