2015年8月12日天津化学爆炸产生的多模式面波分析及其应用研究

2015年8月12日天津滨海新区发生的强烈化学品爆炸造成了巨大的经济损失和社会影响.天津爆炸产生了清晰的大振幅面波信号，分析结果表明这组信号由基阶和高阶面波组成，可以追踪到约135 km外的远处台站.利用这组面波信号分别开展了以下研究：（1）利用附近三个台站记录的四个单频基阶Rayleigh波信号对爆破事件的绝对位置进行了网格搜索，结果与利用GPS测量的位置相差仅0.498 km；（2）分别利用网格搜索和主事件定位法，对两次子事件的相对位置进行了确定，距离约75 m左右，与前人研究结果吻合；（3）从面波记录中测量到36条基阶Rayleigh波、49条第一高阶Rayleigh波、9条基阶Love波和29条第一高阶Love波的频散曲线，并进一步反演获得研究区域地下4 km内的S波速度结构.反演结果显示地表处S波速度低至0.375 km·s^-1，在小于1 km的浅地表速度梯度较大，符合典型的盆地结构特征.本文的研究结果为类似爆炸等突发事件快速定位提供了新的思路，有助于灾后救援的迅速展开；同时得到天津滨海新区及周边浅层精细的速度结构，对于地震灾害评估有很大帮助.

Analysis and application of multiple-mode surface waves from the August 12, 2015 Tianjin chemical explosion

On August 12, 2015, a great chemical explosion occurred in the Tianjin Binhai New Area, resulting in tremendous economic losses and social impact. This explosion produced clear large amplitude surface wave phase. Analysis shows that these signals consist of fundamental and higher-mode surface waves and can be traced about 135 km away. Using these surface wave signals, the absolute location of the explosion event is searched in terms of four frequencies fundamental Rayleigh wave signals of three nearby stations, and the difference between our result and that measured by GPS is only 0.498 km. The relative location of the two sub-events are determined by using grid search and main event location methods, respectively. The difference is about 75 meters, which is consistent with the previous research results. The dispersion curves of 36 fundamental mode Rayleigh waves, 49 first higher mode Rayleigh waves, 9 fundamental mode Love waves and 29 first higher mode Love waves are measured based on surface wave records, and the S-wave velocity structure from the surface down to depth of 4 km is obtained by further inversion. The inversion results show that the S-wave velocity at the surface is as low as 0.375 km·s^-1, and the velocity gradient at shallow depths (<1 km) is relatively large, which conforms to the typical basin structure characteristics. This paper provides a new idea for rapid locating of similar explosions and other emergencies, which would be helpful for the rapid post-disaster rescue. It is also very helpful for earthquake hazard assessment by obtaining the fine velocity structure in shallow layers of the Tianjin Binhai New Area and surrounding areas.