An unsually large ULVZ at the base of the mantle near Hawaii
An unsually large ULVZ at the base of the mantle near Hawaii
复制标题
DOI：
10.1016/j.epsl.2012.09.005
复制
发表时间：
2012-11-15
影响因子：
5.3
通讯作者：
Romanowicz, Barbara
中科院分区：
文献类型：
--
作者：
Cottaar, Sanne;Romanowicz, Barbara
以前的研究已经证明了超低速区（ULVZ）的地幔底部的存在，通过观察体波的复杂性。从几何学上看，它们的高度在5至30公里之间，而由于取样的限制，人们对它们超过10（2）公里的横向范围知之甚少。在这里，我们显示了显着的功能在波形的S/Sdiff阶段观察到的西太平洋事件在北美的站点，表明存在一个非常大的超低速区（ULVZ）在地幔的底部，中心类似于11度的西南夏威夷，内和附近的北方边界的太平洋LLSVP。波形复杂性包括强烈延迟（> 30秒）的后游标。旅行时间的测量、面外能量的波束形成分析以及与3D数值模拟的全波形比较，以某种程度的权衡来约束ULVZ的位置、横向范围、高度和速度降低。简化的三维模型由一个圆柱形超低容量区组成，其高宽比类似于20公里，CMB直径类似于910公里。剪切波速度降低约为20%。据我们所知，这是迄今为止绘制的最大的ULVZ，也是第一次以一定的精度限制ULVZ的横向范围。它的位置表明，它可能是一个长期存在的，稳定的羽流负责夏威夷火山链，热点轨道与最大的浮力通量的根源。由爱思唯尔公司出版
Previous studies have documented the presence of ultra-low-velocity-zones (ULVZs) at the base of the mantle, through observations of body wave complexities. Geometrically their heights are in the range of similar to 5-30 km, while little is known about their lateral extent beyond about 10(2) km, due to limitations in sampling. Here we show remarkable features in the waveforms of S/Sdiff phases of western Pacific events observed at stations in North America that indicate the presence of a very large ultra-low-velocity-zone (ULVZ) at the base of the mantle, centered similar to 11 degrees to the southwest of Hawaii, within and near the northern border of the Pacific LLSVP. Waveform complexities include strongly delayed (> 30 s) postcursors. Measurements of travel times, beamforming analysis of out-of-plane energy, and full waveform comparisons with 3D numerical simulations, constrain the location, lateral extent, height and velocity reduction of the ULVZ with some level of trade-off. The simplified 3D model consists of a cylindrical ULVZ with a large aspect ratio of similar to 20 km in height and similar to 910 km in diameter at the CMB. The shear wave velocity reduction is similar to 20%. This is to our knowledge the largest ULVZ mapped to date and the first time the lateral extent of a ULVZ has been constrained with some precision. Its location suggests that it may be the root of a long-lived, stable plume responsible for the Hawaiian volcanic chain, the hotspot track with the largest buoyancy flux. Published by Elsevier B.V.