Indications for different types of brittle failure due to active coal mining using waveform similarities of induced seismic events
Indications for different types of brittle failure due to active coal mining using waveform similarities of induced seismic events
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DOI：
10.5194/se-4-405-2013
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发表时间：
2013-10
期刊：
影响因子：
3.4
通讯作者：
S. Wehling-Benatelli;D. Becker;M. Bischoff;W. Friederich;T. Meier
中科院分区：
文献类型：
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作者：
S. Wehling-Benatelli;D. Becker;M. Bischoff;W. Friederich;T. Meier
抽象。鲁尔煤矿区的长壁开采活动导致了采矿诱发的地震活动。为了进行详细的研究，在2006年6月至2007年7月期间，利用由15个地震台站组成的密集临时网络，对鲁尔区东部Hamm-Herringen镇地下的一个长壁面板的地震活动进行了监测。在这一时期，探测到并定位了7000多个震级在-1.7 ≤ ML ≤ 2.0之间的地震事件。大多数事件发生在移动长壁工作面附近。为了找到这些事件的脆性破坏类型的可能差异，基于它们的波形特征执行事件与不同聚类的关联。这项任务是使用一种新的聚类算法，利用网络相似性矩阵，这是通过结合所有可用的3-分量单站相似性矩阵。然后，相对于其行的相似性对所得到的网络矩阵进行排序，从而产生立即指示事件目录的聚类的排序矩阵。最后，通过视觉检测提取相似事件的聚类。这种方法的结果是在识别几个大的集群是不同的，它们的空间和时间特性，以及它们的频率幅度分布。用传统的单一连锁方法也发现了类似的聚类，然而，新的例程似乎能够将更多的事件与特定的聚类相关联，而无需合并聚类。九个最大的观察集群可以暂时分为三个不同的组，表明不同类型的脆性破坏。第一组由两个最大的集群组成，占所有记录事件的一半以上。使用互相关数据的相对重新定位的结果表明，这些事件被限制在已开采的长壁的范围内，并在活跃开采的深度处靠近活跃长壁的边缘聚集。这些事件发生在锁步与长壁前进，并表现出高B值的古腾堡-里希特关系（GR）的约1.5至2.5，由小震级的事件。因此，这些事件代表了邻近采空区的即时能量释放。第二组由位于活动开采深度稍上或稍下的群集组成，并且发生在长壁范围内的长壁工作面的当前位置处。它们通常由更强的事件组成，并且不遵循GR。这种活动可能与采空煤层上方和下方更强的层的失效有关，从而导致更大规模的事件。最后，一个集群代表地震活动，B值低于1，部分位于长壁北侧，相对于长壁工作面的推进有所延迟。这些事件被解释为采矿活动重新激活的原有构造结构的脆性破坏。
Abstract. Longwall mining activity in the Ruhr coal mining district leads to mining-induced seismicity. For detailed studies the seismicity of a single longwall panel beneath the town of Hamm-Herringen in the eastern Ruhr area was monitored between June 2006 and July 2007 with a dense temporary network of 15 seismic stations. More than 7000 seismic events with magnitudes between –1.7 ≤ ML ≤ 2.0 were detected and localized in this period. Most of the events occurred in the vicinity of the moving longwall face. In order to find possible differences in the brittle failure types of these events an association of the events to distinct clusters is performed based on their waveform characteristics. This task is carried out using a new clustering algorithm utilizing a network similarity matrix which is created by combining all available 3-component single station similarity matrices. The resultant network matrix is then sorted with respect to the similarity of its rows leading to a sorted matrix immediately indicating the clustering of the event catalogue. Finally, clusters of similar events are extracted by visual inspection. This approach results in the identification of several large clusters which are distinct with respect to their spatial and temporal characteristics as well as their frequency magnitude distributions. Comparable clusters are also found with a conventional single linkage approach, however, the new routine seems to be able to associate more events to specific clusters without merging the clusters. The nine largest observed clusters can be tentatively divided into three different groups that indicate different types of brittle failure. The first group consists of the two largest clusters which constitute more than half of all recorded events. Results of a relative relocation using cross-correlation data suggest that these events are confined to the extent of the mined out longwall and cluster close to the edges of the active longwall at the depth of active mining. These events occur in lockstep with the longwall advance and exhibit a high b value of the Gutenberg–Richter relation (GR) of about 1.5 to 2.5 and consist of small magnitude events. Thus, these events represent the immediate energy release adjacent to the mined out area. The second group consists of clusters located either slightly above or below the depth of active mining and occurring at the current position of the longwall face within the confines of the longwall. They consist of generally stronger events and do not follow GR. This activity might be linked to the failure of more competent layers above and below the mined out seam resulting in larger magnitude events. Finally, one cluster represents seismic activity with a rather low b value below 1 and events located partly towards the north of the longwall which are delayed with respect to the advance of the longwall face. These events are interpreted as brittle failure on pre-existing tectonic structures reactivated by the mining activity.