The conjunct effects of ISO and CLVD sources in underground explosions on the spectral null in Rg waves
-
摘要: 本文利用地震面波激发理论，通过理论计算两种震源不同相对强度、相对埋深及源时间函数情况下的Rg波频谱，研究地下爆炸中各向同性源和补偿线性矢量偶极源共同激发的Rg波信号低谷点特性。结果表明，由于两种震源相对强度、相对埋深及源频谱的影响，混合信号低谷点频率与单一补偿线性矢量偶极（CLVD）源激发的信号有很大差异，因此实际地下爆炸中低谷点频率与CLVD源埋深不能单纯地满足理论的反比关系，直接用理论式估算地下爆炸埋深是不足的。Abstract: The compensated liner vector dipole（CLVD）source is usually induced by underground explosions and could lead to a null in the Rg spectra. There is a theoretical scale between the null frequency and the depth of the CLVD source. Therefore we can estimate the depth of underground explosions with the null frequency. However, this relationship is based on simply considering the CLVD source while the conjunct effects of ISO and CLVD source are neglected. This study researches the conjunct effects of ISO and CLVD sources in underground explosions on the spectral null in Rg waves by numerical calculating the Rg spectra with seismology theory of surface waves. The results indicate that the null in mixed signals is quite different from the results of single CLVD source. Thus the null frequency of Rg waves is not simply corresponding to the theoretical value in practical underground explosions and it is improper to estimate the depth of explosions by directly applying the theoretical formula.
-
Key words:
- Rg wave /
- ISO source /
- CLVD source /
- spectral null
-
图 1 CLVD源埋深h为150 （a），200 （b），250 （c）和300 m （d）时不同相对强度下，ISO和CLVD源共同激发的Rg波归一化频谱.ε为CLVD/ISO相对强度
Figure 1. The normalized Rg spectra excited by conjunct sources of ISO and CLVD in different relative strengths at the CLVD source depths of 150 （a），200 （b），250 （c） and 300 m （d）. ε is the relative strength of CLVD source to ISO source
图 2 低谷点频率与CLVD源埋深h的关系
（a） CLVD源相对强度为0.5时ISO和CLVD源共同激发的Rg波归一化频谱；（b） fnull随h变化与理论式h＝α/（16fnull）的比较
Figure 2. The relationship between null frequency and the depth of CLVD source
（a） The normalized Rg spectra excited by conjunct sources of ISO and CLVD with the relative strength of CLVD 0.5； （b） Comparison between the relationship of fnull to h and the theoretical formula h＝α/（16fnull）
图 3 低谷点频率与CLVD源埋深h的关系
（a） CLVD源相对强度0.8时Rg波归一化频谱；（b） fnull随h变化与理论式h＝α/（16fnull）的比较
Figure 3. The relationship of null frequence to the depth of CLVD source
（a） The normalized Rg spectra excited by conjunct sources of ISO and CLVD with the relative strength of CLVD 0.8；（b） Comparison between the relationship of fnull to h and the theoretical formula h＝α/（16fnull）
图 5 引入源频谱，CLVD源埋深h为50 （a），100 （b），150 （c）和200 m （d）时不同相对强度下，ISO和CLVD源激发的Rg波归一化频谱
Figure 5. The normalized Rg spectra excited by conjunct sources of ISO and CLVD in different relative strengths at the CLVD source depths of 50 （a），100 （b），150 （c）and 200 m （d） with source spectra
-
[1] 何永锋,陈晓非,何耀峰,靳平. 2005. 地下爆炸Rg波低谷点激发机理[J]. 地球物理学报,48(3):643–648. doi: 10.3321/j.issn:0001-5733.2005.03.023 [2] He Y F,Chen X F,He Y F,Jin P. 2005. Generation of null in Rg wave by underground explosions[J]. Chinese Journal of Geophysics,48(3):643–648 (in Chinese). doi: 10.1002/cjg2.697 [3] 徐恒垒,靳平,倪四道,刘文学,王红春,李欣. 2011. 谱元法数值模拟地表起伏对补偿线性矢量偶极源Rg波低谷点的影响[J]. 地球物理学报,54(11):2831–2837. doi: 10.3969/j.issn.0001-5733.2011.11.013 [4] Xu H L,Jin P,Ni S D,Liu W X,Wang H C,Li X. 2011. Investigation of surface fluctuation effects on the spectral null of Rg waves generated by CLVD source with spectral element method simulation[J]. Chinese Journal of Geophysics,54(11):2831–2837 (in Chinese). [5] Aki K, Richards P G. 1980. Quantitative Seismology[M]. San Francisco: W. H. Freeman. [6] Baker G E,Stevens J L,Xu H M. 2012a. Explosion shear-wave generation in high-velocity source media[J]. Bull Seismol Soc Am,102(4):1301–1319. doi: 10.1785/0120110119 [7] Baker G E,Stevens J L,Xu H M. 2012b. Explosion shear-wave generation in low-velocity source media[J]. Bull Seismol Soc Am,102(4):1320–1334. doi: 10.1785/0120110165 [8] Denny M D,Johnson L R. 1991. The explosion seismic source function:Models and scaling laws reviewed[J]. Explo Source Phenomenol,65:1–24. [9] Gupta I N,Chan W W,Wagner R A. 1992. A comparison of regional phases from underground nuclear explosions at east kazakh and nevada test sites[J]. Bull Seismol Soc Am,82(1):352–382. [10] Gupta I N,Zhang T R,Wagner R A. 1997. Low-frequency Lg from NTS and kazakh nuclear explosions:Observations and interpretation[J]. Bull Seismol Soc Am,87(5):1115–1125. [11] Jin P,Xu H L,Wang H C,Pan C Z,Xu X,Wang X L. 2017. Secondary seismic sources behind amplitude ratios between the first 2016 and 2013 North Korean nuclear tests[J]. Geophys J Int,211(1):322–334. doi: 10.1093/gji/ggx289 [12] Massé R P. 1981. Review of seismic source models for underground nuclear explosions[J]. Bull Seismol Soc Am,71(4):1249–1268. doi: 10.1785/BSSA0710041249 [13] Mueller R A,Murphy J R. 1971. Seismic characteristics of underground nuclear detonations:Part I. Seismic spectrum scaling[J]. Bull Seismol Soc Am,61(6):1675–1692. doi: 10.1785/BSSA0610061675 [14] Patton H J,Taylor S R. 1995. Analysis of Lg spectral ratios from NTS explosions:Implications for the source mechanisms of spall and the generation of Lg waves[J]. Bull Seismol Soc Am,85(1):220–236. [15] Patton H J,Taylor S R. 2011. The apparent explosion moment:Inferences of volumetric moment due to source medium damage by underground nuclear explosions[J]. J Geophys Res,116(B3):B03310. [16] Taylor S R, Patton H J. 2013. Can teleseismic mb be affected by rock damage around explosions?[J] Geophys Res Lett, 40（1）: 100–104. -
下载:
查看大图
计量
- 文章访问数: 16
- HTML全文浏览量: 9
- PDF下载量: 3
- 被引次数: 0