2013年芦山MS7.0地震序列S波分裂特征

本文测定了2013年4月20日芦山M_S7.0地震震源区及其附近台站的S波分裂参数,包括快波偏振方向和慢波延迟时间,最终得到了40个台站的S波分裂结果．结果显示:在地震主破裂区内观测到的快波优势取向为NE向,与余震分布的长轴方向一致;位于双石—大川断裂以西台站的快波偏振优势方向为NW向,与区域最大主压应力轴方向一致;位于荥经断裂附近台站的快波偏振优势方向为NW向,与该断裂走向一致．快波偏振优势方向随时间的变化结果显示:主震前位于地震破裂区附近的TQU和BAX台站的快波偏振优势方向均呈NE向;主震后TQU台站的快波偏振优势方向为近EW向,而BAX台站的快波偏振优势方向则不突出,反映出芦山地震主震前快波偏振方向受控于龙门山断裂带,而主震后受构造应力场的作用更加明显．此外,各台站的慢波延迟时间为1.25—5.40ms/km,在余震覆盖密集区域,台站的慢波延迟时间均大于3.0ms/km,反映出震源区的各向异性程度较强．芦山主震后,各台站的延迟时间随时间变化持续减小,反映出震源区地壳应力随余震活动逐渐减小．      

2013年芦山M_s7.0地震震源区横波分裂的变化特征

对2013年芦山Ms7.0级地震序列的横波分裂的时空变化现象进行了研究.通过在横波窗内S波质点运动图的分析,从位于龙门山断裂带南段芦山地震震源区地震台站的记录中提取了S波分裂的快波偏振方向和慢波的到时延迟.在研究区,观测到各台站的快波偏振优势方向从南向北有分区特征,慢波到时延迟的随时间有趋势性变化.空间上,快波偏振优势方向在南部为北东向,与龙门山断裂走向一致,而北部为北西向,与区域主压应力方向一致,位于断裂带上的台站TQU和BAX表现出特殊性,可能受到龙门山断裂带的直接影响,体现了断裂带上的应力场方向变化的特殊性.时间上,慢波到时延迟在主震后迅速增大,持续一段时间后又减小;横波分裂现象主要由台站下方岩层中随应力分布排列的微裂隙控制,本文结果揭示了主震和余震过程中区域应力场的变化,芦山地震震源区的地壳应力在主震后得到了增强,随着余震活动导致的应力释放,后期应力减小.     

2010年玉树7.1级地震震源区横波分裂的变化特征

本文对2010年玉树M_s7.1级地震序列的横波分裂的时空变化现象进行了研究.通过在横波窗内S波质点运动图的分析,从位于甘孜-玉树断裂带台站的地震记录中提取了S波分裂的快波偏振方向和快慢波之间的时间延迟.断裂带上3个台站的S波分裂的结果显示了NEE向快波偏振方向,与区域内最大主压应力方向基本一致.观测到了快、慢波到时延迟的趋势性变化,空间上,位于震源区甘孜-玉树断裂带的北支断裂上L6304和YUS台的到时延迟大于位于南支断裂上的L6303的结果,同时YUS台的到时延迟又大于L6304台的;时间上,YUS台的到时延迟在主震后迅速增大,持续一段时间后又减小.横波分裂现象主要由台站下方岩层中随应力分布排列的微裂隙控制,本文结果揭示了主震和余震过程中区域应力场的变化,玉树地震主震区的应力在主震后得到了释放,地壳应力向东南转移,导致了YUS台的到时延迟大于L6304台的;玉树地震的发震断裂是甘孜-玉树断裂的北支断裂,而南支断裂对其影响较小;YUS台附近的地壳应力在主震后得到了增强,随着余震活动导致的应力释放,后期应力减小.     

