Seismic Sources on the Iberia-African Plate Boundary and their Tectonic Implications
Seismic Sources on the Iberia-African Plate Boundary and their Tectonic Implications
复制标题
伊比利亚-非洲板块边界的震源及其构造意义
DOI：
10.1007/978-3-0348-7899-9_9
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发表时间：
2004
影响因子：
2
通讯作者：
C. Pro
中科院分区：
文献类型：
--
作者：
E. Buforn;M. Bezzeghoud;A. Udías;C. Pro
摘要-利用地震活动性和震源机制数据研究了伊比利亚和非洲之间的板块边界。该区域分为三个地区：A区：加迪斯湾; B区：贝蒂斯、阿尔沃兰海和摩洛哥北方; C区：阿尔及利亚。地震活动表现为复杂的活动特征，A区和C区发生大的浅源地震（h < 30 km），B区发生中强地震; B区发生中深源地震（h <30 km < 150 km）;格拉纳达以南发生深源地震（h 650 km）。对浅层地震的矩率、滑移速度和B值进行了估算，结果表明，加迪斯湾和阿尔及利亚的矩率、滑移速度和b值具有相似的特征，而中部地区的矩率、滑移速度和b值则完全不同。80个选定的浅源地震（8 ≥ mb ≥ 4）的震源机制显示，加迪斯湾和阿尔及利亚湾存在水平NNW-SSE挤压的逆冲断层，阿尔沃兰海存在东西向延伸的正断层。阿尔沃兰海26个中深源地震的震源机制表现为垂直运动，优势面为东西向。非常深的地震的解对应于沿着南北走向沿着的垂直倾滑。Frohlich图和地震矩张量在加迪斯湾、Betic-Alboran海和北方摩洛哥以及北方阿尔及利亚的浅层地震中表现出不同的行为。中深源地震和极深源地震的应力图象具有不同的方向：中深源地震的应力图象为北西-南东向垂直伸展，而极深源地震的应力图象为拉压轴倾斜约45 °。区域应力格局可能是非洲板块与伊比利亚板块碰撞的结果，岩石圈物质在中等深度的阿尔沃兰海伸展和俯冲。极深地震活动可能与更古老的俯冲过程有关。
Abstract—The plate boundary between Iberia and Africa has been studied using data on seismicity and focal mechanisms. The region has been divided into three areas: A; the Gulf of Cadiz; B, the Betics, Alboran Sea and northern Morocco; and C, Algeria. Seismicity shows a complex behavior, large shallow earthquakes (h < 30 km) occur in areas A and C and moderate shocks in area B; intermediate-depth activity (30 < h < 150 km) is located in area B; the depth earthquakes (h 650 km) are located to the south of Granada. Moment rate, slip velocity and b values have been estimated for shallow shocks, and show similar characteristics for the Gulf of Cadiz and Algeria, and quite different ones for the central region. Focal mechanisms of 80 selected shallow earthquakes (8 ≥ mb ≥ 4) show thrust faulting in the Gulf of Cadiz and Algeria with horizontal NNW-SSE compression, and normal faulting in the Alboran Sea with E-W extension. Focal mechanisms of 26 intermediate-depth earthquakes in the Alboran Sea display vertical motions, with a predominant plane trending E-W. Solutions for very deep shocks correspond to vertical dip-slip along N-S trends. Frohlich diagrams and seismic moment tensors show different behavior in the Gulf of Cadiz, Betic-Alboran Sea and northern Morocco, and northern Algeria for shallow events. The stress pattern of intermediate-depth and very deep earthquakes has different directions: vertical extension in the NW-SE direction for intermediate depth earthquakes, and tension and pressure axes dipping about 45 ° for very deep earthquakes. Regional stress pattern may result from the collision between the African plate and Iberia, with extension and subduction of lithospheric material in the Alboran Sea at intermediate depth. The very deep seismicity may be correlated with older subduction processes.