地震研究

针对大范围的地震活动密集区精定位实施中有效划分子区域问题,通过多次模拟数据实验,检验机器学习的各种聚类算法后,得出基于密度聚类的DBSCAN算法最适用于断层或地震丛集的地震聚类。使用DBSCAN算法对川滇地区共322 070个M1.2～5.1地震事件进行了聚类,共得到9个明显地震簇,对其中的鲜水河断裂带南段和安宁河断裂带北段交会区域的地震簇以及鲜水河—安宁河断裂带西北部区域的2014年康定M_S6.3地震序列地震簇,使用双差地震定位方法进行了精定位,并分析了地震空间分布特征。结果表明:鲜水河断裂带南段和安宁河断裂带北段交会区域的地震密集地分布在断裂周围,走向与断裂走向基本一致,纵剖面揭示了该断裂在深部以西倾为主要特征; 康定地震序列具有与走滑断裂地震分布一致的特征,断层在深部倾角几乎垂直。进一步研究了2009年1月—2021年3月鲜水河断裂带南段与安宁河断裂带北段交会区域b值空间分布特征,揭示了2022年9月5日泸定M_S6.8地震的发震位置处于明显的低b值区域。

Aiming at the problem of effectively sub-dividing sub-regions for precise earthquake location in large-scale areas with intensive seismic activity,this paper,through multiple simulated data experiments and evaluations of various clustering algorithms in machine learning,concludes that the DBSCAN algorithm is most suitable for earthquake clustering in faults or earthquake swarms.Based on this,seismic activity studies are conducted to analyze and reveal spatial differences in the relative levels of current tectonic stress accumulation along fault zones,serving as an important foundation for analyzing the current activity patterns of faults(segments)and potential strong earthquake hazard zones.The DBSCAN algorithm was applied to cluster a total of 322 070 earthquake events in Sichuan-Yunnan region,resulting in nine distinct earthquake clusters.Among them,precise locations are determined using the double-difference earthquake location algorithm for the earthquake cluster in the intersection area of the southern segment of the Xianshuihe fault zone and the northern segment of the Anninghe fault zone,as well as for the Kangding M_S6.3 earthquake sequence to the northwest,and the spatial distribution characteristics of earthquakes are also analyzed.The relocated results show that the Kangding earthquake sequence exhibits features consistent with the earthquake distribution on the strike-slip fault.The fault has an almost vertical dip angle.Earthquakes in the intersection area of the southern segment of the Xianshuihe fault zone and in the northern segment of the Anninghe fault zone are also densely distributed around the faults,with orientations generally consistent with the fault strikes.The longitudinal profile reveals the deep structural features of the fault.Furthermore,this paper investigates the spatial distribution characteristics of the b-value in the southern segment of the Xianshuihe fault zone and in the northern segment of the Anninghe fault zone from January 2009 to March 2021,revealing that the location of the Luding M_S6.8 earthquake that occurred on September 5,2022 is in the area where b-value is obviously low.

引言
1 聚类方法在地震丛集划分中的应用实验
2 DBSCAN聚类算法在川滇地区地震活动性中的应用
3 结论

图1 人工合成地震分布<br/>Fig.1 Artificially synthesized seismic distribution

图1 人工合成地震分布
Fig.1 Artificially synthesized seismic distribution

图2 多种聚类方法对合成数据的聚类结果<br/>Fig.2 Clustering results from the synthetic data processed by multiple clustering methods

图2 多种聚类方法对合成数据的聚类结果
Fig.2 Clustering results from the synthetic data processed by multiple clustering methods

图3 随机生成的三维合成数据(a)及DBSCAN算法的聚类结果(b)<br/>Fig.3 Randomly generated 3D synthetic data(a)and clustering results from the DBSCAN method(b)

图3 随机生成的三维合成数据(a)及DBSCAN算法的聚类结果(b)
Fig.3 Randomly generated 3D synthetic data(a)and clustering results from the DBSCAN method(b)

图4 DBSCAN聚类算方法应用于川滇地区地震的聚类结果<br/>Fig.4 Clustering results from the DBSCAN clustering method applied to the earthquakes in Sichuan-Yunnan region

图4 DBSCAN聚类算方法应用于川滇地区地震的聚类结果
Fig.4 Clustering results from the DBSCAN clustering method applied to the earthquakes in Sichuan-Yunnan region

