Crustal stress field in Yunnan: implication for crust-mantle coupling

We applied the g CAP algorithm to determine 239 focal mechanism solutions 3：0≤MW≤ 6：0） with records of dense Chin Array stations deployed in Yunnan,and then inverted 686 focal mechanisms（including 447 previous results） for the regional crustal stress field with a damped linear inversion. The results indicate dominantly strike-slip environment in Yunnan as both the maximum（r1） and minimum（r3） principal stress axes are sub-horizontal. We further calculated the horizontal stress orientations（i.e., maximum and minimum horizontal compressive stress axes： S H and S h, respectively） accordingly and found an abrupt change near ＊26°N. To the north, S H aligns NW-SE to nearly E-W while S h aligns nearly N-S. In contrast, to the south, both S H and S h rotate laterally and show dominantly fan-shaped patterns. The minimum horizontal stress（i.e., maximum strain axis） S h rotates from NW-SE to the west of Tengchong volcano gradually to nearly E-W in west Yunnan, and further toNE-SW in the South China block in the east. The crustal strain field is consistent with the upper mantle strain field indicated by shear-wave splitting observations in Yunnan but not in other regions. Therefore, the crust and upper mantle in Yunnan are coupled and suffering vertically coherent pure-shear deformation in the lithosphere.

通过接收函数和瑞利波联合反演揭示青藏高原东南缘两个壳内低速通道

目前解释青藏高原东缘的生长与扩张有诸多动力学模型,如:刚性块体挤出模型、连续变形和中下地壳流模型。由于受到岩石层结构模型分辨率的限制,青藏高原演化和变形的动力学过程仍不清楚。我们利用最新布设在青藏高原东南缘的地震台阵,通过接收函数和瑞利波联合反演得到了该区高分辨率三维岩石层横波速度模型,更好地揭示了壳内低速带(LVZ)分布特征。我们的速度模型显示研究区壳内存在两个低速通道,这两个低速通道边界与该区主要走滑断裂相对应,且沿着东喜马拉雅构造结顺时针分布,这与该区地壳物质顺时针运动模式比较一致。此外,我们观测到该区域主要大地震分布在这两个低速通道边界区域。据此,我们提出塑性流动和剪切变形在青藏高原的隆升和变形过程中都起了重要作用。

青藏高原东南缘远震S波分裂:对地壳上地幔复杂变形的启示

利用位于青藏高原东南缘云南地区的中国地震科学探测台站（C h in A ra y ）一期3 0 0 多个宽频带流动台站记录到的X K S 波形（包括SKS，S K K S， PKS）进行了 S 波分裂分析.X K S 分裂结果最主要的特征是快波偏振方向（φ） 在26-27°N 附近,从北部的近N -S 向突变为南部的近E-W 向.研究区西部喜马拉雅东构造结附近的结果较好地反映了岩石层左旋剪切变形下发育的各向异性.26°N 以南地区,快波分裂方向以E-W 向为主,与中上地壳最大张应力的方向一致,表明云南地区整个岩石层都可能处于纯剪切变形环境.但是该区岩石层厚度不足80k m ,产生的X K S 分裂快慢波时差（〈0.7s）仅能解释部分观测值（0.9-1.5s） .因此,软流层中的各向异性对于该地区的S 波分裂结果（快波偏振方向为N W -S E 和近E-W 向）可能产生了重要的作用.一方面,N W - S E 向快波偏振方向可能反映了缅甸块体的俯冲及其随后撤退引起的上地幔流动造成的各向异性.另一方面,伴随着高原构造演化发生的从青藏高原向中国东部的软流层物质流动,以及由于绝对板块运动造成的软流层顶部的剪切作用,将产生快波方向为近E-W 向的各向异性.本研究结果为研究青藏高原东南缘不同深度的变形特征及其差异提供了重要的信息,尤其在研究青藏高原的构造抬升及其向东南缘的扩展方面产生了新的认识.

SplitRFLab:A MATLAB GUI toolbox for receiver function analysis based on SplitLab

We add new modules for receiver function （RF） analysis in SplitLab toolbox, which includes the manual RF analysis module, automatic RF analysis and related quality control modules, and H-k stacking module. The updated toolbox （named SplitRFLab toolbox）, espe- cially its automatic RF analysis module, could calculate the RFs quickly and efficiently, which is very useful in RF analysis with huge amount of seismic data. China is now conducting the ChinArray project that plans to deploy thousands of portable stations across Chinese mainland. Our SplitRFLab toolbox may obtain reliable RF results quickly at the first time, which provide essentially new constraint to the crustal and mantle structures.

Interpretations of gravity and Songliao Basin with Wavelet magnetic anomalies in the Multi-scale Decomposition

In this paper, we introduce the method of Wavelet Multi-scale Decomposition （WMD） combined with Power Spectrum Analysis （PSA） for the separation of regional gravity and magnetic anomalies. The Songliao Basin is situated between the Siberian Plate and the North China Plate, and its main structural trend of gravity and magnetic anomaly fields is NNE. The study area shows a significant feature of deep collage-type construction. According to the feature of gravity field, the region was divided into five sub-regions. The gravity and magnetic fields of the Songliao Basin were separated using WMD with a 4th order separation. The apparent depth of anomalies in each order was determined by Logarithmic PSA. Then, the shallow high-frequency anomalies were removed and the 2nd-4th order wavelet detail anomalies were used to study the basin＇s major faults. Twenty-six faults within the basement were recognized. The 4th order wavelet approximate anomalies were used for the inversion of the Moho discontinuity and the Curie isothermal surface.

Inversion of Moho Interface in Northeastern China with Prior Information

Non-uniqueness is always, by nature, the problem we face in inversion processes, and it is caused by the phenomenon of equivalence in field, erroneous, discrete, and finite features in obser- vation and the influence of other sources. Many authors have done lots of researches in this field in order to get more reliable outcomes, and joint inversion is a thriving one where different kinds of data are combined to derive certain information simultaneously or sequentially. One of these studies is that the prior information such as the geological, drilling and seismic data will be used as con- straints, while the inversion procedure can be controlled. In this article we use a new method with the goal of better obtaining the three-dimensional density contrast interface. This prior seismic data integrated in the inversion can play a constrained role in the procedure which means that the depth of the Moho interface at the seismic location will be restricted. It thus can provide a credible result. In order to test its effect, this program is applied in a field example--derivation of Moho geometry in Northeast China.