2008年汶川地震震源区横波分裂的变化特征

对2008年汶川地震序列的横波分裂的时空变化现象进行了研究．通过在横波窗内S波质点运动图的分析,从地震余震区附近台站的近场地震记录中提取了S波分裂的快波偏振方向和快慢波之间的时间延迟．龙门山断裂附近7个台站的S波分裂的结果显示了快波偏振方向的空间分布特征,断裂带东南侧（四川盆地一侧）台站的快波偏振方向总体为北东方向,而在断裂西北侧高原内部的PWU（平武台）则为近东西方向．观测到了快慢波之间到时差的趋势性变化,靠近余震带南端的L5501台的到时差在主震后持续减小,北端PWU台的到时差比主震前明显增大．横波分裂现象主要由台站下方岩层中随应力场方向排列的微裂隙控制,结果显示了主震和余震过程中区域应力场的变化,汶川地震余震活动带南部的应力在主震和余震中得到了释放,地壳应力场在余震带北部集中,导致了PWU台在主震后介质各向异性强度的增强．     

芦山地区S波速度结构讨论

本文利用芦山地震区域中(BAX,TQU,MDS)能记录远震波形的台站,通过坐标转换和时间域迭代反卷积,得到了该区域台站的P波接收函数。初步讨论了初始模型的选择对于芦山地区以及周边地区的S波速度结构结果的影响,对进一步探索该区域精细结构提供参考。     

盈江MS6.1地震序列近场横波分裂研究

使用横波分裂系统分析方法(SAM), 对2014年5月30日盈江M_S6.1地震震区内多个近场流动台站记录到的大量波形数据进行横波分裂研究． 研究结果表明, 盈江M_S6.1地震序列的快S波偏振方向为近NS向, 与区域主压应力方向一致． 主震发生后, 由于震源区应力状态的调整, 卡场台(KAC)快S波偏振方向发生逆时针偏转, 勐弄台(MNO)快S波偏振方向离散度减小, 并且由于受到研究区内断裂的影响, MNO台偏振方向较KAC台偏振方向更加离散． KAC台和MNO台的慢S波时间延迟均表现出主震发生前短时间内突然减小, 震后逐渐增大的变化特征, 这意味着临震前震源区地壳应力的释放和震后地壳应力的增强, 预示了后续余震的持续发生． 地震序列时间延迟平均滑动曲线起伏振荡, 表明了余震的发生伴随着震源区地壳应力的不断调整．      

2017年九寨沟MS7.0地震震源区横波分裂变化特征

对2017年九寨沟M_S7.0地震序列的横波分裂的时空变化特征进行了分析.通过横波窗内S波质点运动图的分析,从九寨沟地震震源区各个地震台站的近震横波记录中提取了横波分裂的快波偏振方向和慢波延迟时间.观测结果显示,震源区各台站的上地壳各向异性在空间上存在分区特征,时间上有随时间的趋势性变化特征.空间上,位于震源区北部余震区内的3个台站中,发震断层东面的台站L5112和L5111只有一个突出的快波偏振优势方向（NNE向）,而西面的L6202台有两个快波偏振优势方向（除了NNE向,还有一个近EW向）,体现了余震区剧烈调整的地壳应力和构造复杂断裂的综合作用;余震区外的3个台站中,震源区东部靠近塔藏断裂（东）附近的JZG台的快波偏振优势方向为NW向,与塔藏断裂（东）的走向一致,南部的台站L5110和L5113的快波偏振优势方向为近EW向,与区域主压应力方向一致;余震区内各台站的平均慢波延迟时间大于余震区外各台站,反映了九寨沟地震孕育过程中余震区的应力积累强于其周边区域.时间上,快波偏振方向在主震后前期离散度较大,随着时间的推移,离散度在后期有逐渐变小的趋势;慢波延迟时间在主震后较大,但随着时间的推移,也表现出逐渐减小,趋于稳定.横波分裂随时间逐渐减小和趋于稳定的变化特征反映了九寨沟地震在孕震中积累的应力,随着主震和余震的发生而导致的应力释放和调整,应力大小和调整幅度逐渐减小,后期趋于稳定.     

