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利用中国区域台网地震波形记录,采用CAP方法反演了香格里拉德钦(位于云南省)—得荣(属于四川省)2013年8月28日MS5.1、8月31日MS5.9地震及8次MS>4余震的震源双力偶断层面解和震源质心深度.结合震区地质构造、余震分布、烈度分布、动力学背景等资料,分析了此次地震序列的震源机制和应力场特征.反演结果表明,此次地震序列为节面倾角倾斜的正断层型地震,发震断层为NWW向活动构造带.序列中最大地震MS5.9和次大地震MS5.1地震的破裂节面分别为走向299°、倾角53°、滑动角-73°;走向290°、倾角55°、滑动角-72°.震源区受到强烈的水平拉张力、垂直挤压力作用.MS5.9地震后续余震T、P轴方位角随时间变化强烈,表明MS5.9地震后震源区应力调整作用明显.震源区应力场反演结果显示,地震发生的构造带上最大主拉应力为NNE-SSW向,最大主压应力为NW-SE向,与GPS观测所反映的地表最大主应力分布方向基本一致,表明震源区的应力状态可能主要受到背景大尺度构造应力场的控制.此次地震序列填充了川滇地区震源机制及应力场的空间分布图像,1976年以来可靠的震源机制解资料表明香格里拉次级块体是川滇块体及周边区域显著的拉张作用区域.香格里拉次级块体和保山次级块体正断层地震的断层节面及震源应力轴分布的空间变化,与GPS观测反映的地表最大主拉应力分布较一致,其空间分布特征反映了在青藏高原物质挤出背景下,块体之间相互作用、地势差异等作用对构造活动的影响.
Based on the seismic waveform records of China’s regional networks, the CAP method was used to inverse the seismic data of Shangri-La Deqin (located in Yunnan Province) - Derong (belonging to Sichuan Province) MS5.1 on August 28, 2013, the MS5.9 on August 31, 2013 and 8 focal earthquakes with MS> 4 aftershocks and focal depth of seismic source center.Combined with the geological structure, aftershock distribution, intensity distribution and dynamic background of the earthquake area, the focal mechanism and stress field characteristics of the earthquake sequence are analyzed. The inversion results show that this earthquake sequence is a nodal fault with nodal tilt and the seismogenic fault is a NWW active tectonic zone.The rupture planes of the largest earthquake MS5.9 and the next MS5.1 earthquake respectively The strike point is 299 °, the inclination angle is 53 °, the sliding angle is -73 °, the direction is 290 °, the inclination angle is -55 ° and the sliding angle is -72 °. The source region is subjected to strong horizontal tension and vertical crushing force. The azimuths of T and P axes vary strongly with time, which indicates that the stress adjustment function of focal zone after MS5.9 earthquake is obvious.The inversion of stress field in the source zone shows that the maximum principal tensile stress in the tectonic zone is NNE-SSW and the maximum The main compressive stress is NW-SE, most of which is reflected by GPS observations The main stress distribution directions are basically the same, indicating that the stress state in the source area may be mainly controlled by the large-scale tectonic stress field in the background. The seismic sequence filled the spatial distribution of focal mechanism and stress field in Sichuan-Yunnan region. Since 1976, The focal mechanism solution data show that the Shangri-La sub-block is a significant tensile region of the Sichuan-Yunnan block and the surrounding area. The space of the section of the fault and the distribution of source stress axes of the normal faults in the Shangri-La sub-block and the Baoshan sub-block Which is consistent with the distribution of the maximum principal tensile stress on the earth’s surface as reflected by the GPS observations. The spatial distribution reflects the effect of block interaction and topography on the tectonic activity under the background of material extrusion in the Qinghai-Tibet Plateau.