Event catalogs of seismic events accompanying the 30 September to 5 October 2015 Skaftá flood

Two subglacial lakes in the western part of Vatnajökull ice cap, southeastern Iceland, 10 and 15 km WNW of Grímsvötn volcano, are the source of regular jökulhlaups in the Skaftá river. The eastern cauldron featured a jökulhlaup that started on 30 September 2015. The seismic signals generated by the flood were recorded using two seismic arrays (clusters of seismometers) operated by the Dublin Institute for Advanced Studies (DIAS) and the Icelandic Meteorological Office’s national seismic network, SIL. The arrays were maintained outside Vatnajökull ice cap. In the Vatnajökull region, the SIL network consists of stations that are partly installed on nunataks and within the ice. We performed array-processing in the frequency domain (FK-analysis) on data filtered 1.2 to 2.6 Hz using the array-processing code as implemented in Obspy to derive back azimuth and slownesses of a tremor source propagating with the flood front. We perform beam stacking in the time domain on data filtered from 5 to 20 Hz to derive the back-azimuth of high-frequency transients moving with the flood front. We used the SIL network for location and magnitude determination of 45 events near the cauldron and the flood path. These are possibly 22 icequakes and 23 earthquakes. We used the array data to apply an STA/LTA filter and template matching approach on data filtered from 1 to 15 Hz to detect 669 events associated with the flood. 30% of these could be clustered into families and are likely due to the ice-shelf collapse once the subglacial lake drained. These catalogs are further discussed and evaluated in Eibl et al. 2020 and Eibl et al. 2023. This data publications releases the catalogs of (i) tremor, (ii) located events and (iii) STA/LTA detected and clustered events.

冰岛东南部瓦特纳冰盖（Vatnajökull ice cap）西部的两处冰下湖，距格里姆斯沃特纳火山（Grímsvötn volcano）西北偏西10千米与15千米，为斯卡夫塔河（Skaftá river）周期性冰湖溃决洪水（jökulhlaup）的源头。其中东侧冰斗于2015年9月30日爆发了一次冰湖溃决洪水。此次洪水产生的地震信号，由都柏林高级研究所（Dublin Institute for Advanced Studies, DIAS）与冰岛气象学会国家地震台网SIL布设的两套地震台阵（地震计集群）记录。两套台阵均部署于瓦特纳冰盖范围之外。在瓦特纳冰盖区域内，SIL台网的台站部分布于冰原岛峰（nunataks）及冰盖内部。本研究采用Obspy库实现的台阵处理代码，对1.2~2.6 Hz频段滤波后的数据开展频域台阵处理（FK分析），以反推随洪水前锋传播的震颤源的反方位角与慢度。此外，针对5~20 Hz频段滤波后的数据，我们在时域进行波束叠加，以获取随洪水前锋移动的高频瞬态信号的反方位角。我们依托SIL台网，对该冰斗及洪水路径附近的45次事件进行定位与震级测定，其中可能包含22次冰震与23次构造地震。我们利用台阵数据，对1~15 Hz频段滤波后的数据应用短时/长时平均比（STA/LTA）滤波与模板匹配方法，共检测到669次与洪水相关的事件。其中30%的事件可聚类为事件簇，推测源于冰下湖排水后引发的冰架坍塌。上述数据集目录已在Eibl等人2020年与2023年的研究中进行了详细讨论与评估。本数据集发布了三类目录：(i) 震颤事件目录，(ii) 定位事件目录，以及(iii) 经STA/LTA检测与聚类的事件目录。