图5 鲜水河断裂带南段和安宁河断裂带北段交会区域地震空间分布(a)和沿不同剖面地震分布(b)<br/>Fig.5 Spatial distribution of the relocated earthquakes in the southern section of the Xianshuihe fault zone and the northern section of the Anninghe fault zone(a)and earthquakes distributed along different profiles(b)

图5 鲜水河断裂带南段和安宁河断裂带北段交会区域地震空间分布(a)和沿不同剖面地震分布(b)
Fig.5 Spatial distribution of the relocated earthquakes in the southern section of the Xianshuihe fault zone and the northern section of the Anninghe fault zone(a)and earthquakes distributed along different profiles(b)

图6 2009年1月—2021年3月鲜水河断裂带南段与安宁河断裂带北段交会区域小震活动的震级-频度关系<br/>Fig.6 Magnitude-frequency relationship of minor earthquakes in the southern section of the Xianshuihe fault zone and in the northern section of the Anninghe fault zone from January 2009 to March 2021

图6 2009年1月—2021年3月鲜水河断裂带南段与安宁河断裂带北段交会区域小震活动的震级-频度关系
Fig.6 Magnitude-frequency relationship of minor earthquakes in the southern section of the Xianshuihe fault zone and in the northern section of the Anninghe fault zone from January 2009 to March 2021

图7 2009年1月—2021年3月鲜水河断裂带南段与安宁河断裂带北段交会区域b值空间分布<br/>Fig.7 Spatial distribution of b-values in the southern section of the Xianshuihe fault zone and in the northern section of the Anninghe fault zone from January 2009 to March 2021

图7 2009年1月—2021年3月鲜水河断裂带南段与安宁河断裂带北段交会区域b值空间分布
Fig.7 Spatial distribution of b-values in the southern section of the Xianshuihe fault zone and in the northern section of the Anninghe fault zone from January 2009 to March 2021

图8 2014年康定MS6.3地震序列空间分布(a)及沿不同剖面地震分布(b)<br/>Fig.8 Spatial distribution of the 2014 Kangding MS6.3 earthquake sequence(a)and distribution of the earthquakes along different profiles(b)

图8 2014年康定MS6.3地震序列空间分布(a)及沿不同剖面地震分布(b)
Fig.8 Spatial distribution of the 2014 Kangding MS6.3 earthquake sequence(a)and distribution of the earthquakes along different profiles(b)