基于密集流动地震台网资料研究古冶—滦县地区上地壳各向异性

自唐山地区发生7.8级地震以来,古冶—滦县地区一直为唐山地震的余震频发区.该地区断裂和地质构造十分复杂,这些断裂的破碎程度有哪些差异?这是地震学家所关心的问题.本文使用在古冶—滦县地区布设的密集流动地震台网2020年8月—2021年7月近一年的波形记录,采用剪切波分裂原理通过对古冶—滦县地区上地壳各向异性研究来揭示这些问题.得到以下结论：(1)古冶—滦县地区快剪切波平均偏振方向为NE86.2°±27.8°,慢剪切波平均时间延迟为2.37±1.25 ms·km^-1.快剪切波偏振第一优势方向为ENE向,与区域背景主压应力方向一致;第二优势方向为NE向,该方向揭示了研究区域断裂主要以NE向为发育的构造意义.(2)唐山断裂带附近台站快剪切波偏振方向均显示出NE向的第二优势方向,与断裂走向一致.断裂附近台站慢剪切波时间延迟较高,各台站时间延迟差异较小,表明区域各向异性程度较强,断裂沿NE向破碎程度较强且破碎均匀.(3)滦县—乐亭断裂和卢龙断裂附近台站快剪切波偏振方向显示出复杂性,表明两条活动断裂的交汇在地壳内部产生了复杂的地壳破裂裂隙结构.断裂附近台站慢剪切波时间延迟较高,...     

喜马拉雅东构造结上地壳各向异性特征

本文利用雅鲁藏布江下游台阵的16个台站2016年度的近震数据,通过横波窗内的横波分裂测量,在各台站总计得到369个有效的横波分裂参数对,分析得出喜马拉雅东构造结上地壳各向异性特征。空间上,各台站的快波偏振优势方向整体上自西向东由近EW向,转为NE向,然后转向近NS或NNE向,最后转向NW向。大部分靠近或位于活动断裂带上的台站的快波偏振优势方向与断裂的走向一致,主要体现在墨竹工卡断裂上的ZOS台,雅鲁藏布江断裂上的WOL,NYG,ZIB和DOJ台站,墨脱断裂上的BEB和DEX台站,以及迫龙—旁辛断裂上的BAX和DAM台站;而距离雅鲁藏布江断裂西段和东段各有一定距离的LAD和YIG台站,以及位于雅鲁藏布江断裂东段与嘉利断裂交会处的TOM台的快波偏振优势方向与断裂走向存在一定角度,但其与喜马拉雅东构造结主压应力场方向NNE向基本一致。上地壳各向异性整体体现了结构控制和应力控制的特征,但各台站的横波分裂参数并未表现出随时间的规律变化特征,这可能与2016年研究区地震活动强度较弱有关。研究区各台站间存在较大的横波分裂参数差异和自身离散度,反映出东构造结复杂的构造特征和剧烈的变形作用。      

