为了研究地壳的应变结构,进一步了解地震的成因,美航宇局已在美国和太平洋地区部署了7个激光卫星跟踪站。据认为,地壳是由12大块坚硬的“板块”组成(见图)。这些板块处在不停的运动之中,各板块边缘都是参差不齐,犬牙交错,而且经常不断的相互碰撞,相互摩擦。当两块板块边缘的岩石卡在一起,应力超过其断裂强度时,地震就发生了。世界上绝大多数地震几乎都是发生在板块交界之处,这些地方往往被称为“地震带”。科学家们根据历史的地质材料推断出,在这12大板块中,其中有些是静止或移动甚慢的,如非洲板块每年大约只移动1厘米;而另一些板块移动 In order to study the strain structure of the earth’s crust and learn more about the causes of earthquakes, the United States has deployed 7 laser satellite tracking stations in the United States and the Pacific. The crust is believed to consist of 12 hard, “plates” (see photo). These plates are kept in motion, the plates are uneven edges, staggered, and often constantly collide with each other, friction. The earthquakes happen when the rocks on the edges of two plates snap together and the stress exceeds their breaking strength. Almost all of the world’s most earthquakes occur at the junction of plates, often referred to as “seismic zones.” Scientists have deduced from historical geological materials that some of these 12 plates are still or moving very slowly, as in the case of Africa, which moves about 1 cm annually, while others move