Investigations of hydraulically induced micro-seismicity are typically connected with magma injections, exploitation of geothermal fields and salt mines. Our study examines the seismicity and seismic sources in a peri-platform region with long salt production history. In addition, a very large site for extraction of aggregates and limestone is presented in the area. Increased seismicity in the region has been observed for several decades as during the study period of the last 12 years, more than 1000 events with magnitude \(M < 4.3\) have been registered. To study the complex seismic sources concentrated in such small area spatial distribution of seismicity and fault plane solutions are analyzed together with available geological and geophysical data, in order to connect registered earthquakes swarms with geological structures. Results show that several faults are outlined from geological information and confirmed by interpretation of geophysical data. Very different focal mechanisms calculated for the 13 earthquakes in the near region of the salt production site cannot propose a dominant fault mechanism and confirm the complexity of the seismic sources in the area. Our results suppose that activation of some of these structures is more likely due to water injected in the salt dome as part of the production process, which changes the stress equilibrium in the Earth crust.

中文翻译：

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保加利亚东北部前巴尔干单元与莫伊斯平台之间过渡带的地震源和地球结构

水力诱发的微地震的研究通常与岩浆注入，地热田开发和盐矿有关。我们的研究检查了具有长盐生产历史的平台周缘地区的地震活动性和地震源。此外，该地区还存在一个很大的提取骨料和石灰石的场所。在过去的12年的研究期内，该地区的地震活动性已经提高了几十年，发生了1000多个级别为\（M <4.3 \）的地震。已注册。为了研究集中在如此小的区域内的复杂地震源的地震活动性和断层平面解，并结合可用的地质和地球物理数据进行分析，以使注册的地震群与地质结构联系起来。结果表明，从地质信息中勾勒出几个断层，并通过解释地球物理数据证实了这些断层。对于盐产区附近地区的13次地震，计算得出的震源机制差异很大，无法提出主要的断层机制，也无法确定该地区地震源的复杂性。我们的结果认为，由于在生产过程中向盐丘中注入了水，这些结构中的一些更有可能被激活，这改变了地壳中的应力平衡。