The 2008 West Bohemia earthquake swarm in the light of the WEBNET network
The 2008 West Bohemia earthquake swarm in the light of the WEBNET network
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WEBNET 网络中的 2008 年西波西米亚地震群
DOI：
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发表时间：
2010
期刊：
影响因子：
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通讯作者：
A. Boušková
中科院分区：
文献类型：
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作者：
T. Fischer;J. Horalek;J. Michałek;A. Boušková
2008年10月，西波希米亚/沃格特兰地区(捷克和德国交界处)发生了一系列震级高达ML = 3.8级的地震。它发生在11月11日的科斯特尔震源区，也是最近所有的震群(1985/1986、1997和2000年)发生的地方，并受到一系列宏观地震观测到的快速地震的冲击。根据已在震中地区运行的捷克本地台网WEBNET(West Bohemia地震台网)的观测，我们给出了该震群的基本特征。震群中心周围的13到23个永久和移动的WEBNET台站记录了这次震群。此外，强震加速度计也记录到了震群的一部分，这是该地区第一批真实的震群地震加速度图。峰值地面加速度达到0.65米/秒2。与以往震群的对比表明，1985/1986年和2008年震群释放的总地震矩相似，约为4E16 Nm，代表了自1908年ML = 5.0震群以来在西波希米亚/沃格特兰地区发生的最大的两个震群。2008年震群的特征是持续时间短(4周)和快速，因此，与之前的震群相比，地震瞬间释放最快。使用自动拾取器检测到的震级范围为0.5 <； ML <； 3.8的地震多达25,000次。在震群中总共可以区分出9个震群阶段，其中5个阶段超过了2.5级。2008年震群活动的震级-频率分布显示b值接近1。震群震源正好落在2000年震群(ML ≤ 3.2)和1985年/1986年震群(ML ≤ 4.6)激活的同一断层部分。考虑到100m左右的定位误差，2000年和2008年震群的陡倾断层面似乎是相同的，而且2008年震群的震源机制与2000年震群的震源机制是相同的，都与活动断裂段的平均走向170°和倾角80°相匹配。观察到活动总体向上迁移，第一个事件在激活的断层斑块的底部，最后一个事件在激活的断层斑块的顶部。活动断裂区的相似性和最近三次最大震群期间释放的地震矩的相似性使我们能够估计震源区的地震潜力。如果整个断裂面同时被激活，则代表ML~5级地震。这与过去西波希米亚/沃格特兰地区发生的最大地震震级的估计很好地一致。
A swarm of earthquakes of magnitudes up to ML = 3.8 stroke the region of West Bohemia/Vogtland (border area between Czechia and Germany) in October 2008. It occurred in the Nový Kostel focal zone, where also all recent earthquake swarms (1985/1986, 1997, and 2000) took place, and was striking by a fast sequence of macroseismically observed earthquakes. We present the basic characteristics of this swarm based on the observations of a local network WEBNET (West Bohemia seismic network), which has been operated in the epicentral area, on the Czech territory. The swarm was recorded by 13 to 23 permanent and mobile WEBNET stations surrounding the swarm epicenters. In addition, a part of the swarm was also recorded by strong-motion accelerometers, which represent the first true accelerograms of the swarm earthquakes in the region. The peak ground acceleration reached 0.65 m/s2. A comparison with previous earthquake swarms indicates that the total seismic moments released during the 1985/1986 and 2008 swarms are similar, of about 4E16 Nm, and that they represent the two largest swarms that occurred in the West Bohemia/ Vogtland region since the ML = 5.0 swarm of 1908. Characteristic features of the 2008 swarm are its short duration (4 weeks) and rapidity and, consequently, the fastest seismic moment release compared to previous swarms. Up to 25,000 events in the magnitude range of 0.5 < ML < 3.8 were detected using an automatic picker. A total of nine swarm phases can be distinguished in the swarm, five of them exceeding the magnitude level of 2.5. The magnitude–frequency distribution of the complete 2008 swarm activity shows a b value close to 1. The swarm hypocenters fall precisely on the same fault portion of the Nový Kostel focal zone that was activated by the 2000 swarm (ML ≤ 3.2) in a depth interval from 6 to 11 km and also by the 1985/1986 swarm (ML ≤ 4.6). The steeply dipping fault planes of the 2000 and 2008 swarms seem to be identical considering the location error of about 100 m. Furthermore, focal mechanisms of the 2008 swarm are identical with those of the 2000 swarm, both matching an average strike of 170° and dip of 80° of the activated fault segment. An overall upward migration of activity is observed with first events at the bottom and last events at the top of the of the activated fault patch. Similarities in the activated fault area and in the seismic moments released during the three largest recent swarms enable to estimate the seismic potential of the focal zone. If the whole segment of the fault plane was activated simultaneously, it would represent an earthquake of ML ~5. This is in good agreement with the estimates of the maximum magnitudes of earthquakes that occurred in the West Bohemia/Vogtland region in the past.