Broadband seismic experiments probe the East African Rift
Broadband seismic experiments probe the East African Rift
复制标题
宽带地震实验探测东非裂谷
DOI：
10.1029/2002eo000296
复制
发表时间：
2002
期刊：
影响因子：
--
通讯作者：
C. Langston
中科院分区：
文献类型：
--
作者：
A. Nyblade;C. Langston
为了进一步加深我们对大陆裂谷的方式和原因的了解，三家联合地震研究所/大陆岩石圈阵列地震研究计划(IRIS/PASSCAL)正在进行宽带地震实验，研究东非下方的上地幔结构。东非新生代裂谷的起源，以及那里发现的火山作用和高原隆起，长期以来一直令地球科学家着迷。裂谷系统可以与与阿法尔三联结发展有关的伸展应力联系在一起，但穿越东非的少量地壳伸展(≤10-15公里)不太可能导致足够的压力释放熔融来解释裂谷系统某些部分存在的大量喷出岩石，或者岩石圈足够薄而导致高原隆起≥1公里。因此，新生代伸展构造运动的一种纯粹的“被动”起源经常被拒绝。相反，它通常被归因于一个或多个地幔热柱，这一观点得到了地球化学证据的有力支持。然而，根据对地幔结构和组成的现有观察，不能完全排除非羽流模型，也不清楚东非地下可能存在多少羽流。
To further advance our understanding of how and why continents rift apart, the upper mantle structure beneath east Africa is being investigated by three Incorporated Research Institutes of Seismology/Program for the Array Seismic Studies of the Continental Lithosphere (IRIS/PASSCAL) broadband seismic experiments. The origin of Cenozoic rifting in east Africa, along with the volcanism and plateau uplift found there, has long fascinated Earth scientists. The rift system can be linked to extensional stresses associated with the development of the Afar triple junction, but it is unlikely that the small amount of crustal extension, ≤10–15 km, across east Africa could have led to sufficient pressure-release melting to account for the large volume of extrusive rock present in some parts of the rift system, or enough thinning of the lithosphere to cause plateau uplift ≥1 km. Consequently, a purely “passive” origin for the Cenozoic extensional tectonism has been frequently rejected. Instead, it has been commonly attributed to one or more mantle plumes, a view supported strongly by geochemical evidence. However, non-plume models cannot be ruled out completely, based on existing observations of mantle structure and composition, nor is it clear how many plumes might be present beneath east Africa.