2014 Mainshock-Aftershock Activity Versus Earthquake Swarms in West Bohemia, Czech Republic
2014 Mainshock-Aftershock Activity Versus Earthquake Swarms in West Bohemia, Czech Republic
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2014 年捷克共和国西波希米亚主震-余震活动与地震群
DOI：
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发表时间：
2017
影响因子：
2
通讯作者：
T. Fischer
中科院分区：
文献类型：
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作者：
Hana Jakoubková;J. Horalek;T. Fischer
2014年，西波西米亚/沃格特兰地震群区发生了3次$$M_{L}$$ ML3.5、4.4和3.6主余震。我们利用WEBNET数据分析了这一活动，并从累积地震矩、统计特征、事件时空分布和主要震源机制等方面与1997年、2000年、2008年和2011年的地震群进行了比较。为此，利用WEBNET改进了地震矩$$M_{0}$$ M0与震级$$M_{L}$$ ML之间的标度关系。2014年事件释放的总地震矩（$$M_{0mathrm{tot}}approx 1.58 imes 10^{15}$$ M0tot≈1.58×1015 Nm）对应于一次$$M_{L}4.6+$$ ML4.6+事件，与2000年、2008年和2011年群的$$M_{0mathrm{tot}}$$ M0tot相当。推断$$M_{L}4.8$$ ML4.8级地震是主震源带Nový Kostel （NK）的最大预期事件。尽管2014年地震序列和地震群的特征不同，但震级-频率分布（MFDs）的b值为$$approx$$≈1，事件间次的概率密度函数（pdf）表明单个地震群的事件率与2014年的活动率相似。只有2014年序列MFD的a值（事件生产力）显著低于群体。一个值得注意的发现是，从2000年到2014年的每一次地震活动中，地震矩释放都有明显的加速，这可能表明地震活动的特征从群状转变为主震-余震特征。三个主震位于位于断层段a、B、C之间的过渡区域的NK区的一个新激活的断层段/陡坡（D在我们的符号中），该断层段主办了2000年、2008年和2011年的地震群。D段以斜冲断层为主，A、B、c段以走滑断裂为主，提出了北克带的基本分段方案，并应逐步完善。
A singular sequence of three episodes of $$M_{L}$$ML3.5, 4.4 and 3.6 mainshock-aftershock occurred in the West Bohemia/Vogtland earthquake-swarm region during 2014. We analysed this activity using the WEBNET data and compared it with the swarms of 1997, 2000, 2008 and 2011 from the perspective of cumulative seismic moment, statistical characteristics, space-time distribution of events, and prevailing focal mechanisms. For this purpose, we improved the scaling relation between seismic moment $$M_{0}$$M0 and local magnitude $$M_{L}$$ML by WEBNET. The total seismic moment released during 2014 episodes ($$M_{0mathrm{tot}}approx 1.58 imes 10^{15}$$M0tot≈1.58×1015 Nm) corresponded to a single $$M_{L}4.6+$$ML4.6+ event and was comparable to $$M_{0mathrm{tot}}$$M0tot of the swarms of 2000, 2008 and 2011. We inferred that the $$M_{L}4.8$$ML4.8 earthquake is the maximum expected event in Nový Kostel (NK), the main focal zone. Despite the different character of the 2014 sequence and the earthquake swarms, the magnitude-frequency distributions (MFDs) show the b-values $$approx$$≈ 1 and probability density functions (PDFs) of the interevent times indicate the similar event rate of the individual swarms and 2014 activity. Only the a-value (event-productivity) in the MFD of the 2014 sequence is significantly lower than those of the swarms. A notable finding is a significant acceleration of the seismic moment release in each subsequent activity starting from the 2000 swarm to the 2014 sequence, which may indicate an alteration from the swarm-like to the mainshocks-aftershock character of the seismicity. The three mainshocks are located on a newly activated fault segment/asperity (D in out notation) of the NK zone situated in the transition area among fault segments A, B, C, which hosted the 2000, 2008 and 2011 swarms. The segment D appears to be predisposed to an oblique-thrust faulting while strike-slip faulting is typical of segments A, B and C. In conclusion, we propose a basic segment scheme of the NK zone which should be improved gradually.