日月引潮力变化与某些地区地震发生时间的相关研究

本文研究了中国西南及华北地区日月引潮力和地震发生时刻的关系，通过对引潮力三分量的分析及把地震按处断裂构造分区，发现潮力的东西方向水平分量与地震发生时刻有密切关系。利用此结论可以提高对地震发生时刻的预报准确性。     

日月引潮力与华北地区的地震

分析讨论了日月引潮力变化与1900-1992年间发生在中国华北地区的29次Ms>5.5的地震之间的关系,结果表明这些地震的发生时间与日月在震源区形成的引潮力南北方向的水平分量的变化存在高相关性,日月引潮力分量的变化对这些地震的发生可能有一定的诱发作用。     

日月引潮力与中国西北地区地震发震时间的深入研究

深入研究了中国西北地区的地震与日月引潮力的关系．通过仔细分析西北地区活动断裂带的特点，把引潮力的水平分量分解为平行及垂直于活动断裂带走向的两个分量，研究其与地震发震时间的关系．研究结果表明，两个水平分量与地震的发震时间密切相关，其中平行于断裂带走向的水平分量与地震发生时间的关系更为密切，对不同的活动断裂带，相关关系又有所不同，这可能与断裂带的构造特点有关．     

日月引潮力与中国西北地区地震发震时间的深入研究

深入研究了中国西北地区的地震与日月引潮力的关系，通过仔细分析西北地区活动断裂带的特点，把引潮力的水平分量分解为平行及垂直于活动断裂带走向的两个分量，研究其与地震发震时间的关系。研究结果表明，两上水平分量与地震的发震时间密切相关，其中平行于断裂带走向的水平分量与地震发生的关系更为密切，对不同的活动断裂带，相关关系又有所不同，这可能与断裂带的构造特点有关。     

日月引潮力触发地震的一个证据--论邢台、河间和唐山地震的时间特性

研究表明,中国河北省是引潮力与强震相关区： 1966年邢台地震、1967年河间地震和1976年唐山地震即均为引潮力触发的地震．本研究对这些地震发震时刻共同特性的研究也证明了这一点．通过对日月半日潮水平引潮力极值时刻的计算发现,上述地震时刻与朔望大潮半日潮水平引潮力极大值时刻极为接近,隆尧6.8级、宁晋7.2级、河间6.3级地震滞后日月半日潮水平引潮力极大值时刻均仅几十分钟,而唐山7.8级大地震仅超前16 min(力的方向均为向西,与太平洋板块对华北块体挤压力方向一致),这就是它们的时间特性．这种地震的时间特性体现了这些地震的发生不是随机的,而是受日月引潮力控制、受引潮力所激发的．这是符合引潮力触发机制的,因而是引潮力触发地震的一个证据．     

引潮力对显著地震触发作用与大震关系的机理讨论

初步讨论了引潮力对显著地震触发作用与大震关系的机理。 结果表明, 这一机理是比较复杂的。 地震发生时水平引潮力方位与地震断层面走向接近, 可能增加断层面上的剪应力, 有利于地震的发生; 水平引潮力方位与地震主张应力轴T轴接近, 可能减小断层面上的正应力, 从而减小断层面上的摩擦力, 也会有利于地震的发生。 所讨论的3个震例中有2个共同点: 其一为大震前显著地震发生时水平引潮力方位相互比较接近; 其二为显著地震破裂面走向和大震破裂面走向基本一致。     

汶川8.0级地震及强余震破裂方式与引潮力之间的关系

本文通过计算汶川8.0级主震及20次M_S≥5.0强余震发震时刻引潮力的方位、 大小及变化率, 并对比其破裂方式, 发现11次逆冲型地震其发震时刻的水平引潮力方位和主压应力轴P轴有6次夹角在33°之内; 8次走滑型地震, 其发震时刻垂向引潮力都处于向上的峰值区间; 而2次具有张性正断分量的地震, 发震时刻垂向引潮力都处于向下的峰值区间。 根据以上的统计特征, 本文就引潮力对三种破裂类型在汶川主震及强余震中可能的触发机制进行了探讨。     

引潮力与潮汐应力对强震触发的研究

本文讨论了在构造应力水平达到岩石破裂临界值时引潮力、潮汐附加应力的动态变化与地震序列之间的关系,选用了中国大陆1970年以来7级以上地震序列资料,分析了引潮力水平分量动态变化与强震发震时间之间的关系,结果显示在一定时空范围内前震、主震及余震序列发震时刻的引潮力存在优势方向,多数地震发震时刻与选取时段引潮力水平分量的方位角相位比平均值仅为35%;对于构造复杂地区,结果显示引潮力水平分量的方位角不仅存在一个优势方向,还明显存在其他优势方向,可能与发震构造有关.根据1966～1976年中国九大地震震源机制解计算潮汐正应力和滑动方向的剪应力及其变化率,结果显示多数地震发震时刻潮汐剪应力接近最大值.     