鄂尔多斯块体西缘地壳介质各向异性:从银川地堑到海原断裂带

通过收集鄂尔多斯块体西缘固定地震台网2010年6月至2017年8月的近场地震资料,选择符合剪切波分裂分析的14个台站记录的共137个有效事件波形,得到了剪切波分裂参数,即快剪切波（简称快波）偏振方向和慢剪切波（简称慢波）时间延迟.结果表明,研究区的快波偏振方向和慢波时间延迟具有明显的分区特征,快波偏振方向主要与构造应力场方向或者断层走向大体一致.鄂尔多斯西缘紧邻块体边界的台站,快波偏振方向自北向南呈现NS、NNE、NE向的变化,与青藏高原东北缘主压应力方向变化基本一致.银川地堑东西两侧的快波偏振方向有差异,东侧区域主要受青藏高原NNE向挤压和黄河-灵武断裂共同影响,而西侧区域可能受到阿拉善块体与鄂尔多斯块体之间的NW方向的主张应力和阿拉善块体内部应力分布的影响;鄂尔多斯块体、阿拉善块体与青藏高原的交汇区快波优势偏振方向为NE向,与青藏高原东北缘主压应力方向一致;海原断裂带及以南区域快剪切波优势偏振方向为WNW向,与断裂走向基本一致,较好的说明了海原断裂带为活跃的活动断裂.构造与断裂分布都是控制快波偏振方向的主要因素,走滑断裂上的台站快波偏振方向与断裂走向一致,表明这些台站主要受到断裂的强烈影响;走滑断裂附近的个别台站快波偏振方向呈现与构造应力场一致的方向,表明几乎没有受到断裂的影响.鄂尔多斯、阿拉善与青藏高原的交汇区平均时间延迟高于其他地区,反映了青藏高原在NE向运动过程中,受到稳定的鄂尔多斯块体阻挡作用,导致了交汇区地壳介质各向异性程度增加.以海原断裂带到六盘山断裂带为界,其两侧区域的各向异性差异性明显,揭示了应力与介质特性的差异,暗示其邻近区域,特别在海原断裂带东端到六盘山断裂带与鄂尔多斯块体西缘交汇区域,可能有较高的强震危险背景.本研究还对该区域的地壳和上地幔的耦合问题进行了初步讨论.     

The characteristics of shear wave splitting in the source region of the April 20, 2013 Lushan earthquake

Using seismic data of the aftershocks sequence of the April 20, 2013 Lushan earthquake recorded by seismic temporary and permanent stations in the source region, with the visual inspection of particle motion diagrams, this paper preliminarily contains the polarization directions of fast shear wave and the time-delays of split shear waves at every station, and analyzes the crustal anisotropic characteristics in the source region. In the study area, the polarization directions at stations BAX, TQU, L132, L133, L134, and L135 are northeast, which is consistent with the strike of Dachuan–Shuangshi fault. There are two polarization directions at MDS and L131, which are northeast and southeast. The scatter of polarization directions suggests the complex stress field around these two stations where two faults intersect. For the normalized time-delays at every station, the range is 1.02–8.64 ms/km. The largest time-delay is from L134 which is closest to the mainshock, and the smallest one is from L133. The variations in time-delays show the decreasing at stations BAX, L134, and L135 because of the stress–relaxation after earthquake.     

Variations of shear wave splitting in the 2013 Lushan Ms7.0 earthquake region

In this paper, variations of shear wave splitting in the 2013 Lushan Ms7.0 earthquake sequence were studied. By analyzing shear wave particle motion of local events in the shear wave window, the fast polarization directions and the delay time between fast and slow shear waves were derived from seismic recordings at eight stations on the southern segment of the Longmenshan fault zone. In the study region, the fast polarization directions show partition characteristics from south to north. And the systematic changes of the time delays between two split shear waves were also observed. As for spatial distribution, the NE fast polarization directions are consistent with the Longmenshan fault strike in the south of focal region, whereas the NW fast direction is parallel to the direction of regional principal compressive stress in the north of focal region. Stations BAX and TQU are respectively located on the Central and Front-range faults, and because of the direct influence of these faults, the fast directions at both stations show particularity. In time domain, after the main shock, the delay times at stations increased rapidly, and decreased after a period of time. Shear-wave splitting was caused mostly by stress-aligned microcracks in rock below the stations. The results demonstrate changes of local stress field during the main shock and the aftershocks. The stress on the Lushan Ms7.0 earthquake region increased after the main shock, with the stress release caused by the aftershocks and the stress reduced in the late stage.     

