Seismic analysis and amplitude-style spectrum ratio study of the 21 March blast at Xiangshui
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摘要: 使用P/S谱比法重点对响水爆炸中信噪比较高的几个台站记录进行了处理分析。选取2013年1月19日发生在距其7 km左右的一次天然地震事件作为对比。得出频率在2—15 Hz范围内,90%以上的台站,爆炸P/S谱比大于1,天然地震这一值小于1,而在4—15 Hz范围内,这一结果达到了100%。为了进一步验证此方法判断爆炸与天然地震的可行性,本文又对2015年天津港爆炸事件进行计算,得到了相同的结果。此研究为使用P/S谱比法验证低震级爆炸提供案例。本文在研究的同时,对响水爆炸事件进行了波形特征及频谱特征分析。得出此事件地震记录的震相较单一,与普通的爆破记录较相似,并没有出现像2015年天津港爆炸中那样低速的空气声波与地面耦合的Rayleigh波。得到此事件有两个主频率,分别为0.2—1 Hz和4—10 Hz。Abstract: The P/S-style spectral ratio method is used to process and analyze the records of several stations with high SNR in Xiangshui explosion. An earthquake that occurred about 7 kilometers away from it on January 19, 2013 was selected as the comparison event. In the frequency range of 2—15 Hz, for more than 90% stations, the P/S amplitude spectrum ratio of explosion is greater than 1, and the value of natural earthquake is less than 1, while it reaches 100% in the range of 4—15 Hz. In order to further verify the feasibility of this method in judging explosions and earthquakes, this paper calculated the Tianjin Port explosion on August 12, 2015, and obtained the same results. This study provides a case study for using P/S-style spectral ratio method to verify low magnitude explosion. At the same time, this paper analyzes the waveform characteristics and spectrum characteristics of the Xiangshui explosion. We concluded that the seismic phase of this event is relatively single, which is similar to an ordinary blasting record, and there is no low-speed air-pressure and ground coupled Rayleigh wave as in the Tianjin Port explosion. And the event has two main frequencies, which are between 0.2—1 Hz and 4—10 Hz respectively.
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Key words:
- 3•21 blast of Xiangshui /
- P/S-style spectral ratio /
- seismometer record /
- recognitions
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图 2 图1滤波后到时随震中距变化图
Figure 2. Time variation with epicentral distance after filtering
图 7 两次事件中Pg/Sg型振幅谱比对比图(其中纵坐标为Pg/Sg振幅谱比值的对数,圆形表示响水爆炸事件中各台站在不同频段上的Pg/Sg谱比情况;十字形表示灌云天然地震事件中各台站在不同频段上的Pg/Sg谱比情况)
Figure 7. Pg/Sg type amplitude spectrum ratio comparison graph for the two events(the ordinate is the logarithm of the ratio of Pg/Sg amplitude spectrum;circle represents the Pg/Sg spectrum ratio of each station at different frequency bands in the Xiangshui blast event;cross shape represents the Pg/Sg spectrum ratio of each station at different frequency bands in earthquake event of Guanyun)
图 9 两次事件中Pg/Sg型振幅谱比均值对比图(其中纵坐标为Pg/Sg振幅谱比值的对数,圆形表示响水爆炸事件中各台站在不同频段上的Pg/Sg谱比情况;十字形表示灌云天然地震事件中各台站在不同频段上的Pg/Sg谱比情况)
Figure 9. The average of Pg/Sg type amplitude spectrum ratio comparison graph for the two events(the ordinate is the logarithm of the ratio of Pg/Sg amplitude spectrum;circle represents the Pg/Sg spectrum ratio of each station at different frequency bands in the Xiangshui blast event;cross shape represents the Pg/Sg spectrum ratio of each station at different frequency bands in earthquake event of Guanyun)
图 10 两次事件中Pg/Sg型振幅谱比均值对比(其中纵坐标为Pg/Sg振幅谱比值的对数,圆形表示爆炸事件中各台站在不同频段上的Pg/Sg谱比情况;十字形表示天然地震事件中各台站在不同频段上的Pg/Sg谱比情况)
Figure 10. The average of Pg/Sg type amplitude spectrum ratio comparison graph for the two events(the ordinate is the logarithm of the ratio of Pg/Sg amplitude spectrum;circles represents the Pg/Sg spectrum ratio of each station at different frequency bands in the Tianjin port blast;crosses shape represents the Pg/Sg spectrum ratio of each station at different frequency bands in the earthquake of Tangshan)
表 1 响水爆炸周围天然事件详细信息
Table 1. Detailed information about earthquake surrounding the Xiangshui explosion
发生时刻 震中地名 经度/°E 纬度/°N 震级(ML) 年-月-日 时:分:秒 2013-05-25 10:56:32 江苏滨海 120.2 34.1 3.2 2016-08-18 13:47:52 江苏盐城 120.8 33.2 2.8 表 2 天津港爆炸与周围一天然事件详细信息
Table 2. Details of the Tianjin Port blast and an earthquake nearby
发生时刻 事件类型 震中地名 经度/°E 纬度/°N 震级(ML) 年-月-日 时:分:秒 2015-08-12 23:34:37 爆炸 天津滨海 117.7 39.0 3.2 2016-02-12 13:47:52 天然地震 河北唐山 117.9 39.4 3.0 -
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