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2011年1月19日发生的安庆MS4.8地震,在较远范围引起了明显震感.通过仔细辨认此次地震不同频段的波形记录,发现在一些台站记录到了清晰的SmS震相.采用CAP方法反演了其震源机制解,并利用理论地震图与实际观测数据对比进一步确认了SmS震相的存在.结合已有实验结果,推断在人类有感频率(1Hz至几Hz)范围内,震中距70—200km内SmS震相往往是振幅最大的震相,是引起远距离有感的主要原因.利用理论地震图研究了震源深度对SmS震相的影响.结果表明,震源深度可改变SmS震相发育的临界震中距,震源越深对应的临界震中距越小.进一步通过对比SmS与S的振幅比,定性讨论了震源机制解中倾角、滑动角和地壳浅层衰减等因素对SmS震相的影响.结果表明,倾角和滑动角对其振幅比影响呈现比较复杂的关系,而SmS与S振幅比随地壳浅层衰减的增大而减小,说明浅层衰减对SmS震相影响较大.综合分析认为,除当地地壳速度结构的影响外,SmS震相的发育受到震源机制解的倾角、滑动角,震源深度以及地壳浅层衰减等多种因素的影响.
The Anqing MS4.8 earthquake, which occurred on January 19, 2011, caused obvious seismic sensation in the far range. By carefully identifying the waveform records in different frequency bands of this earthquake, it was found that clear SmS phases were recorded at some stations. Method was used to invert the focal mechanism solution and the existence of SmS phases was further confirmed by comparing the theoretical seismograms with the actual observed data.According to the existing experimental results, it is inferred that in the range of human sensed frequency (1 Hz to several Hz), the epicenter The main phase of the SmS seismic phase is the seismic phase with the largest amplitude within 70-200 km, which is the main reason that causes the long-distance feeling.The theoretical seismic diagram is used to study the influence of focal depth on the SmS seismic phase.The results show that the depth of the source can change SmS And the critical epicentral distances corresponding to the hypocenter are smaller.With the comparison of the amplitude ratio of SmS and S, the influence of the dip angle, sliding angle and shallow crustal attenuation on the SmS seismic phase The results show that the inclination angle and the sliding angle have a complex relationship with the amplitude ratio, and the amplitude ratio of SmS and S decreases with the increase of shallow crustal crustal attenuation, indicating that shallow crustal attenuation has a great influence on the phase of SmS . Close analysis, in addition to affecting the local velocity structure, development phases of SmS by the inclination of the focal mechanism solution, slip angle, a variety of factors shallow focal depth and crustal attenuation.