Complex distribution of large thrust and normal fault earthquakes in the Chilean subduction zone
Complex distribution of large thrust and normal fault earthquakes in the Chilean subduction zone
复制标题
智利俯冲带大逆冲地震和正断层地震的复杂分布
DOI：
10.1111/j.1365-246x.1983.tb03326.x
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发表时间：
1983
影响因子：
2.8
通讯作者：
R. Madariaga
中科院分区：
文献类型：
--
作者：
M. Malgrange;R. Madariaga
摘要本文对智利北方（20-33“S）1963 - 1971年M_（1）> 6的事件作了系统的研究。该地区海岸附近的中强地震有三种类型：（1）下行板块与上覆南美板块交界处的板间地震。这些事件可以非常大，达到大于8的震级。(2)下行板块内20-30公里的板内地震。它们具有断层机制，指示沿板状体的倾角沿着延伸，并且可能具有高达7.5的震级。(3)不太频繁的M- 6事件发生在下行板块顶部附近，具有几乎水平的东西向挤压轴的逆冲机制。这类机制与第一类由浅倾逆断层作用引起的地震机制有很大不同。在类型（1）和（3）的事件之间，在垂直平面上存在约30”的压缩轴旋转。详细研究了32.5”、25.5”和21“s附近的三组事件。深度和机制重新确定的P波建模和相对位置获得的主事件技术。在32.5 ° S附近，本研究期间仅发现了类型1和类型2的事件。在另外两个地点，确定了三种类型的事件。这清楚地表明，在板的顶部存在压应力，而在中心存在拉伸，这种情况通常出现在地震活动中已确定存在双贝尼奥夫带的地区。
Summary. We present the results of a systematic study of events with M, > 6 in northern Chile (20-33"S), for the period between 1963 and 1971. Medium to large earthquakes near the coast of this region are of three types: (1) Interplate events at the interface between the downgoing slab and the overriding South American plate. These events can be very large reaching magnitudes greater than 8. (2) Intra-plate earthquakes 20-30 km inside the downgoing slab. They have fault mechanisms indicating extension along the dip of the slab and may have magnitudes up to 7.5. (3) Less frequent,M, - 6 events that occur near the top of the downgoing slab and have thrust mechanisms with an almost horizontal E-W compressional axis. This type of mechanism is very different from that of the events of type 1 which are due to shallow dipping reverse faulting. There is a rotation of about 30" of the compressional axis in the vertical plane between events of types (1) and (3). Three groups of events near 32.5", 25.5" and 21"s were studied in detail. Depth and mechanisms were redetermined by P- wave modelling and relative locations were obtained by a master event technique. Near 32.5"S, only events of types 1 and 2 were found in the time period of this study. At the two other sites, the three types of events were identified. This shows clearly that there are compressive stresses at the top of the slab and extension at the centre, a situation which is usually found in the areas where a double Benioff-zone has been identified in the seismicity.