加州兰德斯7.3级地震远距离触发的地震活动

１９９２年６月２８日７．３级兰德斯地震在美国西部大部分地区触发了地震活动的异常迅速而广泛的增强。所触发的地震发生在距兰德斯主震１２５０ｋｍ（震源尺度的１７倍）处，范围局限于具有持久地震活动性的地区，并呈走滑到正断层机制。其中许多还是地热和近代火山活动场所。根据计算的地震弹性模型的静应力变化似乎很小，并不足以导致触发。最有可能的解释是，伴随主震地震波的大的动应变和地壳流体（或许还包括地壳岩浆）之间的     

Seismicity induced by gas production: I. Correlation of focal mechanisms and dome structure

From August 1976 to June 1979, more than 220 seismic events were recorded by a 7-station network operating over an active gas field in France. 120 earthquakes with magnitudes greater than 1.0 were selected for a detailed study in order to understand the seismic response to a decrease in the gas reservoir pressure of 50 MPa. Composite focal mechanisms were determined for these events. We found that where preexisting fractures were known from well-logs, faults with the most favorable orientation were reactivated. In the part of the gas field where no preexisting faults were known, orientation of the fracture planes was close to the orientations of stratigraphic interfaces.Our kinematic model, constrained by the distribution of the earthquakes and their focal mechanisms, consists of the downward dropping of a block located close to the top of the gas field. The main faults, as defined by the spatial density of the seismic activity, define the limits of this block. The displacements observed along these faults can be either normal or reverse mechanism, dependent on the preexisting orientation of each fault. Another important result is the evidence that the depletion of the gas reservoir exerts the major influence on local seismic displacements, obscuring the effect of regional setting.     

Research on distinguishing method and mechanism of tidal deformation anomalies before large earthquakes

Introduction There are many researches on modulating and triggering seismic activities by tidal force in China and abroad. Heaton (1975) studied the tidal triggering of seismic activity and discovered that the tidal stress did have an obvious triggering action on the dip-slip or oblique slip great earthquakes. Tidal triggering of earthquakes has been studied for a long time in China, especially in recent years. For example, LI et al (2001) provided the relationship between the solar and luna…     

Can Damage Mechanics Explain Temporal Scaling Laws in Brittle Fracture and Seismicity?

Time delays associated with processes leading to a failure or stress relaxation in materials and earthquakes are studied in terms of continuum damage mechanics. Damage mechanics is a quasi-empirical approach that describes inelastic irreversible phenomena in the deformation of solids. When a rock sample is loaded, there is generally a time delay before the rock fails. This period is characterized by the occurrence and coalescence of microcracks which radiate acoustic signals of broad amplitudes. These acoustic emission events have been shown to exhibit power-law scaling as they increase in intensity prior to a rupture. In case of seismogenic processes in the Earth's brittle crust, all earthquakes are followed by an aftershock sequence. A universal feature of aftershocks is that their rate decays in time according to the modified Omori's law, a power-law decay. In this paper a model of continuum damage mechanics in which damage (microcracking) starts to develop when the applied stress exceeds a prescribed yield stress (a material parameter) is introduced to explain both laboratory experiments and systematic temporal variations in seismicity.     

环太平洋大震的时空特征分析

本文基于聚类分析方法和聚类树图, 对1890年以来环太平洋周边7.5级以上大震的时间间隔特征进行分析, 发现起始震级低于8.0级的地震分类特征一致, 而起始震级在8.0级以上地震分类特征比较详细: 在初步分为地震活跃期和地震平静期时, 在地震活跃期内, 又可细分为地震活动相对高活跃期(时间间隔1年左右)和地震活动相对低活跃期(时间间隔6年左右)。 进而, 以8.0级以上地震最后一个活跃期为例, 揭示了在地震活跃期内, 地震的空间迁移表现出逆时针旋转的特征。     

Seismicity in the Vogtland/Western Bohemia Earthquake Region Between 1962 and 1998

The Vogtland/Western Bohemia region is part of the Saxothuringian Earthquake Province. It is an isolated area of active intraplate seismicity. Observations of the seismicity between 1962 and 1998 are summarized. More than 17000 earthquakes have been detected microseismically with M _L reaching from about –1.5 to 4.6. In the considered time interval, the catalogue of Vogtland events can be regarded as complete for magnitudes larger than 1.8. The region is well known for the occurrence of earthquakes clustered contemporarily in time and space. In this study, altogether 82 clusters are defined. Among them, clusters with swarm properties are distinguished from clusters with main shock accompanied by fore- and aftershocks, and from single events. 48 swarms are detected.The magnitude-frequency distribution of the maximum magnitudes of the clusters is studied. In the magnitude range 1.8  M _L  3.1, a bimodal character of the magnitude-frequency distribution is detected for both swarms and nonswarm-like events. The slope is greater for larger magnitudes than in the small-magnitude range. A gap in the magnitude-frequency distribution of clusters is observed for maximum magnitudes between 3.1 and 4.3. Furthermore, clusters themselves are characterized by the b-values of their magnitude-frequency distributions. Swarms show b-values greater than 0.7. Epicenters of swarms are confined to a few subregions. Epicenters of nonswarm-like events are distributed over a larger region than epicenters of swarms but hypocenters of swarms and nonswarm-like clusters may be located close to each other.The envelope of the distribution of magnitudes as a function of time is investigated. In the considered time interval, a statistically significant recurrence of strong events of about 72 months is discovered by a frequency analysis. Comparing the seismicity between 1897 and 1908 with the seismicity between 1962 and 1998 temporal variations in the recurrence become obvious. The Nový Kostel zone is discussed in more detail. The average hypocenters of swarms are located on a SW-dipping fault segment that intersects the Eger Rift in NNW-SSE direction.Discussing properties of the seismicity in the Vogtland/Western Bohemia region it is concluded that the increased seismicity may be explained by the presence of fluids on deep reaching faults. The occurrence of swarms, their variability as well as the small distances between hypocenters of swarms and nonswarm-like events point to strong lateral and possibly temporal changes of the properties of the fault system.     

