三维地震断层动力破裂的显式并行有限元解法

本文在近场波动有限元的基础上,根据断层动力破裂的摩擦模型,详细地推导出了断层面节点在破裂的不同时刻的计算公式,提出了一种模拟断层动力破裂的显式并行有限元方法,利用此方法,可以模拟断层的破裂过程、地表破裂及由此产生的地面运动。     

Inversion of near-field waveform data for earthquake source rupture process (I): Method and numerical test

In seismological study, most of the earthquake source rupture processes are inverted via matching the waveforms. The hypocenter location and fault parameters (such as strike direction, dip angle, etc.) are assumed firstly, and the fault is divided into a …     

活断层地震地表破裂“避让带”宽度确定的依据与方法

基于不同类型活断层产生的地震地表破裂带宽度和跨断层探槽地质剖面的地层强变形带宽度等观测事实 ,结合地面建筑设施毁坏带与活断层密切的空间位置关系 ,采用统计分析方法 ,确定了活断层“避让带”宽度为 30m。各活断层更为准确的避让带宽度可通过分析跨断层探槽地质剖面上地层的变形特征加以验证或修订 ;活断层斜列阶区、平行次级断层围限区、走向弯曲区等特殊地域的避让带宽度为这些地域宽度与两外侧各 15m之和。建议有关部门进行活断层“避让带”立法与执法管理 ,并加强活断层鉴定及其地表活动线几何结构形态的准确定位工作 ,积极而有效地减轻地震灾害     

Source process of the southeast Beni-Suef, northern Egypt earthquake Using Empirical Green's Function Technique

The rupture process of a moderateearthquake (ML4.9) occurred southeastBeni-Suef, northern Egypt was analyzed. Thecharacterization of the rupture process andsource properties were extracted fromstudying the relative moment rate function(RMRF). RMRFs were retrieved bydeconvolution of small aftershock recordsusing an inversion procedure for onlyP-wave part of the records.Although, this event is a moderateearthquake, its RMRFs exhibitedcomplexity and directivity of the rupturebehavior. The deconvolution pulses reflectthree subevents or more. The detailedanalysis of the distinct subevents revealedgross temporal and spatial characteristicsof the rupture propagation. The azimuthalvariation in the time delay of thesubevents with respect to the initiationrupture indicates that the subevents arelocated at 0.85 ± 0.17 and3.5 ± 0.07 km in directions of320^° ± 45^° and330^° ± 15^° with rupturevelocities 3.4 ± 0.45 and4.0 ± 0.7 km/sec, respectively. Thismeans that the rupture is predominatelypropagated toward the North. Estimation ofthe rupture direction was combined withP-wave focal mechanism to identify thefault plane for the initial rupture ofmainshock.Source parameters were calculated for eachdistinct subevent, including seismicmoments 8.53E14 to 6.80E15 Nm, fault radii713 to 1800 m and stress drops 0.725 to2.932 MPa. The large estimated stress dropfor the main subevent reflects failureasperity.     

Seismic Hazard Evaluation Using Markov Chains: Application to the Japan Area

Seismogenic regions within some geographic area are interrelated through tectonics and seismic history, although this relation is usually complex, so that seismicity in a given region cannot be predicted in a straightforward manner from the activity in other region(s). We present a new statistical method for seismic hazard evaluation based on modeling the transition probabilities of seismicity patterns in the regions of a geographic area during a time interval, as a Markov chain. Application of the method to the Japan area renders good results, considering the occurrence of a high probability transition as a successful forecast. For magnitudes M5.5 and time intervals t=0.10 year, the method yields a 78% aftcast (forecast of data already used to evaluate the hazard) success rate for the entire catalog, and an indicative 80% forecast success rate for the last 10 transitions in the catalog. A byproduct of the method, regional occurrence probabilities determined from the transition probabilities, also provides good results; aftcasts of regional activity have a 98% success rate, and those of activity in the highest probability region about 80.5% success rate. All results are superior to those from the null hypotheses (a memory-less Poissonian, fixed-rate, or uniform system) and have vanishingly small probabilities of resulting from purely random guessing.     

Paleoearthquake rupture behavior and recurrence of great earthquakes along the Haiyuan fault,northwestern China

Paleoseismological studies have shown that indi-vidual past large-magnitude earthquakes can be recog-nized in the geological record and the timing betweenevents can be measured through Quaternary datingtechniques[1—6]. Thus, through paleoseismological st-udies, it is possible to determine age of each prehis-toric event so that recurrence intervals of large earth-quakes may be evaluated which provides a means toexpand the limited view of earthquakes offered by thehistorical and instrumental re…     

Attenuation characteristics of ground motion intensity from earthquakes with intermediate depth

Data of the intermediate depth (the Geioyo and the Shizuoka) earthquakes in Japan recorded in a dense network is analysed and compared with various available attenuation relations. The approach of Midorikawa (Midorikawa S., 1993, Technophysics 218, 287–295) based on the empirical Greens function technique of Irikura (Irikura, K., 1986, Proceedings of the 7th Japan Earthquake Engineering Symposium, pp. 151–156.) has been used to model the rupture responsible for these earthquakes and peak ground acceleration are simulated at selected observation points. The method presented in this work includes the transmission effect in a multiple layer crustal model for a finite fault earthquake source model. Sharp attenuation rate is seen for such intermediate depth earthquakes which is difficult to explain through conventional attenuation relations. Detail study of the methodology and comparison of results shows that the transmission factor plays an important role for the sharp attenuation rate for intermediate-to deep-focus earthquakes.     

Aftershock Propagation Characteristics During the First Three Hours Following the 26 December 2004 Sumatra-Andaman Earthquake

Within three hours of the mainshock rupture of the 26 December 2004 Sumatra-Andaman earthquake, 45 aftershocks occurred that are distributed all along the mega-thrust fault plane and also along the West Andaman fault. Seven of these aftershocks struck sequentially and unilaterally from the mainshock in the south towards north within 2h 9m 50.76s indicating an overall rate of aftershock propagation to the tune of 167 meters/sec. Seismic moment calculated from fault parameters gives a value of 1.2 × 10³⁰ dyne cm. Three separate fault segments are identified from distribution of aftershocks with propagation rates 330, 250 and 85 meters/sec in the southern, central and northern segments. These 7 unilaterally propagating shocks along the mega-thrust are probably not aftershocks of the mainshock rather these are sequentially triggered shocks each rupturing a small segment of the fault. Location of the mainshock and several aftershocks are guided by several lithospheric hinge faults identified previously.     

Steadiness and stop of brittle fracture driven by the forces in different distances

Introduction The problem of crack stop of fault is of special importance in geosciences. This is because the risk of rupture of large scale fault is taken as the object of investigation in the geosciences. In some meaning, the stop of earthquake rupture is more important than initial because of its influ-ence on the prediction of energy releasing during the earthquake. There are quite a few of factors that cause stop of the fault. For example, the effect of barriers, the rapid healing of shea…