论文部分内容阅读
地震动的方向性效应在分析震源物理及活断层附近的地震危险性方面有广泛的影响。由于受到观测台站方位角的限制,详细地确定小地震的破裂方向性存在一定困难。在2013年4月20日和21日的4次震级较大的芦山余震(分别记为事件1,事件2,事件3,事件4)中,中国数字强震动台网收集了大量强震动记录。这4次芦山余震震源位置靠近且震级相近,但触发的强震动台站空间分布有显著差异。通过分析地震动参数,包括峰值、反应谱和持时,认为事件2和事件3的地震动有明显的方向性效应。采用傅里叶谱比方法证实了破裂方向性的存在,通过反演峰值参数确定了震源破裂方向和破裂速度,并用多次随机反演过程来分析反演结果的不确定性。结果表明,这4次余震有相近的北东-南西走向的破裂面,且震源破裂速度接近,大约为2.1km/s。尽管反演结果存在不确定性,但事件1为对称双向破裂的可能性很高,事件2和事件3的主破裂方向为西南方向,事件4近似为对称双向破裂,略偏向东北方向。破裂方向性效应与周期的相关性也得到了证实。
Directional effects of earthquakes have a wide range of implications in the analysis of seismic physics and the seismic hazard near live faults. Due to the limitation of azimuth of observational stations, it is difficult to determine in detail the fracture direction of small earthquakes. In the 4 major Lushan aftershocks (events 1, 2, 3 and 4 respectively) on April 20 and April 21, 2013, China Strong Digital Strong Motion Network collected a large number of strong earthquake records. The focal locations of the Lushan aftershocks are close to each other and similar in magnitude, but there are significant differences in the spatial distribution of the strong vibration stations triggered. By analyzing the parameters of ground motion, including the peak value, response spectrum and duration, it is considered that the ground motions of events 2 and 3 have significant directional effects. The existence of rupture direction was confirmed by the Fourier spectrum ratio method. The rupture direction and rupture velocity of the source were confirmed by the inversion of peak parameters, and the uncertainty of inversion results was analyzed by multiple random inversions. The results show that these four aftershocks have similar north-south-west rupture and the source rupture velocity is close to about 2.1km / s. Although there is uncertainty in the inversion results, event 1 is highly likely to be symmetric two-way rupture. The main rupture direction of events 2 and 3 is southwest, and event 4 is approximately symmetrical two-way rupture, slightly northeast. The correlation between fracture directionality and period has also been confirmed.