中国科学院地质和地球物理研究所王旭课题组报道了中国东北盆地-山岭带浅层地壳横波速度结构的两步多频接收函数反演方法及其应用。相关论文于2024年2月26日发表于国际顶尖学术期刊《中国科学：地球科学》杂志上。

为了解决这些挑战，研究人员提出了一种两步反演方法，该方法使用多频P-RF波形和P-RF水平与垂直振幅比。综合实验表明，两步反演方法能有效地减轻反演的非唯一性，并增强反演结果的稳定性。将该方法应用于东北地区横贯沉积盆地的线性地震台阵的远震数据，获得了台阵上浅层地壳S波速度结构的高分辨率图像。

研究结果揭示了盆地和山脉之间的显著差异。在二连盆地下不到1km和松辽盆地下不到2.5km的深度识别出低速异常(<2.8km s^-1)表明存在沉积层。此外，松辽盆地深度超过7km处出现高速异常(约3.4-3.8 km s^-1)发，可能反映了早白垩世侵位的基性岩体。研究成像结果中的速度异常分布与主要断裂、隆升和沉积坳陷的位置以及活动源地震结果一致。该应用进一步验证了该方法在限制具松散沉积盖层的盆地中S波速度随深度变化特征方面的有效性。

据介绍，浅层地壳速度结构(10km深度以上)对了解地壳结构变形、评价自然资源勘探前景至关重要，也为更深层地壳和地幔结构成像提供了先验信息。与主动地震方法相比，被动地震方法在浅层构造区域尺度成像方面具有成本效益的优势。在这些被动方法中，利用接收函数波形和/或体波振幅比的技术，最近因其相对较高的空间分辨率而获得了重视。然而，在盆地地区，由近地表松散沉积层引起的反射往往具有很强的非唯一性和不确定性，限制了这种方法的适用性。

附：英文原文

Title: A two-step multi-frequency receiver function inversion method for shallow crustal S-wave velocity structure and its application across the basin-mountain range belts in Northeast China

Author: Ruihao YANG, Xu WANG, Ling CHEN, Mingye FENG, Qifu CHEN

Issue&Volume: 2024/02/26

Abstract: A shallow crustal velocity structure (above 10km depth) is essential for understanding the crustal structures and deformation and assessing the exploration prospect of natural resources, and also provides priori information for imaging deeper crustal and mantle structure. Passive-source seismic methods are cost-effective and advantageous for regional-scale imaging of shallow crustal structures compared to active-source methods. Among these passive methods, techniques utilizing receiver function waveforms and/or body-wave amplitude ratios have recently gained prominence due to their relatively high spatial resolution. However, in basin regions, reverberations caused by near-surface unconsolidated sedimentary layers often introduce strong non-uniqueness and uncertainty, limiting the applicability of such methods. To address these challenges, we propose a two-step inversion method that uses multi-frequency P-RF waveforms and P-RF horizontal-to-vertical amplitude ratios. Synthetic tests indicate that our two-step inversion method can mitigate the non-uniqueness of the inversion and enhance the stability of the results. Applying this method to teleseismic data from a linear seismic array across the sedimentary basins in Northeast China, we obtain a high-resolution image of the shallow crustal S-wave velocity structure along the array. Our results reveal significant differences between the basins and mountains. The identification of low-velocity anomalies (<2.8kms ^-1) at depths less than 1.0km beneath the Erlian Basin and less than 2.5km beneath the Songliao Basin suggests the existence of sedimentary layers. Moreover, the high-velocity anomalies (~3.4–3.8km s-1) occurring at depths greater than 7km in the Songliao Basin may reflect mafic intrusions emplaced during the Early Cretaceous. Velocity anomaly distribution in our imaging result is consistent with the location of the major faults, uplifts, and sedimentary depressions, as well as active-source seismic results. This application further validates the effectiveness of our method in constraining the depth-dependent characteristics of the S-wave velocity in basins with unconsolidated sedimentary cover.

DOI: 10.1007/s11430-023-1250-3

Source: https://www.sciengine.com/10.1007/s11430-023-1250-3