图  1   非洲中东部地区地形图以及本文使用的非洲台阵部分台站(三角形)分布

Figure  1.   Topographic map of mid-eastern Africa and distribution of Africa Array stations(triangles)

图  2   SONG台站得到的“好”(good)的剪切波分裂分析结果 (a)灰色区域为所选取的用于SKS分析的时间窗；(b)事件的反方位角分布；(c)利用旋转相关法得到的归一化快慢波波形对比；(d)利用旋转相关法得到的径向分量(R)与切向分量(T)的波形对比；(e)利用旋转相关法分析前后的水平质点运动图对比；(f)互相关系数关于快轴方向与走时差的分布；(g)利用最小能量法得到的归一化快慢波波形对比；(h)利用最小能量法得到的径向分量(R)与切向分量(T)的波形对比；(i)利用最小能量法分析前后的水平质点运动图对比；(j)切向分量能量关于快轴方向与走时差的分布

Figure  2.   An example illustrating “good” measurement of SKS waveform recorded by the station SONG (a)Shaded area illustrates selected time window for SKS splitting analysis；(b)Back-azimuthal distribution of the event；(c)Comparison of normalized fast and slow waveforms with rotation correlation(RC)method；(d)Comparison ofR andT components with RC method；(e)Horizontal particle motion before and after utilizing RC method;(f)Distribution of correlation coefficients with respect to delay time and fast axis;(g)Comparison of normalized fast and slow waveforms with minimum energy(SC)method;(h)Comparison ofR andT component with SC method;(i)Horizontal particle motion before and after utilizing SC method;(j)Distribution of transverse energy with respect to delay time and fast axis

图  3   非洲台阵各台站剪切波分裂分析结果

Figure  3.   Rose diagrams at stations of Africa Array illustrating the fast directions measured in this study

图  4   世界应力场分布图(引自Heidbachet al，2009) 不同符号表示利用不同的方法得到的水平主压应力方向．详细说明请参考www. world-stress-map.org

Figure  4.   2008 world stress map(afterHeidbachet al，2009) Downloaded from GFZ-Potsdam. Different symbols illustrate results from different methods. For more details，please see www. world-stress-map.org

图  5   非洲中东部地区的地表断层出露(引自Lenoiret al，1994) TC: 坦桑尼亚克拉通; Ub: 本汀山带; Us: 乌萨加拉山带; Bb: 班韦乌卢块体; Kb: 基巴拉山带; Ir: 艾露麦得山带; Mb: 莫桑比克造山带; La: 鲁非尼安弧; LT: 坦噶尼喀湖; LV: 维多利亚湖; LR: 鲁夸湖; LM: 马拉维湖; L: 其它湖．更为详细的说明请参考原文

Figure  5.   Geological outline of mid-eastern Africa showing the surface outcrops(afterLenoiret al，1994) TC: Archaean Tanzanian craton; Ub: Ubendian belt; Us: Usagaran belt; Bb: Bangweulu block; Kb: Kibaran belt; Ir: Irumide belt; Mb: Mozambique belt; La: Lufilian arc; LT: Lake Tanganyika; LV: Lake Victoria; LR: Lake Rukwa; LM: Lake Malawi; L: other lakes. For more details，please see the original paper

图  6   本文剪切波分裂分析结果与Forte等(2010)250 km深度处地幔流动模型的对比

Figure  6.   Comparison of the results presented in this study with the mantle flow(blue arrows) model at the depth of 250 km from Forte et al(2010)

图  7   D″各向异性示意图 图中红色区域为D″各向异性可能存在的区域(Lynner，Long，2012)；玫瑰图表示KTWE、WINO和MAFI等3个台站所记录到事件的反方位角分布；红色短棒表示WINO台站下层快轴方向，黄色短棒表示上层快轴，黑色短棒表示MAFI和KTWE台站快轴方向

Figure  7.   Illustration of D″ anisotropy The red-shaded region denotes the location of possible D″ anisotropy(Lynner，Long，2012). Rose diagrams illustrate back-azimuth coverage of the stations KTWE，WINO and MAFI. Red bars at WINO indicate lower layer fast direction，while yellow bars correspond with upper layer. Black bars at MAFI and KTWE measure fast directions

图  8   WINO台站的视分裂参数拟合结果

Figure  8.   Fitness of apparent splitting parameters of the station WINO Blue crosses represent observed data with error bars，while black lines illustrate predicted data

图  9   非洲中东部地区各向异性的主导因素示意图 玫瑰图表示各台站的快轴方向．蓝色箭头表示地幔流动模型(Forteet al，2010)，黑色细线表示地表断层出露(Lenoiret al，1994)

Figure  9.   The dominant origins of seismic anisotropy in middle-eastern African region Rose diagrams illustrate the fast directions measured in this study. Light blue arrows indicate mantle flow model(Forteet al，2010) and thin black lines are surface outcrops(Lenoiret al，1994)