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给出了南美洲及周边洋盆一套新的地震波结构等值线图。这些图使用了新数据,因而更好地约束了地壳厚度、全地壳P波和S波的平均速度以及地幔顶部的地震波速度(Pn和Sn)。我们发现:(1)南美洲地壳厚度的加权平均值为38.17km(标准差为±8.7km),这比全球陆壳平均值39.2km要薄约1km;(2)南美洲全地壳P波速度的直方图呈双峰形态,其低峰值发生在缺失下地壳高速层(6.9~7.3km)的区域;(3)结晶地壳的P波平均速度(Pcc)为6.47km/s(标准差为±0.25km/s),这与全球平均值6.45km/s基本相同;(4)南美洲下方的Pn平均速度为8.00km/s(标准差为±0.23km/s),略低于全球平均值8.07km/s;(5)横贯智利北部与阿根廷东北部的地壳内存在一个P波和S波低速异常带,地理上正对应于纳斯卡板块浅俯冲部分[Isacks等在1968年首次提出的南美大草原(Pampean)平缓板块],同时也是一地壳拉张区域;(6)巴西克拉通的厚地壳一直延伸到委内瑞拉和哥伦比亚;(7)亚马逊盆地以及沿巴西克拉通西部边缘地壳可能由于拉伸作用而变薄;(8)东太平洋海床之下的地壳P波平均波速要大于其在西大西洋海床的数值,这可能源于较古老的大西洋海床覆盖了更厚的沉积层。
A new contour map of seismic waves in South America and the surrounding oceanic basin is given. These figures use new data and thus better constrain the crustal thickness, the average P-and S-wave velocities of the entire crust, and the seismic velocity (Pn and Sn) at the top of the mantle. We find that: (1) The weighted average of crustal thickness in South America is 38.17km (standard deviation is ± 8.7km), which is about 1km thinner than the global crustal average of 39.2km; (2) the P-wave velocity (3) The average P-wave velocity (Pcc) of the crystalline crust is 6.47km / s (standard deviation is ± 0.25km / s), which is basically the same as the global average of 6.45km / s. (4) The mean Pn of South America is 8.00km / s (standard deviation ± 0.23km / s), slightly lower than the global average 8.07km / s; (5) A P-wave and S-wave anomalous zone exists in the crust across the north of Chile and northeastern Argentina, corresponding geographically to the shallow subduction of the NASCAR plate [Isacks et al., First proposed in 1968 (6) the thick crust of the Brazilian craton extends into Venezuela and Colombia; (7) the crust of the Amazon basin and along the western edge of the Brazil craton may be due to pull (8) The average P-wave velocity of crust below the East Pacific Ocean floor is greater than that of the western Seaworld, From the older Atlantic sea bed covered with a thicker layer deposition.