Abstract
Abstract. Geothermal systems in the Hengill volcanic area, SW Iceland, started to be exploited for electrical power and heat production since the late 1960s. Today the two largest operating geothermal power plants are located at Nesjavellir and Hellisheiði. This area is a complex tectonic and geothermal site, located at the triple junction between the Reykjanes Peninsula (RP), the Western Volcanic Zone (WVZ), and the South Iceland Seismic Zone (SISZ). The region is seismically highly active with several thousand earthquakes located yearly. The origin of such earthquakes may be either natural or anthropogenic. The analysis of microseismicity can provide useful information on natural active processes in tectonic, geothermal and volcanic environments as well as on physical mechanisms governing induced events. Here, we investigate the microseismicity occurring in Hengill area, using a very dense broadband seismic monitoring network deployed in Hellisheiði since November 2018, and apply sophisticated full-waveform based method for detection and location. Improved locations and first characterization indicate that it is possible to identify different types of microseismic clusters, which are associated with either production/injection or the tectonic setting of the geothermal area.
Highlights
The Hengill volcanic system is located in Iceland in the southern end of the western volcanic zone (WVZ), at the triple junction between the Western Volcanic Zone (WVZ), the Reykjanes Peninsula (RP), the landward extension of the Reykjanes spreading ridge, and the South Iceland Seismic Zone (SISZ), i.e. the left-lateral transform zone (Saemundsson, 1979; Einarsson, 2008)
We note that shallower events are mostly located in the geothermal area, whereas most of deeper events appear as a big separate cluster in the southern part of the area, in the neighbouring SISZ
We applied an automated waveform-based method for earthquake location to a dataset characterized by a significant number of low-magnitude events in the Hengill geothermal area, which provide robust results even with low signal-tonoise ratio datasets (Grigoli et al, 2018)
Summary
The Hengill volcanic system is located in Iceland in the southern end of the western volcanic zone (WVZ), at the triple junction between the WVZ, the Reykjanes Peninsula (RP), the landward extension of the Reykjanes spreading ridge, and the South Iceland Seismic Zone (SISZ), i.e. the left-lateral transform zone (Saemundsson, 1979; Einarsson, 2008). The area is characterized by a complex local geology and tectonic setting, and intense seismicity. South of 64◦ N, in the SISZ, the area is characterized by a transform faulting with the main tectonic structures striking N–S. The natural geothermal activity is expressed by numerous hot springs and fumaroles spread throughout the area around the volcanic system
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