High-resolution mid-mantle imaging with multiple-taper SS -precursor estimates
High-resolution mid-mantle imaging with multiple-taper SS -precursor estimates
复制标题
具有多锥度 SS 前体估计的高分辨率中地幔成像
DOI：
10.1093/gji/ggac491
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发表时间：
2022
影响因子：
2.8
通讯作者：
Park, Jeffrey
中科院分区：
文献类型：
--
作者：
Frazer, William D.;Park, Jeffrey
SS-前兆成像用于成像地球地幔内的清晰界面。当前的SS前体技术需要紧密带通信号（例如0.02- 0.05Hz），限制了垂直和水平分辨率。更高的频率含量将允许探测地幔过渡带（MTZ）内部和周围的更精细结构。在这里，我们提出了一种新的SS前兆反褶积技术的基础上多锥相关（MTC）。我们表明，应用MTC到SS-前兆反褶积可以将截止频率增加到0.5 Hz，这可能会使垂直分辨率提高到10 km。此外，高通频率可以降低（<0.01 Hz），允许在计算中包含更多的长周期能量，以更好地约束信号并减少旁瓣。我们的方法是基准上的全波形合成地震图计算通过AxiSEM 3D的PREM 1-D地球模型。我们将我们的新MTC-SS前兆反褶积到全球地震台网的宽带钻孔传感器记录的7000个地震图中，震源-接收器反弹点在太平洋中北部。该区域的MTZ较薄，这与前人的研究结果一致。在我们的SS-前兆估计中，我们没有观察到520公里的不连续。此外，我们检测到一个低速区以上的MTZ夏威夷群岛的北部，以前推断旁瓣振幅的不对称性。我们的高频分析表明，这一特征是一个尖锐的界面（≤ 10公里厚度），而不是厚的波速梯度。
SS-precursor imaging is used to image sharp interfaces within Earth’s mantle. CurrentSS-precursor techniques require tightly bandpassed signals (e.g. 0.02–0.05 Hz), limiting both vertical and horizontal resolutions. Higher frequency content would allow for the detection of finer structure in and around the mantle transition zone (MTZ). Here, we present a newSS-precursor deconvolution technique based on multiple-taper correlation (MTC). We show that applying MTC toSS-precursor deconvolution can increase the frequency cut-off up to 0.5 Hz, which potentially sharpens vertical resolution to ∼10 km. Furthermore, the high-pass frequency can be lowered (≪ 0.01 Hz), allowing more long-period energy to be included in the calculation, to better constrain the signal and reduce side lobes. Our method is benchmarked on full-waveform synthetic seismograms computed via AxiSEM3D for the PREM 1-D Earth model. We apply our novel MTC-SS-precursor deconvolution to ∼7000 seismograms recorded at broad-band borehole sensors of the Global Seismographic Network with source–receiver bounce points in the North-Central Pacific Ocean. The MTZ in this region appears to be thin, which agrees with previous results. We do not observe the 520-km discontinuity in ourSS-precursor estimates. Additionally, we detect a low-velocity zone above the MTZ to the north of the Hawaiian Islands that has previously been inferred from asymmetry in side lobe amplitudes. Our high-frequency analysis demonstrates this feature to be a sharp interface (≤ 10-km thickness), rather than a thick wave speed gradient.