On the Relationship Between the Crustal Strain Rate and Seismicity:Detect the Source-Field Relation from the Crustal Strain Field

The relationship between the strain cumulative rate (i.e., the crustal strain rate, or CSR in short) and seismic activity is analyzed to develop a new method to determine risky regions for strong shocks within recent years by the recorded crustal strain field. Seismic activity, especially the recurrence period, is different in different areas. Ding Guoyu (1984) pointed out that, for different seismic regions, the difference in the recurrence period of strong earthquakes is mainly controlled by their difference in the rate of the tectonic movement, which is controlled by the seismogenic environment and the tectonic conditions. The method of determining the risky regions for strong shocks from the gradient of vertical strain rates observed in a geodetic survey is preliminarily tested with the earthquakes in recent years; the results show that this method is effective and useful for earthquake prediction. The relationship between CSR and seismicity in a specific region is studied with strain theories, obse     

Statistical Analysis of Triggered Seismicity in the Kresna Region of SW Bulgaria (1904) and the Umbria-Marche Region of Central Italy (1997)

A version of the restricted trigger model is used to analyse the temporal behaviour of some aftershock sequences. The conditional intensity function of the model is similar to that of the Epidemic Type Aftershock-Sequence (ETAS) model with the restriction that only the aftershocks of magnitude bigger than or equal to some threshold M_tr can trigger secondary events. For this reason we have named the model Restricted Epidemic Type Aftershock-Sequence (RETAS) model. Varying the triggering threshold we examine the variants of the RETAS model which range from the Modified Omori Formula (MOF) to the ETAS model, including such models as limit cases. In this way we have a quite large set of models in which to seek the model that fits best an aftershock sequence bringing out the specific features of the seismotectonic region struck by the crisis. We have applied the RETAS model to the analysis of two aftershock sequences: The first is formed by the events which followed the strong earthquake of M=7.8 which occurred in Kresna, SW Bulgaria, in 1904. The second includes three main shocks and a large swarm of minor shocks following the quake of 26 September 1997 in the Umbria-Marche region, central Italy. The MOF provides the best fit to the sequence in Kresna; that leads to the thought that just the stress field changes due to the very strong main shock generate the whole sequence. On the contrary, the complex behaviour of the seismic sequence in Umbria-Marche appears when we make the threshold magnitude vary. Setting the cut-off magnitude M₀=2.9 the best fit is provided by the ETAS model, while if we raise the threshold magnitude M₀=3.6 and set M_tr=5.0, the RETAS model turns out to be the best model. In fact, observing the time distribution of this reduced data set, it appears more evident that especially the strong secondary events are followed by a cluster of aftershocks.     

1998年全球地震活动综述

１９９８年第四季度,全球共发生６级以上地震１１次,其中１１月２９日塞兰海地震为７．７级,地震频度低而强度高。１９９６￣１９９８年,全球地震活动呈逐年下降趋势。１９９８年全年共发生６级以上地震（包括深震）７８次,其中有２次７．７级以上大地震。本年度６级以上浅源地震频数继续减少,全年只有６４次。１９９６￣、９９８年,Ⅰ带和Ⅱ带地震活动逐年减弱;亚欧带有起伏,１９９７年最高,１９９８年回落。中国大陆地震     

山西断陷带地球物理场特征与强震活动

从重力场、地磁场和地热场等方面分析了山西断陷带地球物理场所具有的特征,论述了地球物理场特征及其揭示的深部构造与强震活动的关系,初步建立了山西断陷带强震发生的模式,指出,与强震活动密切相关的区域地球物理场特征及深部构造,是进行地震预报和地震区划等不可缺少的依据,也是今后进一步研究地震成因必须十分重视的问题.     

千佛山断裂综合地球物理探测与地震活动性分析

千佛山断裂是济南市的一条重要隐伏断裂,研究该断裂的具体位置,断裂展布以及断裂的活动性具有重要意义。本文利用遥感技术、地球物理勘探(CT)、地质勘察等综合地质与地球物理探测手段,对该断裂地形地貌特征、地质构造特点、地层年代进行研究,分析其地震活动性。结果表明该断层中更新世早中期以来没有明显的活动证据,该断层的活动年代为早更新世-中更新世早期。千佛山断裂的运动性质以张性正断层为主,兼有左旋走滑运动的特点。从断层的几何结构分析,中更新世早中期以前断层经历了多期活动。