贾漯昭,孟令媛,闫睿.2024.深度学习在地震监测预报中的应用进展[J].地震研究,47(3):336-349.
Jia L Zh,Meng L Y,Yan R.2024.Advancements of deep learning in seismic monitoring and prediction[J].Journal of Seismological Research,47(3):336-349.(in Chinese)
李正芳,周本刚.2014.利用断裂带上的低b值识别凹凸体方法的探讨——以龙门山断裂带和鲜水河断裂带为例[J].震灾防御技术,9(2):213-225.
Li Z F,Zhou B G.2014.Asperity identification based on low b-value:Application to the Longmenshan and Xianshuihe fault zone[J].Technology for Earthquake Disaster Prevention,9(2):213-225.(in Chinese)
龙锋,祁玉萍,易桂喜,等.2021.2021年5月21日云南漾濞MS6.4地震序列重新定位与发震构造分析[J].地球物理学报,64(8):2631-2646.
Long F,Qi Y P,Yi G X,et al.2021.Relocation of the MS6.4 Yangbi earthquake sequence on May 2l,2021 in Yunnan province and its seismogenic structure analysis[J].Chinese Journal of Geophysics,64(8):2631-2646.(in Chinese)
石永祥,蒋一然,宁杰远,等.2021.基于震源聚类方法确定川滇交界东部地区微震的空间分布特征[J].华北地震科学,39(2):10-16.
Shi Y X,Jiang Y R,Ning J Y,et al.2021.Spatial distribution characteristics of microearthquakes in east Sichuan-Yunnan boundary area from epicentral clustering[J].North China Earthquake Sciences,39(2):10-16.(in Chinese)
苏有锦,李永莉,李忠华,等.2003.川滇地区区域地震目录完整性最小震级分析[J].地震研究,26(S1):10-16.
Su Y J,Li Y L,Li Z H,et al.2003.Analysis of minimum complete magnitude of earthquake catalog in Sichuan-Yunnan region[J].Journal of Seimological Research,26(S1):10-16.(in Chinese)
王辉,曹建玲,荆燕,等.2012.川滇地区强震活动前b值的时空分布特征[J].地震地质,34(3):531-543.
Wang H,Cao J L,Jing Y,et al.2012.Spatio temporal pattern of b-value before major earthquakes in the Sichuan-Yunnan region[J].Seismology and Geology,34(3):531-543.(in Chinese)
王未来,房立华,吴建平,等.2021.2021年青海玛多MS7.4地震序列精定位研究[J].中国科学:地球科学,51(7):1193-1202.
Wang W L,Fang L H,Wu J P,et al.2021.The refined positioning study of the Qinghai Maduo MS7.4 earthquake sequence in 2021[J].Scientia Sinica Terrae,51(7):1193-1202.(in Chinese)
易桂喜,闻学泽.2007.多地震活动性参数在断裂带现今活动习性与地震危险性评价中的应用与问题[J].地震地质,29(2):254-271.
Yi G X,Wen X Z.2007.The application and limitation of multiple seismicity parameters to assessing current faulting behavior and seismic potential of active faule zones[J].Seismology and Geology,29(2):254-271.(in Chinese)
Aggarwal C C,Erik Z.2000.A survey of techniques for density based clustering of high dimensional data[J].Journal of pattern recognition,33(11):1659-1674.
Fang L H,Wu J P,Liu J,et al.2015.Preliminary report on the 22 November 2014 MW6.1/MS6.3 Kangding earthquake,western Sichuan,China[J].Seismological Research Letters,86(6):1603-1613.
Fang L H,Wu J P,Wang W L,et al.2013.Relocation of the mainshock and aftershock sequences of MS7.0 Sichuan Lushan earthquake[J].Chinese Science Bulletin,58(28):3451-3459.
Feng T,Wu J P,Fang L H,et al.2021.Foreshocks of the 2018 ML4.0 Shimian earthquake in the Anninghe fault and its implications for earthquake nucleation[J].Seismological Research Letters,92:1937-1949.
Jiang G Y,Wen Y M,Liu Y J,et al.2015.Joint analysis of the 2014 Kangding,southwest China,earthquake sequence with seismicity relocation and InSAR inversion[J].Geophysical Research Letters,42(9):3273-3281.
Mendoza M M,Ghosh A,Karplus M S,et al.2019.Duplex in the Main Himalayan Thrust illuminated by aftershocks of the 2015 MW7.8 Gorkha earthquake[J].Nat Geosci,12(12):1018-1022.
Ross Z E,Idini B,Jia Z,et al.2019.Hierarchical interlocked orthogonal faulting in the 2019 Ridgecrest earthquake sequence[J].Science,366(6463):346-351.
Shearer P,Hauksson E,Lin G Q.2005.Southern California hypocenter relocation with waveform cross-correlation,Part 2:Results using source-specific station terms and cluster analysis[J].Bulletin of the Seismological Society of America,95(3):904-915.
Shelly D R,Hardebeck J L.2019.Illuminating faulting complexity of the 2017 Yellowstone Maple Creek earthquake swarm[J].Geophysical Research Letters,46(5):2544-2552.
Waldhauser F,Ellsworth W L.2000.A double-difference earthquake location algorithm:Method and application to the northern Hayward fault,California[J].Bulletin of the Seismological Society of America,90(6):1353-1368.
Wiemer S,Wyss M.2000.Minimum magnitude of completeness in earthquake catalogs:example from Alaska,the western United States,and Japan[J].Bulletin of the Seismological Society of America,90(4):859-869.
Yadav R B,Bormann P,Rastogi B K,et al.2009.A homogeneous and complete earthquake catalog for northeast India and the adjoinning region[J].Seismological Research Letters,80(4):609-627.
Zhou Y J,Yue H,Fang L H,et al.2022.An earthquake detection and location architecture for continuous seismograms:phase picking,association,location,and matched filter(PALM)[J].Seismological Research Letters,93(1):413-425.

备注

引言

1 聚类方法在地震丛集划分中的应用实验

2 DBSCAN聚类算法在川滇地区地震活动性中的应用

3 结论

期刊信息