The Åknes rockslide in Western Norway is characterised by a steady movement of a rock mass with an extent of about 1 km² and a yearly deformation rate in the range of 2 to 4 cm. A seismic network consisting of 8 three-component geophones records tens to hundreds of local and distant seismic events daily. Depending on their character, local seismic events show a variety of waveforms, both with abrupt and emergent onsets. Along with the relatively low frequencies of the waveforms, standard location procedure using arrival time measurements is difficult to apply. Based on the event envelopes, we classify local events and obtain their approximate location by stacking STA/LTA ratios of back-projected waveforms. To suppress the influence of complex surface morphology and related complicated wave propagation, we constrain hypocentres to the surface of the slope and determine only horizontal coordinates. The method was successfully tested by locating two types of ground truth data: calibration shots and a block collapse. The test proved the ability of the method to determine the position of sliding events with an uncertainty of less than 36 m, which allows to distinguish amongst several foci of rockslide activity. Application of the method to 8 years of monitoring data shows continuous seismic activity, which is concentrated in the centre and at the western edge of the monitored area. Most likely, microseismic events recorded by the seismic network originate within the body of the rock slope and are related to its disintegration or potentially to sliding on the detachment fault.

中文翻译：

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通过反投影方法确定挪威Åknes岩质滑坡上的微地震事件

挪威西部的Åknes滑坡的特征是岩体的稳定运动范围约为1 km ²年变形率在2到4厘米之间。一个由8个三分量检波器组成的地震网络每天记录数十至数百个本地和远程地震事件。根据其特征，局部地震事件会显示出各种波形，包括突然的和紧急的发作。伴随着相对较低的波形频率，使用到达时间测量的标准定位程序很难应用。基于事件包络，我们对局部事件进行分类，并通过堆叠反向投影波形的STA / LTA比值来获得它们的大概位置。为了抑制复杂的表面形态和相关的复杂的波传播的影响，我们将震中限制在斜坡表面，仅确定水平坐标。通过定位两种类型的地面真实数据成功地测试了该方法：校准镜头和块坍塌。该测试证明了该方法确定滑动事件位置的能力，其不确定度小于36 m，从而可以区分岩体滑坡活动的几个震源。该方法在8年的监测数据中的应用表明连续的地震活动，集中在监测区域的中心和西部边缘。地震网络记录的微地震事件最有可能起源于岩石边坡的内部，并且与它的崩解有关，或者可能与脱离断层上的滑动有关。该测试证明了该方法确定滑动事件位置的能力，其不确定度小于36 m，从而可以区分岩体滑坡活动的几个震源。该方法在8年的监测数据中的应用表明连续的地震活动，集中在监测区域的中心和西部边缘。地震网络记录的微地震事件最有可能起源于岩石边坡的内部，并且与它的崩解有关，或者可能与脱离断层上的滑动有关。该测试证明了该方法确定滑动事件位置的能力，其不确定度小于36 m，从而可以区分岩体滑坡活动的几个震源。该方法在8年的监测数据中的应用表明连续的地震活动，集中在监测区域的中心和西部边缘。地震网络记录的微地震事件最有可能起源于岩石边坡的内部，并且与它的崩解有关，或者可能与脱离断层上的滑动有关。