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Imaging paleoslabs and inferring the Clapeyron slope in D″ beneath the northern Pacific based on high-resolution inversion of seismic waveforms for 3-D transversely isotropic structure
Physics of the Earth and Planetary Interiors ( IF 2.4 ) Pub Date : 2021-06-19 , DOI: 10.1016/j.pepi.2021.106751
Yuki Suzuki , Kenji Kawai , Robert J. Geller

We use waveform inversion to infer high-resolution 3-D models of the S-velocity perturbation δVS and the anisotropy parameter δξ in the lowermost 400 km of the mantle beneath the northern Pacific. Our inferred models show three prominent features: (i) a widespread positive δVS layer with ~100 km thickness that exists ~250 km above the core-mantle boundary (CMB), which could be due to a bridgmanite to post-perovskite phase transition related to the D″ discontinuity; (ii) distinct positive -δVS anomalies with positive δξ resolved from 100 km to more than 400 km above the CMB, which could be the subducted Izanagi, Farallon, and Telkhinia slabs; (iii) a vertically continuous low-δVS anomaly with negative δξ at the edge of the subducted slab, which we interpret as an upwelling plume induced by slab sinking. We infer the Clapeyron slope of the post-perovskite phase transition in the lowermost mantle beneath the northern Pacific to be 10.2 ± 1.3 MPa/K, based on the δVS gradient as a function of depth for the inferred 3-D VS structure. Our estimated large positive Clapeyron slope at the CMB suggests vigorous convection in the lowermost mantle.



中文翻译:

基于3-D横向各向同性构造地震波形高分辨率反演的古板成像和北太平洋下方D″克拉珀龙斜坡推断

我们使用波形反演来推断北太平洋下方地幔最低 400 公里处的S 速度扰动δV S和各向异性参数δξ的高分辨率 3-D 模型。我们推断的模型显示了三个突出的特征:(i)在核-地幔边界(CMB)上方约 250 公里处存在一个约 100 公里厚的广泛的正δV S层,这可能是由于桥式锰矿到后钙钛矿相变与 D″不连续有关;(ii)具有正δξ 的明显正 - δV S异常在CMB上方100公里至400多公里处解析,可能是俯冲的Izanagi、Farallon和Telkhinia板块;(iii)在俯冲板片边缘具有负δξ的垂直连续低δV S异常,我们将其解释为由板片下沉引起的上涌羽流。我们根据推断的 3-D V S结构的δV S梯度作为深度的函数,推断北太平洋下方最下地幔中钙钛矿后相变的 Clapeyron 斜率为 10.2 ± 1.3 MPa/K 。我们估计在 CMB 的大正 Clapeyron 斜率表明最下层地幔有强烈的对流。

更新日期:2021-06-19
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