Upper crustal anisotropy observed around the Longmenshan fault in the 2013 MS7.0 Lushan earthquake region

Based on the shear wave splitting analysis of the seismic recordings at 17 temporary stations and three permanent stations, we measured the shear wave splitting parameters (i.e., the polarization direction of fast shear wave and the time delay of slow wave) to perform a systematic analysis of the crustal seismic anisotropy around the Longmenshan fault in the 2013 M_S7.0 Lushan earthquake region. We observed apparent spatio-temporal characteristics in the shear wave splitting parameters. The spatial distribution of fast polarization directions showed a clear partitioning in the characteristics from northwest to southeast in the focal region, which changed from NW-SE to NE-SW. In the northwest of the focal region, the fast polarization direction was oriented to NW-SE, which was parallel to the maximum horizontal compressive stress direction. However, the NE-SW fast polarization direction in the southeast of the focal region was parallel to the Longmenshan fault strike. For station BAX on the Central fault in the middle of the focal region, the distribution of fast polarization directions showed a bimodal pattern, with one dominant in the NE-SW direction and the other in the NW-SE direction. With regard to the temporal variation, the time delays were large in the initial stage after the mainshock but then gradually decreased over time and tended to be stable in the later period. This indicated that stress in the focal region increased to a maximum when the main shock occurred, with the stress release caused by the mainshock and aftershock activity, and the stress gradually decreased after a period of time. The scatter of fast polarization directions was large after the main shock, but over time the scatter gradually decreased, indicating that the Lushan earthquake caused a large perturbation in the local stress field. As the stress gradually decreased and was adjusted by the aftershock activity, the perturbation gradually weakened.     

龙门山断裂带的分段性特征——来自密集震源机制解的约束

龙门山断裂带沿倾向和走向具有明显的分带性和分段性特征,通常以4条主干断裂为界将龙门山断裂带自西向东分为5条构造带,但是对沿走向的分段性特征仍未达成共识.本文利用四川区域地震台网记录的汶川地震后近10年的波形数据,采用全波形反演获取了龙门山断裂带1495个M≥3的震源机制解.通过“滑动窗”扫描方法提取不同地震类型的数量沿龙门山断裂带走向的变化曲线,据此将龙门山断裂带的震源区划分为S1—S9段.根据反演的震源机制解,进一步采用阻尼线性反演技术求取龙门山断裂带高分辨率的构造应力场信息,从地震类型、断面结构和构造应力场等角度探讨龙门山断裂带的分段性特征.结果表明:(1)地震类型存在明显的分段性特征.其中S1的逆冲型地震比例最高,S8的走滑型地震比例最高,S9的正断型地震比例最高.汶川地震后龙门山断裂带可能存在差异性断层调整运动,且余震晚期沿断裂带走向普遍存在应力的补充和协调,芦山地震的发生可能还对S2造成了应力扰动.汶川主震附近及余震区远端经历了更长的震后调整过程,且余震区远端S9具有更复杂、强度更高的震后调整过程.(2)断面结构存在明显的分段性特征.断面结构揭示汶川主震附近和余震区远端的隐伏断裂,以及虎牙断裂南端参与了汶川余震活动.断面倾角与走滑分量具有较好的一致性,在具有明显逆冲分量的分段断面倾角主要分布在50°~70°,而在具有明显走滑分量的分段断面倾角基本在60°以上,且断面倾角增大与汶川余震带宽度收缩变窄相吻合.(3)龙门山断裂带的应力环境非常复杂.σ1方向的分段性差异导致了汶川—芦山地震空区的地壳撕裂和地幔物质上涌、汶川主震附近和余震区远端的隐伏断裂活动以及虎牙断裂南端大量的逆冲型地震.结合构造应力场与大地测量资料认为,龙门山的隆升主要是受构造应力场作用下的上地壳缩短增厚所致.     

