Between February 16 and April 5, 2019, a series of earthquakes took place around the village of Somogyszob, Somogy county, Hungary. The mainshock occurred on March 7 with a local magnitude \(M_L=4.0\) and epicentral intensity of 5 on the EMS scale. The main event was preceded by four foreshocks and followed by four aftershocks. The largest foreshock (\(M_L=2.6\)) was also felt with maximum intensity of 4 EMS. This earthquake sequence is the first remarkable one in the region that was recorded by a significant number of high-quality broadband digital seismographs. We have estimated the hypocenters of the 9 earthquakes using the hypoDD multiple-event location algorithm. The events occurred in a tight region around the mainshock at around 13–14 km depth. For the main event, we obtained an average moment magnitude of \(M_w=3.75\), source radii of \(r^P=509\) m and \(r^S=400\) m, and static stress drops of \(\varDelta \sigma ^P=1.19\times 10^6\) Pa and \(\varDelta \sigma ^S=4.00\times 10^6\) Pa from the analysis of displacement P- and S-wave spectra, respectively. The resulting spectral source parameters for the investigated events agree well with the results of earlier research. We have also shown that our recently developed probabilistic waveform inversion techniques applied in this study are suitable to retrieve the source mechanism for weak local earthquakes. We have successfully estimated the focal mechanism for the mainshock, a foreshock and an aftershock. Each earthquake was a thrust faulting event with a sub-horizontal P-axis pointing towards N-NE, coinciding with the general trend of the compressional stress field in the epicentral region.

中文翻译：

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2019年3月7日$$ \ mabbf {M_L = 4.0} $$ M L = 4.0匈牙利Somogyszob地震序列的来源分析

在2019年2月16日至4月5日之间，匈牙利Somogy县Somogyszob村周围发生了一系列地震。主震发生在3月7日，局部震级为\（M_L = 4.0 \），震中强度为EMS等级5。主赛事之前发生了四次前震，随后发生了四次余震。最大前震（\（M_L = 2.6 \）最大强度为4 EMS的情况下也感觉到）。该地震序列是该地区第一个由大量高质量宽带数字地震仪记录的地震序列。我们使用hypoDD多事件定位算法估算了9次地震的震源。这些事件发生在主震周围的一个狭窄区域中，深度约13-14 km。对于主要事件，我们获得了平均矩量\（M_w = 3.75 \），源半径\（r ^ P = 509 \）  m和\（r ^ S = 400 \）  m以及静态应力降为\（\ varDelta \ sigma ^ P = 1.19 \乘以10 ^ 6 \）  Pa和\（\ varDelta \ sigma ^ S = 4.00 \乘以10 ^ 6 \） 分别从位移P波谱和S波谱分析得出Pa。所研究事件的光谱源参数结果与早期研究的结果非常吻合。我们还表明，我们在本研究中使用的最新开发的概率波形反演技术适用于找回局部弱地震的震源机制。我们已经成功地估算了主震，前震和余震的震源机制。每次地震都是一次冲断层断裂事件，其次水平的P轴指向N-NE，与震中区域的压应力场总体趋势一致。