Seismic Structure of the Crust and Uppermost Mantle of North America and Adjacent Oceanic Basins: A Synthesis
Seismic Structure of the Crust and Uppermost Mantle of North America and Adjacent Oceanic Basins: A Synthesis
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DOI：
10.1785/0120010188
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发表时间：
2002-08
影响因子：
3
通讯作者：
G. S. Chulick;W. Mooney
中科院分区：
文献类型：
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作者：
G. S. Chulick;W. Mooney
我们提出了一套新的等值线图的地震结构的北美和周围的海洋盆地。这些图包括地壳厚度、全地壳平均P波和S波速度以及最上地幔的地震速度Pn和Sn。结果表明：（1）北美地壳平均厚度为36.7km（标准差）; 8.4 2000年，世界平均降水量为39.2公里，比2000年减少了2.5公里。8.5)大陆地壳;（2）北美地壳全地壳P波和S波速度直方图为双峰型，低峰出现在没有高速波的地壳上，高峰值出现在没有高速波的地壳上。（3）地壳P波平均速度异常高的区域与前寒武纪和古生代造山带有关，地壳P波平均速度低的区域与现代伸展体制有关;（4）北美海底Pn的平均速度为8.03 km/s（s.d.）。0.19 km/sec）;（5）美国西部的薄地壳延伸到加拿大西北部;（6）大洋地壳第3层的平均P波速度为6.61 km/ sec（s.d.）。0.47 km/sec）。然而，由于较老的大西洋海底沉积层较厚，东太平洋海底下的地壳平均P波速度高于西大西洋海底。
We present a new set of contour maps of the seismic structure of North America and the surrounding ocean basins. These maps include the crustal thickness, whole-crustal average P-wave and S-wave velocity, and seismic velocity of the up- permost mantle, that is, Pn and Sn. We found the following: (1) The average thickness of the crust under North America is 36.7 km (standard deviation (s.d.) 8.4 km), which is 2.5 km thinner than the world average of 39.2 km (s.d. 8.5) for continental crust; (2) Histograms of whole-crustal P- and S-wave velocities for the North Amer- ican crust are bimodal, with the lower peak occurring for crust without a high-velocity (6.9-7.3 km/sec) lower crustal layer; (3) Regions with anomalously high average crustal P-wave velocities correlate with Precambrian and Paleozoic orogens; low average crustal velocities are correlated with modern extensional regimes; (4) The average Pn velocity beneath North America is 8.03 km/sec (s.d. 0.19 km/sec); (5) the well-known thin crust beneath the western United States extends into north- west Canada; (6) the average P-wave velocity of layer 3 of oceanic crust is 6.61 km/ sec (s.d. 0.47 km/sec). However, the average crustal P-wave velocity under the eastern Pacific seafloor is higher than the western Atlantic seafloor due to the thicker sediment layer on the older Atlantic seafloor.