Mechanical model of precursory source proces for strong earthquakes in western Yun－nanarea——conceptandnumericalsimula┐tion

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Negative Dislocation Model and the Movement Pattern of a Fault:Determination of Potential Earthquake Sources in Western Yunnan

To determine the locked and slip parts on a fault,we simulated the movement pattern of the fault with a combined model consisting of a negative dislocation in the locked area superimposed on a relative movement between two sides of the fault.In this way,we determined the locked parts of faults by inversion with multiple epochs of geodetic data.In this paper,we have determined the movement patterns of four main faults in western Yunnan by inversion with two epochs of geodetic surveys and some crossing-fault observations.From the inversion result,we have identified the areas around Dali and Xiangyun to be the locked area,which is regarded as a sign of potential earthquake sources.     

小滇西地区M≥5地震前b值时空变化特征

同时使用完整地震目录和去余震目录,采用最大似然法对小滇西地区进行b值时空扫描,研究该地区M≥5.0地震前b值的时空变化特征。结果显示:2种地震目录b值时间曲线的整体变化趋势无明显的差异,去余震目录的空间扫描结果低值异常更加突出;小滇西地区M≥5.0地震前,b值随时间变化趋势呈现出多样化的特征,但是75%的地震发生之前,该地区处于低b值状态;该地区M≥5.0地震均发生在低b值区域或者高低b值过渡地区。另外,在不同空间尺度的b值时间曲线中,均发现了较长时间的低b值现象,尽管起始时间不同,但是结束时间相同,分析认为该现象可能是2014年盈江M6.1地震的前兆异常。因此,小滇西地区低b值是本区M≥5.0地震的一个异常指标,可以根据空间扫描的低b值地区确定未来可能的震源位置,但是b值无法单独作为一个临震指标,需要与其他地震活动性参数联合使用;b值时间曲线上的长期低值,可能是较大地震的前兆异常。     

矿震成核过程的公里尺度研究

成核过程是地震机理研究的重要部分.通过岩石实验、高温高压和数值模拟认为,地震成核的临界尺度为大地震总破裂长度的十分之一,一般为10~20 km左右;地震成核时间从年到秒、甚至毫秒.本文利用山东省宁阳县华丰煤矿立体台网的岩爆观测,进行了公里尺度的破裂成核过程实验研究.通过对华丰煤矿1995年2月~1996年5月期间的地脉动记录和12000次小震记录资料的分析,计算了它们的地脉动、S波和P波振幅比以及S波波峰的到时差,得到ML=2.9矿震的成核时间为50天,成核临界尺度为5 km.     

龙陵-澜沧断裂带双震型强震活动破裂模型讨论

龙陵地震和澜沧－耿马地震是龙陵－澜沧断裂带上两次典型的双震型强震活动,但它们在地质构造背景、应力场分布、发震构造和烈度分布等方面却具有截然不同的特点。龙陵地震发生在主要由花岗岩构成的地块内,地质构造比较均一;地震处在ＮＮＷ向挤压的统一应力场中;两主震的发震构造走向和两个Ⅸ度区长轴近于直交。澜沧－耿马地震发生在一古板块边界附近,震区构造复杂,耿马７．２级地震和澜沧７．６级地震发生于不同的应力环境中,发震构造和极震区长轴近于平行,呈斜列状分布。通过对龙陵地震和澜沧－耿马地震的对比分析,提出了双震型强震活动的共轭型和牵动型两种破裂模型,并对各自的特点及形成条件进行了初步分析     

Subarea characteristics of earthquake types in Yunnan

Studies on the earthquake sequences and the source mechanisms of the strong earthquakes show that Yunnan hasmore obvious subarea characteristics of earthquake type.Strike-slip seismic fault and mainshock-aftershockearthquake sequences are dominant in whole Yunnan area.Considering the ratio of non strike-slip faults and nonmainshock-aftershock,Yunnan area can be divided into four subareas with different characteristics,which arestrike-slip mainshock-aftershock in central Yunnan(A1),incline-slip swarm in northwestern Yunnan(A2),strike-slip double shocks in western Yunnan(B1)and quasi-strike-slip mainshock-aftershock in southwestern Yun-nan(B2),respectively.     

Investigation of Fine Velocity Structure of the Basement Layer of the Shallow Crust in Western Yunnan Region

In this paper the authors have discussed the results of investigation of fine velocity structure in the basement layer of the Simao-Zhongdian DSS profile in western Yunnan region.The depth of upper Pz interface of the basement layer is about 0-3.5 km,and the depth of the lower P1 interface is 11.0-17.0 km.The velocity of the basement layer on the southern side of the Jinhe-Erhai deep fault is 5.70-6.30 km/s,and has increased to 6.30-6.50 km/s on the northern side.Their transitional zone is situated near Jianchuan County.Along the profile some localities,where the faults cut across the lateral variation of Pz interface velocity,are quite obvious in addition to the variation in depth.The velocity isopleths are relatively sparse in the southern region of JYQ S.P.(shot - point),near the DC S.P.,and in the south ZT S.P.The magma has apparently risen up along the deep faults to the upper crust in these localities,forming a large intrusive rock zone in the basement layer.In Jinggu region the basaltic magma has     

滇西南地区M≥5级地震活动特征及预报方案

通过对滇西南地区Ｍ≥５级地震前地震、前兆和环境因子变化特征的分析,发现滇西南中强震前小震频度增加、出现窗口信号地震,前兆异常数量多,气压涨落突出等特征,并以此为依据建立了滇西南地区Ｍ≥５级地震的预报方案。     

云南地震类型分区特征研究

对云南地震序列和强震震源机制的分析与研究表明,云南地区具有较明显的地震类型分区特征.总体上云南全区地震断层以走向滑动为主，地震序列以主余震型为主.考虑到非走滑地震断层和非主余震型地震序列所占的比例，可以将云南地区划分为4个具有不同特点的分区: 滇中(A1)走滑-主余震型区、 滇西北(A2)斜滑-震群型区、滇西(B1)走滑-双震型区和滇西南(B2)准走滑-主余震型区.      

Source model of Noto-Hanto-Oki earthquake tsunami of 7 February 1993

A source model was discussed for a small tsunami accompanied by the Noto-Hanto-Oki earthquake (M _s 6.6), striking Japan on 7 February, 1994. Assuming a fault model under the sea bottom, we estimated the focal parameters jointly, using synthesized tsunami source spectra as well as the tsunami numerical simulation. The fault proposed by this study consists of a plane sized 15×15 km, dipping N47°W with the dip angle of 42°, which is almost pure reverse fault (slip angle 87°) with a dislocation of 1 meter. The numerical simulation shows that the shallow sea in the source region caused a comparatively long recurring tsunami (the periods are 12–18 minutes) in spite of its small size. The model fault is corresponding to an aftershock area of this earthquake.