Revealing the deeper structure of the end-glacial Pärvie fault system in northern Sweden by seismic reflection profiling
Revealing the deeper structure of the end-glacial Pärvie fault system in northern Sweden by seismic reflection profiling
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DOI：
10.5194/se-6-621-2015
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发表时间：
2015-06
期刊：
影响因子：
3.4
通讯作者：
O. Ahmadi;C. Juhlin;M. Ask;B. Lund
中科院分区：
文献类型：
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作者：
O. Ahmadi;C. Juhlin;M. Ask;B. Lund
抽象。2014年6月，在瑞典北方进行了一次新的地震反射勘测，以便对冰末Parvie断层系统的更深层次进行成像。帕维断层系统是斯堪的纳维亚半岛北方迄今为止最大的断层陡坎，无论是从其长度还是计算出的地震震级来看，都是如此。现今的微震沿着断层陡坎东侧的断层陡坎长度发生，与东倾的主断层大体一致。在断层系统的中央部分，在主要的帕尔维陡崖以东有许多次级断层，目前还不清楚地震与地表测绘的结构有何关系。2007年，以机械锤为震源，在Parvie断层系统上采集的地震剖面图显示，地表映射断层与中度至陡倾反射之间存在良好的相关性。最明显的反射体可以映射到大约3公里的深度。在新的地震勘探中，为了进行更深的穿透，在20米深的炮孔中使用了最大装药量为8.34公斤的爆炸源。反射层现在可以追溯到更深的层次，主要的65°东倾断层被解释为弱反射结构。与上一剖面图一样，在主断层以东存在一个强反射的60°西倾构造，现在可以映射到约8 km的深度。主、副断层的外推结果在现今地震活动集中的11.5km左右的深度处汇合，表明它们的交汇为地震应力释放创造了有利条件。根据目前和以前的地震反射数据，我们提出了未来钻孔的潜在位置，以便科学地钻探断层系统。这些钻孔将使人们更好地了解断层结构的反射性质和沿着断层的深部应力场。
Abstract. A new seismic reflection survey for imaging deeper levels of the end-glacial Parvie fault system in northern Sweden was acquired in June 2014. The Parvie fault system hosts the largest fault scarp so far documented in northern Scandinavia, both in terms of its length and calculated magnitude of the earthquake that generated it. Present-day microearthquakes occur along the length of the fault scarp on the eastern side of the scarp, in general agreement with an east-dipping main fault. In the central section of the fault system, where there is a number of subsidiary faults east of the main Parvie scarp, it has been unclear how the earthquakes relate to the structures mapped at the surface. A seismic profile across the Parvie fault system acquired in 2007, with a mechanical hammer as a source, showed a good correlation between the surface mapped faults and moderate to steeply dipping reflections. The most pronounced reflectors could be mapped to about 3 km depth. In the new seismic survey, for deeper penetration an explosive source with a maximum charge size of 8.34 kg in 20 m deep shot holes was used. Reflectors can now be traced to deeper levels with the main 65° east-dipping fault interpreted as a weakly reflective structure. As in the previous profile, there is a strongly reflective 60° west-dipping structure present to the east of the main fault that can now be mapped to about 8 km depth. Extrapolations of the main and subsidiary faults converge at a depth of about 11.5 km, where current earthquake activity is concentrated, suggesting their intersection has created favorable conditions for seismic stress release. Based on the present and previous seismic reflection data, we propose potential locations for future boreholes for scientific drilling into the fault system. These boreholes will provide a better understanding of the reflective nature of the fault structures and stress fields along the faults at depth.