Analysis of the Accuracy of Focal Mechanism Solutions for M3.0 Earthquakes with Different Methods
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摘要: 本文采用TDMT_INV、FOCMEC和CAP 3种方法对网缘、网外和网内地震震源机制解进行计算，并对3种方法所得结果进行对比分析。研究发现，TDMT_INV方法的结果稳定性高度依赖于震相准确性，但只需5个台站参与定位即可获得相对准确的震源机制解。对于网外地震，3种方法都无法反演稳定的震源机制解；对于网缘地震，CAP方法受台站分布的影响较大，使用时需谨慎。若波形质量好、信噪比高，可使用FOCMEC方法进行计算，若无清晰的P波初动可使用TDMT_INV方法进行计算；对于网内地震3种方法所得结果较为一致，但TDMT_INV方法可快速获得震源机制解。
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关键词:
- 震源机制解 /
- TDMT_INV方法 /
- CAP方法 /
- FOCMEC方法
Abstract: In this study, we employed the TDMT_INV, FOCMEC, and CAP methods to calculate the focal mechanism solutions for earthquakes with magnitudes greater than 3, focusing on events at the edge of the seismic network, outside the network, and within the network. We then compared the results obtained from these three methods. The stability of the TDMT_INV method is significantly affected by the accuracy of seismic phase data; however, reliable focal mechanism solutions can be achieved when at least five stations are involved in the event location. None of the methods consistently produce stable focal mechanism solutions for earthquakes occurring within the seismic network. For network-edge events, the CAP method is highly sensitive to station distribution and should be applied with caution. The FOCMEC method can be used for calculation when waveform quality is high and the signal-to-noise ratio is favorable. In cases where the P-wave onset is unclear, the TDMT_INV method is recommended. Overall, the results for intra-network earthquakes from the three methods are relatively consistent, with the TDMT_INV method providing quick focal mechanism solutions.-
Key words:
- Focal mechanism solution /
- TDMT_INV method /
- CAP method /
- FOCMEC method
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图 1 地震震中及台站分布图
Figure 1. The distribution of the epicenter and location of seismic stations
图 2 TDMT_INV方法反演东台M3.0地震震源机制解
Figure 2. Focal mechanism solution of the Dongtai M3.0 earthquake with the TDMT_INV method
图 3 CAP方法反演东台M3.0地震震源机制解
Figure 3. Focal mechanism solution of the Dongtai M3.0 earthquake with the CAP method
图 4 FOCMEC方法反演东台M3.0地震震源机制解
Figure 4. Focal mechanism solution of the Dongtai M3.0 earthquake with the FOCMEC method
图 5 TDMT_INV方法反演微山M3.2地震震源机制解
Figure 5. Focal mechanism solution of the Weishan M3.2 earthquake with the TDMT_INV method
图 6 CAP方法反演微山M3.2地震震源机制解
Figure 6. Focal mechanism solution of the Weishan M3.2 earthquake with the CAP method
图 7 FOCMEC方法反演微山M3.2地震震源机制解
Figure 7. Focal mechanism solution of the Weishan M3.2 earthquake with the FOCMEC method
图 8 TDMT_INV方法反演江都M3.1地震震源机制解
Figure 8. Focal mechanism solution of the Jiangdu M3.1 earthquake with the TDMT_INV method
图 9 CAP方法反演江都M3.1地震震源机制解
Figure 9. Focal mechanism solution of the Jiangdu M3.1 earthquake with the CAP method
图 10 FOCMEC方法反演江都M3.1地震震源机制解
Figure 10. Focal mechanism solution of the Jiangdu M3.1 earthquake with the FOCMEC method
图 11 东台M3.0地震中心震源机制解
Figure 11. Central focal mechanism of the Dongtai M3.0 earthquake
图 12 江都M3.1地震中心震源机制解
Figure 12. Central focal mechanism of the Jiangdu M3.1 earthquake
表 1 东台M3.0地震震源机制解
Table 1. The focal mechanism solution results of the Dongtai M3.0 earthquake
方法 走向/° 倾角/° 滑动角/° TDMT_INV方法（2个人工标注台站波形震相） 158 87 177 TDMT_INV方法（5个人工标注台站波形震相） 68 66 −39 TDMT_INV方法（所有人工标注台站波形震相） 74 63 −27 CAP方法 103 38 −12 FOCMEC方法 81 61 −29 
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表 2 微山M3.2地震震源机制解
Table 2. The focal mechanism solution results of the Weishan M3.2 earthquake
方法 走向/° 倾角/° 滑动角/° TDMT_INV方法（2个人工标注台站波形震相） 263 77 −162 TDMT_INV方法（5个人工标注台站波形震相） 265 89 −161 TDMT_INV方法（所有人工标注台站波形震相） 266 88 −166 CAP方法 282 62 −13 FOCMEC方法 293 66 −21
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表 3 江都M3.1地震震源机制解
Table 3. The focal mechanism solution results of the Jiangdu M3.1 earthquake
方法 走向/° 倾角/° 滑动角/° TDMT_INV方法（2个人工标注台站波形震相） 214 89 −3 TDMT_INV方法（5个人工标注台站波形震相） 215 78 −7 TDMT_INV方法（所有人工标注台站波形震相） 214 79 −8 CAP方法 211 72 −8 FOCMEC方法 210 80 −9
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表 4 东台M3.0地震震源机制解及中心震源机制解
Table 4. The focal mechanism solution results and central focal mechanism of the Dongtai M3.0 earthquake
序号 方法 震源机制解走向/°、
倾角/°、滑动角/°作为初始解得到的中心震源机制
走向/°、倾角/°、滑动角/°作为初始解得到
标准差S/°中心震源机制与其他震源机制的
最小空间旋转角/°1 TDMT_INV方法
（5个人工标注台站波形震相）68、66、−39 79.50、56.27、−28.92 15.411978 14.72 2 TDMT_INV方法
（所有人工标注台站波形震相）74、63、−27 79.53、56.24、−28.93 15.411980 9.52 3 CAP方法 103、38、−12 79.55、56.26、−28.91 15.411939 24.86 ４ FOCMEC方法 81、61、−29 79.55、56.26、−28.91 15.411938 4.97
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表 5 江都M3.1地震震源机制解及中心震源机制解
Table 5. The focal mechanism solution results and central focal mechanism of the Jiangdu M3.1 earthquake
序号 机构 震源机制解节面
Ⅰ走向/°、倾角/°、滑动角/°作为初始解得到的中心震源
机制节面Ⅰ走向/°、
倾角/°、滑动角/°作为初始解得到
标准差S/°中心震源机制与其他震源
机制的最小空间旋转角/°1 TDMT_INV方法
（5个人工标注台站波形震相）215、78、−7 212.47、 77.22、−7.99 3.731334 2.63 2 TDMT_INV方法
（所有人工标注台站波形震相）214、79、−8 212.46、 77.23、 −8.00 3.731370 2.35 3 CAP方法 211、72、−8 212.47、 77.20、 −8.03 3.731732 5.42 ４ FOCMEC方法 210、80、−9 212.45、77.22、 −8.02 3.731664 3.73
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