Possible thermal brightness temperature anomalies associated with the Lushan (China) MS7.0 earthquake on 20 April 2013

Lushan M_S7.0 earthquake occurred in Lushan county, Ya'an city, Sichuan province of China, on 20 April 2013, and caused 196 deaths, 23 people of missing and more than 12 thousand of people injured. In order to analyze the possible seismic brightness temperature anomalies which may be associated with Lushan earthquake, daily brightness temperature data for the period from 1 June 2011 to 31 May 2013 and the geographical extent of 25°E-35°N latitude and 98°E-108°E longitude are collected from Chinese geostationary meteorological satellite FY-2E. Continuous wavelet transform method which has good resolution both in time and frequency domains is used to analyze power spectrum of brightness temperature data. The results show that the relative wavelet power spectrum (RWPS) anomalies appeared since 24 January 2013 and still lasted on 19 April. Anomalies firstly appeared at the middle part of Longmenshan fault zone and gradually spread toward the southwestern part of Longmenshan fault. Anomalies also appeared along the Xianshuihe fault since about 1 March. Eventually, anomalies gathered at the intersection zone of Longmenshan and Xianshuihe faults. The anomalous areas and RWPS amplitude increased since the appearance of anomalies and reached maximum in late March. Anomalies attenuated with the earthquake approaching. And eventually the earthquake occurred at the southeastern edge of anomalous areas. Lushan earthquake was the only obvious geological event within the anomalous area during the time period, so the anomalous changes of RWPS are possibly associated with the earthquake.     

Analysis of Dynamic Characteristics of Crustal Horizontal Deformation in the South Segment of Longmenshan Fault Zone Revealed by GPS Data after the Wenchuan Earthquake

In order to obtain deformation parameters in the south segment of Longmenshan fault zone,Euler datum transformation and the least square collocation for data interpolation and smoothing are used to process GPS displacement time series data in the south segment of Longmenshan fault zone,and the rigid and elastic-plastic block motion model is used to calculate the strain parameters in each subarea. Conjoint analysis of displacement,velocity of each station and strain parameters of each subarea reveals that the influence of the Wenchuan earthquake on the south segment of Longmenshan fault zone increases from southeast to northwest,causing a highest deformation rate 6 times the background value and heightening the influence of the hidden faults on the difference of the earth surface along its two sides,which leads to the seismic risk of the southern segment increasing from north to south. The comparison of seismic risk among subareas based on the tectonic and seismicity background indicates that the most dangerous area is on the southeast of Longmenshan faults,and the background strain accumulation and the promoting effect of the Wenchuan earthquake advanced the occurrence of Lushan earthquake and the sinistral strike-slip on the rupture plane. The Wenchuan earthquake also caused a slight two-year long continuous strain release in the south segment of Xianshuihe fault,but the influence is far less than the effect of the compressive strain caused by the Sichuan-Yunnan block.     

THE RESEARCH OF THE SEISMOGENIC STRUCTURE OF THE LUSHAN EARTHQUAKE BASED ON THE SYNTHESIS OF THE DEEP SEISMIC DATA AND THE SURFACE TECTONIC DEFORMATION

The seismogenic structure of the Lushan earthquake has remained in suspensed until now. Several faults or tectonics, including basal slipping zone, unknown blind thrust fault and piedmont buried fault, etc, are all considered as the possible seismogenic structure. This paper tries to make some new insights into this unsolved problem. Firstly, based on the data collected from the dynamic seismic stations located on the southern segment of the Longmenshan fault deployed by the Institute of Earthquake Science from 2008 to 2009 and the result of the aftershock relocation and the location of the known faults on the surface, we analyze and interpret the deep structures. Secondly, based on the terrace deformation across the main earthquake zone obtained from the dirrerential GPS meaturement of topography along the Qingyijiang River, combining with the geological interpretation of the high resolution remote sensing image and the regional geological data, we analyze the surface tectonic deformation. Furthermore, we combined the data of the deep structure and the surface deformation above to construct tectonic deformation model and research the seismogenic structure of the Lushan earthquake. Preliminarily, we think that the deformation model of the Lushan earthquake is different from that of the northern thrust segment ruptured in the Wenchuan earthquake due to the dip angle of the fault plane. On the southern segment, the main deformation is the compression of the footwall due to the nearly vertical fault plane of the frontal fault, and the new active thrust faults formed in the footwall. While on the northern segment, the main deformation is the thrusting of the hanging wall due to the less steep fault plane of the central fault. An active anticline formed on the hanging wall of the new active thrust fault, and the terrace surface on this anticline have deformed evidently since the Quaterary, and the latest activity of this anticline caused the Lushan earthquake, so the newly formed active thrust fault is probably the seismogenic structure of the Lushan earthquake. Huge displacement or tectonic deformation has been accumulated on the fault segment curved towards southeast from the Daxi country to the Taiping town during a long time, and the release of the strain and the tectonic movement all concentrate on this fault segment. The Lushan earthquake is just one event during the whole process of tectonic evolution, and the newly formed active thrust faults in the footwall may still cause similar earthquake in the future.     

