Recent and present‐day stresses in the Granada Basin (Betic Cordilleras): Example of a late Miocene‐present‐day extensional basin in a convergent plate boundary
Recent and present‐day stresses in the Granada Basin (Betic Cordilleras): Example of a late Miocene‐present‐day extensional basin in a convergent plate boundary
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DOI：
10.1029/1999tc900016
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发表时间：
1999-08
期刊：
影响因子：
4.2
通讯作者：
J. Galindo‐Zaldívar;A. Jabaloy;I. Serrano;J. Morales;F. González-Lodeiro;F. Torcal
中科院分区：
文献类型：
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作者：
J. Galindo‐Zaldívar;A. Jabaloy;I. Serrano;J. Morales;F. González-Lodeiro;F. Torcal
地中海西部欧亚板块和非洲板块之间的弥散汇聚边界与宽度超过 300 公里的地震活动区相关。尽管这两个板块正向西北-东南交汇，但贝蒂科和里夫科迪勒拉山脉包含自中新世以来一直活跃的伸展结构。利用地震震源机制、通过研究微断层的方向和运动学确定古应力以及研究主要构造，分析了该地区中新世晚期至近代格拉纳达盆地东南部与山脉隆起同时发生的伸展构造。地质表面数据和震源机制都表明了当今东北-西南延伸的区域条件，具有三轴到长长的应力椭球体。然而，应力场是不均匀的，随着时间的推移，应力会发生局部变化，不同的应力有时甚至同时作用在相邻区域。最常见的变化包括受应力椭球的长长特征影响的多向或北东-西南延伸，以及受区域构造环境影响的北西-东南次水平挤压。尽管走滑断层是西南-北东延伸和西北-东南挤压地区最有可能出现的构造，但走滑断层却很少见。地震活动集中在上地壳，可能与类似于地表断层的低角度到高角度正断层的活动相对应，尽管它们不能与它们相关。该地震活动的下限可能与 300°C 等温线一致，表明该地区的热梯度较低。目前的区域应力在地表处垂直，但在深度处向西南方向倾斜。
The diffuse convergent boundary between the Eurasian and African plates in the western Mediterranean is associated with a seismicity zone more than 300 km wide. Although the two plates are converging NW–SE, the Betic and Rif Cordilleras contain extensional structures that have been active since the Miocene. The extensional tectonics in the region, which occurred simultaneously with the uplift of the cordillera, have been analyzed in the southeastern sector of the late Miocene to recent Granada Basin, using earthquake focal mechanisms, the determination of paleostresses from the study of the orientation and kinematics of microfaults, and the study of the major structures. Both the geological surface data and the focal mechanisms indicate present‐day regional conditions of NE–SW extension, with triaxial to prolate stress ellipsoids. However, the stress field is heterogeneous, with local variations in stress over time, with different stresses sometimes even acting simultaneously in adjacent areas. The most frequent changes consist of pluridirectional or NE–SW extension, favored by the prolate character of the stress ellipsoids, and NW–SE subhorizontal compression, favored by the regional tectonic setting. Strike‐slip faults are scarce even though they are the most likely structure to be expected in a region with SW–NE extension and NW–SE compression. Seismicity is concentrated in the upper crust and may correspond to the activity of low‐ to high‐angle normal faults similar to the surface faults, although they can not be correlated with them. The lower cutoff of this seismicity probably coincides with the 300°C isotherm and suggests a low thermal gradient for the region. Present‐day regional stresses have σ1 vertical at the surface but in depth plunge toward the SW.