四川芦山7.0级地震及其与汶川8.0级地震的关系

2013年4月20日在四川省雅安市芦山县发生M7.0级地震.根据四川省台网资料和收集的国内外相关资料,我们分析了芦山地震的基本参数、余震分布、序列衰减等特征.结果表明:芦山地震位于龙门山断裂南段,其震源力学机制显示为纯逆冲性质,与龙门山断裂构造特征相符合;芦山地震的余震较丰富,震后15天震区已发生7800多次余震,其中,5级以上余震4次,最大余震是4月21日17时5分芦山、邛崃交界M5.4级地震;余震分布形成的图形显示其长轴走向与龙门山断裂构造走向一致,余震分布显示密集区长轴约40 km,短轴约20 km.与汶川M8.0级地震在震源力学机制、破裂过程、余震空间展布以及地表破裂等对比分析后表明:芦山地震与汶川地震的震源错动类型、破裂过程、地表破裂以及余震活动等特征存在明显差异;芦山地震与汶川地震震中位置相距90 km,两次地震的余震密集区相距50 km;汶川8.0级地震造成龙门山断裂中北段较充分破裂,芦山7.0级地震则展布于龙门山断裂南段且破裂尺度有限;两者有发震构造上的联系,但两次地震是相对独立的地震事件.     

利用图像信息方法研究芦山MS7.0地震前川滇及附近地区的图像异常

图像信息方法是一种基于统计物理学的地震预测方法. 该方法通过严格的统计检验给出地震活动状态显著偏离平均状态的地区(即显著平静或显著活跃的地区), 称为“地震热点”. 以往研究结果表明该方法是一个预测效能较高的中长期地震预测方法. 本文利用中国地震台网中心提供的1970年以来的地震目录, 在剔除余震、 选取完备震级的基础上, 基于前期研究工作结果中预测效能较高的计算参数, 即网格尺度为2°×2°、 预测时间窗为9年, 分析2008年汶川M_S8.0地震后到2013年芦山M_S7.0地震前川滇地区的图像信息演化过程. 结果表明, 2009—2010年间芦山M_S7.0地震震中附近的鲜水河断裂带、 龙门山断裂带和安宁河断裂带交汇区(29°—31°N, 101°—105°E)存在明显的地震热点, 2011—2012年该地震热点缩小至(29°—31°N, 101°—103°E)范围, 2012年以后消失, 继而于2013年发生芦山M_S7.0地震. 本文还对比研究了网格尺度为1°×1°时的图像信息演化过程, 结果显示2009—2010年芦山地震附近的新津—成都—德阳断裂南部、 龙泉山西缘断裂南段、 马边—盐津断裂带、 峨边断裂带、 天全—萦经断裂带(29°—30°N, 103°—104°E)也出现过地震热点, 2011年以后该热点消失, 2013年发生芦山M_S7.0地震. 本文讨论了计算参数对预测结果的影响, 并根据目前存在的地震热点分析了川滇及附近地区今后强震发生的可能地点.